THE DECLINE OF A GLOSSINA-MORSITANS-SUBMORSITANS BELT IN THE EGBE AREA OF THE DERIVED SAVANNA ZONE, KWARA STATE, NIGERIA

In the the early 1970s the Egbe area of Nigeria was known to be one of high trypanosomiasis risk, with four Glossina species G.morsitans submorsitans Newstead, G.longipalpis Wiedemann, G.palpalis palpalis Robineau-Desvoidy and G.tachinoides Westwood present. Grazing by Fulani pastoralists used to be short-term and only in the dry season. In recent years these pastoralists have grazed their cattle in the area throughout the year and this has prompted a reappraisal of the tsetse situation. Tsetse populations were sampled for 3 years using hand-net catches from man or an ox and biconical traps. Resident livestock, slaughter cattle and some of the flies were examined for trypanosome infection. Of the four tsetse species previously reported from the area, only the riverine species, G.p palpalis and G.tachinoides, were encountered during the investigation. None of the 152 G.p.palpalis and 52 G.tachinoides examined was infected with trypanosomes. No infection was detected in 101 slaughtered cattle, 65 live Muturu, twelve goats and two pigs by wet film examination. However, a 14.3% Trypanosoma vivax infection rate was detected by Haematocrit Centrifugation Technique (HCT) examination in twenty-one slaughtered cattle. Increased human activities over the years had destroyed much of the vegetation and depleted the wild-life population to an extent that resulted in the disappearance of G.m.submorsitans and G.longipalpis, resulting in turn in a greatly reduced trypanosomiasis risk. It is likely that a similar trend is occurring in other areas of the Derived Savanna and Forest zones of West Africa as the human population expands. As a result, more cattle are resident in these zones now than in the past and a reappraisal of cattle distribution in Nigeria is required.