Tick-Borne Diseases in Dogs: Lyme Disease, Ehrlichiosis, Anaplasmosis, and Babesiosis
Introduction
Tick-borne diseases (TBDs) represent a significant and growing threat to canine health globally. The complex interplay between tick vectors, pathogen biology, and host immune responses results in a spectrum of clinical syndromes ranging from subclinical infection to severe, life-threatening disease [1]. The primary pathogens responsible for TBDs in dogs include the spirochete Borrelia burgdorferi (Lyme disease), the rickettsial organisms Ehrlichia canis and Anaplasma species, and the protozoan parasites of the genus Babesia [2, 3]. Understanding the biophysical and molecular mechanisms of these infections is critical for accurate diagnosis and effective management. This article provides a detailed, publication-grade review of these four major dog tick transmitted diseases, focusing on their etiology, epidemiology, clinical pathology, diagnostic methodologies, and therapeutic control.
Etiology and Vector Biology
Lyme Disease (Borreliosis)
Lyme disease in dogs is caused by infection with the spirochete Borrelia burgdorferi sensu lato, primarily B. burgdorferi sensu stricto in North America and B. afzelii and B. garinii in Europe [4, 5]. The primary vectors are hard ticks of the Ixodes ricinus complex, including I. scapularis in North America and I. ricinus in Europe [6, 5]. Transmission requires a minimum feeding period of 24 to 48 hours, as the spirochetes reside in the tick midgut and must migrate to the salivary glands before inoculation [7]. The spirochete's outer surface proteins (Osps) facilitate adhesion to tick midgut epithelium and mammalian extracellular matrix components, enabling systemic dissemination [5].
Ehrlichiosis
Canine monocytic ehrlichiosis is primarily caused by Ehrlichia canis, an obligate intracellular Gram-negative bacterium that infects monocytes and macrophages [8, 9]. The principal vector is the brown dog tick, Rhipicephalus sanguineus sensu lato [10, 11]. Transmission can occur within 3 to 6 hours of tick attachment, as E. canis is present in tick salivary glands [7]. The pathogen evades host defenses by inhibiting phagolysosomal fusion and modulating host cell apoptosis, establishing persistent infection within the mononuclear phagocyte system [12].
Anaplasmosis
Canine anaplasmosis is caused by two distinct species: Anaplasma phagocytophilum, which infects granulocytes, and Anaplasma platys, which infects platelets [12, 13]. A. phagocytophilum is transmitted by Ixodes species ticks, while A. platys is vectored by R. sanguineus [4, 14]. A. phagocytophilum utilizes type IV secretion systems to inject effector proteins into host neutrophils, subverting innate immune signaling and promoting bacterial survival within neutrophil vacuoles [5]. A. platys causes cyclical thrombocytopenia through immune-mediated destruction of infected platelets [15].
Babesiosis
Canine babesiosis is caused by intraerythrocytic protozoan parasites of the genus Babesia. Large Babesia species include B. canis (vectored by Dermacentor reticulatus in Europe) and B. vogeli (vectored by R. sanguineus in tropical and subtropical regions) [5, 11]. Small Babesia species include B. gibsoni and B. conradae, with B. gibsoni being highly prevalent in Asia and transmitted by R. sanguineus and Haemaphysalis species [16, 17]. Transovarial transmission occurs in tick vectors for Babesia species, allowing ticks to serve as both vectors and reservoirs [7]. The parasite's merozoites invade erythrocytes via a complex process involving apical complex organelles and surface lectins, leading to hemolytic anemia [18].
Epidemiology and Global Distribution
The prevalence of these pathogens varies significantly by geographic region, climate, and vector distribution. A comprehensive study in Nepal reported an overall TBD prevalence of 31.09% in dogs, with Babesia spp. (26.09%) being most common, followed by E. canis (5.87%), Hepatozoon canis (3.52%), and A. platys (2.93%) [2]. In northern Vietnam, a molecular survey found a 73.9% infection rate, with Babesia vogeli (30.5%), Rickettsia spp. (27%), and A. platys (22%) being predominant [13]. In Hong Kong, B. gibsoni was detected in 27% of dogs suspected of tick-borne infection, with E. canis found in 7.4% [17].
In Europe, seroprevalence data from Finland showed A. phagocytophilum antibodies in 5.3% of dogs and B. burgdorferi in 2.9%, with significantly higher rates in the Aland Islands (45% and 20%, respectively) [4]. A study in Poland during autumn-winter months confirmed active transmission of Babesia spp., Anaplasma spp., and Borrelia spp., emphasizing year-round risk [3]. In the United Kingdom, a retrospective study of 76 TBD cases identified ehrlichiosis (25 dogs), babesiosis (23 dogs), Lyme borreliosis (8 dogs), and anaplasmosis (6 dogs), with 14 dogs having co-infections [19].
