Journal of Vector Borne Diseases (Mar 2007)
Behaviour and population dynamics of the major anopheline vectors in a malaria endemic area in southern Nigeria
Abstract
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 <0.01).Interpretation & conclusion: The present study highlights some aspects of the behaviour ofanopheline mosquitoes in southern Nigeria which is an important component of epidemiologicalstudy of malaria. This information provides basis to the understanding of the role played by theidentified anopheline species in malaria transmission and a baseline to formulate malaria controlprogramme.
