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 americanum and to determine if bone lesions attributable to H. americanum were present. Although eight of the 20 free-ranging coyotes were found to be naturally infected with H. americanum, no bone lesions were detected. In addition, two coyote pups were exposed to H. americanum oocysts collected from experimentally infected ticks and the course of the resulting infection was followed. Both experimentally infected coyotes developed hepatozoonosis detectable 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 hypercellularity and thickening of the periosteum, with minor degrees of osteogenesis, to extensive proliferation of woven bone and periosteal hypercellularity and thickening. Nymphal Amblyomma maculatum that fed on one of the experimentally infected coyote pups became infected and mature H. americanum oocysts were recovered when the ticks molted to adults. These results demonstrate that coyotes in some parts of Oklahoma are naturally infected with H. americanum, that experimentally infected coyotes can develop clinical disease, including characteristic bone lesions, and that A. maculatum nymphs can acquire infections by feeding on them.