CANINE MONOCYTIC EHRLICHIOSIS: PATHOGENESIS, DIAGNOSIS, TREATMENT AND CLINICAL OUTCOMES

S.P. Abhijith; A. Abdul Kalam; H.J. Apoorva

doi:10.56093/ijvasr.v55i1.175114

Authors

S.P. Abhijith Consultant Veterinarian, RMV Multispecialty Veterinary Clinic, Bengaluru
A. Abdul Kalam Consultant Veterinarian, CUPA, Bengaluru
H.J. Apoorva M.V.Sc. Scholar, Department of Veterinary Medicine, Veterinary College, KVFASU, Bengaluru

https://doi.org/10.56093/ijvasr.v55i1.175114

Keywords:

doxycycline, pcr, thrombocytopenia, rhipicephalus

Abstract

Canine ehrlichiosis is a globally significant, tick-borne disease of dogs, primarily transmitted by Rhipicephalus sanguineus, the brown dog tick. The etiological agents, belonging to the genus Ehrlichia (notably Ehrlichia canis, E. chaffeensis, and E. ewingii), are obligate intracellular Gram-negative bacteria that parasitize monocytes, granulocytes, or platelets, leading to a complex spectrum of clinical manifestations. The disease is classically divided into acute, subclinical, and chronic phases, each associated with varying degrees of hematological abnormalities, including thrombocytopenia, anaemia, and leukocyte dysfunction, accompanied by nonspecific systemic signs such as fever, lethargy, weight loss, lymphadenopathy, and bleeding tendencies. In chronic infections, pancytopenia and bone marrow suppression often carry a poor prognosis. Diagnosis relies on a combination of hematological evaluation, serology, and advanced molecular techniques such as PCR, which remain the gold standard for species-specific identification. Therapeutic approaches commonly involve tetracycline derivatives, especially doxycycline, often combined with supportive management to address secondary complications. Preventive strategies emphasize tick control and emerging vaccine research. Despite significant advances in understanding host-pathogen interactions, immune evasion mechanisms, and diagnostic modalities, challenges persist in early detection, resistance management, and regional epidemiological surveillance. This review consolidates current knowledge on canine ehrlichiosis with emphasis on epidemiology, pathogenesis, clinical features, diagnosis, treatment, prevention, and future perspectives.

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References

Aguiar, D.M., Saito, T.B., Hagiwara, M.K., Machado, R.Z., Labruna, M.B. and Moraes-Filho, J. (2007). Serological diagnosis of canine monocytic ehrlichiosis with Brazilian isolates of Ehrlichia canis. Veterinary Parasitology, 149: 286–292.

Amyx, H.L. and Huxsoll, D.L. (1973). Redescription of Ehrlichia canis (Donatien and Lestoquard) in the dog. American Journal of Veterinary Research, 34: 145–152.

Beaufils, J.P., Inokuma, H., Martin- Granel, J. and Fournier, P.E. (2002). Transovarial transmission of Ehrlichia canis in Rhipicephalus sanguineus ticks: A laboratory study. Annals of the New York Academy of Sciences, 990: 181–185.

Beugnet, F. and Larsen, D. (2015). A review of the efficacy of isoxazoline compounds against ticks in dogs. Parasite, 22: 28.

Carvalho, F.S., Wenceslau, A.A., Albuquerque, G.R., Munhoz, A.D. and Silva, F.L. (2008). Epidemiological and molecular study of canine ehrlichiosis in northeastern Brazil. Veterinary Parasitology, 155:159–163.

Cicuttin, G.L., Brambati, D.F., Nava, S. and Guglielmone, A.A. (2015). Seasonal dynamics of Rhipicephalus sanguineus sensulato in dogs from Buenos Aires, Argentina. Veterinary Parasitology, 210: 145–149.

Codner, E.C. and Farris-Smith, L.L. (1986). Characterization of the subclinical phase of ehrlichiosis in dogs. Journal of the American Veterinary Medical Association189: 47–50.

Dantas-Torres, F. (2008). The brown dog tick, Rhipicephalus sanguineus (Latreille, 1806) (Acari: Ixodidae): From taxonomy to control. Veterinary Parasitology, 152: 173–185.

Dantas-Torres, F. (2010). Biology and ecology of the brown dog tick, Rhipicephalus sanguineus. Parasites and Vectors, 3: 26.

