Blood and ticks were collected from 31 mule deer (Odocoileus hemionus hemionus) in three bovine anaplasmosis enzootic areas of Oregon. Blood from each deer was inoculated into nonsplenectomized anaplasmosis-free calves to determine whether latent anaplasmosis was present. Each of five calves received blood from five and one received blood from six deer. Anaplasmosis did not occur in any of the calves during a 106 to 111 day post-inoculation observation period. The susceptibility of the calves was subsequently challenged with blood from an infected (Anaplasma marginale) carrier. All proved susceptible based on blood parasitemia, reduced packed cell volume, and reduced hemoglobin values. These observations were subsequently confirmed when the calves became seropositive to the card and complement-fixation tests.

Ticks, most of which were Dermacentor albipictus were collected from the deer and fed on anaplasmosis-free splenectomized calves. None of the calves became infected.

Both the card and complement fixation tests proved unreliable when conducted on mule deer serum.