MALARIA PREVALENCE IS INVERSELY RELATED TO VECTOR DENSITY IN THE GAMBIA, WEST-AFRICA

Baseline epidemiological and entomological studies were conducted in 5 different areas of The Gambia before the introduction of a national m alaria control programme, the objective of which was to treat all the bed nets belonging to people living in primary health care villages wi th insecticide. Air malariometric indices used (parasite density, para site rates, splenomegaly, and packed cell volume) indicated that malar ia transmission was more intense in the east of the country than elsew here. High transmission in the east was associated with a high sporozo ite rate but not with the greatest vector abundance; the lowest malari a prevalence rates were found in villages which were close to very pro ductive breeding sites of Anopheles gambiae s.l. Bed net usage was str ongly correlated with vector density and the highest malaria rates wer e found in villages where bed net usage was relatively low. These resu lts suggest that in The Gambia malaria prevalence rates are reduced wh ere nuisance biting by mosquitoes is sufficient to encourage the popul ation to protect themselves with bed nets.