Canine babesiosis continues to create challenges for practitioners

Canine babesiosis continues to create challenges for practitioners

Transplacental transmission from dam to offspring is thought to occur, as Babesia gibsoni has been detected in puppies as young as 3 days old. Transmission can also occur through direct blood contamination. Blood donors should be tested negative for babesiosis. Pit Bull type dogs or dogs with positive titers should not be used as blood donors.

Blood contamination can also occur through practices such as sharing needles for vaccinations or re-using surgical instruments for tail docking or ear cropping. The organism can also be transmitted through dog fighting. All of these potential methods of transmission may help explain the high prevalence in the Pit Bull breed.

Diagnosis Babesiosis is usually diagnosed by finding parasitized red blood cells on a blood smear stained with Wright's, Giemsa or Diff-Quick® stain. Because parasitized cells may be more prevalent in capillary blood, the smear should be made from the pinna of the ear or the nail bed to increase the chances of finding them. Parasitized cells can also be found on buffy coat smears, as the parasitized cells are just below the white blood cells in a centrifuged capillary tube.

Serology can be used to detect dogs with occult parasitemia. B. canis and B. gibsoni cross-react on the IFA test and must be differentiated based on parasite recognition on the blood smear unless PCR testing is available. IFA titers > 1:80 are considered positive for B. canis infection, and titers > 1:320 are generally seen with B. gibsoni infection. PCR analysis is currently the most sensitive assay for detecting subclinical infections. The cross-reactivity between B. canis and B. gibsoni is variable. The PCR test for B. canis is specific and will not detect other species. The PCR test for B. gibsoni, however, will detect a variety of species.

Treatment The only drug approved for definitive treatment of babesiosis in the United States is imidocarb diproprionate (Imizol, Schering-Plough, Union, New Jersey). The recommended dosage is 6.6 mg/kg IM, repeated in two weeks. Side effects of imidocarb include pain at the injection site, salivation, lacrimation, gastrointestinal signs and tremors. Pre-treatment with atropine (0.04 mg/kg SC) may prevent these cholinergic side effects. Imidocarb is very effective against B. canis, but less effective against B. gibsoni. In many dogs, the degree of parasitemia is markedly reduced within 24-48 hours after administration, but three or four treatments may be required to clear the parasitemia. Even then, many dogs apparently develop subclinical infections and remain chronic carriers.

Another babesiacidal drug is diminizene aceturate. This drug is not available in the United States but can be obtained in other countries. A single injection of 3.5 mg/kg IM will clear parasitemia and improve clinical signs in dogs with B. canis. A higher dosage (5-7.5 mg/kg IM, repeated two or three times at two-week intervals) has been recommended for dogs with Babesia gibsoni.

Other drugs that may be effective against babesiosis include clindamycin and metronidazole. Clindamycin has been used to treat B. microti in people, and metronidazole (25- 65 mg/kg q 24 h for 10 days) resulted in clinical improvement in one group of dogs with B. gibsoni.

Supportive care is required in dogs with acute or peracute disease. A blood transfusion or Oxyglobin® is indicated in dogs with severe hemolytic anemia. In one study, 85 percent of babesia infected dogs had a positive direct antiglobulin (Coomb's) test and 21 percent exhibited autoagglutination. The use of glucocorticoids in these cases is controversial because immunosuppression may exacerbate the parasitemia. The author prefers to treat these dogs with imidocarb and supportive care, and will only use glucocorticoids if hemolysis continues to cause severe anemia. Once the parasitemia has cleared, glucocorticoids can be tapered off fairly quickly in most cases. Other supportive measures include fluid therapy to correct dehydration and acidosis, and management of concurrent diseases, such as ehrlichiosis. Sucralfate is generally indicated to minimize gastrointestinal bleeding associated with thrombo-cytopenia or immunosuppressive doses of steroids.