Canine Rotavirus

Overview and Taxonomy of Canine Rotavirus

Canine rotavirus (CRV) represents a significant, albeit historically underappreciated, etiological agent of viral gastroenteritis in domestic dogs and a growing concern in the context of interspecies transmission and zoonotic potential. As a member of the family Sedoreoviridae, genus Rotavirus, CRV is a non-enveloped, double-stranded RNA (dsRNA) virus characterized by a distinctive wheel-like morphology when visualized by electron microscopy, a feature from which the genus derives its name (Latin rota, meaning "wheel") [8, 30]. The virus was first visualized in the feces of clinically normal dogs and subsequently isolated and propagated in cell culture, establishing its identity as a distinct pathogen of canines [8, 30]. Early experimental inoculations of neonatal gnotobiotic dogs definitively demonstrated the virus's capacity to induce diarrhea, confirming its pathogenic role in a controlled host setting [9, 10]. Since these foundational discoveries, CRV has been recognized as a ubiquitous pathogen with a global distribution, detected across diverse geographic regions including Asia, Europe, the Americas, and the Middle East [1, 6, 7, 16, 25, 29].

Taxonomic Classification and Genomic Architecture

The taxonomy of rotaviruses is complex, governed by the Rotavirus Classification Working Group (RCWG), which utilizes a binary classification system based on the two outer capsid proteins: VP7 (a glycoprotein, defining the G genotype) and VP4 (a protease-sensitive protein, defining the P genotype) [3, 5]. Canine rotaviruses are predominantly classified within Rotavirus A (RVA) , the species most commonly associated with disease in mammals, including humans. However, metagenomic surveys have also identified the presence of other rotavirus species in canids, including Rotavirus C (RVC) and Rotavirus I (RVI) , underscoring the genetic diversity within the canine host [24, 26]. RVC has been detected in dogs, with evolutionary analyses suggesting that canine and bovine RVC populations share a common ancestor, having evolved independently for centuries [24]. RVI, a more divergent species, was first identified in canine feces and has since been detected in cats, with its NSP1-1 protein exhibiting functional characteristics of a fusion-associated small transmembrane (FAST) protein, a feature that may influence viral pathogenesis and host range [12, 17, 26].

The CRV genome is composed of 11 segments of dsRNA, each encoding either a structural viral protein (VP1-VP4, VP6, VP7) or a non-structural protein (NSP1-NSP5/6). The complete genotype constellation of a rotavirus strain is described by the formula Gx-P[x]-Ix-Rx-Cx-Mx-Ax-Nx-Tx-Ex-Hx, corresponding to the genes encoding VP7-VP4-VP6-VP1-VP2-VP3-NSP1-NSP2-NSP3-NSP4-NSP5/6, respectively [3, 5]. For canine RVA, the most frequently documented and globally predominant genotype constellation is G3-P[3]-I3-R3-C3-M3-A9-N2-T3-E3-H6 [3, 5, 14, 27]. This specific constellation is a hallmark of the AU-1-like genetic group, a lineage originally identified in a human rotavirus strain (AU-1) but now understood to have a close evolutionary relationship with feline and canine rotaviruses [13, 15, 22]. The AU-1-like group is considered a third major human RVA genotype constellation, alongside the Wa-like (genogroup 1) and DS-1-like (genogroup 2) groups, and its presence in humans is a direct consequence of interspecies transmission from companion animals [13, 15].

Genetic Diversity and Reassortment

The segmented nature of the rotavirus genome is a powerful driver of its evolution, enabling a process known as reassortment. During co-infection of a single host cell with two or more distinct rotavirus strains, gene segments can be exchanged, generating progeny viruses with novel genetic combinations. This mechanism is a primary source of genetic diversity and is critical for the emergence of strains with altered host range, virulence, or antigenicity [3, 5, 14]. Canine rotaviruses are not passive participants in this evolutionary dance; they are both donors and recipients of gene segments in complex reassortment networks involving humans, cats, bats, and other animal species.

Whole-genome sequencing of CRV strains from around the world has repeatedly provided evidence of multiple reassortment events. For instance, a G3P[3] CRV strain isolated in Wuhan, China, was found to have a genomic constellation (G3-P[3]-I3-R3-C3-M3-A9-N2-T3-E3-H6) that, while typical of the AU-1-like group, contained gene segments closely related to reassortant rotaviruses from diverse animal sources, including bats [3]. Similarly, CRVs from Thailand have been characterized as "multiple-reassortants," with phylogenetic analyses indicating that their gene segments may have originated from human, bat, and feline rotaviruses [5, 14]. This is not a one-way street; canine rotavirus gene segments have been identified in porcine rotavirus strains. A porcine G9P[20] rotavirus (strain ZJ03) was found to possess a VP3 gene with highest homology to a giant panda rotavirus and an NSP1 gene with highest homology to a canine rotavirus, demonstrating the flow of genetic material from canids into swine populations and highlighting the ecological risks for wildlife conservation [4].

The biological implications of reassortment are profound. The emergence of the G3P[9] genotype in humans, for example, is believed to have resulted from a feline-derived G3P[3] strain that acquired a human-like P[9] gene through reassortment, successfully crossing the species barrier and establishing onward transmission in the human population [15, 28]. This underscores the role of companion animals as a reservoir for generating novel human rotavirus variants.

Zoonotic Potential and Interspecies Transmission

The zoonotic potential of canine rotavirus is a topic of intense research and public health significance, recognized by organizations such as the World Health Organization (WHO) and the World Organisation for Animal Health (WOAH) in the context of emerging zoonoses. The AU-1-like genetic group serves as the primary conduit for this cross-species transmission. Multiple lines of evidence support the direct transmission of canine/feline rotaviruses to humans:

1. Whole-Genome Evidence: Human rotavirus strains such as Ro1845 and HCR3A (both G3P[3]) have been subjected to complete genome sequencing. Phylogenetic analyses revealed that all 11 gene segments of these human strains are of canine/feline origin, with no evidence of reassortment with typical human rotavirus genes. This provides the strongest possible evidence for direct, whole-virion transmission from a companion animal to a human [15, 22].
2. Amino Acid Identity: The VP7 and VP4 proteins of the human-derived canine-like strain IAL-R2638, detected in Brazil, displayed 99.2% and 96.4% amino acid identity to the canine-derived human strain HCR3A and the canine strain RV52/96, respectively, further confirming its canine origin [21].
3. Clinical Case Reports: A G3P[3] rotavirus strain (PA260/97) was isolated from a child with acute gastroenteritis in Italy. Sequence analysis of its VP7, VP4, VP6, and NSP4 genes showed a close resemblance to a G3P[3] canine strain identified in Italy the previous year, providing a direct epidemiological link between a sick dog and a sick child [23].
4. Epidemiological Surveillance: Large-scale surveillance studies using advanced molecular tools, such as the quadruplex RT-qPCR assay developed by Shi et al. (2024), have confirmed the circulation of CRV in dog populations, with positivity rates ranging from 0.7% to 9.2% in various studies [1, 6, 7]. The detection of CRV in 0.97% of 1,028 clinical samples in China, alongside other zoonotic pathogens like canine coronavirus, reinforces the need for vigilant monitoring at the human-animal interface [1].

The implications of this zoonotic potential are significant. The RotaTeq® vaccine, a live attenuated human rotavirus vaccine, has been theoretically predicted to offer protection against G3P[3] infections based on the lack of an extra VP7 N-linked glycosylation site at amino acid 238 in the canine-like strains, which is also absent in the vaccine's G3 component [21]. However, the constant evolution and reassortment of these viruses could lead to the emergence of vaccine-escape variants. The detection of a rare human G2P[4] strain with an unusual canine-origin NSP1 A15 genotype further illustrates the complex ways in which canine rotaviruses can contribute to the genetic diversity of human strains, potentially impacting vaccine efficacy [11].

Host Range and Susceptibility

While the dog is the primary host, the host range of canine-like rotaviruses extends well beyond canids. The G3P[3] genotype, in particular, has been identified in a wide array of species, including cats, horses, giant pandas, and humans [2, 4, 19, 22]. An Argentinean equine G3P[3] rotavirus strain (E3198) was found to have a genotype constellation (G3-P[3]-I3-R3-C3-M3-A9-N3-T3-E3-H6) reminiscent of feline/canine-like strains, and phylogenetic analyses suggested it was the result of an interspecies transmission event from a feline, canine, or related host to a horse [19]. The detection of rotavirus in giant pandas (GPRV) using multiplex PCR, with a prevalence of 6.42%, further highlights the vulnerability of endangered species to these pathogens and the importance of conservation medicine [2].

Within the canine population, susceptibility to CRV infection is strongly age-dependent. Epidemiological studies consistently demonstrate that puppies under three months of age are at the highest risk of infection and clinical disease. A study in Iran reported a prevalence of 48.15% in dogs less than three months old, compared to just 2.63% in dogs over six months [6]. This age-related susceptibility is attributed to the waning of maternally derived antibodies and the immaturity of the neonatal immune system. Co-infections are also a hallmark of CRV epidemiology. CRV is frequently detected in mixed infections with other enteric pathogens, most notably canine parvovirus type 2 (CPV-2), canine coronavirus (CCoV), and canine distemper virus (CDV) [1, 18, 25]. In Mexico, 14% of dogs with gastroenteritis were co-infected with both rotavirus and parvovirus, and these co-infected animals exhibited more severe clinical signs [25]. This synergistic pathology underscores the importance of comprehensive diagnostic panels, such as the quadruplex RT-qPCR and multiplex PCR assays, for accurate diagnosis and effective clinical management [1, 2, 31].

