SOURCE:

Faculty: Biosences
Department: Parasitology And Entomology

CONTRIBUTORS:

Irikannu K. Chidi
Onyido A. E

ABSTRACT:

The knowledge of the breeding ecology, resting and biting habits and identification of mosquito vectors of human diseases is important for vector control measures. A study of ecology and molecular characterisation of mosquito vectors was conducted in Awka South Local Government Area, Anambra State, from October, 2016 to July, 2018. Six out of the nine communities that made up the Local Government Area namely; Amawbia, Awka, Okpuno, Nibo, Nise, and Mbaukwu were selected. The objectives of the study were to determine the abundance and breeding habitats of mosquito species, the biting and resting behaviour of the adult mosquitoes, the physiological state and malaria sporozoite rates of the female Anopheles gambiae mosquitoes. Physicochemical factors of the aquatic habitats and climatic factors were determined. Mosquito larvae were collected from the breeding habitats by dip method. Emergence traps were used to collect mosquitoes breeding in septic tanks. Indoor and outdoor biting mosquitoes were collected by human bait and pyrethrum knockdown methods. The physiological states of female mosquitoes, indoor resting density, biting rates, and influence of physicochemical parameters were studied using standard methods. Sporozoite index was determined with Enzyme-linked Immunosorbent Assays (ELISA). Molecular characterization of sibling species was done with Polymerase Chain Reaction (PCR) while extraction of the Deoxy Ribonucleic Acid (DNA) of the mosquitoes was conducted using Blood-Animal-Plant DNA preparation Kit. The sibling species of the Anopheles gambiae and Culex pipiens complex were identified in the gel image using the DNA ladder in the photo documentation machine. A total of 3,478 mosquitoes were collected from the study using different methods. Of this number, 815 (23.43%) were larvae, 1393(40.05%) were outdoor biting adults while 1270(36.51%) were indoor biting adults. There was no significant difference in the number of mosquitoes collected using different methods (P value = 0.122). Four mosquito genera and eight species were collected from the study. The eight mosquito species were An. gambiae 284(8.16%), An. funestus 143(4.11%), Aedes aegypti 333(9.57%), Ae. albopictus 227(6.52%), C. quinquefasciatus 2448(70.38%), C. tigripes 41(1.17%) while C. annuloris and Eretmapodites chrysogaster were 1(0.02%) each. The Culex species (C. quinquefasciatus, C. tigripes and C. annuloris) were the most abundant mosquito collected in the area 2490(71.57%) while E. chrysogaster was the least 1(0.02%). There was a significant difference in mosquito species collected (P value = 0.000). Only 5(10%) of An. gambiae were positive for sporozoites while 45(90.0%) were negative. Out of 150 An. gambiae complex mosquitoes that were subjected to PCR, 124(82.67%) were identified as An. gambaie s.s while 26(17.33%) were not identified. None of the 200 C. pipiens complex subjected to PCR was amplified. High abundance of the different genera of mosquitoes namely Culex, Aedes and Anopheles which are proven vectors of public health diseases in the study area indicates that the community is exposed to a variety of mosquito bites and probably mosquito-borne diseases. Also, PCR showed that An. gambiae s.s was the only sibling species of the An. gambiae complex in the study area. Rainfall had positive significant relationship to mosquito abundance (r=0.897), temperature had negative significant relationship (r=-0.775) while relative humidity had positive significant relationship (r=0.700). Total dissolved oxygen also had a positive significant relationship to the abundance of mosquito larvae in their breeding site (r=0.581). Integrated vector control which includes physical, chemical, biological and environmental management was recommended.