Risk factors for tick attachment to smallholder dairy cattle in Tanzania

A cross-sectional study was conducted in Tanga and Iringa regions of Tanzania, and a longitudinal study in Tanga, to investigate tick-control methods and other factors influencing tick attachment to the cattle of smallholder dairy farms. Most farmers reported applying acaricides at intervals of 1-2 weeks, most used acaricides that require on-farm dilution and most farmers incorrectly diluted the acaricides. Rhipicephalus appendiculatus and Boophilus spp. ticks were those most-frequently encountered on the cattle, but few cattle carried ticks of any species (only 13 and 4.6% of tick counts of the cattle yielded adult R. appendiculatus and Boophilus spp., respectively). Animals were more likely to carry one or more adult Boophilus spp. ticks if they also carried one or more R. appendiculatus adults (OR=14.4, CI=9.2, 22.5). The use of pour-on acaricides was associated with lower odds that animals carried a R. appendiculatus tick (OR=0.29, CI=0.18, 0.49) but higher odds that they carried a Boophilus spp. tick (OR=2.48, CI=1.55, 3.97). Animals >4 months old and those with a recent history of grazing had higher odds of carrying either a R. appendiculatus (ORs=3.41 and 2.58, CIs=2.34, 4.98 and 1.80, 3.71), or a Boophilus spp. tick (ORs=5.70 and 2.18, CIs=2.34, 4.98 and 1.49. 3.25), but zero-grazing management did not prevent ticks attaching to cattle even when combined with high-frequency acaricide treatments. The odds that animals carried ticks varied amongst the agro-ecological zones (AEZs) and administrative districts where the farms were situated-but there was still considerable residual variation in tick infestation at the farm level.