Mechanical transmission of anaplasmosis by tabanids (Diptera: Tabanidae).

The role of tabanids in the mechanical transmission of anaplasmosis was further clarified by determining the number of horse fly bites needed to transmit the disease and the length of time that horse flies remain mechanically infective. Transmission of anaplasmosis from acutely infected calves to susceptible splenectomized calves was accomplished with as few as 10 horse fly bites. These flies were shown to remain mechanically infective for at least 2 hours after they had obtained a partial blood meal from an acutely infected calf. These data emphasize the efficiency of horse flies in the mechanical transmission of anaplasmosis and indicate that relatively short-distance barriers may not be adequate to prevent transmission between infected and noninfected herds.