Experimental transmission of Hepatozoon americanum Vincent-Johnson et al.,1997 to dogs by the Gulf Coast tick, Amblyomma maculatum Koch

Experimental transmission of Hepatozoon americanum to dogs was attempted wi th four ixodid ticks, viz., Rhipicephalus sanguineus, Amblyomma americanum, Amblyomma maculatum and Dermacentor variabilis. Ticks that dogs ingested i ncluded some that were laboratory-reared and experimentally fed as nymphs o n a dog with naturally occurring hepatozoonosis; other ticks were collected as replete or partially engorged larvae, nymphs and adults from dogs that had hepatozoonosis and natural infestations of ticks. Whole ticks used to e xpose susceptible dogs orally were partially dissected to help release oocy sts. Among eight dogs exposed, only the three that were fed A. maculatum ad ults experimentally acquisition fed as nymphs became infected. Dogs develop ed elevated body temperature and other evidence of clinical disease startin g 4 weeks after exposure. 'Cysts' typical of H. americanum were found in sk eletal muscle when samples were first examined 5 weeks after dogs ingested ticks, and parasites were also observed in peripheral blood smears at appro ximately the same time. Our study demonstrates that A. maculatum nymphs can acquire H. americanum by feeding on a parasitemic dog and that transstadia l transmission of the protozoan occurs, with dogs acquiring infection when they ingest newly molted adult ticks. (C) 1998 Elsevier Science B.V. All ri ghts reserved.