Species Composition and Infection Rate of Mosquito Vectors Following the Indoor Residual Spraying Exercise in three Communities in Awka North L.G.A of Anambra State, Nigeria

Aims: Mosquitoes constitute important vectors of diseases of public health importance. The study was carried out to determine the species composition of man-biting mosquitoes and their infection rate following indoor residual spraying (IRS) in order to currently assess the epidemiology of mosquito-borne diseases in the study communities.

Study Design: A six-month study was carried out in Urum, Mgbakwu and Isuaniocha communities in Awka North L.G.A where no information exists on the infection rates of mosquitoes following the indoor residual spraying exercise. Sample collection was carried out between June and December 2015 using Knockdown and Human Landing Catches (HLC) techniques.

Methodology: Adult indoor and outdoor man-biting mosquitoes were collected in the three study communities. Ten houses were randomly selected in each community using Simple Random Sampling method. Adult female mosquitoes were morphologically identified and dissected following standard keys and procedures.

Results: A total of 684 indoor adult biting mosquitoes comprising of 3 species were collected. Culex quinquefasciatus had the highest distribution of 414 (60.5%) followed by Anopheles gambiae 269 (39.3%) and An. moucheti 1 (0.2%). One hundred and forty-three (143) outdoor adult biting mosquitoes comprising 4 species were collected. Aedes aegypti had the highest distribution of 104 (72.7%) followed by Ae. albopictus 33 (23.1%), Ae. africanus 4 (2.8%) and Ae. simpsoni 2 (1.4%). There was a significant difference among the species of the indoor and outdoor biting mosquitoes collected in the communities (P<0.05). Female mosquitoes dissected for infection showed zero infection rates.

Conclusion: Our data demonstrates that the IRS exercise may have been effective in reducing mosquito infection rates in the study area. This work may provide an entomological baseline data required for evaluation and implementation of future vector control interventions in the study area.