The spread of Rhipicephalus microplus and the detection of acaricide resistance: Impact on the epidemiology of bovine babesiosis in Zimbabwe

Rhipicephalus microplus is the most important pest of livestock recognized worldwide. It is responsible for huge economic losses in the livestock industry through direct and indirect losses related to blood sucking activities and it being a vector of diseases like Babesiosis and Anaplasmosis. The tick R. microplus has a pan-tropical distribution and as a one host tick it has gained a competitive advantage over other ticks especially when it comes to worldwide spread by the movement of animals particularly cattle. In Zimbabwe, Babesiosis is one of the tickborne diseases of socio-economic importance in the country after Anaplasmosis, Heartwater and Theilerosis. In Zimbabwe, it has been traditionally spread by the tick R. decoloratus which is common in many parts of the country. Rhipicephalus decoloratus is responsible for spreading the less pathogenic form of bovine babesiosis whereas R. microplus transmits the more pathogenic form of bovine babesiosis. Rhipicephalus microplus has been traditionally confined to the more humid and favorable Eastern Highlands of the country where it has been responsible for considerable economic losses in the livestock sector. More importantly, R. microplus is known for its displacement behaviour of local ticks, high reproductive output and acaricide resistance making it a real threat for subsistence livestock production in the tropics. Over the years, there has been a significant change in land use and ownership patterns in the country which has also affected livestock populations and distributions. It still remains to be seen to what extent these changes particularly the movement of livestock from one ecological environment to the other could have affected tick distributions as well.