Transmission of Babesia spp by the cattle tick (Boophilus microplus) to cattle treated with injectable or pour-on formulations of ivermectin and moxidectin

摘要

The efficacy of ivermectin and moxidectin to prevent transmission of Babesia bovis and B. bigemina by Boophilus microplus to cattle was evaluated under conditions of relatively intense experimental challenge. Naive calves were treated with either pour-on or injectable formulations of either ivermectin or moxidectin and then exposed to larvae of B. microplus infected with B. bovis or larvae or adults of B. microplus infected with B. bigemina. One calf was used for each combination of haemoparasite,B. microplus life stage, drug and application route. Cattle treated with either pour-on or injectable formulations of ivermectin and moxidectin became infected with B. bovis after infestation with infected larvae. Similarly, larvae infected with B. bigemina survived to the nymphal stage to transmit the haemoparasite to animals treated with each drug preparation. Cattle treated with pour-on formulations of ivermectin and moxidectin then infested with adult male ticks infected with B. bigemina did not become infected with B. bigemina whereas those treated with the injectable formulations of ivermectin and moxidectin did show a parasitaemia. It is concluded that injectable or pour-on formulations of ivermectin and moxidectin do not prevent transmission ofBabesia to cattle by B. microplus. Use of these drugs cannot be recommended as a primary means of protecting susceptible cattle from the risk of Babesia infection.