In South America, a serosurvey in the Brazilian Eastern Amazon found anti-B. canis vogeli antibodies in 42.6% of dogs and anti-E. canis antibodies in 16.2% [8]. In Egypt, molecular screening detected B. canis vogeli, A. phagocytophilum, A. platys, and E. canis in dog blood samples [35]. These data underscore the global distribution and variable prevalence of these pathogens.
Clinical Signs and Pathophysiology
Lyme Disease
Clinical signs of Lyme disease in dogs are often nonspecific and include acute onset of lameness, fever, lethargy, and lymphadenopathy [19, 5]. The hallmark is immune-mediated polyarthritis, resulting from deposition of immune complexes in synovial membranes [5]. A severe complication is Lyme nephritis, a protein-losing glomerulopathy associated with high mortality, characterized by glomerulonephritis and renal failure [5]. The anti-C6 antibody concentration correlates with proteinuria and disease severity [5].
Ehrlichiosis
Canine ehrlichiosis progresses through three phases: acute, subclinical, and chronic. The acute phase, occurring 1 to 3 weeks post-infection, is characterized by fever, depression, anorexia, lymphadenomegaly, and thrombocytopenia [9, 15]. Thrombocytopenia is a consistent hematological finding, resulting from immune-mediated destruction and platelet consumption [2, 9]. The subclinical phase can persist for months to years, with dogs appearing healthy but remaining PCR-positive [12]. The chronic phase, most severe in certain breeds (e.g., German Shepherds), involves pancytopenia, epistaxis, and secondary infections due to bone marrow hypoplasia [12, 20].
Anaplasmosis
Anaplasma phagocytophilum infection typically presents with acute fever, lethargy, anorexia, and lameness, often with polyarthritis [4, 5]. Thrombocytopenia is common, though less severe than in ehrlichiosis [15]. Anaplasma platys infection is characterized by cyclical thrombocytopenia, with platelet counts dropping every 10 to 14 days, often without overt clinical signs [12, 13]. Coagulation abnormalities, including prolonged bleeding times, have been documented [21].
Babesiosis
Clinical babesiosis ranges from peracute to chronic. Peracute disease, often seen with B. rossi in Africa, presents with severe hemolytic anemia, hemoglobinuria, icterus, and shock [12]. Acute babesiosis, common with B. canis and B. gibsoni, includes fever, anemia, thrombocytopenia, splenomegaly, and dark urine [3, 15]. Chronic infections, particularly with B. gibsoni, may present with intermittent lethargy and mild anemia [17]. Hemolytic anemia results from both direct erythrocyte lysis by merozoites and immune-mediated destruction of infected and uninfected erythrocytes [18]. Thrombocytopenia is a frequent finding, even in the absence of anemia [17].
Diagnostic Approaches
Hematological and Biochemical Abnormalities
Complete blood count (CBC) analysis using automated impedance analyzers reveals characteristic abnormalities. Thrombocytopenia is a hallmark of ehrlichiosis, anaplasmosis, and babesiosis [2, 9, 15]. Anemia, often regenerative, is prominent in babesiosis and chronic ehrlichiosis [3, 18]. Leukopenia or leukocytosis may be present, with lymphocytosis associated with Hepatozoon canis co-infections [2]. Serum biochemistry may show hyperglobulinemia (especially in ehrlichiosis), hypoalbuminemia, and elevated liver enzymes [18, 20]. Proteinuria is a key finding in Lyme nephritis [5].
Direct Detection Methods
Blood Smear Microscopy: Examination of Giemsa-stained thin blood smears allows direct visualization of Babesia merozoites within erythrocytes and Ehrlichia morulae within monocytes [10, 22]. Sensitivity is low, particularly in chronic or low-parasitemia infections [9].
Molecular Diagnostics: Polymerase chain reaction (PCR) assays are the gold standard for detection of active infection, offering high sensitivity and specificity [2, 9]. Species-specific PCR targeting the 18S rRNA gene for Babesia spp., the 16S rRNA gene for Ehrlichia and Anaplasma spp., and the flaB or ospA genes for B. burgdorferi is standard [13, 23]. Real-time PCR (qPCR) allows quantification of pathogen load [17]. High-throughput sequencing can identify co-infections and novel variants [24].
