Distribution and infectivity of anopheles mosquitoes and asymptomatic malaria infection in a home-setting of Gboko, Nigeria

Abstract

Malaria still remains a major public health problem in Nigeria, despite serious efforts to lessen its adverse impact. A malaria survey was conducted to determine the distribution and infectivity rate of Anopheles species, and asymptomatic malaria infections in Gboko. Mosquitoes were collected at selected sites, using aspirators and Pyrethrum Spray Catches (PSC), while malaria diagnosis was carried out with Parachek Pf® malaria rapid diagnostic test. The aim was to identify and characterize the major vectors of malaria transmission, and to determine the prevalence of asymptomatic malaria, that could serve as a reservoir for malaria transmission by the local vector species. The result showed that less than 10% of mosquitoes caught were Anopheles species. The majority of mosquitoes were Culex species with a small number of Aedes species. Two vector species; Anopheles gambiae and Anopheles funestus were identified and incriminated in malaria transmission in the Gboko area. The distribution of the vectors was clumped with a variance mean ratio (VMR)= 85.12. The female An. gambiae, 74.20% were significantly more abundant than An. funestus, 25.80% (x²= 13.24, df= 3, p= 0.004). However, their relative infectivity was not significantly different (x²= 0.24, df= 1, p= 0.63). The prevalence of asymptomatic malaria determined at home was 4.0 %, and regularly  distributed with VMR= 0.34 in an apparently healthy population. These results indicate that although malaria vectors may  assume aggregate distribution, they can cause a uniform pattern of malaria infection in an area. There is a need to interfere with the asymptomatic reservoir of malaria, available for continuous vector transmission of the disease in Gboko.

Keywords: Infectivity; anopheles mosquitoes; asymptomatic malaria.