The effect of short-interval deltamethrin applications to control tsetse on the seroprevalence of babesiosis in cattle.

For the past decade, treatment of cattle with 0.00375% deltamethrin (Decatix, Coopers) at two-weekly intervals has been part of an integrated approach to counteract continuous invasion of Zimbabwe by tsetse from the Mozambique fly-belt. To determine the effect of these regular deltamethrin treatments on the epidemiology of babesiosis, a survey was conducted to estimate the prevalence of antibodies against Babesia bigemina in adult communal cattle. The seroprevalence of antibodies against B. bigemina in adjacent areas, where cattle are treated with short-residual acaricides, was also determined for comparison. The prevalence of antibodies to B. bigemina was much higher in areas where dipping with a non-pyrethroid acaricide was conducted. This was attributed to the successful control of Boophilus spp. and hence a very low level of B. bigemina transmission in the 'deltamethrin treatment zone'. This low level of disease transmission was confirmed by the low prevalence of antibodies against B. bigemina in sentinel cattle that were introduced to the 'deltamethrin treatment zone'. The potential adverse effects of severely reducing the tick population should be taken into consideration at the onset of tsetse control operations in which cattle are to be treated with deltamethrin at short treatment intervals.