Duck Diseases: Viral, Bacterial, and Parasitic Infections

Introduction

Domestic ducks (Anas platyrhynchos domesticus) are susceptible to a wide spectrum of infectious agents, including viruses, bacteria, and parasites, which collectively cause significant economic losses in commercial and backyard production systems worldwide. Ducks also serve as reservoir hosts for several pathogens with zoonotic potential, particularly avian influenza viruses [1, 2, 3, 4]. The clinical manifestations of duck diseases range from acute mortality and neurological signs to chronic wasting and reduced egg production. Understanding the etiology, epidemiology, clinical signs, pathology, diagnostic approaches, treatment, and control measures for each pathogen class is essential for effective flock management and disease prevention.

What Is Duck Disease?

The term "duck disease" historically referred to any flock-level illness affecting ducks, but in contemporary veterinary medicine it encompasses a defined set of infectious diseases caused by viral, bacterial, and parasitic agents. The question "what is ducks disease" often arises in the context of differential diagnosis among the major pathogens that cause high morbidity and mortality in duck populations. Clinically, duck diseases can present as acute septicemic syndromes (e.g., Riemerella anatipestifer infection [5, 6, 7, 8, 9]), enteric or hepatic necrosis (e.g., duck hepatitis A virus [10, 11, 12, 13] or duck plague [14, 15, 16, 17, 18, 19, 20]), respiratory distress (e.g., avian influenza [1, 2, 3, 4, 21, 22, 23]), or neurological impairment (e.g., duck Tembusu virus [24, 25]). Parasitic infections such as eustrongylidosis also cause proventricular lesions and wasting [26]. A systematic diagnostic framework is required to differentiate these conditions.

Viral Diseases of Ducks

Duck Plague (Duck Viral Enteritis)

Duck plague, caused by duck enteritis virus (DEV, an alphaherpesvirus), is a highly contagious and often fatal disease of ducks, geese, and swans. Virulent strains can cause outbreaks even in vaccinated flocks, as demonstrated by Sang et al. [14]. The virus encodes multiple virulence factors: the UL36 protein (pUL36) is critical for virulence, and deletion of its N-terminal 400 amino acids attenuates the virus while conferring protective immunity [15]. The US2 protein promotes p62-mediated autophagic degradation of RIG-I, thereby suppressing antiviral signaling [16]. LORF2 utilizes RNF34 to ubiquitinate and degrade IRF7, inhibiting innate immunity [19]. LORF5 is a late gene that interacts with 19 viral and 111 host proteins and is essential for virulence [18]. Targeted mutagenesis of the ICP4 transactivation domain yields a DIVA (differentiating infected from vaccinated animals) vaccine [17]. Diagnostic methods include real-time fluorescence recombinase polymerase amplification (RPA) for rapid detection of virulent strains [20].

Duck Hepatitis A Virus (DHAV)

Duck hepatitis A virus (DHAV) is a picornavirus causing acute hepatitis in ducklings, with high mortality in young birds. Three genotypes exist; DHAV-3 has emerged as a significant threat in Asia and Africa. Complete genome sequencing of Egyptian isolates revealed evolutionary dynamics [11]. A novel strain of DHAV-3 was isolated from a vaccinated flock in China, indicating vaccine breakthrough [13]. Host resistance to DHAV-3 is mediated by DNA methylation that suppresses endocytosis [10]. Inactivated DHAV-1 vaccines elicit robust B cell responses characterized by single-cell RNA sequencing and B cell receptor analysis [12].

Duck Tembusu Virus (DTMUV)

Duck Tembusu virus (DTMUV) is a flavivirus causing severe egg drop and neurological signs in ducks. Epidemiological investigation in China (2024) using partial NS5 sequencing revealed ongoing circulation [25]. An inactivated cluster 2.1 vaccine induces cross-genotype immune responses and protects against heterologous challenge [24].

Avian Influenza Virus (AIV)

Ducks are the natural reservoir for most avian influenza virus subtypes. H5Ny clade 2.3.4.4b viruses have acquired hemagglutinin double mutations that enhance binding to human and SLeX receptors [1]. An NS1-F161L substitution in H5N6 virus enhances virulence in ducks [2]. H3 subtype viruses are maintained in duck populations in Eastern China [3]. Interannual differences in exposure to AIV occur in wild common eider ducks at Arctic colonies [4]. Vaccination with updated vaccine strains remains a key control measure [21]. Duck interferon-stimulated genes, including duIFI35, inhibit H5N6 replication by promoting apoptosis [22]. Baloxavir marboxil shows therapeutic efficacy against high pathogenicity AIV in ducks [23].

