Experimental evidence against transmission of Hepatozoon canis by Ixodes ricinus

Hepatozoon canis is among the most widespread tick-borne protozoa infecting domestic and wild carni-vores. Its distribution is related to the occurrence of its major vector, the brown dog tick Rhipicephalussanguineus. However, the role of Ixodes ricinus as a vector of H. canis has been hypothesized. In the presentstudy, the development of H. canis was investigated in I. ricinus and R. sanguineus nymphs collected froma naturally infested dog. All I. ricinus ticks examined (n = 133) were negative by cytological examinationat days 20, 30, and 90 post collection, although H. canis DNA was detected in one nymph at day 20 and in2 nymphs at day 30 post collection. On the other hand, H. canis sporogony was documented by cytology, and H. canis DNA was detected by PCR in R. sanguineus at day 30 post collection. These results indicatethat H. canis sporogony does not occur in I. ricinus, but in R. sanguineus, suggesting that I. ricinus does notact as a vector of H. canis.