Failure of imidocarb dipropionate and toltrazuril/emodepside plus clindamycin in treating Hepatozoon canis infection.

Hepatozoonosis caused by Hepatozoon canis (Eucoccidiorida, Hepatozoidae) is among the most widespread vector-borne infections of dogs, primarily transmitted by Rhipicephalus sanguineus sensu lato ticks. Based on the absence of a consensus on the treatment regimes for canine hepatozoonosis, the present study aimed to evaluate the efficacy of imidocarb dipropionate (5-6 mg/kg subcutaneously once a week for 6 weeks), and of toltrazuril/emodepside (Procox(®), 15 mg/kg once a day for 6 days) in association with clindamycin (15 mg/kg once a day for 21 days) in treating naturally infected dogs. At the enrollment time (T0), 32 dogs, cytologically or molecularly positive for H. canis, were assigned to test and control groups. Animals were treated according to the specific therapeutic protocol, and the presence of H. canis gamonts was assessed weekly by cytology and PCR throughout six months (T1-T19). In addition, any abnormality in leucocyte morphology was evaluated and recorded. Results indicate that, in spite of a reduction in the percentage of infected dogs, both treatments did not provide parasitological cure. Accordingly, new treatment protocols or active compounds against H. canis should be investigated.