Naturally occurring and experimentally transmitted Hepatozoon americanum in coyotes from Oklahoma

Twenty free-ranging coyotes (Canis latrans) in Oklahoma (USA) were examined for the presence of naturally occurring infections with Hepatozoon america num and to determine if bone lesions attributable to H. americanum were pre sent. Although eight of the 20 free-ranging coyotes were found to be natura lly infected with H. americanum, no bone lesions were detected. In addition , two coyote pups were exposed to H. americanum oocysts collected from expe rimentally infected ticks and the course of the resulting infection was fol lowed. Both experimentally infected coyotes developed hepatozoonosis detect able by specific muscle lesions beginning 4 wk after exposure. Bone lesions were detected grossly and histologically at necropsy. Histologic evidence of periosteal bone proliferation ranged from segmental areas of plump hyper cellularity and thickening of the periosteum, with minor degrees of osteoge nesis, to extensive proliferation of woven bone and periosteal hypercellula rity and thickening. Nymphal Amblyomma maculatum that fed on one of the exp erimentally infected coyote pups became infected and mature H. americanum o ocysts were recovered when the ticks molted to adults. These results demons trate that coyotes in some parts of Oklahoma are naturally infected with H. americanum, that experimentally infected coyotes can develop clinical dise ase, including characteristic bone lesions, and that A. maculatum nymphs ca n acquire infections by feeding on them.