Molecular Pathogenesis of Canine Rotavirus Infection

The molecular pathogenesis of canine rotavirus (CRV) infection is a multifaceted process that begins at the interface of the virus with the host intestinal epithelium and culminates in a cascade of cellular destruction, malabsorptive diarrhea, and, in severe cases, systemic physiological derangement. Unlike many enteric pathogens that rely on potent exotoxins, rotaviruses, including CRV, employ a sophisticated arsenal of structural and nonstructural proteins to hijack host cellular machinery, evade immune surveillance, and induce pathology primarily through direct cytolysis and the action of a viral enterotoxin. Understanding these mechanisms at the molecular level is critical for appreciating the clinical spectrum of disease, the potential for interspecies transmission, and the development of targeted therapeutic interventions.

Viral Entry and Cellular Tropism

The initial step in CRV pathogenesis is the attachment and entry into mature enterocytes lining the villi of the small intestine. The outer capsid is composed of two critical proteins: VP7 (a glycoprotein defining the G genotype) and VP4 (a protease-sensitive protein defining the P genotype). The predominant genotype circulating in dogs globally is G3P[3], a constellation that has been consistently identified in isolates from Asia, Europe, and the Americas [3, 5, 14]. VP4 must be cleaved by trypsin-like proteases in the intestinal lumen into VP5* and VP8* subunits, a process that dramatically enhances infectivity. Interestingly, early studies demonstrated that CRV replication in cell culture is less dependent on exogenous trypsin than human, bovine, or porcine rotaviruses, suggesting a unique adaptation of the VP4 cleavage site or an enhanced intrinsic fusogenic capacity of the canine virus [8].

The VP8* subunit mediates initial attachment to sialic acid-containing receptors on the enterocyte surface. Following this, VP5* facilitates membrane penetration. The specific cellular receptors for CRV remain incompletely defined, but the virus is known to replicate efficiently in MA-104 cells (fetal rhesus monkey kidney epithelial cells), indicating a broad tropism for primate and canine intestinal epithelium [8, 30]. Once internalized, the virus uncoats, releasing the double-layered particle into the cytoplasm. This particle is transcriptionally active, and the viral RNA-dependent RNA polymerase (VP1), complexed with VP3, initiates the synthesis of capped, non-polyadenylated mRNAs. A remarkable and recently elucidated aspect of CRV molecular pathogenesis is the discovery that rotavirus species I, which includes canine rotaviruses, encodes a fusion-associated small transmembrane (FAST) protein, NSP1-1. This nonstructural protein is not involved in viral entry but mediates cell-cell fusion, leading to the formation of multinucleated syncytia. Studies have confirmed that the NSP1-1 protein from canine rotavirus I is a functional FAST protein capable of inducing syncytia in primate cells, and its N-terminal and transmembrane domains are critical determinants of this cell-type-specific fusion activity [12, 17]. This fusogenic capability may facilitate direct cell-to-cell spread of the virus, allowing it to evade extracellular neutralizing antibodies and accelerate the infection of adjacent enterocytes.

Intestinal Pathogenesis and Villus Atrophy

The hallmark of CRV-induced enteritis is the destruction of absorptive enterocytes, leading to villus atrophy and a consequent malabsorptive diarrhea. The molecular events driving this pathology have been elegantly characterized in the neonatal gnotobiotic dog model, which remains the gold standard for studying CRV pathogenesis in vivo [9, 10]. Following oral inoculation, viral replication is detectable within 12 hours post-inoculation (PIH), with group-specific rotaviral antigen first appearing in the absorptive epithelial cells of the duodenum, jejunum, and ileum [10]. The primary target is the columnar epithelial cell located on the upper one-third of the villus. These cells are terminally differentiated and possess the highest metabolic activity for digestion and absorption.

The infection triggers a rapid and profound cytopathic effect. By 18 to 48 hours PIH, these cells undergo necrosis, and foci of epithelial denudation become apparent on the villus tips [9]. The loss of these cells is not merely a passive consequence of viral replication; it is actively driven by the viral nonstructural protein NSP4. NSP4 acts as a viral enterotoxin. It is localized to the endoplasmic reticulum (ER) of infected cells and disrupts intracellular calcium homeostasis by mobilizing Ca²⁺ from ER stores. This elevation in cytosolic calcium activates chloride channels on the apical membrane of enterocytes, leading to a secretory diarrhea that precedes the onset of significant structural damage. Furthermore, NSP4 can directly disrupt tight junctions between epithelial cells, increasing paracellular permeability and contributing to fluid loss.

The combined effect of direct cytolysis and NSP4-mediated toxicity results in the characteristic histopathological changes: villus blunting and fusion, crypt hyperplasia, and a shift from tall columnar to cuboidal or flattened squamous-like epithelial cells covering the denuded villi [9]. Morphometric analyses have confirmed significantly reduced villus-crypt ratios in the duodenum, jejunum, and ileum of infected pups [9]. This architectural collapse drastically reduces the absorptive surface area of the gut, leading to the accumulation of osmotically active particles in the lumen and osmotic diarrhea. The crypt cells, which are less differentiated and not the primary target of CRV, undergo compensatory hyperplasia, but this response is often insufficient to restore normal function during the acute phase of illness. The clinical consequence is a profuse, watery, non-hemorrhagic diarrhea, which is a key distinguishing feature from canine parvovirus infection, though co-infections can occur and exacerbate clinical signs [25].

Host Immune Evasion and Systemic Dissemination

CRV has evolved sophisticated mechanisms to subvert the host innate immune response, primarily through the action of its nonstructural proteins. The NSP1 protein of group A rotaviruses is a well-characterized interferon (IFN) antagonist. It functions as an E3 ubiquitin ligase that targets host proteins for proteasomal degradation. Specifically, NSP1 induces the degradation of interferon regulatory factors (IRFs), such as IRF3 and IRF7, thereby blocking the transcription of type I interferons (IFN-α/β). This allows the virus to replicate for several cycles before the host can mount a robust antiviral state. The ability of CRV to establish a productive infection in the face of an intact immune system is a testament to the potency of this evasion strategy.

Despite this local immune suppression, the host does eventually mount a response. In the gnotobiotic dog model, serum rotavirus antibody was detected by indirect immunofluorescence as early as PIH 96, and viral antigen was observed not only in enterocytes but also within mononuclear cells in the villus lamina propria [10]. This finding suggests that CRV can infect or be phagocytosed by resident immune cells, potentially serving as a mechanism for antigen presentation but also for viral dissemination. Critically, rotaviral antigen was detected in the mesenteric lymph nodes of some inoculated pups by PIH 48, providing clear evidence of extra-intestinal spread [10]. While CRV is primarily considered an enteric pathogen, this lymphatic involvement indicates that the virus can breach the intestinal barrier and access the systemic circulation, at least transiently. The clinical significance of this is underscored by hematological alterations observed in naturally infected dogs, including significant increases in hemoglobin, packed cell volume (PCV), and total erythrocyte count (TEC), likely reflecting dehydration, alongside elevations in liver enzymes (AST, ALT) and renal markers (BUN, creatinine), suggesting systemic metabolic stress and potential organ involvement [32].

Molecular Basis of Interspecies Transmission and Zoonotic Potential

Perhaps the most compelling aspect of CRV molecular pathogenesis is its role as a reservoir for genetic diversity and a source of zoonotic infection. The segmented nature of the rotavirus genome (11 segments of dsRNA) allows for genetic reassortment when a single cell is co-infected with two different rotavirus strains. Whole-genome sequencing of CRV isolates has revealed that the predominant canine genotype constellation is G3-P[3]-I3-R3-C3-M3-A9-N2-T3-E3-H6, which belongs to the AU-1-like genetic group [3, 5, 14]. This constellation is not exclusive to dogs; it is also found in feline rotaviruses and, critically, in human rotavirus strains.

Molecular phylogenetic analyses have provided irrefutable evidence that several human rotavirus strains, including Ro1845 and HCR3A, are the result of direct virion transmission of canine or feline rotaviruses to humans. Each of the 11 gene segments of these human strains is of canine/feline origin, with no evidence of reassortment with human strains [22]. This demonstrates that CRV can cross the species barrier and cause clinical disease in humans without the need for prior adaptation. Furthermore, the detection of a G3P[3] strain (PA260/97) in a child with acute gastroenteritis in Italy, which showed high sequence identity to a canine strain identified in the same country the previous year, provides a compelling case for contemporary spillover [23]. The zoonotic risk is further amplified by the ability of CRV to reassort with human strains. The emergence of G1P[9] and G9P[9] strains in humans, which carry the P[9] genotype typically found in feline/canine strains, suggests that after an initial spillover event, these animal-derived viruses can reassort with human rotaviruses and acquire the capacity for sustained human-to-human transmission [15].

The molecular determinants that allow CRV to overcome the host-species barrier are complex and likely involve multiple gene segments. The VP4 and VP7 proteins are primary targets of neutralizing antibodies, and amino acid substitutions in these proteins can alter antigenicity and receptor binding specificity. For instance, amino acid analysis of a human-derived canine G3P[3] strain from Brazil (IAL-R2638) showed 99.2% identity to the canine-derived human strain HCR3A in VP7 and 96.4% identity to a canine strain in VP4, reinforcing the close genetic relationship [21]. Additionally, the NSP1 gene, with its potent IFN-antagonist activity, may play a role in host range restriction. A porcine G9P[20] rotavirus was recently found to have an NSP1 gene segment with highest homology to canine strains, suggesting that this gene may be a key factor in enabling cross-species jumps [4]. The World Health Organization (WHO) and the Centers for Disease Control and Prevention (CDC) recognize rotavirus as a major cause of severe diarrheal disease in children globally, and the evidence that companion animals like dogs serve as a reservoir for novel human strains underscores the importance of a One Health approach to rotavirus surveillance. The detection of CRV in giant pandas, an endangered species, further highlights the ecological implications of this virus and its ability to circulate among diverse mammalian hosts [2, 4].