Other Viral Pathogens

Novel goose parvovirus (NGPV) is a major risk factor for red skin and bristle feather syndrome in meat ducks, with epidemiological associations to duck circovirus (DuCV) and reovirus [27]. Waterfowl circovirus and goose parvovirus co-circulate and co-evolve [28]. DuCV exhibits genetic variability and intra-genotype recombination [29]. Duck astrovirus (DAstV) has been isolated from domestic ducklings in Egypt and characterized pathomolecularly [30]. Duck variant orthoreovirus can be detected using loop-mediated isothermal amplification (LAMP) [31]. Duck adenovirus 3 is detected using RAA-CRISPR/Cas12a lateral flow dipsticks [32]. Avian coronaviruses (including infectious bronchitis virus) have been characterized in China from 2020–2023, though their significance in ducks requires further study [33].

The following table summarizes major viral pathogens of ducks:

Bacterial Diseases of Ducks

Riemerella anatipestifer Infection

Riemerella anatipestifer is a Gram-negative bacterium causing septicemia and serositis (often called "new duck disease" or "duck septicemia") in ducklings, with high mortality and economic impact. A comprehensive visual detection strategy using versatile LAMP with phenol red and lateral flow dipstick enables on-site diagnosis [5]. Adaptive evolution has resulted in three subtypes of the crpR1 gene, which may correlate with virulence [6]. The PorV protein serves as a cross-protective antigen across serotypes [7]. OMP85, a BamA family outer membrane protein, enhances virulence by recruiting host complement regulator vitronectin to evade complement-mediated killing [8]. Intranasal delivery of a live attenuated vaccine confers efficient protection against serotype 1 in ducklings [9]. This pathogen is also covered in detail on the site: Riemerella anatipestifer Infection in Ducks: Septicemia and Serositis.

Salmonella Infections

Non-typhoidal Salmonella is a major concern in ducks due to its zoonotic potential and contribution to antimicrobial resistance. A prospective study from West Bengal, India, characterized antimicrobial resistance dynamics in Salmonella isolates from chickens and ducks [34]. Flock management and judicious antibiotic use are critical to mitigate resistance. The general site articles Bacterial Infections in Poultry: Salmonella, Escherichia coli, and Food Safety Considerations and Salmonella in Poultry: Comprehensive Guide to Chicken-Associated Bacterial Pathogens provide additional context.

Other Bacterial Pathogens

Ducks are also susceptible to Pasteurella multocida (fowl cholera), Escherichia coli (colibacillosis), Mycoplasma species, and Clostridium perfringens (necrotic enteritis). Standard diagnostic techniques include culture, biochemical profiling, and antimicrobial susceptibility testing. For a broader overview of bacterial threats, see Major Pathogens Associated with Poultry: Bacterial, Viral, and Parasitic Threats and Duck Bacterial Diseases and Zoonotic Risks: A Comprehensive Guide.

Parasitic Diseases of Ducks

Eustrongylidosis

Eustrongylides tubifex (Nitzsch 1819) Jägerskiöld 1909 is a nematode parasite that infects the proventriculus of ducks. Transcriptomic analysis of domestic ducks infected with E. tubifex revealed upregulated immune responses and tissue damage pathways [26]. Heavy infections lead to proventricular rupture, peritonitis, and death. Diagnosis is by necropsy and identification of the large red worms. For additional parasitic infections in ducks, refer to Parasitic Infections in Poultry: Endoparasites and Ectoparasites.

Other Helminths and Protozoa

Ducks harbor various other helminths, including nematodes (Ascaridia, Capillaria), cestodes, and trematodes. Protozoan infections such as coccidiosis (Eimeria spp.) and histomoniasis (Histomonas meleagridis) also occur. Diagnosis relies on fecal flotation, direct smear, and postmortem examination. The site articles Poultry Parasites and Diseases: Clinical Signs, Diagnosis, and Integrated Control and Parasitic Infections in Chickens: A Clinical Guide to Diagnosis and Treatment provide additional details.

