Dynamics and intensity of Wuchereria bancrofti transmission in the savannah and forest regions of Liberia.

In four villages in the savannah and in the rain forest of Liberia, regular assessment of the biting activity and infection rates of anthropophilic mosquitoes have been carried out through full annual cycles. The microfilaremia rates in the localities in the savannah were 18.3% and 20.0% and in those of the forest 10.3% and 12.5%. The all-night catches were performed inside ordinary inhibited houses at monthly or fortnightly intervals. Presence of infective larvae of Wuchereria bancrofti proved Anopheles gambiae, A. funestus and A. nili to be the local vectors. Biting densities were high in the savannah, and low in the forest. From the mosquito catches and the results of their dissections for filarial larvae it could be estimated, that during the observation year a person in the savannah villages would be bitten annually by 18,165 and 36,450 vector mosquitoes respectively, and would receive 236 and 536 infective bites with 570 and 1211 infective larvae. In the two forest villages the number of vector bites per person per year was calculated to be in the order of 6120 and 1102 of which 64 and 8 would be infective bites transmitting 101 and 8 larvae. The findings of considerable differences in transmission intensities between villages of the same bioclimatic zone and of comparable microfilaremia rates indicates instable epidemiological conditions in at least some of the localities investigated.