Isolation and in vitro cultivation of Babesia parasites from free-ranging desert bighorn sheep (Ovis canadensis nelsoni) and mule deer (Odocoileus hemionus) in California.

Protozoal parasites of the genus Babesia were isolated for the first time from free-ranging desert bighorn sheep (Ovis canadensis nelsoni) and mule deer (Odocoileus hemionus) populations in California by in vitro culture of host blood. These naturally infected animals did not have microscopically detectable parasitemia at the time blood was collected for parasite cultivation. Three isolates of small Babesia parasites were cultured from different sample groups of bighorn sheep, and 2 isolates of large Babesia parasites were cultured from a group of bighorn sheep and a group of mule deer, respectively. The size and structure of the various forms of piroplasms from each isolate remained consistent throughout the period of cultivation. Statistical comparison of the sizes of the piroplasms among the isolates indicated that there were at least 2 distinct morphotypes. Four of the 5 isolates were maintained with continuous growth in cultures containing erythrocytes from uninfected donor bighorn sheep, mule deer, and domestic sheep. Cryopreservation or storage of cultures at 4 C for 7 days did not affect viability of the isolates. These results demonstrate the potential for use of in vitro cultivation methods for the isolation of Babesia parasites from free-ranging artiodactylids.