Summary
Splenectomized cattle and mature, splee-nintact cattle were used as sentinels in a 4-year study to assess the seasonality of naturally transmitted anaplasmosis. Sentinels were exchanged and/or monitored monthly on 4 study areas of desert mountain range land in Idaho, Oregon, and Utah. Acute Anaplasma infections were diagnosed in sentinels every month of the year. Of 44 total infections, 29 (66%) were detected during March through August, the primary arthropod season. From December through February, 8 (18%) of the total 44 Anaplasma infections were diagnosed; the winter tick, Dermacentor albipictus, was the probable disease vector. Susceptible cattle were determined to be at risk throughout the year, and anaplasmosis should be considered as a possible diagnosis in cattle with anemia during any season.