Serological Methods
Serological assays detect antibodies against specific pathogens. Indirect immunofluorescence assay (IFA) and enzyme-linked immunosorbent assay (ELISA) are commonly used [8, 25]. Commercial ELISA kits detect antibodies against B. burgdorferi C6 peptide, E. canis, A. phagocytophilum, and A. platys [4, 14]. Serology cannot distinguish active from past infection and may show cross-reactivity between Ehrlichia and Anaplasma species [25, 5].
Diagnostic Decision Tree
graph TD
A[Clinical Suspicion of TBD], > B{CBC & Biochemistry}
B, > C[Thrombocytopenia, Anemia, Hyperglobulinemia]
C, > D[Blood Smear Microscopy]
D, > E{Morulae or Merozoites Seen?}
E, >|Yes| F[Presumptive Diagnosis]
E, >|No| G[PCR Panel: Babesia, Ehrlichia, Anaplasma, Borrelia]
G, > H{Positive for Pathogen?}
H, >|Yes| I[Confirm Species via Sequencing]
H, >|No| J[Serology: ELISA/IFA]
J, > K{Antibodies Detected?}
K, >|Yes| L[Consider Past Exposure or Active Infection]
K, >|No| M[Re-evaluate or Consider Other Diseases]
F, > N[Targeted Treatment]
I, > N
L, > N
Treatment Protocols
Lyme Disease
Doxycycline (10 mg/kg orally every 24 hours for 30 days) is the treatment of choice [19, 5]. Amoxicillin or cefovecin may be used as alternatives. Supportive care for Lyme nephritis includes immunosuppressive doses of corticosteroids and angiotensin-converting enzyme inhibitors [5].
Ehrlichiosis
Doxycycline (10 mg/kg orally every 24 hours for 28 days) is the first-line therapy [19, 9]. Imidocarb dipropionate (5 to 6.6 mg/kg intramuscularly or subcutaneously, repeated once after 14 days) is an alternative [12]. Supportive care includes fluid therapy and blood transfusions for severe anemia or thrombocytopenia [19].
Anaplasmosis
Doxycycline (10 mg/kg orally every 24 hours for 14 to 28 days) is highly effective for both A. phagocytophilum and A. platys infections [4, 5]. Clinical improvement is typically rapid within 24 to 48 hours [5].
Babesiosis
Treatment depends on the species. For large Babesia (e.g., B. canis, B. vogeli), imidocarb dipropionate (5 to 6.6 mg/kg intramuscularly or subcutaneously, repeated once after 14 days) is standard [19, 5]. For small Babesia (e.g., B. gibsoni), a combination of atovaquone (13.3 mg/kg orally every 8 hours for 10 days) and azithromycin (10 mg/kg orally every 24 hours for 10 days) is recommended [17]. Supportive care includes intravenous fluids, blood transfusions, and corticosteroids for immune-mediated hemolysis [19].
Prevention and Control
Prevention relies on rigorous tick control using acaricides (collars, spot-on formulations, oral medications) and environmental management [7, 5]. Vaccination against B. burgdorferi is available in endemic areas but does not prevent infection, only clinical disease [5]. Regular screening of dogs in endemic regions using PCR and serology is recommended for early detection [2, 26]. Owners should be educated on year-round tick prevention, as studies demonstrate transmission during autumn and winter months [3, 27].
Co-infections and Complex Presentations
Co-infections with multiple tick-borne pathogens are common, particularly in endemic regions, and can complicate diagnosis and treatment [12, 24]. In Romania, 45% of sick dogs were infected with protozoan parasites, with co-infections of Babesia and Mycoplasma species detected [24]. In Sri Lanka, co-infections of Ehrlichia, Babesia, and Hepatozoon are frequently encountered [12]. Co-infections may result in more severe clinical signs, including pancytopenia and multi-organ dysfunction [18]. Molecular diagnostics are essential for identifying all pathogens present [24, 13].
Conclusion
Tick-borne diseases in dogs, including Lyme disease, ehrlichiosis, anaplasmosis, and babesiosis, are complex, globally distributed infections with significant morbidity. Accurate diagnosis requires a combination of hematological analysis, molecular detection, and serological testing. Treatment is generally effective when initiated promptly, but prevention through rigorous tick control remains the cornerstone of management. The increasing geographic range of tick vectors due to climate change underscores the need for continuous surveillance and updated clinical guidelines.