Dawson, J.E., Warner, C.K., Baker, V., Ewing, S.A. and Stallknecht, D.E. (1996). The North American human ehrlichiosis agent, Ehrlichia chaffeensis: Molecular cloning, expression, and characterization of an immunoreactive protein. Journal of Clinical Microbiology, 34: 1666–1671.

Donatien, A. and Lestoquard, F. (1935). Existence en Algérie d’une rickettsiose du chien. Bulletin de la Société de Pathologie Exotique, 28: 418–419.

Dumler, J.S., Barbet, A.F., Bekker, C.P., Dasch, G.A., Palmer, G.H., Ray, S.C., Rikihisa, Y. and Rurangirwa, F.R. (2001). Reorganization of genera in the families Rickettsiaceae and Anaplasmataceae in the order Rickettsiales: Unification of some species of Ehrlichia with Anaplasma, Cowdria with Ehrlichia and Ehrlichia with Neorickettsia, descriptions of six new species combinations and designation of Ehrlichia equi and ‘HGE agent’ as subjective synonyms of Ehrlichia phagocytophila. International Journal of Systematic and Evolutionary Microbiology, 51: 2145–2165.

Fourie, J.J., Beugnet, F., Smidt, J., Otranto, D. and Lebon, W. (2013). Efficacy of topical acaricides in dogs against Rhipicephalus sanguineus: A review. Parasites and Vectors, 6: 128.

Gaunt, S.D., Beall, M.J., Stillman, B.A., Lorentzen, L., Diniz, P.P.V.P. and Breitschwerdt, E.B. (1996). Experimental infection and co- infection of dogs with Ehrlichia canis and Ehrlichia chaffeensis. Veterinary Parasitology, 57: 61–73.

Groves, M.G., Dennis, G.L., Amyx, H.L. and Huxsoll, D.L. (1975). Transmission of Ehrlichia canis to dogs by ticks (Rhipicephalus sanguineus). American Journal of Veterinary Research, 36: 937–940.

Gupta, S., Bansal, R., Singh, H., Kaur, P. and Singh, N.K. (2018). Experimental transmission of Ehrlichia canis by Haemaphysalis longicornis ticks. Journal of Parasitic Diseases, 42:623–627.

Harrus, S. and Waner, T. (2011). Diagnosis of canine monocytic ehrlichiosis. Veterinary Parasitology, 181: 182–186.

Harrus, S., Aroch, I., Lavy, E. and Bark, H. (1997). Clinical manifestations of infectious canine cyclic thrombocytopenia. Veterinary Record,141: 247–250.

Harrus, S., Perlman-Avrahami, A., Mumcuoglu, K.Y. and Waner, T. (2010). The prevalence of Ehrlichia canis infection among dogs in Israel – a retrospective study. Veterinary Parasitology, 167: 55–61.

Harrus, S., Waner, T., Aizenberg, I., Foley, J.E. and Poland, A. (1998). Amplification of Ehrlichia canis DNA from blood and spleen aspirates in naturally infected dogs. Journal of Clinical Microbiology, 36: 2680–2682.

Harrus, S., Waner, T., Bark, H., Jongejan, F. and Cornelissen, A.W. (2004). Amplification of DNA of Ehrlichia canis from dogs using the polymerase chain reaction. Veterinary Parasitology, 119: 147–155.

Huxsoll, D.L., Amyx, H.L., Hemelt, I.E., Hildebrandt, P.K., Nims, R.M. and Gochenour, W.S. Jr. (1972). Laboratory studies of tropical canine pancytopenia. Experimental Parasitology, 31: 53–59.

Inokuma, H., Oyamada, M., Davoust, B., Boni, M., Dereure, J., Bucheton, B., Hammad, A., Watanabe, M., Itamoto, K., Okuda, M. and Brouqui, P. (2006). Epidemiological survey of Ehrlichia canis and related species infection in dogs in eastern Sudan. Annals of the New York Academy of Sciences, 1078: 461–463.

Lewis, G.E., Huxsoll, D.L., Ristic, M. and Johnson, A.J. (1977). Ehrlichia canis: aetiology of a canine disease in Vietnam. Veterinary Record, 100: 102–105.

McBride, J.W., Corstvet, R.E., Breitschwerdt, E.B., Walker, D.H. and Davidson, W.R. (1999). Characterization of Ehrlichia canis antigens by Western immunoblot analysis. Journal of Clinical Microbiology, 37: 381–388.

