Babesia spp

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Clinical anemia in a dog infected with Babesia canis canis protozoa[1]
Blood smear, dog, Wright’s stain. Large, slightly irregular piroplasms of Babesia canis are present within erythrocytes[2]

Babesia spp are a intraerythrocytic protozoan parasite of dogs and cause babesiosis, a disease which manifests as anemia, renal disease and sometimes death.

Species which are pathogenic include:

  • Babesia canis canis
  • Babesia canis vogeli[3]
  • Babesia bovis[4]
  • Babesia rossi[5][6]
  • Theileria annae (recently reclassified)
  • Babesia conradae

Infections are usually transmitted by ticks such as Ixodes spp, Dermacentor spp and Rhipicephalus spp[7].

Following attachment of an infected tick, Babesia spp trophozoites are released into the blood, infecting erythrocytes. Within the erythrocytes, the parasite multiplies by binary fission, an asexual form of schizogony. Naïve ticks attach to the dog and become infected with Babesia spp when they ingest a blood meal[8].

Clinical signs are variable but fever, pale mucus membranes, depression, lymphadenopathy, splenomegaly and general malaise are common.

Diagnosis is based on clinical signs and auxillary testing. Blood tests usually reveal a normocytic, normochromic, and nonregenerative anemia, neutropenia, thrombocytopenia, hypoalbuminemia and bilirubinuria[9][10]. In some dogs, secondary immune-mediated thrombocytopenia has been reported[11].

Light microscopic visualization of intraerythrocytic trophozoites on a blood smear using Giemsa, Romanowsky, Field's, and modified Wright's stains is often confirmatory[12]. Sampling of blood from a capillary bed (from the ear, for instance) yields more diagnostic smears than sampling blood from a larger vein. The degree of parasitemia is very low with B. canis, but may range from 2% to 6% (or greater) of the erythrocyte population with B. gibsoni[13].

Definitive testing usually requires commercial ELISA tests or PCR assays[14].

Treatment is usually effective with two injections of imidocarb diproprionate at 5.0 - 6.6 mg/kg given subcutaneously or intramuscularly at an interval of 2 to 3 weeks.

Alternative drug therapies include a single intramuscular injection of dimenazene aceturate (5 mg/kg), pentamidine isethionate (16 mg/kg intramuscularly every 24 hours for 2 doses) or atovaquone (13.3mg/kg orally three times daily for 10 days) and azithromycin (10 - 12.5mg/kg orally every 24 hours for 10 days)[15].

Supportive therapy such as intravenous fluids and blood transfusions should be employed when necessary.

Eradication of the parasite is difficult and relapses are not uncommon.

No commercially vaccines are available against babesiosis[16].

References

  1. Bada-UK
  2. Cornell University
  3. Wyatt Cleveland, C et al (2007) An Overview of Canine Babesiosis
  4. Lemos TD et al (2012) Detection and molecular characterization of piroplasms species from naturally infected dogs in southeast Brazil. Rev Bras Parasitol Vet 21(2):137-142
  5. Yisaschar-Mekuzas Y et al (2012) Identification of Babesia species infecting dogs using reverse line blot hybridization for six canine piroplasms, and evaluation of co-infection by other vector-borne pathogens. Vet Parasitol pii:S0304-4017
  6. Zahler M, et al (2000) Babesia gibsoni of dogs from North America and Asia belong to different species. Parasitology 120:365-369
  7. Ano H, Makimura S, Harasawa R (2001) Detection of Babesia species from infected dog blood by polymerase chain reaction. J Vet Med Sci 63:111-113
  8. Birkenheuer AJ, et al (1999) Babesia gibsoni infections in dogs from North Carolina. J Am Anim Hosp Assoc 35:125-128
  9. Gardiner CH, Fayer R, Dubey JP (1988) An Atlas of Protozoan Parasites in Animal Tissues. U. S. Department of Agriculture, Agriculture Handbook No. 651, pp 70-71
  10. Taboada J (1998) Babesiosis. In: Greene CE (ed), Infectious Diseases of the Dog and Cat. WB Saunders, Philadelphia, PA, pp:473-481
  11. Scheepers E et al (2011) Serial haematology results in transfused and non-transfused dogs naturally infected with Babesia rossi. J S Afr Vet Assoc 82(3):136-143
  12. Carret C, et al (1999) Babesia canis canis, Babesia canis vogeli, Babesia canis rossi: Differentiation of the three subspecies by a restriction fragment length polymorphism analysis on amplified small subunit ribosomal RNA genes. J Eukaryot Microbiol 46:298-303
  13. Schetters TP, et al (1998) Parasite localization and dissemination in the Babesia-infected host. Ann Trop Med Parasitol 92:513-519
  14. Comazzi S, et al (1999) Diagnosis of canine Babesiosis by Percoll gradient separation of parasitized erythrocytes. J Vet Diagn Invest 11:102-104
  15. Di Cicco MF et al (2012) Re-emergence of Babesia conradae and effective treatment of infected dogs with atovaquone and azithromycin. Vet Parasitol 187(1-2):23-27
  16. Schetters TP, et al (1997) Vaccination of dogs against Babesia canis infection. Parasitol 73:35-41.
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