References
[1] Elsheikha H. Tick-borne diseases in dogs. Journal. 2016. https://www.semanticscholar.org/paper/c2e8e07053950677bd99a99c4d6c4dda42498fe5
[2] Aryal S, Bhattarai RK, Thapa K. Comprehensive study of ticks and tick-borne diseases in dogs in Nepal: molecular identification, risk analysis and hematological alterations. BMC Veterinary Research. 2025. https://www.semanticscholar.org/paper/fba6144fa2683cc6ea349a49884166537f34cf6e
[3] Gałęcka I, Ma Z, Xuan X, et al. Clinical Cases of Tick-Borne Diseases in Dogs During the Autumn-Winter Season in Poland. Pathogens. 2024. https://www.semanticscholar.org/paper/cd39ba7f5b8e931022e0c38f8f9299d813c1baef
[4] Pérez Vera C, Kapiainen S, Junnikkala S, et al. Survey of selected tick-borne diseases in dogs in Finland. Parasites & Vectors. 2014. https://www.semanticscholar.org/paper/38103d4089fec91391b82b7602eda0ee4e52cdf5
[5] Pantchev N, Pluta S, Huisinga E, et al. Tick-borne Diseases (Borreliosis, Anaplasmosis, Babesiosis) in German and Austrian Dogs: Status quo and Review of Distribution, Transmission, Clinical Findings, Diagnostics and Prophylaxis. Parasitology Research. 2015. https://www.semanticscholar.org/paper/55f68cd5b55f65d04cd7f645915a60f52407a535
[6] Sormunen J, Vesterinen E, Klemola T. Ticks and Tick-Borne Pathogens Encountered by Dogs and Cats: A North European Perspective. Transboundary and Emerging Diseases. 2025. https://www.semanticscholar.org/paper/609d6ef818451a93380a43164dae99a362b7df21
[7] Kidd L, Breitschwerdt E. Transmission Times and Prevention of Tick-Borne Diseases in Dogs. Journal. 2003. https://www.semanticscholar.org/paper/c4bc8dd733d5af74cf8c63e1d19254946d5bc4e5
[8] Spolidorio M, Minervino A, Valadas S, et al. Serosurvey for tick-borne diseases in dogs from the Eastern Amazon, Brazil. Revista Brasileira de Parasitologia Veterinaria. 2013. https://www.semanticscholar.org/paper/9d91a2b37474f459987f56608d7e0308c16959fb
[9] Guimarães M, de Aguiar e Silva PT, Monteiro T, et al. Occurrence of tick-borne diseases in domestic dogs in Belém, Pará, Brazil. Acta Veterinaria Brasilica. 2021. https://www.semanticscholar.org/paper/446326496677c109401ef7431d8699b600d2548c
[10] Hadi U, Soviana S, Pratomo IRC. Prevalence of Ticks and Tick-Borne Diseases in Indonesian Dogs. Journal. 2015. https://www.semanticscholar.org/paper/24ea23d78cc1931d3b5a4870526d1e776453600a
[11] Wu Y, Gao Y, Tian C, et al. Identification of Rhipicephalus sanguineus sensu lato infected with tick-borne pathogens from pet and stray dogs in Guangzhou, Southern China. Ticks and Tick-borne Diseases. 2023. https://www.semanticscholar.org/paper/74dc03d9f6e2b167371a0918350a42174c109c16
[12] Silva ID. Complex clinical presentations of tick-borne diseases in dogs in Sri Lanka. Journal. 2017. https://www.semanticscholar.org/paper/da97025df4a60ad85d5dc5bc6aa3e33ebf327c19
[13] Do T, Bui K, Zafar I, et al. Molecular detection, risk factors, and phylogenetic analysis of tick-borne pathogens in dogs from northern Vietnam. Tropical Biomedicine. 2024. https://www.semanticscholar.org/paper/6a9e5b971ca14367aeb18105f2a976ee8d64b35a
[14] Hussain S, Hussain A, Aziz MU, et al. First molecular confirmation of multiple zoonotic vector-borne diseases in pet dogs and cats of Hong Kong SAR. Ticks and Tick-borne Diseases. 2023. https://www.semanticscholar.org/paper/32cb365db34ad3e1462699882b276f2c136db568
[15] Siriporn B, Juasook A. Clinical and hematological changes of canine tick-borne diseases in Thailand. Comparative Clinical Pathology. 2022. https://www.semanticscholar.org/paper/15dbef58387bef2dcaedf8320739ad2c7c9e43a3
[16] Inokuma H, Yamamoto S, Morita C. Survey of tick-borne diseases in dogs infested with Rhipicephalus sanguineus at a kennel in Okayama Prefecture, Japan. Journal of Veterinary Medical Science. 1998. https://www.semanticscholar.org/paper/d5a041d385d9cb952e436ef97bb2681d9e6515ca
