Detection of Anaplasma bovis-like agent in the Southcentral United States

Anaplasma bovis is primarily an infectious agent of ruminants, and has most commonly been reported in Asia, the Middle East, and Africa. Although the primary cause of human anaplasmosis is Anaplasma phagocytophilum, humans may rarely be infected by other Anaplasma spp. Human disease attributed to A. bovis has been occasionally reported, including an A. bovis-like agent in the United States. DNA of an A. bovis-like agent has been amplified from humans and the tick Dermacentor variabilis in the central region of the U.S., but larger prevalence studies among potential vectors or reservoir hosts in the U.S. have not been reported. The aim of this study was to evaluate the prevalence of A. bovis-like agent among D. variabilis and cattle in the Southcentral U.S. Previously extracted DNA from adult D. variabilis collected from Oklahoma (n = 38) and Kansas (n = 93), and blood of cattle from Oklahoma (n = 140) were tested by conventional PCR. Overall prevalence of A. bovis-like DNA within ticks was determined to be 3.1% (4/131), and all positive ticks originated from Oklahoma. Overall prevalence in bovine blood was determined to be 0% (0/140). These findings confirm the presence of an A. bovis-like agent, a potentially zoonotic pathogen, among ticks in the Southcentral U.S.; this agent is likely underrecognized and has been detected in parts of the U.S. that lie outside of the established geographic range for A. phagocytophilum. Further investigation and surveillance are necessary to elucidate possible reservoirs of A. bovis in the U.S., further evaluate the burden of human infection, and fully characterize genetic differences between the A. bovis-like agent detected in the U.S. and A. bovis in other regions of the world.