Diagnostic Approaches

A systematic diagnostic workflow for duck diseases integrates clinical history, necropsy, histopathology, microbiology, molecular assays, and serology. The following mermaid diagram outlines a decision tree for approaching a duck disease outbreak:

flowchart TD
    A[Sudden mortality or flock illness], > B{Clinical signs?}
    B, > C[Neurological/head tremors]
    B, > D[Respiratory distress/gasping]
    B, > E[Hemorrhagic lesions/diphtheritic membranes]
    B, > F[Hepatic necrosis/opisthotonos]
    B, > G[Egg drop/ataxia]
    C, > H[Consider DTMUV, AIV, DHAV]
    D, > I[Consider AIV, Pasteurella, R. anatipestifer]
    E, > J[Consider DEV (duck plague)]
    F, > K[Consider DHAV, DAstV, reovirus]
    G, > L[Consider DTMUV, AIV, bacterial egg peritonitis]
    H & I & J & K & L, > M[Collect samples: brain, lung, liver, spleen, cloacal swabs]
    M, > N{Diagnostic tests}
    N, > O[Molecular: PCR, LAMP, RPA, CRISPR]
    N, > P[Virology: virus isolation in eggs or cell culture]
    N, > Q[Bacteriology: culture, MALDI-TOF, AST]
    N, > R[Parasitology: fecal flotation, necropsy]
    N, > S[Serology: ELISA, HI, VN]
    O & P & Q & R & S, > T[Identify etiological agent]
    T, > U[Implement treatment and control measures]

Molecular methods are especially valuable for rapid diagnosis. LAMP assays have been developed for R. anatipestifer [5] and duck variant reovirus [31]. RAA-CRISPR/Cas12a lateral flow dipsticks detect duck adenovirus 3 [32]. Real-time RPA is used for virulent duck enteritis virus [20]. These techniques enable on-site or field-based detection without sophisticated equipment.

Treatment and Control

Antiviral therapy in ducks remains limited, but baloxavir marboxil has shown efficacy against high pathogenicity avian influenza virus in a duck model [23]. Supportive care, including fluid therapy and vitamin supplementation, is essential. Vaccination is the mainstay of prevention for viral diseases: inactivated DTMUV vaccines [24], attenuated DEV vaccines [15, 17], and recombinant AIV vaccines [21] are available. For R. anatipestifer, intranasal live attenuated vaccines show promise [9]. Antimicrobial therapy for bacterial infections must be guided by susceptibility testing to combat resistance [34]. Biosecurity measures, including all-in-all-out management, disinfection, and vector control, are critical for preventing outbreaks. For a comprehensive list of bacterial disease prevention strategies, see Bacterial Diseases of Chickens: A Comprehensive Overview (applicable to ducks).

References

[1] Jin X, Han P, Wang Y, et al. Hemagglutinin double-mutation enhances binding of human-infecting avian influenza virus clade 2.3.4.4b H5Ny to human and SLe(X) receptors. EMBO Rep. 2026. https://pubmed.ncbi.nlm.nih.gov/42303811/

[2] Wu Y, Li Z, Xu N, et al. An NS1-F161L Substitution Determines Host-Driven Virulence Enhancement of H5N6 Avian Influenza Virus in Ducks. Viruses. 2026. https://pubmed.ncbi.nlm.nih.gov/42198691/

[3] Miao X, Zhao X, Zhang N, et al. Surveillance and biological characterization of H3 subtype avian influenza viruses in Eastern China. Virulence. 2026. https://pubmed.ncbi.nlm.nih.gov/42154626/

[4] Provencher JF, Morrill A, Hennin HL, et al. Interannual differences in common eider duck exposure to avian influenza viruses at an Arctic colony. Conserv Physiol. 2026. https://pubmed.ncbi.nlm.nih.gov/42125671/

[5] Wu J, Jiang N, Liang Q, et al. A Comprehensive Visual Detection Strategy: Versatile LAMP Assay with Phenol Red and Lateral Flow Dipstick for On-Site Detection of Riemerella anatipestifer. Microorganisms. 2026. https://pubmed.ncbi.nlm.nih.gov/42197423/

