EFFECT OF CONTROLLING NATURAL FIELD-TICK INFESTATION ON THE GROWTH OFNDAMA AND GOBRA ZEBU CATTLE IN THE GAMBIA

The effect of tick infestations on liveweight gain (LWG) was assessed by comparison of weight changes in flumethrin-treated N'Dama and Gobra zebu cattle (16-20 months old) with respective control groups submitt ed to natural tick challenge over 1 year. Flumethrin was applied month ly, fortnightly or weekly. Preventive treatments against anaplasmosis, babesiosis and trypanosomosis were given. Mortality rate was recorded and post mortem examinations carried out. In both treated and control animals, significantly fewer Hyalomma spp. and Amblyomma variegatum w ere found on N'Dama than on Gobra zebu cattle. Both breeds were equall y susceptible to Rhipicephalus senegalensis infestation. Total annual tick burdens did not cause significant differences in LWG between acar icide-treated and control cattle in either breeds. LWG was also not af fected during or after the annual peak of tick infestation (composed m ainly by A. variegatum and R. senegalensis). Equally-high mortality (3 5%), due to unidentified causes, was recorded in acaricide-treated and control Gobra cattle; mortality in N'Dama cattle was 7.5%. In both br eeds, about the 90% of mortality occurred at the end of the dry season . Breed differences in tick burden confirm previous results. If tick-b orne infections do nor influence LWG or mortality, then it is conclude d that intensive tick control is not justifiable in Gambian livestock. (C) 1998 Elsevier Science B.V.