Description and epidemiology of Theileria youngi n. sp from a northern Californian dusky-footed woodrat (Neotoma fuscipes) population

An epidemiologic study designed to identify the small mammal reservoir for the zoonotic WA1-type babesial parasite resulted in the discovery of a smal l, intraerythrocytic piroplasm in smeared blood from dusky-footed woodrats (Neotoma fuscipes) in northern California. The woodrat parasites were isola ted and compared to other piroplasm parasites based on their morphology, an tigenicity, and genetic characteristics. These studies indicated that the w oodrat parasites were not the WA1-type babesial agent but were of the genus Theileria. We accordingly named it Theileria youngi. The prevalence in the woodrat population was high (61%). Infection was unrelated to gender or ag e of the woodrats. potential vectors for this tick-transmitted parasite inc luded 3 species of ticks recovered from the woodrats, Dermacentor occidenta lis, Ixodes woodi, and Ixodes pacificus. Mostly larval or nymphal stages we re recovered, suggesting transstadial transmission is possible. This is the first piroplasm fully characterized from a dusky-footed woodrat.