Epidemiology and Zoonotic Potential of Canine Rotavirus

Global Prevalence and Distribution of Canine Rotavirus Infection

Canine rotavirus (CRV) is a globally distributed enteric pathogen with prevalence rates that vary dramatically based on geographic region, diagnostic methodology, target population, and temporal factors. The cumulative body of evidence, drawn from epidemiological surveys conducted across Asia, Europe, the Middle East, and the Americas, reveals a pathogen that, while often overshadowed by more frequently diagnosed enteric viruses such as canine parvovirus type 2 (CPV-2) and canine coronavirus (CCoV), nonetheless maintains a persistent and epidemiologically significant presence in canine populations worldwide [1, 33, 34]. The true burden of CRV infection is likely underestimated, as many infections are subclinical or mild, and routine diagnostic panels do not uniformly include rotavirus among their targets [8, 34, 36].

In China, a nation where canine viral enteropathogens have been the subject of intensive surveillance, CRV detection rates have been documented with notable consistency. A landmark 2024 study employing a quadruplex reverse transcription quantitative polymerase chain reaction (RT-qPCR) assay targeting the CRV VP7 gene, alongside CCoV, CPV, and canine distemper virus (CDV), reported a CRV positivity rate of 0.97% among 1,028 clinical samples, a figure that closely aligned with the 0.88% rate obtained using a reference assay [1]. More recently, a comprehensive multi-province investigation encompassing 2,492 canine samples collected between 2018 and 2024 identified a CRV prevalence of approximately 1.5% across 22 provinces, demonstrating a relatively low but consistent endemicity [33]. Intriguingly, within specialized populations, such as the giant panda (Ailuropoda melanoleuca), an endangered species highly susceptible to canine-origin pathogens, multiplex PCR screening of 218 animals detected rotavirus in 6.42% of cases, with over half of these positive samples representing mixed infections with CPV-2 and CDV [2]. This finding underscores the cross-species transmission potential of rotaviruses in conservation settings.

In Thailand, a country characterized by a high-density human-animal interface, two independent surveillance campaigns spanning 2016–2019 and 2020–2021 yielded CRV detection rates of 0.70% (5/710) and 2.75% (8/290), respectively, in domestic dogs [5, 14]. These rates are notably lower than those reported in canine populations of the Middle East. A seroprevalence and antigen-detection study conducted in the Ahvaz district of southwestern Iran, utilizing immunochromatography assays on diarrheic dogs, reported a striking 16.33% CRV positivity rate (16/98), with a 95% confidence interval spanning 9.1% to 23.6% [6]. This marked disparity may reflect genuine geographic variation in viral circulation, differences in host susceptibility due to genetic or environmental factors, or the differential performance characteristics of diagnostic platforms (e.g., rapid antigen tests versus molecular assays). In Western Taiwan, a PCR-based survey of 240 diarrheic dogs detected CRV in 9.2% (22/240) of cases, with a pronounced winter and spring seasonal peak [7]. In Europe, data from Italy, derived from a recent molecular survey using multiplex real-time RT-PCR targeting the RVA NSP3 gene, indicated a 1.4% positivity rate (4/278) in owned dogs, while a separate retrospective analysis in Sicily detected rotavirus in approximately 5% of domestic cats [16, 35]. Together, these data illustrate a robust but geographically heterogeneous epidemiological landscape, with CRV prevalence spanning from less than 1% to over 16% depending on the context.

Age, Seasonal, and Demographic Risk Factors

Epidemiological analyses have consistently identified young age as the most significant risk factor for CRV infection. In the aforementioned Iranian study, the prevalence of CRV in dogs under three months of age (48.15%; 13/27) was dramatically higher than in dogs aged 3–6 months (6.06%; 2/33) or older than 6 months (2.63%; 1/38), a difference that was statistically significant (p < 0.05) [6]. This age distribution mirrors the well-established pattern observed in human pediatric rotavirus infections, wherein the immature immune system and the waning of maternally derived antibodies create a window of heightened susceptibility. In China, a large-scale multi-pathogen survey similarly confirmed that dogs under six months of age were significantly more vulnerable to CRV infection than older cohorts [33]. The biological basis for this age-dependent susceptibility is multifaceted, encompassing the immaturity of the neonatal gut mucosa, the absence of fully developed adaptive immune responses, and the increased prevalence of co-infections that may exacerbate clinical disease.

Seasonal patterns, though less uniformly reported, also appear to influence CRV epidemiology. Multiple studies from Taiwan and China have documented higher detection rates during the winter and spring months, a pattern reminiscent of human rotavirus seasonality in temperate climates [7, 33]. In Iran, while winter showed the highest point prevalence (21.74%; 5/23), this difference did not achieve statistical significance (p > 0.05) relative to other seasons, possibly due to the modest sample size [6]. The mechanisms driving seasonal variation are poorly understood in the canine context but may relate to environmental stability of the virus at lower temperatures, crowding of animals indoors, and potential changes in host immune competence due to nutritional or stress-related factors.

Regarding host demographic factors, the data are more equivocal. Some studies have reported a slight male preponderance (17.54% in males versus 14.63% in females), while others have found no significant sex-based differences [6, 7]. Breed-associated risk has been suggested in some reports, German Shepherd dogs exhibited a numerically higher infection rate (19.05%) in the Iranian study, but again, these differences have not reached statistical significance in most controlled analyses [6]. Mixed-breed dogs and suburban populations have been identified as potentially higher-risk groups in Taiwan, though confounding factors such as vaccination status, access to veterinary care, and environmental exposure likely contribute to these observational trends [7].

Co-infection Dynamics and Clinical Implications

One of the most critical epidemiological features of CRV is its frequent involvement in polymicrobial enteric infections. The clinical significance of rotavirus as a sole pathogen appears to be relatively limited in immunocompetent adult dogs, but when combined with other enteropathogens, particularly CPV-2, CCoV, or CDV, the resulting disease can be markedly more severe. In a Mexican investigation, 14% of dogs with gastroenteritis were found to be co-infected with both rotavirus and parvovirus, and clinicians reported more severe clinical signs in these co-infected animals compared to those infected with either virus alone [25]. Similarly, in China, a study of 218 giant pandas revealed that over half of the rotavirus-positive animals harbored concurrent infections with CPV-2 and/or CDV, a finding that was confirmed via sequencing and phylogenetic analysis [2]. In Thailand, metagenomic surveys have documented co-infections of CRV with canine kobuvirus, canine astrovirus, and canine coronavirus in stray dog populations, underscoring the complexity of the enteric virome [18].

The biological mechanisms underlying this synergy are multifaceted. Parvovirus-induced immunosuppression and damage to the intestinal epithelium likely facilitate rotavirus invasion and replication, while rotavirus-mediated disruption of enterocyte integrity may, in turn, exacerbate parvoviral enteritis. Mixed infections can also confound clinical diagnosis, as overlapping symptom profiles, vomiting, hemorrhagic diarrhea, dehydration, and leukopenia, make it difficult to attribute pathology to a single agent [20, 25]. This has driven the development of multiplex molecular assays capable of simultaneously detecting multiple pathogens, including the quadruplex RT-qPCR developed by Shi et al., which demonstrated excellent sensitivity (limit of detection: 1.1 × 10² copies/reaction) and specificity for CRV alongside CPV, CDV, and CCoV [1].

Molecular Epidemiology and Genotypic Diversity

The genotypic landscape of canine rotavirus A (RVA) is dominated by the G3P[3] genotype, a classification based on the antigenic properties of the VP7 (glycoprotein) and VP4 (protease-sensitive) outer capsid proteins. Whole-genome sequencing of CRV strains isolated from diverse geographic locales, including China, Thailand, Italy, Japan, Brazil, and the United States, has established that the canonical genomic constellation for canine RVA is G3-P[3]-I3-R3-C3-M3-A9-N2-T3-E3-H6 [3, 5, 14, 22, 27]. This constellation is strikingly similar to that of the AU-1-like genetic group, a lineage initially identified in a human rotavirus strain but now recognized to be of feline/canine origin [13, 15, 22]. The AU-1-like group is defined by a specific backbone of gene segments (I3-R3-C3-M3-A9/A3-N2/T2-T3-E3-H6) that distinguishes it from the Wa-like (human) and DS-1-like (human/bovine) genogroups [28].

Phylogenetic analyses have revealed that CRV strains from different regions are not monophyletic but rather represent a constantly evolving mosaic of reassortment events. A 2022 study of a CRV strain isolated in Wuhan, China, demonstrated that its 11 gene segments were closely related to rotaviruses from a variety of animal sources, including cats, bats, and humans, leading the authors to conclude that the strain was a reassortment product [3]. Similarly, Thai CRVs characterized between 2016 and 2019 exhibited a novel genetic constellation that had previously been reported only in human rotaviruses, suggesting multiple recent interspecies transmission events had shaped their genome [5, 14]. The VP6 gene, encoding the inner capsid protein and used for group classification, frequently shows evidence of heterologous origins, with some dog-derived CRV strains clustering with human RVA strains at this locus, while others encode a feline-like I8 genotype [14, 27]. The NSP1 gene, which encodes a protein with interferon-antagonist activity and, in some species, fusion-associated small transmembrane (FAST) protein functionality, is another hotspot for reassortment. Canine rotaviruses of species I have been shown to encode functional FAST proteins (NSP1-1) capable of inducing syncytium formation in a cell type-specific manner, a trait that may influence host range and tissue tropism [12, 17]. This molecular plasticity, driven by the segmented nature of the rotavirus genome, represents a powerful evolutionary engine that continuously generates new viral variants with unpredictable pathogenic and zoonotic potential.

