The effect of chemotherapy on Babesia bigemina in the tick vector Boophilus microplus

Percentages of feeding ticks in which Babesia bigemina could be detected (infection rates) were determined following treatment of bovine hosts with each of four babesicides. Infection rates were suppressed by imidocarb dipropionate, quinuronium sulphate and amicarbalide, reaching minimum levels 3–4 days after treatment, but imidocarb dihydrochloride had comparatively little effect. Total elimination of the parasite from ticks was not achieved. Treatment of tick infested hosts with imidocarb dipropionate or quinuronium sulphate failed to prevent transmission of B. bigemina by transovarian passage or by transfer of adult male ticks. These findings indicate that the use of babesicides for chemotherapy is unlikely to have a significant effect on the rate of transmission of B. bigemina.