A ten year old spayed female American Pit Bull Terrier initially presented to the PVESC Emergency Department for evaluation of clinical signs that included diarrhea, lethargy, and inappetence. Biochemical abnormalities included regenerative anemia (hematocrit 29.5), leukopenia/neutropenia, and severe thrombocytopenia (platelet count 28K). The patient was also hyperbilirubinemic (total bilirubin 1.2) and had mild elevations in her liver enzymes (ALT 172). An abdominal ultrasound and thoracic x-rays were unremarkable. Agglutination of red blood cells was not identified. Initially, the patient was treated for tickborne disease with doxycycline. Neither a positive clinical nor a positive biochemical response was noted. In fact, the patient clinically declined and the biochemical changes progressed. Severe hypoalbuminemia, peripheral edema, and a fever also developed. Corticosteroids were added to the treatment regimen to cover for immune-mediated destruction of the red blood cells and platelets. Eventually, a packed red blood cell transfusion was required. The patient’s clinical response was still minimal.

Testing for babesiosis (PCR and serology) was eventually submitted to North Carolina State University given the patient’s clinical and biochemical changes, and her breed. PCR testing was negative (perhaps a false negative due to recent antimicrobial administration). A low positive titer for Babesia gibsoni was noted with serology. Atovaquone and azithromycin were prescribed, and the patient stabilized both clinically and biochemically.

Babesiosis is a protozoal infection.  Babesia organisms colonize and multiply within the red blood cells of their host. Babesia spp. are typically spread through ticks, however direct transmission between dogs through fighting or transplacentally has been reported as well. This disease is endemic in the Americas, Africa, Asia, Australia, and continental Europe. In the United States, the disease is most prevalent, but not restricted to, southern regions.

Common features of Babesia infection sinclude fever, hemolytic anemia, thrombocytopenia, and splenomegaly. The clinical signs of babesiosis are non-specific and include lethargy, weakness, anorexia, and pale to icteric mucus membranes. Other changes possible with babesiosis include ascites, peripheral edema, vomiting, diarrhea, and lymphadenopathy. The patient described above had nearly all of these clinical and biochemical changes. Furthermore, index of suspicion for the condition was somewhat heightened given the breed, as Babesia gibsoni is most prevalent in pit bulls.

Treatment includes antiprotozoal drugs and supportive therapy. Most dogs show clinical improvement in 24-48 hours once therapy is initiated, however some dogs may take longer to respond. Treatment depends on the species of Babesia identified. Babesia canis, the most common species, can be completely cleared using a single injection of imidocarb. Other species of Babesia, such as Babesia gibsoni, may respond to combination therapy with atovaquone and azithromycin. Testing for babesiosis should be considered in those with corresponding clinical and biochemical changes, especially in breeds predisposed to this disease (pit bulls, greyhounds).

Authored by: Barbara Follett, BVMS and Adam Shoelson, DVM, ACVIM (Small Animal Internal Medicine)