Zoonotic Potential: Evidence for Interspecies Transmission

The zoonotic potential of canine rotavirus is a subject of intense scientific scrutiny and substantial public health concern. The World Health Organization (WHO) has long recognized rotavirus as a leading cause of severe diarrheal disease in children under five years of age globally, and while human-to-human transmission of Wa-like and DS-1-like strains accounts for the vast majority of pediatric infections, a growing body of molecular evidence confirms that animal rotaviruses, including those of canine and feline origin, can breach the species barrier and cause disease in humans [13, 15, 22]. The AU-1-like genetic group, which encompasses canine G3P[3] strains, feline G3P[3] and G3P[9] strains, and human strains such as AU-1, HCR3A, and Ro1845, provides the most compelling evidence for this phenomenon [15, 22, 28].

Direct molecular proof of zoonotic spillover comes from multiple independent case reports and phylogenetic studies. In 2007, investigators in Italy identified a G3P[3] rotavirus strain (PA260/97) in a child hospitalized with acute gastroenteritis in Palermo. Sequence analysis of the VP7, VP4, VP6, and NSP4 genes revealed that this human strain was virtually indistinguishable from a canine G3P[3] strain that had been circulating in the same geographic region in 1996, providing strong evidence for direct transmission from a dog to a human host [23]. Similarly, in Brazil, the human G3P[3] strain IAL-R2638 exhibited 99.2% amino acid identity in its VP7 protein and 96.4% identity in its VP4 protein to the canine-derived human strain HCR3A and the canine strain RV52/96, respectively, further supporting a canine origin [21]. Whole-genome sequencing of human strains Ro1845 and HCR3A, originally isolated from children, confirmed that all 11 gene segments of these viruses were of canine or feline origin, with no evidence of human rotavirus gene segments having been acquired via reassortment [22]. These data indicate that these strains represent examples of direct virion transmission of an entire, intact canine/feline rotavirus into the human population, rather than a reassortment event between human and animal viruses.

The epidemiological significance of these spillover events extends beyond isolated case reports. A comprehensive review of the AU-1-like genetic group, synthesizing decades of molecular data, concluded that feline and canine rotaviruses have likely given rise to multiple human lineages, some of which have acquired the capacity for onward human-to-human transmission. The emergence of G1P[9] and G9P[9] strains in human populations, for example, appears to be a consequence of the feline-derived G3P[9] strain having crossed the species barrier and subsequently reassorted with human rotaviruses [15]. This distinguishes genuine zoonotic establishment from simple dead-end spillover events. However, the review also cautioned that definitive confirmation of sustained human transmission requires stringent phylogenetic criteria, such as the identification of multiple human strains sharing >99% sequence identity across all genome segments within a monophyletic lineage [15]. Nevertheless, the Centers for Disease Control and Prevention (CDC) and the World Organisation for Animal Health (WOAH) have both emphasized the importance of integrated human-animal surveillance to detect such emerging reassortants before they become widespread.

Mechanisms of Interspecies Transmission and Host Range Determinants

Understanding the biological mechanisms that permit CRV to overcome the species barrier is critical for assessing zoonotic risk. Rotaviruses are, in general, highly species-specific, a restriction that is thought to be mediated by multiple factors, including receptor specificity, cellular restriction factors, and host immune responses. However, the segmented nature of the rotavirus genome provides a ready mechanism for host range expansion through reassortment. When a cell is co-infected with two different rotavirus strains, say, a canine G3P[3] strain and a human Wa-like G1P[8] strain, the viral RNA segments can become mixed during packaging, giving rise to progeny viruses with novel combinations of genes. This can result in a virus that retains the antigenic properties of the animal strain (e.g., VP7 and VP4) while acquiring human-adapted internal genes (e.g., VP6, NSP1, NSP4) that enhance replication efficiency in the human host. Conversely, a human strain may acquire one or more animal-derived segments, potentially altering its pathogenicity, transmissibility, or vaccine susceptibility [11, 13, 28].

Recent research into rotavirus NSP1-1 proteins has uncovered a potentially important determinant of host range. NSP1-1, which is encoded by species B, G, and I rotaviruses, functions as a fusion-associated small transmembrane (FAST) protein that mediates cell-cell fusion and syncytium formation. Importantly, the canine rotavirus species I NSP1-1 protein has been shown to induce syncytia in primate epithelial cells but not in rodent fibroblasts or certain other cell types, indicating a degree of cell-type specificity that may influence which hosts the virus can efficiently infect [12, 17]. The N-terminal and transmembrane domains of NSP1-1 were identified as the primary determinants of this cell-specific fusion activity, suggesting that even subtle amino acid changes in these regions could alter host tropism. This raises the intriguing

Clinical Manifestations and Pathological Damage in Canine Rotavirus Infections

Canine rotavirus (CRV) infection presents a spectrum of clinical manifestations that range from subclinical shedding to severe, life-threatening gastroenteritis, with the severity of disease being profoundly influenced by host age, immune status, nutritional condition, and the presence of concurrent enteric pathogens. The pathological damage induced by CRV is primarily localized to the small intestine, though emerging evidence suggests that extra-intestinal dissemination and systemic effects are more common than historically appreciated. Understanding the full clinical and pathological profile of CRV is essential for differential diagnosis, appropriate clinical management, and the implementation of effective biosecurity measures, particularly given the zoonotic potential of this pathogen as recognized by the World Health Organization (WHO) and the World Organisation for Animal Health (WOAH).

Clinical Presentation and Disease Spectrum

The clinical hallmark of canine rotavirus infection is acute-onset diarrhea, typically observed in puppies and young dogs. In experimental infections using neonatal gnotobiotic dogs, diarrhea was consistently observed between postinoculation hours (PIH) 20 and 24, persisting through PIH 154 in some cases [10]. This protracted diarrheal course underscores the virus's capacity to induce sustained intestinal dysfunction even in the absence of secondary bacterial invaders. The diarrhea is characteristically non-hemorrhagic, a feature that has been statistically validated in field studies. In a comprehensive survey of 98 diarrheic dogs in Iran, rotavirus infection was significantly more prevalent in dogs with non-hemorrhagic diarrhea (23.08%) compared to those with hemorrhagic diarrhea (p < 0.05) [6]. This distinction is clinically relevant, as hemorrhagic diarrhea is more classically associated with canine parvovirus type 2 (CPV-2) infection, and the presence of non-hemorrhagic, watery to semiliquid feces should raise suspicion for CRV, particularly in young animals.

The consistency and color of diarrheic feces in CRV infections have been described in detail. Gross pathological observations in experimentally infected gnotobiotic dogs revealed moderate amounts of semiliquid-to-liquid, greenish-yellow intestinal contents [9]. This greenish-yellow coloration likely reflects the rapid transit of bile-stained intestinal contents through the compromised small intestine, where absorptive function is severely impaired. The diarrhea is often accompanied by clinical signs of dehydration, which became apparent in experimental models after PIH 24 [10]. Dehydration in CRV-infected puppies can progress rapidly, leading to sunken eyes, loss of skin turgor, dry mucous membranes, and, in severe cases, hypovolemic shock. The severity of dehydration is directly proportional to the extent of villous atrophy and the consequent malabsorptive diarrhea.

Vomiting is a variable but frequently reported clinical sign in CRV infections. While not as consistently observed as in CPV-2 enteritis, emesis can occur, particularly in cases of mixed infection. In a study of dogs with gastroenteritis in Mexico, clinical signs in dogs co-infected with both rotavirus and parvovirus were more severe than in dogs infected with either virus alone [25]. This synergistic exacerbation of clinical disease highlights the importance of considering CRV as a contributing factor in cases of severe gastroenteritis, even when more common pathogens are identified. Anorexia, lethargy, and depression are common accompanying signs, reflecting the systemic impact of the infection.

Age-Related Susceptibility and Epidemiological Patterns

The age distribution of CRV infections is one of the most striking epidemiological features of the disease. Multiple independent studies across diverse geographical regions have consistently demonstrated that puppies under three months of age are at the highest risk for clinical disease. In the Iranian study, the prevalence of rotavirus infection was 48.15% in dogs less than three months old, compared to only 6.06% in dogs aged 3–6 months and 2.63% in dogs older than six months [6]. This dramatic age-related susceptibility is biologically plausible, as puppies in this age window have waning maternal antibody titers but have not yet developed robust active immunity through natural exposure or vaccination. Furthermore, the intestinal epithelium of neonates is more mitotically active and may provide a more permissive environment for rotavirus replication.

In Taiwan, the highest occurrence of CRV was also observed in puppies, with the disease showing a seasonal predilection for winter and spring [7]. This seasonal pattern may be related to environmental stability of the virus in cooler, more humid conditions, as well as potential crowding of animals indoors during colder months. The prevalence of CRV in various canine populations has been reported with considerable variation. In a large-scale Chinese study involving 2,492 samples collected from 2018 to 2024, CRV was detected at a relatively low rate compared to CPV-2, but the virus was nonetheless present across multiple provinces [33]. In Thailand, CRV was detected in 2.75% of dogs sampled from animal hospitals in Bangkok [14, 27], while in Italy, a more recent survey found RVA in 1.4% of owned dogs [16]. These prevalence figures likely underestimate the true burden of infection, as many subclinical infections go undetected, and diagnostic testing for CRV is not routinely performed in most veterinary practices.