Mekuzas, Y., Gradoni, L., Oliva, G., Foglia Manzillo, V., Baneth, G. and Shkap, V. (2009). Ehrlichia infection in dogs: a serological and molecular survey in Israel. Veterinary Parasitology, 162: 228–232.

Mylonakis, M.E., Koutinas, A.F., Breitschwerdt, E.B., Hegarty, B.C., Billinis, C.D., Leontides, L.S. and Kontos, V.S. (2004). Chronic canine ehrlichiosis (Ehrlichia canis): a retrospective study of 19 natural cases. Journal of the American Animal Hospital Association, 40: 174–184.

Neer, T.M. (1998). Canine monocytic ehrlichiosis: diagnosis and treatment. Compendium on Continuing Education for the Practicing Veterinarian, 20: 601–615.

Neer, T.M., Eddlestone, S.M., Gaunt, S.D. and Corstvet, R.E. (2002). Clinical and laboratory features of Ehrlichia canis infection in dogs from Oklahoma and Louisiana. Journal of the American Animal Hospital Association, 38: 105–112.

Nyindo, M.B.A., Ristic, M., Huxsoll, D.L., Kakoma, I. and Brown, J.L. (1980). Cell-mediated and humoral immune responses of German Shepherd dogs to experimental infection with Ehrlichia canis. American Journal of Veterinary Research, B: 250–254.

Perez, M., Rikihisa, Y. and Wen, B. (1996). Ehrlichia canis-like agent isolated from a man in Venezuela: Antigenic and genetic characterization. Journal of Clinical Microbiology, 34: 2133– 2139.

Philip, C.B. (1962). Comments on the classification of rickettsial diseases. Journal of Infectious Diseases, 111: 1–8.

Popov, V.L., Yu, X., Walker, D.H., Chen, S.M., Feng, H.M. and Wear, D. (1998). Ultrastructural study of Ehrlichia canis in naturally infected dogs. Veterinary Pathology, 35: 201–209.

Rikihisa, Y. (1991). The tribe Ehrlichieae and ehrlichial diseases. Clinical Microbiology Reviews, 4: 286–308.

Ristic, M. (1991). Canine ehrlichiosis. In: Ristic, M. and Woldehiwet, Z. (eds.), Rickettsial and Chlamydial Diseases of Domestic Animals. Pergamon Press, Oxford, pp. 169–186.

Ristic, M. and Holland, C.J. (1993). Canine ehrlichiosis. In: Woldehiwet, Z. and Ristic, M. (eds.), Rickettsial and Chlamydial Diseases of Domestic Animals. Pergamon Press, Oxford, pp. 169–186.

Stich, R.W., Schaefer, J.J., Bremer, W.G., Needham, G.R. and Jittapalapong, S. (2004). Host acquisition of Ehrlichia canis from infected Rhipicephalus sanguineus ticks. Journal of Clinical Microbiology, 42: 1358–1363.

Szabó, M.P.J., Castro, M.B., Ramos, H.G., Garcia, M.V., Castagnolli, K.C. and Pinter, A. (2005). Tick infestations on dogs in the state of São Paulo, Brazil: prevalence and seasonal dynamics. Veterinary Parasitology, 130: 1–7.

Trapp, S.M., Messick, J.B., Vidotto, O., Jojima, F.S. and Morais, H.S.A. (2006). Prevalence of Ehrlichia canis infection among dogs and ticks from Parana State, Brazil. Veterinary Parasitology, 140: 239–248.

Unver, A., Perez, M., Orellana, N., Huang, H. and Rikihisa, Y. (2001). Molecular and antigenic comparison of Ehrlichia canis isolates from dogs, ticks, and a human in Venezuela. Journal of Clinical Microbiology, 39: 2788– 2793.

Walker, J.B., Keirans, J.E. and Horak, I.G. (2000). The Genus Rhipicephalus (Acari: Ixodidae): A Guide to the Brown Ticks of the World. Cambridge University Press, Cambridge, UK.

Wen, B., Rikihisa, Y., Mott, J.M., Greene, R., Kim, H.Y., Zhi, N., Couto, G.C., Unver, A. and Bartsch, R. (1997). Comparison of nested PCR with immunofluorescent-antibody assay for detection of Ehrlichia canis infection in dogs treated with doxycycline. Journal of Clinical Microbiology, 35: 1852–1855.

Woody, B.J. and Hoskins, J.D. (1991). Ehrlichial diseases of dogs. Veterinary Clinics of North America: Small Animal Practice, 21: 75–98.