[17] Muguiro DH, Nekouei O, Lee KY, et al. Prevalence of Babesia and Ehrlichia in owned dogs with suspected tick-borne infection in Hong Kong, and risk factors associated with Babesia gibsoni. Preventive Veterinary Medicine. 2023. https://www.semanticscholar.org/paper/2a69798881f9c5df56aede79f3d17eff7a26bb8c
[18] Sarma K, Mondal D, Saravanan M, et al. Evaluation of haemato-biochemical and oxidative indices in naturally infected concomitant tick borne intracellular diseases in dogs. Journal. 2015. https://www.semanticscholar.org/paper/7765bb942ed26d549488ad433d81cf1e75a5158a
[19] Silvestrini P, Lloyd-Bradley B, Glanemann B, et al. Clinical presentation, diagnostic investigations, treatment protocols and outcomes of dogs diagnosed with tick-borne diseases living in the United Kingdom: 76 cases (2005-2019). Journal of Small Animal Practice. 2023. https://www.semanticscholar.org/paper/5420042d7e35ae67219ca32526719bb086fc10ab1
[20] Sarma K, Mondal D, Saravanan M. Ultrasonographic changes in dogs naturally infected with tick borne intracellular diseases. Journal of Parasitic Diseases. 2016. https://www.semanticscholar.org/paper/9efe1def5152f265fe60dc4c051ed2e5b31d4e28
[21] Lubas G, Caldin M, Furlanello T. Leishmaniasis and tick borne diseases in dogs. Evaluation of the coagulation profile. Journal. 2004. https://www.semanticscholar.org/paper/a488e00214931b6b9851e46f3032bb3e8fdc0fcf
[22] Bhagwan J, Singh Y, Jhambh R, et al. Molecular and microscopic detection of haemoprotozoan diseases in dogs from Haryana, India. Parasitology Research. 2024. https://www.semanticscholar.org/paper/f11b8e64b9e2b233b96a28d5d2fd5908aff09bf7
[23] Ayanniyi O, Lu Z, Zhang H, et al. Epidemiological survey of tick-borne pathogens in dogs in Anhui Province, China. Comparative Immunology, Microbiology & Infectious Diseases. 2023. https://www.semanticscholar.org/paper/9304789de78eceb6f90d541ab29022acbe473c93
[24] Andersson MO, Tolf C, Tamba P, et al. Canine tick-borne diseases in pet dogs from Romania. Parasites & Vectors. 2017. https://www.semanticscholar.org/paper/23d65b8a7fe88f980d299ba9701c3d707bff3978
[25] Alcon-Chino MET, De-Simone S. Recent Advances in the Immunologic Method Applied to Tick-Borne Diseases in Brazil. Pathogens. 2022. https://www.semanticscholar.org/paper/0007eccf3244c61e76f05e4d5b93321a84ef56d1
[26] Hii S, Traub R, Thompson M, et al. Canine tick-borne pathogens and associated risk factors in dogs presenting with and without clinical signs consistent with tick-borne diseases in northern Australia. Australian Veterinary Journal. 2015. https://www.semanticscholar.org/paper/ecc3b5c9dd886a68237489fcf550a2bc2de6a5fd
[27] Kocoń A, Asman M, Nowak-Chmura M, et al. Exposure of domestic dogs and cats to ticks (Acari: Ixodida) and selected tick-borne diseases in urban and recreational areas in southern Poland. Scientific Reports. 2022. https://www.semanticscholar.org/paper/133cb8921e3f8042c1e473d3f643b285c6caef11
[28] Jikuya M, Tateno M, Takahashi M, et al. The presence of tick-borne diseases in domestic dogs and cats living on Iriomote-jima and Tsushima islands. Journal of Veterinary Medical Science. 2017. https://www.semanticscholar.org/paper/16025a7af24760ed8c862a833ba8c3def3d98247
[29] Disler G, Schlaht RM, Hahn MB. Perspectives on and prevalence of ticks and tick-borne diseases in Alaskan veterinary clinics. Journal of the American Veterinary Medical Association. 2022. https://www.semanticscholar.org/paper/95231b741fb5b1fa0c5eb9b9f33ab803374a3b54
[30] Chitimia-Dobler L, Bröker M, Wölfel S, et al. Ticks and tick-borne diseases from Mallorca Island, Spain. Parasitology. 2024. https://www.semanticscholar.org/paper/423e69901899ad1d5c6ece6cec01efb00891acce
[31] Yousaf A, Rehman A, Abbas T, et al. Tick-borne diseases of Canine and Feline in Pakistan. Trends in Animal and Poultry Sciences. 2023. https://www.semanticscholar.org/paper/cb603ca912302bab7407e69a5f1d4c66a550513b