Pathological Damage to the Intestinal Mucosa

The pathological damage induced by CRV is centered on the small intestine, with the jejunum and ileum being the most severely affected segments. The sequence of histopathological events has been meticulously characterized in gnotobiotic dog models, providing a detailed timeline of disease progression. By PIH 12, group-specific rotaviral antigen can be detected within absorptive villus epithelial cells using indirect immunofluorescence [10]. This early localization of viral antigen confirms that the mature enterocytes lining the upper third of the villi are the primary targets of CRV infection, a tropism shared with rotaviruses of other species.

By PIH 18 to 48, the pathological changes become histologically apparent. Columnar villus epithelial cells on the upper one-third of the villus undergo necrosis, and foci denuded of epithelium are observed on the upper regions of villi [9]. This denudation is a direct consequence of virus-induced cell death, as rotavirus replication leads to the lysis of infected enterocytes. The loss of these mature, absorptive cells is catastrophic for intestinal function, as these cells are responsible for the final stages of nutrient digestion and absorption, as well as the expression of brush-border enzymes such as lactase, sucrase, and maltase. The resulting disaccharidase deficiency contributes to osmotic diarrhea, as undigested carbohydrates remain in the intestinal lumen, drawing water into the bowel by osmosis.

By PIH 24 to 72, the hallmark lesion of rotavirus enteritis, villus atrophy, becomes evident. Inoculated pups killed during this period had mild-to-moderate villus atrophy in the jejunum and ileum [9]. The villi are shortened, blunted, and sometimes fused, dramatically reducing the surface area available for absorption. The denuded villi become covered with cuboidal-to-flat squamous-like epithelial cells, which represent immature crypt cells that have migrated up the villus to cover the denuded areas. These immature cells are functionally deficient; they lack the full complement of brush-border enzymes and transport proteins, further compounding the malabsorptive state. A striking finding in these experimental infections was the absence of large, clear vacuoles in the jejunal and ileal villus epithelial cells, which were normally present in control pups [9]. These vacuoles are thought to be involved in the transport of lipids and other nutrients, and their absence underscores the profound functional derangement of the infected epithelium.

Morphometric analysis has provided quantitative confirmation of these qualitative observations. Mean villus-crypt ratios were significantly lower in the duodenum, jejunum, and ileum of inoculated pups compared to controls [9]. This reduction in villus-crypt ratio is a sensitive indicator of mucosal damage and is used in both research and diagnostic pathology to assess the severity of enteritis. Interestingly, the morphometric data also revealed that crypt cell hyperplasia occurred in the duodenum early during infection, even in the absence of obvious villus atrophy [9]. This early crypt hyperplasia represents a compensatory regenerative response, as the intestinal epithelium attempts to replace the lost villus enterocytes. In the jejunum and ileum, crypt cell hyperplasia was observed later during the infection, suggesting a wave of regeneration following the initial insult. This regenerative capacity is remarkable; in surviving animals, the intestinal mucosa can return to near-normal architecture within days to weeks, provided the animal remains adequately hydrated and nourished.

Gross Pathological Findings

At necropsy, the gross pathological changes in CRV-infected dogs are consistent with a severe enteritis. The small intestine appears moderately dilated, with thinning of the intestinal walls [9]. This thinning is a consequence of villus atrophy and the loss of mucosal mass. The intestinal serosa may appear hyperemic, reflecting increased blood flow to the inflamed tissue. The intestinal lumen contains a moderate amount of semiliquid-to-liquid, greenish-yellow content, as previously described [9]. In severe cases, the intestinal contents may be watery and frothy, indicative of maldigestion and fermentation of undigested nutrients by the resident microbiota. The mesenteric lymph nodes may be enlarged and edematous, reflecting the immune response to the infection. In some cases, rotaviral antigen has been detected in the mesenteric lymph nodes of inoculated pups killed at PIH 48 [10], indicating that the virus can drain from the intestinal mucosa to the regional lymphatics, though this does not necessarily imply systemic dissemination.

Hematological and Biochemical Alterations

The systemic impact of CRV infection extends beyond the gastrointestinal tract, as evidenced by significant hematological and biochemical alterations. In a study of naturally infected dogs in Assam, India, CRV-positive dogs exhibited a significant increase in hemoglobin concentration, packed cell volume (PCV), and total erythrocyte count (TEC) [32]. These changes are most likely a consequence of dehydration and hemoconcentration, rather than a direct effect of the virus on erythroid precursors. As fluid is lost through diarrhea and vomiting, the plasma volume contracts, leading to an apparent increase in the concentration of cellular elements in the blood. This hemoconcentration is a clinically useful indicator of dehydration severity and should prompt aggressive fluid therapy.

The leukocyte profile in CRV infection is characterized by a significant decrease in total leukocyte count (TLC) and neutrophil count, accompanied by a significant increase in lymphocyte and monocyte counts [32]. The leukopenia and neutropenia may reflect the sequestration of neutrophils at the site of intestinal inflammation, as well as the direct effects of viral infection on bone marrow precursors, though this has not been definitively proven for CRV. The relative lymphocytosis and monocytosis are consistent with the antiviral immune response, as lymphocytes and monocytes are recruited to the intestinal mucosa to combat the infection. This pattern contrasts with the profound panleukopenia characteristic of CPV-2 infection, providing another potential diagnostic differentiator.

Biochemical analyses have revealed significant alterations in serum chemistry profiles. CRV-infected dogs showed significant increases in serum aspartate aminotransferase (AST), alanine aminotransferase (ALT), blood urea nitrogen (BUN), and creatinine [32]. The elevation of liver enzymes (AST and ALT) suggests hepatocellular injury, which may be secondary to dehydration-induced hepatic hypoperfusion, direct viral effects, or the systemic inflammatory response. The increases in BUN and creatinine are consistent with prerenal azotemia resulting from dehydration and reduced renal perfusion. More concerning are the significant decreases in serum total protein, sodium, potassium, and chloride [32]. The hypoproteinemia reflects protein-losing enteropathy, as damaged intestinal mucosa leaks plasma proteins into the gut lumen. The electrolyte disturbances, hyponatremia, hypokalemia, and hypochloremia, are consequences of gastrointestinal losses and are critical to address in fluid therapy, as severe electrolyte imbalances can lead to cardiac arrhythmias, neuromuscular dysfunction, and metabolic acidosis.

Extra-Intestinal Dissemination and Systemic Involvement

While CRV is traditionally considered an enteric pathogen, there is mounting evidence for extra-intestinal dissemination. In experimental infections, rotaviral antigen was detected not only in the small intestine but also in mononuclear cells within the villus lamina propria [10]. This suggests that the virus can infect and potentially replicate within local immune cells, which may serve as a vehicle for dissemination to other sites. The detection of rotaviral antigen in the mesenteric lymph nodes of some inoculated pups [10] further supports the concept of lymphatic spread.

The potential for extra-intestinal involvement is also suggested by studies of related rotaviruses. In a porcine G9P[20] rotavirus with gene segments linked to canine and giant panda strains, experimental infection induced severe diarrhea and intestinal damage in piglets within 48 hours, with high replication efficiency in cell culture [4]. While this study was conducted in pigs, the genetic linkage to canine strains raises the possibility that similar pathogenic mechanisms could operate in dogs. Furthermore, the detection of rotavirus I in the feces of a cat with diarrhea, where no other eukaryotic viral pathogens were identified, suggests that rotaviruses can be primary pathogens capable of causing disease in the absence of co-infections [26].

The clinical significance of extra-intestinal CRV infection in dogs remains to be fully elucidated. However, given the zoonotic potential of CRV, with documented cases of direct virion transmission of canine/feline rotaviruses to humans [22, 23], the possibility of systemic involvement in immunocompromised animals warrants further investigation. The WHO has recognized rotavirus as a major cause of severe diarrheal disease in children globally, and the detection of canine-origin G3P[3] strains in children with acute gastroenteritis [23] underscores the public health importance of understanding the full pathogenic potential of this virus in its natural canine host.

Co-Infection and Disease Severity

The clinical course of CRV infection is frequently complicated by co-infection with other enteric pathogens. In a study from Mexico, 14% of dogs with gastroenteritis were co-infected with both rotavirus and parvovirus, and the clinical signs in these co-infected dogs were more severe than in dogs infected with either virus alone [25]. This synergistic effect is likely due to the combined damage to the intestinal epithelium: CPV-2 targets the rapidly dividing crypt cells, while CRV targets the mature villus enterocytes. The simultaneous destruction of both the regenerative crypt compartment and the absorptive villus compartment leads to a more profound and prolonged intestinal dysfunction than either virus alone could achieve.

Co-infection with canine coronavirus (CCoV) is also common. In a large-scale Chinese study, the positivity rates for CCoV and CRV were 9.53% and 0.97%, respectively [1], and mixed infections with these viruses have been reported. The clinical presentation of mixed infections can be particularly challenging to diagnose based solely on clinical signs and pathological damage, as the symptoms overlap considerably [1]. This diagnostic difficulty underscores the need for molecular diagnostic tools, such as multiplex RT-qPCR assays, which can simultaneously detect and differentiate multiple enteric pathogens [1, 31]. The development of such assays by the WOAH and other international bodies has been instrumental in improving the accuracy of diagnosis and the understanding of the true prevalence of CRV in canine populations.

