Controlling tsetse with insecticide-treated cattle

Are insecticide-treated cattle better than targets?

A single insecticide-treated ox kills about as many tsetse as a single odour-baited target. So if there are already many cattle in an area, then treating cattle appears to offer several advantages over using targets.

First, treating an animal is cheaper than constructing and deploying an insecticide-treated target.

Second, cattle owners are strongly inclined to treat their cattle with insecticide, maintain them and protect them from theft. So several problems associated with using targets - such as the loss of targets due to general wear and tear, theft, and animal damage - are less with insecticide-treated cattle.

So is there any point in using targets?

The problem with insecticide-treated cattle is that they tend to be confined to certain areas. Indeed, farmers will often avoid grazing their cattle where tsetse are abundant, and the imperatives of finding adequate water and grazing further limit their distribution (Warnes et al., 1999; Hargrove et al., 2000, Rowland et al., 2000). Cattle are also generally grouped into herds, and a group of ten cattle does not kill ten times as many tsetse as a single animal. In fact, a herd of ten cattle will only kill about three times as many tsetse as a single animal (Hargrove et al., 1995). The upshot of this is that densities of four cattle per square kilometre are generally not sufficient to control savanna species of tsetse, whereas this density of targets is. The crucial difference is that we can deploy targets in an even manner, and in areas where tsetse are abundant. So targets can have a very important role to play, even in areas where cattle are present.

Most tsetse control strategies will require a combination of insecticide-treated cattle and targets, with the latter being used to plug the inevitable gaps in the local distribution of cattle (Hargrove et al., 2003). Tsetse Plan will help you to decide how many targets, if any, must be used with cattle.

References
Baylis, M. & Stevenson, P. (1998) Trypanosomiasis and tsetse control with insecticidal pour-ons – fact or fiction? Parasitology Today 14, 77-82.

Hargrove, J. W., Holloway, M.T.P., Vale, G. A., Gough, A.J.E. & Hall, D.J. (1995) Catches of tsetse flies (Glossina spp.) (Diptera: Glossinidae) from traps baited with large doses of natural and synthetic host odour. Bulletin of Entomological Research, 85, 215-227.

Hargrove, J. W., Omolo Silas, Msalilwa, J.S.I. & Fox, B. (2000) Insecticide-treated cattle for tsetse control: the power and the problems. Medical and Veterinary Entomology, 14, 123-130.

Hargrove, J.W., Torr, S.J. & Kindness, H.M. (2003). Insecticide-treated cattle against tsetse (Diptera: Glossinidae): what governs success? Bulletin of Entomological Research 93, 203-217.

Rowland, G.J., Leak, S.G.A, Mulatu, W., Nagda, S.M., Wilson, A. & d’Ieteren, G.D.M. (2000) Use of deltamethrin ’pour-on’ insecticide for the control of cattle trypanosomosis in the presence of high tsetse invasion. Medical and Veterinary Entomology 15, 87-96.

Warnes, M. L., Van den Bossche, P., Chihiya, J, Mudenge, D., Robinson, T.P., Shereni, W. & Chadenga, V. (1999) Evaluation of insecticide-treated cattle as a barrier to re-invasion of tsetse to cleared areas in northeastern Zimbabwe. Medical and Veterinary Entomology, 13, 177-184.