Influence of geographical location on abundance assortment of <i>Anopheles</i> mosquito species (Diptera: Culicidae) on malaria parasite rate in Enugu State, Nigeria

Abstract

Assessment of geographical distribution of malaria vectors is essential to effective malaria parasite control. This study evaluated the influence of geographical locations on distribution of Anopheles mosquito species and malaria parasite vectorial efficacy in Enugu State, Nigeria. Mosquitoes were collected, using indoor resting pyrethrum spray collection (IRPSC) method. They were morphologically identified and molecularly (PCR) characterised. The M form (now called Anopheles coluzzii) and S form (now called nominotypical Anopheles gambiae s.s.), were identified using Restriction Fragment Length Polymorphism (RFLP). Plasmodium falciparum sporozoite rates of sampled mosquitoes and malaria status of households were evaluated microscopically and by using rapid diagnostic kits. An. gambiae Giles (sensu stricto), and bands resembling An. melas and An. arabiensisspecies complexes were observed. Out of 300 An. gambiae s.l. identified using PCR, 243 were An. gambiae Giles (sensu stricto), 6 were An. melas and 5 were An. arabiensis. Out of the 243 An. gambiae Giles (sensu stricto), 184 were M form (now An. coluzzii) and 59 were S form (now nominotypical An. gambiae s.s).
The M form (now An. coluzzii) constituted 99% of Anopheles mosquitoes from southernmost part of the study area while northernmost part showed 100% S form (An. gambiae s.s.). The median location had the M form (An. coluzzii) and S form (An. gambiae s.s.) in  sympatric. Sporozoite rate in northernmost area was highest when compared with median and southernmost parts. The S form (An. gambiae s.s.) was observed as more important malaria parasite vector, and the results revealed that geographical location affected species diversities which is an important consideration for malaria control  programme.

Keywords: Anopheles, distribution, sporozoite, malaria parasite