Malaria vector population density and man-biting rate in three selected areas of Taraba State, north-east Nigeria

Abstract

The prevalence and risks of malaria depend on Anopheles vectorial capacity which includes the vector’s density, contact with humans and longevity. Therefore, this study was conducted to investigate the Anopheles species density and Man-Biting Rate in three riverine communities of Taraba State, north-east Nigeria. Monthly sampling of indoor mosquitoes was done between September, 2015 and August 2017 in Ardo Kola, Bali and Donga using Pyrethrum-Spray Catch (PSC), taking note the number of persons that slept overnight in the sampled-rooms and size of the rooms. The collected female Anopheles mosquitoes were identified to species level and sorted out based on gonotrophic status. The fed-ones were tested for human blood antigen using ELISA.1, 073. Anopheles identified contained 14 species. Human Blood Index (HBI) of the fed ones (n = 188) was 1(100%). Indoor-Resting Density of Anopheles were higher in wet season 1.38(60.3%) than in the dry season 0.91(39.7%). t-test analysis showed significant difference in seasonal variations in the Indoor Resting Densities of Anopheles species (p<0.05). Anopheles species with highest densities in the study areas were: An. gambiae 1.23(53.7%), An. funestus 0.44(19.2%), An. constani 0.19(8.1%). Density of Anopheles species was highest in Ardo Kola 8.39(36.5%) followed by Bali 7.5(33.1%) and the least was Donga 7.0(30.4%). Analysis of variance showed no significant difference in IRD in study areas (p>0.05). Man-biting rate of Anopheles species in seasons showed that Anopheles bite more in wet season 0.78/ night/person (53.1%) than in dry season 0.69/night/person (46.9%). The Anopheles species that bite most in all the seasons were, An.gambiae 0.75(51.0%), An.funestus 0.29(19.7%) and An. constani 0.36(24.5%). No significant differences in MBR in seasons (p>0.05). Anopheles species had highest Man-Biting Rate in Ardo Kola 0.89(60.5%) followed by Bali 0.39(26.5%) and the least was Donga 0.19(13.0%) Analysis of variance showed no significant difference in Man-Biting Rate of Anopheles in study areas (p<0.05). This study shows that Anopheles funestus and Anopheles constani, are competing for second position as major malaria vectors in the study-areas and seasons after An. gambiae. Study of longevity of the vectors is essential to ascertain this. The study-areas need to be given equal treatment in intervention on malaria control.

Keywords: Anopheles species; Man-Biting Rate; vector density; vectorial capacity.