A novel large un-named Babesia species was described recently. This Babesia species was first detected in a dog undergoing chemotherapy for lymphoma. It was unknown whether or not this was an isolated event or if this parasite is an under-recognized pathogen of dogs. The primary goals of this study were to report the historical and clinicopathological findings in five additional cases of babesiosis caused by this novel large Babesia sp. and characterize the Babesia sp. 18S ribosomal ribonucleic acid (rRNA) genes in each case.
The medical records of 5 dogs with naturally occurring disease were reviewed. Additionally, the Babesia sp. 18S rRNA genes were amplified, cloned, and sequenced in each case.
All five cases had a history of splenectomy prior to diagnosis. The dogs lived in North Carolina (3), New York (1), and New Jersey (1). Travel history was unremarkable in all cases. Non-specific signs including lethargy and anorexia were the most common owner complaints. Pigmenturia was noted by the owner in 3/5 cases. Mild fever was a common physical examination finding. Common laboratory findings included mild anemia (5/5 cases, HCT range 28.2-36.5%) and severe thrombocytopenia (4/5 cases, PLT range <5-28 x 103/µl). Cross-reactive antibodies against B. canis vogeli (1/2 negative), B. gibsoni (Asian Genotype) (2/2 negative), and B. conradae (2/2 negative) were not always detectable. Four cases were treated with imidocarb dipropionate and responded well; the remaining case had a normal platelet count (478 x 103/µl) and recovered without treatment with anti-protozoal medications. All of the 18S rRNA gene sequences were 100% identical to the originally described novel large Babesia sp.
In conclusion, dogs with pigmenturia, anemia and/or thrombocytopenia should be tested for Babesia by PCR assay. Serology may not be a useful method to diagnose infection with all types of pathogenic Babesia spp. Asplenia may represent a risk factor for clinical signs due to this novel large Babesia sp.