[6] Wang J, Du X, Yin H, et al. Adaptive evolution resulted in three subtypes of the Riemerella anatipestifer crpR1 gene. J Bacteriol. 2026. https://pubmed.ncbi.nlm.nih.gov/42133709/

[7] Li S, Wang Y, Liu X, et al. The PorV protein as a cross-protective antigen against Riemerella anatipestifer infection. Vet Microbiol. 2026. https://pubmed.ncbi.nlm.nih.gov/42030888/

[8] Ning C, Li S, Wu Y, et al. Riemerella anatipestifer OMP85, a BamA family outer membrane protein, enhances virulence through recruiting host complement regulator vitronectin to mediate complement evasion. J Immunol. 2026. https://pubmed.ncbi.nlm.nih.gov/42019960/

[9] Hou Y, Zhang Y, Huang J, et al. Intranasal delivery of a live attenuated vaccine confers efficient protection against Riemerella anatipestifer serotype 1 in ducklings. Vet Microbiol. 2026. https://pubmed.ncbi.nlm.nih.gov/41967162/

[10] Li S, Hu D, Mei X, et al. DNA methylation-mediated suppression of endocytosis confers resistance to duck hepatitis A virus type 3. Microbiol Spectr. 2026. https://pubmed.ncbi.nlm.nih.gov/42294723/

[11] Yehia N, AbdelSabour MA, Said D, et al. Complete genome sequencing and evolutionary analyses of duck hepatitis A viruses in Egyptian duck farms. BMC Vet Res. 2026. https://pubmed.ncbi.nlm.nih.gov/42249479/

[12] Fan Y, Zhao S, Qin Y, et al. ScRNA-Seq and BCR Analysis of Murine Immune Responses to Inactivated DHAV-1 as a Model Antigen. Viruses. 2026. https://pubmed.ncbi.nlm.nih.gov/42043237/

[13] Dan Y, Li L, Wang H, et al. Isolation, characterization and whole-genome analysis of a potentially novel strain of duck hepatitis A virus type 3 from a vaccinated duck flock in China. Front Microbiol. 2026. https://pubmed.ncbi.nlm.nih.gov/41960435/ *** Disclaimer: This article is for educational and informational purposes only. It is not intended to substitute for professional veterinary advice, diagnosis, treatment, or regulatory guidance. Always consult a licensed veterinarian or qualified specialist regarding animal health, disease diagnosis, and therapeutic decisions.

[14] Sang S, Wang H, Dan Y, et al. Isolation, identification and pathogenicity analysis of a virulent duck enteritis virus strain causing outbreak in vaccinated duck flocks. Poult Sci. 2026. https://pubmed.ncbi.nlm.nih.gov/42322961/

[15] Yang Q, Yu H, Ai L, et al. Deletion of the N-terminal 400 amino acids of DPV pUL36 attenuated virulence and conferred effective protection against virulent challenge. Poult Sci. 2026. https://pubmed.ncbi.nlm.nih.gov/42214186/

[16] Hao Y, Xiong M, Wang M, et al. Duck plague virus US2 promotes p62-mediated autophagic degradation of RIG-I to suppress antiviral signaling. Poult Sci. 2026. https://pubmed.ncbi.nlm.nih.gov/42190475/

[17] Yang Q, Pan C, Wang L, et al. Targeted mutagenesis of the ICP4 transactivation domain generates a protective DIVA vaccine against duck plague. Poult Sci. 2026. https://pubmed.ncbi.nlm.nih.gov/42061247/

[18] Li H, Cheng A, Wang M, et al. Avian herpesvirus-specific LORF5 is a late gene, interacts with 19 viral and 111 host proteins, critical for virulence of Duck plague virus. Poult Sci. 2026. https://pubmed.ncbi.nlm.nih.gov/42048789/

[19] Tian Y, Tian B, Ran R, et al. Duck plague virus LORF2 utilizes RNF34 to inhibit antiviral innate immunity by ubiquitination and degradation of IRF7. PLoS Pathog. 2026. https://pubmed.ncbi.nlm.nih.gov/42030364/

[20] Wan J, Zhu Y, Xu X, et al. Development of a rapid detection method for a virulent strain of duck enteritis virus based on real-time fluorescence recombinase polymerase amplification. Sheng Wu Gong Cheng Xue Bao. 2026. https://pubmed.ncbi.nlm.nih.gov/42009547/