Chronic and Subclinical Infections

Not all CRV infections result in overt clinical disease. Subclinical infections, where the virus is shed in the feces without causing diarrhea, are well-documented. In the original isolation of a canine rotavirus, viral particles were visualized by direct electron microscopy in the feces from a clinically normal dog [8]. This finding has profound implications for disease transmission, as apparently healthy dogs can serve as asymptomatic shedders, contaminating the environment and infecting susceptible puppies. The duration of viral shedding can be prolonged; in experimental infections, rotavirus particles were detected in feces from PIH 12 through PIH 154 [10], indicating that shedding can persist for weeks after the resolution of clinical signs.

Chronic infections, characterized by persistent or intermittent diarrhea lasting for weeks, have been observed in some cases. In gnotobiotic dogs, diarrhea persisted through PIH 154 [10], suggesting that in the absence of a fully developed immune system, the virus can establish a protracted infection. In field settings, chronic CRV infection should be considered in cases of persistent diarrhea in puppies, particularly those from multi-dog households, shelters, or breeding kennels where the virus can circulate endemically. The role of CRV in chronic enteropathies of adult dogs is less clear, but it is plausible that the virus could contribute to the pathogenesis of conditions such as inflammatory bowel disease in genetically predisposed individuals, though this remains speculative.

Pathological Differential Diagnosis

The clinical manifestations and pathological damage of CRV infection must be distinguished from other common causes of canine gastroenteritis. Canine parvovirus type 2 (CPV-2) is the most important differential diagnosis, as it is the most frequently detected viral enteropathogen in dogs worldwide, with positivity rates ranging from 23.3% to 64.8% in various studies [7, 34]. While both viruses cause diarrhea and vomiting, CPV-2 is more commonly associated with hemorrhagic diarrhea, profound leukopenia, and higher mortality rates, particularly in unvaccinated puppies. The pathological hallmark of CPV-2, crypt necrosis and loss of intestinal architecture, is distinct from the villus tip necrosis seen in CRV, though co-infections can blur these distinctions.

Canine coronavirus (CCoV) is another important differential, with prevalence rates of 9.53% in some Chinese studies [1]. CCoV typically causes milder, self-limiting diarrhea in adult dogs but can cause severe disease in puppies, particularly when co-infected with CPV-2. Canine distemper virus (CDV) can also cause gastrointestinal signs, though respiratory and neurological signs are more characteristic. Canine astrovirus, canine kobuvirus, and canine norovirus are emerging enteric pathogens that can cause similar clinical signs [18, 34, 37]. The overlapping clinical presentations of these viral enteritides make definitive diagnosis based solely on clinical signs and gross pathology unreliable, reinforcing the need for laboratory confirmation using molecular techniques such as RT-qPCR, which has been validated for the detection of CRV with high sensitivity and specificity [1, 31].

Advanced Diagnostic Approaches for Canine Rotavirus Detection

The accurate and timely detection of canine rotavirus (CRV) is a cornerstone of both clinical management and epidemiological surveillance, particularly given the virus’s zoonotic potential and its propensity for genetic reassortment with strains from other species [1, 3, 5]. Diagnostic approaches have evolved from classical virological methods to sophisticated nucleic acid–based platforms capable of high throughput, multiplexing, and genotyping. This section provides an exhaustive analysis of the advanced diagnostic modalities currently available, evaluating their principles, performance characteristics, and suitability for various applications, from routine veterinary practice to molecular epidemiology and outbreak investigations.

1. Molecular Detection Platforms: Reverse Transcription Polymerase Chain Reaction and Its Variants

Molecular amplification techniques represent the gold standard for CRV detection due to their unparalleled sensitivity, specificity, and capacity for differentiation among co-infecting pathogens. The double-stranded RNA genome of rotavirus A (RVA) necessitates a reverse transcription step prior to amplification, and numerous assay formats have been validated across diverse canine populations.

1.1 Conventional and One-Step RT-PCR

Conventional reverse transcription PCR (RT-PCR) targeting conserved regions, most commonly the VP6 gene, which encodes the group-specific inner capsid protein, has been widely employed for initial screening. Studies in Thailand [5, 14] and Italy [16] have utilized one-step RT-PCR assays targeting the VP6 gene to detect RVA in dogs and cats, reporting positivity rates ranging from 0.7% to 2.75% depending on the population. The VP6 gene is an ideal target because it is highly conserved within group A rotaviruses, enabling pan-RVA detection. Alternatively, the VP7 gene (outer capsid glycoprotein) is often targeted for subsequent genotyping, as demonstrated in the development of a quadruplex RT-qPCR that simultaneously detects CRV (VP7), canine coronavirus, parvovirus, and distemper virus [1]. This assay achieved a limit of detection (LOD) of 1.1 × 10² copies/reaction for all four plasmid constructs, with intra- and inter-assay coefficients of variation below 1%, demonstrating exceptional reproducibility [1].

The choice of target gene influences diagnostic scope. For example, a study of giant pandas used a multiplex PCR targeting the VP7 gene for GPRV (giant panda rotavirus) alongside CPV-2 and CDV, confirming results by sequencing [2]. Similarly, conventional PCR for CRV in Taiwan targeted a 320 bp fragment of the VP7 gene, achieving a sensitivity of 10 ng to 100 ng of total DNA extracted from 0.1 g of feces [7]. While conventional RT-PCR is cost-effective and suitable for low-resource settings, it lacks the quantitative capacity of real-time methods and requires post-amplification handling, increasing contamination risk.

1.2 Quantitative Real-Time RT-PCR (RT-qPCR)

Real-time RT-PCR (RT-qPCR) has supplanted conventional formats in many reference laboratories due to its ability to quantify viral load, monitor amplification in real time, and offer higher throughput. The quadruplex RT-qPCR developed by Shi et al. (2024) [1] exemplifies the state of the art; it employs TaqMan probes specific to the M gene of canine coronavirus, VP7 of CRV, VP2 of parvovirus, and N gene of distemper virus. The assay was validated on 1,028 clinical samples from China, yielding a CRV positivity rate of 0.97% (10/1,028), with 99.32% agreement compared to a reference monoplex RT-qPCR. Importantly, no cross-reactivity was observed with other canine enteric viruses (e.g., canine adenovirus, canine herpesvirus), confirming high specificity [1].

Another notable multiplex RT-qPCR panel, the Canine Enteric Assay_2 (CEA_2), simultaneously detects RVA (targeting the NSP3 gene), SARS-CoV-2, and can be combined with other enteric pathogens [31]. This assay demonstrated analytical sensitivity as low as 5–35 genome copies/µL in multiplex format, with coefficients of variation below 4% across repeatability and reproducibility studies. The use of the NSP3 gene as a target is strategic because it is highly conserved across RVA strains and is also the target of the widely used World Health Organization (WHO)-recommended human rotavirus genotyping assays. Incorporating such internationally standardized targets facilitates comparability across veterinary and human surveillance systems, a critical consideration given the zoonotic implications of CRV [3, 5, 13].

1.3 Multiplex and Quadruplex Assays for Differential Diagnosis

Canine gastroenteritis often involves mixed infections, and differentiating among viral, bacterial, and parasitic etiologies is essential for appropriate therapy and outbreak control. Multiplex RT-PCR and RT-qPCR platforms allow simultaneous detection of multiple pathogens from a single sample. In addition to the quadruplex assay mentioned above [1], a study of 475 dogs in India using real-time PCR for six viruses (CPV-2, CDV, CAdV-2, CCoV, CaAstV, and CRV) found that 16.8% of samples harbored two to four viruses, although CRV was not detected in that cohort [34]. In contrast, a Mexican study employing separate PCR and RT-PCR for parvovirus and rotavirus, respectively, reported 7% exclusive CRV infection and 14% co-infection with CPV-2, with co-infected dogs exhibiting more severe clinical signs [25]. These findings underscore the need for multiplex approaches that can capture the full virological landscape of canine diarrhea.

For giant pandas, a multiplex PCR assay developed by Liu et al. (2025) [2] simultaneously detected CPV-2, CDV, and GPRV, with a CRV positivity rate of 6.42% (14/218) and over half of the positive samples showing mixed infections. The use of the VP7 gene for rotavirus detection in this assay allowed subsequent sequencing to confirm genotype (G3P[3]), demonstrating that multiplex assays can be seamlessly integrated with genotyping workflows [2].

1.4 SYBR Green–Based Real-Time PCR

An alternative to probe-based qPCR is SYBR Green–based real-time PCR, which relies on intercalating dye to detect amplification. Although less specific than TaqMan probes, it is more cost-effective and can be used for pan-pathogen screening. A SYBR Green assay for canine parvovirus has been standardized [39], and similar principles can be applied to CRV detection using rotavirus-specific primers. However, dye-based methods require rigorous melt-curve analysis to confirm amplicon identity, and they are susceptible to primer-dimer artifacts. As such, they are more appropriate for research settings than for routine clinical diagnosis where high specificity is paramount.

2. Genotyping by Whole-Genome Sequencing and Phylogenetic Analysis

Beyond mere detection, characterizing CRV strains at the genomic level is essential for understanding molecular evolution, reassortment events, and zoonotic risk. Whole-genome sequencing (WGS) has become increasingly accessible due to next-generation sequencing (NGS) technologies, including nanopore sequencing.

2.1 Traditional Sanger Sequencing for Targeted Genes

Sanger sequencing of specific gene segments, most commonly VP7, VP4, VP6, and NSP4, has been the mainstay of rotavirus genotyping for decades. The Rotavirus Classification Working Group (RCWG) has established a genotype nomenclature system (Gx-P[x]-Ix-Rx-Cx-Mx-Ax-Nx-Tx-Ex-Hx) based on the 11 gene segments [3, 5]. For canine RVA, the predominant genotype constellation is G3-P[3]-I3-R3-C3-M3-A9-N2-T3-E3-H6, which belongs to the AU-1-like genetic group [3, 5, 14]. This constellation has also been identified in human strains Ro1845 and HCR3A, providing strong evidence of direct interspecies transmission of canine/feline rotaviruses to humans [22]. Sanger sequencing of the VP7 and VP4 amplicons from clinical samples has confirmed the circulation of G3P[3] strains in Thailand [14], China [3], India [21], and Italy [23].

