Species which are pathogenic include:
- Babesia canis canis
- Babesia canis vogeli
- Babesia bovis
- Babesia rossi
- Theileria annae (recently reclassified)
- Babesia conradae
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.
Diagnosis is based on clinical signs and auxillary testing. Blood tests usually reveal a normocytic, normochromic, and nonregenerative anemia, neutropenia, thrombocytopenia, hypoalbuminemia and bilirubinuria. In some dogs, secondary immune-mediated thrombocytopenia has been reported.
Light microscopic visualization of intraerythrocytic trophozoites on a blood smear using Giemsa, Romanowsky, Field's, and modified Wright's stains is often confirmatory. 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.
Definitive testing usually requires commercial ELISA tests or PCR assays.
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).
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.
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