The effect of incubation and prefeeding of infected Rhipicephalus simus nymphae and adults on the transmission of Anaplasma marginale.

Two batches of unfed Rhipicephalus simus nymphae carrying Anaplasma marginale were incubated for 72 h and 96 h respectively at 37 degrees C. Fifty ticks were triturated at a time and the homogenates were used to infect susceptible cattle. Others were prefed on a bovine host for 72 h before tick suspensions were prepared. The same procedure was followed, using a single batch of infected adult ticks. Incubation had no effect on the infectivity of the nymphal homogenates, but prefeeding of nymphae reduced the prepatent period by 8 days in 1 of the 2 attempts. In the case of the adult ticks both incubation and prefeeding reduced prepatent periods by 5 and 8 days respectively.