[21] Nguyen BL, Isoda N, Hew YL, et al. Efficacy and Limitations of an Improved Vaccine Derived from an Updated Vaccine Strain Against H5 High Pathogenicity Avian Influenza. Vaccines (Basel). 2026. https://pubmed.ncbi.nlm.nih.gov/42042767/

[22] Zhang T, Yang N, Ma L, et al. Identification of duck type II interferon-stimulated genes and revelation of duIFI35 inhibition of H5N6 AIV replication by promoting apoptosis. Vet Res. 2026. https://pubmed.ncbi.nlm.nih.gov/41992349/

[23] Shimazu Y, Isoda N, Hiono T, et al. Evaluation of therapeutic efficacy of baloxavir marboxil against high pathogenicity avian influenza virus infection in duck model. PLoS One. 2026. https://pubmed.ncbi.nlm.nih.gov/41984915/

[24] Rungprasert K, Areeraksakul P, Tunterak W, et al. Immunogenicity and protective efficacy of an inactivated cluster 2.1 duck Tembusu virus vaccine in ducks: Evidence of cross-genotype immune responses. Vaccine. 2026. https://pubmed.ncbi.nlm.nih.gov/42320385/

[25] Li W, Li Y, Ren Q, et al. Epidemiological Investigation and Partial NS5 Sequence Analysis of Duck Tembusu Virus in Several Regions of China in 2024. Viruses. 2026. https://pubmed.ncbi.nlm.nih.gov/42043190/

[26] Hao C, Bai Y, Xia S, et al. Transcriptomic Analysis of Domestic Ducks' Proventriculus Infected with Eustrongylides tubifex (Nitzsch 1819) Jägerskiöld 1909. Vet Sci. 2026. https://pubmed.ncbi.nlm.nih.gov/42188957/

[27] Sun Z, Wang X, Shi H, et al. Novel goose parvovirus as a major risk factor for red skin and bristle feather syndrome in meat ducks: Epidemiological associations with duck circovirus and reovirus. Poult Sci. 2026. https://pubmed.ncbi.nlm.nih.gov/42308732/

[28] Lu X, Li M, Xu Q, et al. Genomic surveillance and evolution of co-circulating goose parvovirus and waterfowl circovirus in China. Vet Res. 2026. https://pubmed.ncbi.nlm.nih.gov/42231473/

[29] Wang H, Dong Y, Hu X, et al. Genetic variability and intra-genotype recombination of DuCV from ducks and geese in central and north China. Front Vet Sci. 2026. https://pubmed.ncbi.nlm.nih.gov/42052340/

[30] El-Nagar EMS, Gamal MAN, El-Saied MA, et al. Pathomolecular characterization of recently isolated duck Astrovirus from domestic ducklings in Egypt. Sci Rep. 2026. https://pubmed.ncbi.nlm.nih.gov/42173943/

[31] Zhang S, Wei X, Han M, et al. Specific and quantitative assay for duck variant orthoreovirus utilizing the loop-mediated isothermal amplification technique. J Immunol Methods. 2026. https://pubmed.ncbi.nlm.nih.gov/42167441/

[32] Zhang W, Tang Z, He S, et al. Detection of duck adenovirus 3 using RAA-CRISPR/Cas12a based lateral flow dipstick method. Front Microbiol. 2026. https://pubmed.ncbi.nlm.nih.gov/42164672/

[33] Wang S, Sui J, Pan J, et al. Characteristics of Avian Coronaviruses in China From 2020 to 2023. Transbound Emerg Dis. 2026. https://pubmed.ncbi.nlm.nih.gov/41971020/

[34] Nath S, Habib M, Banerjee J, et al. Understanding antimicrobial resistance dynamics of non-typhoidal Salmonella in chickens and ducks - a prospective study from West Bengal, India. Braz J Microbiol. 2026. https://pubmed.ncbi.nlm.nih.gov/42113384/

[35] Liu Y, Li Y, Xie Y, et al. Characterization of a Goose-Origin Avian Orthoreovirus with Interferon Suppression Activity. Viruses. 2026. https://pubmed.ncbi.nlm.nih.gov/42043236/