Molecular identification and population dynamics of the major malaria vectors in a rainforest zone of Nigeria

Abstract

Adult female mosquito vectors were collected from three villages in a typical rain forest area of Nigeria where no information exists on the major malaria vectors associated with human malaria. Sampling was carried out between January 2004 and January 2005 using pyrethrum and Human landing catch (HLC) techniques. A total catch of 2010 mosquitoes was recorded out of which 1800 were morphologically identified as female Anopheline mosquitoes. Further identification of the Anopheline species using the morphological keys revealed that 1399 (77.7%) belonged to the Anopheles gambiae s.l. and 401 (22.3%) to Anopheles funestus. A PCR based test on the Anopheles gambiae group identified 636 (45.5%) as Anopheles gambiae s.s and 763 (54.5%) as Anopheles arabiensis respectively. The cocktail PCR-assay on the total Anopheles funestus group showed 307 (76.6%), to be Anopheles funestus s.s and 94 (23.4%) to be Anopheles leesoni. The total number of Anopheles gambiae collected across the 3 villages was significantly higher (P<0.05) than the number of Anopheles funestus caught within the same period. However, there was a seasonal difference in the population of Anopheline species collected in which the wet season collections constitute 45.4% An.gambiae s.l and 17.7% An.funestus while the dry season population constitutes 32.3% An.gambiae s.l and 4.5% An.funestus. The dry season collections were predominantly An. arabiensis producing 23.9% of the total catch in. The overall number of Anopheles mosquitoes collected in the wet season was significantly higher than that of the dry season (P<0.01). Generally, low sporozoite rates were recorded in all the communities and this may be an indication that transmission in this area is less intense. This study provides information on mosquito ecology, genetic and molecular techniques for identification of species complexes which are important strategies for planning malaria control programmes.

Keywords: An. gambiae, An arabiensis, An.funestus, An. Lessoni, PCR, ELISA, Nigeria

Biokemistri Vol. 17(2) 2005: 171-178