Behaviour and population dynamics of the major anopheline vectors in a malaria endemic area in southern Nigeria

Background & objectives: Anopheline mosquitoes consist of a large number of species each of whichdiffers from another in population, resting and feeding behaviour in relation to the prevailing conditionsin the locality. A longitudinal study was carried out to investigate the population dynamics, restingand feeding behaviour of the major anopheline species found in a rain forest zone of Nigeria.Methods: Mosquitoes resting and biting indoors were collected using WHO standard techniques andsupplemented with outdoor-biting collections in the study areas between January and December2004. Samples were sorted and identified microscopically for morphological features while molecularidentification was carried out using polymerase chain reaction (PCR) techniques.Results: PCR-based tests showed that both indoor and outdoor collections constitute three groups ofAnopheles mosquitoes, An. gambiae s.l. Giles (68.6%), An. funestus Giles (30.7%) and An. mouchetiEvans (0.7%). Of the 1,342 female Anopheles mosquitoes collected indoors, 799 were caught restingand 543 were caught biting. The outdoor-biting population accounted for 28.8% of the total collections(n =1885). There was no significant difference (p >0.05) in the biting activities (indoors and outdoors)of these species in four villages. However, An. arabiensis and An. moucheti were more exophagicwith >60% of their biting occurring outdoors while An. gambiae and An. funestus were moreendophagic with >55% of their biting occurring indoors. The human-vector contact with An. gambiaeand An. funestus (indoors) was about 73.3 and 66.7%, respectively as against 27.7% in An. arabiensisand 25.3% in An. moucheti. This gave the corresponding man-biting rates (MBR) of 17.5 bites/man/night for An. gambiae, 14.6 bites/man/night for An. funestus, 6.7 bites/man/night for An. arabiensisand 4.3 bites/man/night for An. moucheti. Moreover, the number of An. gambiae and An. funestuscaught resting indoors was significantly higher than the other two species (p <0.05). The wet seasoncollections showed that An. gambiae caught were more than 67% of the total catch while An. arabiensiswas predominant in the dry season (χ2 = 75.44, df = 3, p