SUSCEPTIBILITY TO DIFFERENT TICK GENERA IN GAMBIAN NDAMA AND GOBRA ZEBU CATTLE EXPOSED TO NATURALLY-OCCURRING TICK INFESTATIONS

Tick collection on one side of the body and whole tail was performed w eekly over one year on 11 Gambian N'Dama (Bos taurus) and 11 Gobra zeb u (Bos indicus) cattle to assess breed susceptibility to naturally occ urring ticks. Enzyme-linked immunosorbant assay was also performed to assess the serological prevalence of Anaplasma marginale antigen and B abesia bigemina antibody. Packed red cell volume was measured and live weight gain was recorded. Significantly higher numbers of Amblyomma va riegatum (P < 0.002) and Hyalomma spp. (P < 0.001) were found on Gobra zebu than on N'Dama cattle. The serological prevalence of A. marginal e antigen was significantly (P < 0.001) lower in N'Dama breed, whilst no difference in the serological prevalence of B. bigemina antibody wa s found between N'Dama and Gobra cattle. Packed red cell volume was ne gatively affected by A. marginale infection in both breeds, but to a l esser extent in N'Dama cattle. Liveweight gain was significantly (P < 0.003) higher in N'Dama in comparison with Gobra cattle during the per iod of abundance of A. variegatum and Hyalomma spp. adults. The signif icantly lower burdens of A. variegatum and Hyalomma spp. ticks in Gamb ian N'Dama in comparison with Gobra zebu cattle confirms previous find ings. It also shows a more deleterious effect of ticks and tick-borne diseases on animal production and health in Gobra zebu than in N'Dama cattle. The presence of a tick resistant trait in N'Dama cattle is sug gested.