Assessing the Entomological Parameters of Malaria Vectors in Anambra State, Southeast Nigeria

Adequate knowledge of entomological parameters within a defined geographic endemic area is basic for effective planning of malaria vector control for malaria elimination. The study investigated sibling species of malaria vectors, indoor resting density (IRD), human biting rate (HBR), blood meal source (BMS), human blood index (HBI), sporozoite rate (SR) and entomological inoculation rate (EIR) of malaria vectors in Awka North, Awka South and Njikoka Local Government Areas in Anambra State, southeast Nigeria. Pyrethrum spray collection (PSC), Centre for Disease Control (CDC) light trap, and human landing catch (HLC) techniques were the methods used for collection of indoor and outdoor malaria vectors. Mosquitoes collected were sorted according to species and sex; and identified using standard morphological and molecular techniques. Chi-square test was used for data analysis. A total of 2,870 Anopheles mosquitoes were collected, male 1949 (67.9%) and female 921 (32.1%). All female species identified morphologically belong to the Anopheles gambiae s. l. complex. From the molecular and siblings species separation, Anopheles gambiae recorded the highest abundance of 54.2% and Anopheles coluzzii the least abundance of 45.8%. The IRD was found to be 1.40 per man per night with an average HBR of 5.05. The blood meal source showed that human blood source was the highest number with 46.2%, followed by goat blood source with 32.7%, and combination of human and goat blood was the least with 21.2%. The result also showed a HBI of 0.51 whereas the test for the presence of circumsporozoite protein (CSP) of Plasmodium falciparum shows that none of the malaria vectors was positive for sporozoite; thus, the EIR could not be determined and compared among the study population. The values of the entomological parameters and the allopatric breeding of the two sibling species of Anopheles gambiae and Anopheles coluzzii reported in this study which is probably the second of such report in Nigeria has a huge implications for malaria vector control and malaria control in Anambra State, Southeast Nigeria.