Populations of the cattle tick (Boophilus microplus) on purebred Nellore, Ibage and Nellore X European crossbreds in the Brazilian savanna.

Studies on purebred Nellore cattle and their crosses with Fleckvieh, Chianina, Charolais and the Ibagé breed (5/8 Aberdeen Angus, 3/8 Nellore) during 39 months in the field gave mean daily counts for engorging female ticks of 3.3, 25.2, 22.2, 21.0 and 59.7 per animal respectively. Annual fluctuations were similar in all groups; with the exception of the purebred Nellore mean counts are at levels considered dangerous for the stability of enzootic tick fever.