2.2 Next-Generation and Nanopore Sequencing for Whole Genomes

The advent of NGS has enabled complete genome characterization of CRV strains, revealing complex reassortment patterns. Using Illumina or nanopore platforms, researchers have sequenced entire genomes of canine RVA isolates from Thailand, demonstrating that Thai CRV strains possess a novel genetic constellation distinct from previously reported canine strains, with gene segments potentially originating from human and bat rotaviruses [5, 27]. Similarly, a G3P[3] strain isolated in Wuhan, China, was found to be a reassortant with segments closely related to AU-1-like and Cat97-like strains, as well as bat rotaviruses [3]. These findings highlight the role of WGS in tracing the evolutionary history and zoonotic pathways of CRV.

Metagenomic sequencing of the canine fecal virome has also been employed as a detection tool. A metatranscriptomic study of pooled fecal samples from dogs in Gansu, China, identified CRV reads among 16 viral genera, along with astrovirus, norovirus, and vesivirus [37]. While metagenomics is not yet a frontline diagnostic tool for individual animals, its ability to detect novel or divergent rotaviruses (e.g., rotavirus I in a cat) [26] makes it invaluable for surveillance and discovery.

3. Traditional and Immunological Detection Methods

Although molecular assays have become dominant, traditional and immunological methods retain relevance in specific contexts, particularly for rapid bedside testing, retrospective studies, and validation of new molecular assays.

3.1 Electron Microscopy

Direct electron microscopy (EM) of fecal samples was historically the first method to visualize CRV particles. Hoshino et al. (2005) observed rotavirus particles by negative-contrast EM in feces from a clinically normal dog and subsequently isolated the virus in cell culture [8]. Similarly, the original isolation of a CRV from a diarrheic newborn dog relied on EM of intestinal homogenates [30]. While EM is highly specific for rotavirus morphology, its low throughput, requirement for expensive equipment, and limited sensitivity (≥10⁶ particles/mL) preclude its use for routine diagnosis. Nonetheless, it remains a gold standard for detecting unusual rotavirus species (e.g., rotavirus I) that may be missed by group A–specific molecular assays [26].

3.2 Polyacrylamide Gel Electrophoresis (PAGE) of Viral RNA

RNA-PAGE exploits the segmented nature of the rotavirus genome: the 11 double-stranded RNA segments migrate in a characteristic pattern (4-2-3-2) upon electrophoresis. This technique was used by Mazumder et al. (2023) to detect CRV in Indian dogs, yielding 8 positive samples out of 157 (5.1%) compared to 17 (10.8%) by RT-PCR [32]. The lower sensitivity of PAGE compared to RT-PCR is well documented; however, PAGE offers the advantage of providing a visual profile that can distinguish between group A, B, C, and I rotaviruses based on segment migration patterns. It is also inexpensive and does not require prior knowledge of the viral sequence, making it useful for detecting divergent strains.

3.3 Enzyme-Linked Immunosorbent Assay (ELISA)

Antigen-capture ELISA (double-antibody sandwich ELISA) and antibody-detection ELISA have been developed for rotavirus in dogs. An early study in The Netherlands established a complex trapping blocking (CTB) ELISA for rotavirus antigen detection in fecal samples, alongside serological assays [36]. The study demonstrated that CPV was the predominant cause of acute diarrhea in Dutch dogs, but rotavirus ELISA showed utility for population-level screening. Another study from Iran used a commercial immunochromatography assay (ICA) targeting rotavirus group A antigen, reporting a prevalence of 16.33% in diarrheic dogs [6]. Immunochromatography (lateral flow) tests offer rapid results (15–20 minutes) without the need for specialized equipment, making them suitable for in-clinic use. However, their sensitivity is generally lower than that of RT-PCR; in the Iranian study, the LOD was not quantitatively assessed, and false negatives may occur in samples with low viral loads.

3.4 Immunofluorescence and Immunohistochemistry

Indirect immunofluorescence (IFA) has been used both for virus isolation confirmation and for detecting rotavirus antigen in tissue sections. In gnotobiotic dogs experimentally infected with CRV, IFA detected rotaviral antigen in absorptive villus epithelial cells and mononuclear cells of the lamina propria from post-inoculation hour 12 through 154 [10]. Immunohistochemistry (IHC) has also been applied to paraffin-embedded intestinal tissues to confirm extra-intestinal spread, though its diagnostic role is primarily research-oriented rather than clinical [38].

4. Comparative Evaluation and Selection of Diagnostic Approaches

The choice of diagnostic method for CRV depends on the objective, clinical case confirmation, epidemiological surveillance, or genomic characterization, as well as resource availability.

• For clinical diagnosis in individual dogs: Rapid antigen tests (ICA) offer speed and simplicity, but their limited sensitivity (estimated at 60–80% compared to RT-PCR) can lead to underdiagnosis, especially in subclinical infections or during early disease stages. RT-qPCR is preferred for its high sensitivity and ability to differentiate mixed infections. The quadruplex RT-qPCR [1] or CEA_2 [31] are excellent options for veterinary hospitals with access to real-time PCR platforms, as they also screen for other common enteric pathogens with a single assay.

• For epidemiological surveys: Conventional or real-time RT-PCR targeting VP6 or VP7 provides robust data on prevalence. Multiplex assays reduce cost and labor when screening for multiple agents [2, 16]. Sequencing of PCR amplicons (e.g., VP7, VP4) is essential for identifying circulating genotypes and monitoring for novel reassortants with zoonotic potential [3, 5, 14]. Whole-genome sequencing, while expensive, is crucial for understanding the evolutionary dynamics of CRV and its relationship with human strains.

• For outbreak investigations and One Health surveillance: The zoonotic implications of CRV, particularly of G3P[3] strains that have been documented in children with acute gastroenteritis [22, 23], mandate a coordinated diagnostic approach between veterinary and public health laboratories. The WHO has called for enhanced surveillance of rotaviruses at the human-animal interface. Using standardized RT-qPCR assays that target the NSP3 gene (common to WHO-recommended human rotavirus detection) facilitates interoperability. The detection of CRV in dogs from Italy [16] and its co-circulation with feline rotaviruses carrying AU-1-like constellations [14] underscores the need for ongoing molecular surveillance to identify spillover events.

• For resource-limited settings: PAGE and ELISA may still be viable alternatives when molecular facilities are unavailable. RNA-PAGE, while less sensitive, provides visual confirmation of rotavirus presence and can detect group A, C, and I strains [26, 32]. However, these methods are gradually being replaced by point-of-care RT-LAMP (loop-mediated isothermal amplification) assays, though such assays for CRV have not yet been widely published.

5. Future Directions and Emerging Technologies

Several cutting-edge approaches are poised to enhance CRV diagnostics:

• CRISPR-based detection: Cas13 or Cas12 systems coupled with isothermal amplification could provide rapid, field-deployable detection of CRV RNA with sensitivity approaching RT-qPCR.

• Digital droplet RT-PCR (ddRT-PCR): This method offers absolute quantification without standard curves and may be particularly useful for detecting low-level shedding in subclinical carriers, which is relevant for understanding transmission dynamics.

• Targeted NGS panels: Custom panels targeting all 11 rotavirus gene segments could streamline whole-genome characterization at a fraction of the cost of shotgun metagenomics.

• Automated liquid biopsy platforms: Integration of fecal sample processing with automated nucleic acid extraction and multiplex RT-qPCR in a single cartridge (e.g., FilmArray-like technology) could bring comprehensive enteric pathogen panel testing to veterinary practice.

In summary, the diagnostic landscape for canine rotavirus has matured from basic virology to a multifaceted array of molecular tools. The adoption of multiplex RT-qPCR panels that include CRV alongside other enteric pathogens represents the current standard of care for clinical and surveillance purposes. Whole-genome sequencing provides the resolution necessary to track the emergence of zoonotic strains and inform public health interventions. As the recognized zoonotic potential of CRV continues to drive research, harmonization of diagnostic methods with those used in human rotavirus surveillance will be essential for a unified One Health response.

Prevention, Control, and Public Health Implications of Canine Rotavirus

The intersection of canine rotavirus (CRV) with human populations and the broader ecosystem presents a complex web of ecological, evolutionary, and clinical challenges that demand meticulous scrutiny. Unlike many other canine enteric pathogens for which robust vaccines and widely implemented control programs exist, CRV occupies a uniquely precarious position: it is a pathogen of moderate clinical concern in dogs, yet it represents a potential conduit for the emergence of novel human rotavirus strains with unpredictable epidemiological trajectories. The establishment of rational, evidence-based prevention and control strategies, as well as a comprehensive appreciation of the zoonotic risk, must be grounded in a deep understanding of the virus's molecular biology, its genetic plasticity, and the ecological interfaces that facilitate its transmission.

Public Health Implications: The Zoonotic Imperative

The most profound and unsettling implication of CRV circulation is its demonstrated potential to breach the host-species barrier and contribute to the diversity of human rotavirus A (RVA) strains. This is not a theoretical risk but a documented reality, supported by multiple independent lines of molecular and epidemiological evidence spanning several decades and continents. The genetic hallmark of this interspecies traffic is the consistent detection of human RVA strains bearing genotype constellations and whole-genome sequences that are phylogenetically indistinguishable from contemporary or historic canine and feline strains.

