Darned ticks! Anaplasmosis is a tick-borne disease caused by the bacterium Anaplasma phagocytophilum* that infects white blood cells. The Anaplasma organism typically infects horses from late fall to early spring and is spread by Ixodes ticks* which also spread Lyme disease, says Jean-Yin Tan, DVM, Dipl. ACVIM.
*previously known as Ehrlichia phagocytophila and Ehrlichia equi
*deer tick and western black-legged tick
Source: The Horse, November 15, 2022. Link. Treatments for PHF and anaplasmosis are similar so some veterinarians pursue treatment prior to confirming infection. Intravenous antimicrobial oxytetracycline treatment usually helps resolve fever after 12-24 hours, and veterinarians typically continue with a course of doxycycline or continued oxytetracycline.
INSIGHTS: Tan shares that 20 percent of Ixodes ticks in equine-inhabited areas of the southwestern U.S. are infected with the organism. Horses are frequently exposed to the disease, with researchers reporting 41 percent exposure in Pennsylvania, 66 percent in Texas and up to 100 percent in New York. The regional exposure metrics are important and make tick repellent an key consideration along with tick removal on premises.