A PCR study of piroplasms in 166 dogs and 111 horses in France (March 2006 to March 2008)

Positive PCR results for piroplasms were obtained on EDTA blood samples from 166 dogs and 111 horses between March 2006 and March 2008. The organisms were initially identified using common primers, followed by restriction enzyme profiles to determine the species and types of Babesia/Theileria. In 27 dogs and eight horses with positive results, the size of the specimen was insufficient to separate species/types. We identified Babesia canis canis in 105 of the 166 dogs (63%) and Theileria equi in 89 of the 111 horses (80%). Babesia caballi was also present, but rare, in only two Babesia/Theileria of the 111 horses (1.2%). Unexpected findings were the identification of T. equi in 31 of the 166 dogs (19%), of B. caballi in one of the 166 dogs (0.6%), of B. canis canis in 11 of 111 horses (10%), as well as of Babesia canis rossi in one of 111 horses (0.9%). A positive result for B. canis rossi was also obtained in one of the 166 dogs (0.6%). A single case of the California type of "Babesia gibsoni" (presumably Babesia conradae) was found in a dog. We did not detect Babesia canis vogeli, possibly because of the geographic distribution of our clients. The unusual results were confirmed by DNA sequencing in several cases for B. canis canis and B. canis rossi in horses, as well as T. equi in dogs. Such infections might explain the difficulties met in some unsuccessfully treated animals using the standard dosage of imidocarb dipropionate at 3 mg/kg in dogs.