The most well-characterized zoonotic pathway involves RVA strains with the G3P[3] genotype, which is considered the predominant genotype circulating in dogs globally [3, 5, 14]. Whole-genome sequencing of human G3P[3] strains, such as Ro1845 and HCR3A, has provided irrefutable evidence of direct virion transmission from canines or felines to humans. In these seminal studies, each of the 11 gene segments of the human strains was found to be of canine/feline origin, establishing them not as reassortants but as the result of a complete animal-to-human transmission event [22]. A subsequent case in southern Italy involving a child with acute gastroenteritis infected with a G3P[3] strain (PA260/97) demonstrated >99% sequence identity to a canine strain isolated in the same geographic region the previous year, providing compelling evidence for recent, local spillover [23]. In Brazil, the detection of the IAL-R2638 G3P[3] strain in a child, which shared 99.2% VP7 amino acid identity with the canine-derived human strain HCR3A, further reinforces that these spillover events are a global phenomenon [21].

The biological mechanisms underlying this zoonotic potential are rooted in the segmented nature of the rotavirus genome, which facilitates reassortment, and in the specific genetic architecture of the AU-1-like genetic group. The AU-1-like genotype constellation (G3-P[3]-I3-R3-C3-M3-A9-N2-T3-E3-H6), which is the backbone of most characterized canine RVAs, is also a template for human strains that have been sporadically identified worldwide [3, 5, 13, 14]. This constellation represents a distinct lineage that has circulated within both canine and human populations, blurring the traditional lines of host species restriction. The implications extend beyond isolated spillover events. Evidence from comprehensive reviews indicates that these feline/canine-derived strains, once introduced into the human population, are capable of onward human-to-human transmission and have even contributed to the emergence of novel reassortant lineages. The emergence of G1P[9] and G9P[9] strains in humans, for example, is hypothesized to have originated from a feline-derived G3P[9] strain that entered the human population, reassorted with co-circulating human strains, and established sustained transmission chains [15]. This suggests that companion animals are not merely dead-end spillover hosts but can act as a dynamic reservoir that seeds genetic diversity into the human RVA gene pool.

The public health risk is further amplified by the detection of CRV with gene segments closely related to those found in other species, including bats, pigs, and giant pandas, indicating a complex network of interspecies reassortment [3-5]. The detection of a porcine G9P[20] rotavirus with VP3 and NSP1 segments linked to giant panda and canine strains, respectively, demonstrates that the canine rotavirus gene pool can contribute to the evolution of strains in livestock, which themselves have significant zoonotic potential [4]. The World Health Organization (WHO) continues to monitor the emergence of novel rotavirus strains as a priority for global diarrheal disease surveillance, and the consistent identification of canine-like strains in human clinical specimens mandates that veterinary and public health authorities collaborate closely.

A particularly concerning aspect of this zoonotic risk is the potential for virulence in human hosts. The canine-derived strain PA260/97 was isolated from a child with acute gastroenteritis [23]. Furthermore, co-infection with CRV and other pathogens, such as canine parvovirus, in dogs has been documented to result in more severe clinical outcomes [25]. While direct evidence of increased virulence in humans is limited, the potential for a novel, immunologically naive human population to be exposed to a strain with a distinct antigenic profile (G3P[3]) poses a risk that should not be underestimated, especially considering that routine human rotavirus vaccines (e.g., Rotarix, RotaTeq) may have differential efficacy against these animal-derived strains [15, 21]. The presence of fusion-associated small transmembrane (FAST) proteins in some rotavirus species, including species I rotavirus found in dogs, introduces another layer of complexity. These proteins mediate cell-cell fusion and syncytium formation, which could influence viral replication efficiency, cell tropism, and potentially pathogenesis in a species-specific manner [12, 17]. The characterization of canine rotavirus FAST proteins and their activity in human cells underscores the need for continued research into the molecular determinants of host range.

Prevention and Control Strategies in Canine Populations

Current prevention and control strategies for CRV in dogs are hampered by the absence of a licensed, commercially available vaccine specifically targeting rotavirus. This is a critical gap in preventative veterinary medicine. While multivalent vaccines (e.g., DHPPiL) effectively protect against canine distemper virus, adenovirus, parvovirus, and parainfluenza virus, they do not include rotavirus antigens. Consequently, CRV infection is not statistically associated with vaccination status, meaning that a fully vaccinated dog is just as susceptible to infection as an unvaccinated one, barring any cross-protective immunity from other infections [33]. This reality places the entire burden of control on stringent biosecurity, management practices, and rapid diagnostic intervention.

The cornerstone of CRV prevention in kennels, shelters, and multi-dog households is rigorous hygiene and isolation. Rotaviruses are non-enveloped, double-stranded RNA viruses that are remarkably stable in the environment. They are resistant to many common disinfectants and can persist on contaminated surfaces, fomites, and in fecal matter for extended periods. Effective decontamination requires the use of disinfectants with proven activity against non-enveloped viruses, such as accelerated hydrogen peroxide, sodium hypochlorite (bleach) at appropriate dilutions, or chlorine dioxide-based products. Regular cleaning and disinfection of food and water bowls, bedding, kennel floors, and any surfaces that may become contaminated with feces is non-negotiable. Isolation of diarrheic dogs, particularly puppies, from the general population for a minimum of 10–14 days post-resolution of clinical signs is crucial to break the fecal-oral transmission cycle.

Because CRV infection can present subclinically, particularly in adult dogs, any introduction of a new animal into a group setting represents a risk. Quarantine protocols for incoming animals, including fecal screening using sensitive molecular assays, are advisable, especially in high-value or vulnerable populations such as breeding kennels or sanctuaries. The use of advanced diagnostic tools is a key component of modern control. The development of high-throughput, multiplex quantitative reverse transcription PCR (RT-qPCR) assays enables the simultaneous detection of CRV alongside other common enteric pathogens such as canine parvovirus, canine coronavirus, and canine distemper virus [1, 31]. These assays offer high sensitivity (with limits of detection as low as (1.1 \times 10^2) copies/reaction) and specificity, allowing for rapid differentiation of etiologic agents [1]. This is particularly important because concurrent infections are common; CRV is frequently found in mixed infections, and co-infections can lead to more severe clinical disease [2, 25]. Early, accurate diagnosis allows for the prompt implementation of targeted biosecurity and symptomatic management, reducing the risk of widespread outbreak within a facility.

In the absence of a vaccine, the primary clinical management of CRV infection is supportive care focused on fluid and electrolyte replacement to combat dehydration and diarrhea, the most significant threats to the patient. Based on studies of haematological alterations, infected dogs often present with significant increases in packed cell volume (PCV), hemoglobin, and total erythrocyte count, indicative of hemoconcentration from fluid loss [32]. Similarly, electrolyte imbalances including hyponatremia, hypokalemia, and hypochloremia are common [32]. Prompt correction of these abnormalities is essential. The use of probiotics and other gut-modulating therapies may aid in restoring intestinal homeostasis, though specific antiviral therapies remain unavailable [20].

Control efforts must also consider the role of feral and stray dog populations. Studies in China have shown that CRV is significantly more prevalent in samples collected from dog shelters and stray dogs compared to owned pets, and these populations often have high rates of co-infection with other enteric viruses [18]. Stray populations serve as a persistent environmental reservoir and a source of infection for other animals and potentially humans. Effective population management, including trap-neuter-return (TNR) programs combined with vaccination against core pathogens, can reduce the density of susceptible hosts and lower the overall viral burden in the environment. Surveillance in these at-risk populations, as recommended by the World Organisation for Animal Health (WOAH) for emerging zoonotic pathogens, is critical for early detection of novel strains.

Integrated One Health Surveillance and Final Considerations

Addressing the public health implications of CRV effectively requires moving beyond a purely veterinary or human medical perspective and embracing a holistic One Health approach. This is not merely an academic exercise; it has tangible consequences for disease control. Surveillance systems must be integrated, connecting diagnostic data from companion animal veterinary clinics with human enteric disease surveillance networks. The detection of a G2P[4] strain in a human patient who had received the Rotarix vaccine, which possessed an unusual canine-origin NSP1 A15 genotype, highlights how easily animal-derived genetic material can infiltrate the human rotavirus landscape and underscores the limitations of current vaccine strategies [11].

The evidence clearly demonstrates that domestic dogs and cats act as a significant reservoir for RVA strains that have the capacity to infect humans [13, 16, 27]. The detection of CRV in metagenomic studies of the canine fecal virome and its identification during routine molecular surveys across multiple continents, including Asia [1, 7, 33], Europe [16, 23], the Americas [21, 25], and the Middle East [6], demonstrates that the virus has a truly global distribution. The public health significance is therefore a global concern, not a localized phenomenon.

Preventive measures at the human-animal interface should include public health education for pet owners, particularly those with immunocompromised individuals or young children in the household. While the risk of a healthy adult contracting a clinically significant CRV infection from a dog is likely low, the risk is demonstrably non-zero. Salient recommendations include careful hand hygiene after handling pets, especially those with diarrhea; preventing dogs from licking the faces of infants and young children; and ensuring that children do not have direct contact with pet feces.

In conclusion, the prevention and control of CRV must be built on a foundation of robust biosecurity, advanced molecular diagnostics, and vigilant surveillance. The absence of a vaccine for dogs and the demonstrable zoonotic potential of the virus, as documented by over two decades of molecular epidemiological research, make this a pathogen of significant public health importance. The medical and veterinary communities must remain alert to the emergence of novel reassortant strains at the human-animal interface, and future research must prioritize the development of effective vaccines for companion animals and the continued genomic surveillance of rotaviruses across species boundaries to preemptively identify and mitigate future pandemic risks.

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