Abstract:
Malaria remains a major public health problem in Africa, with An. funestus as one of the principal vectors. In the control of malaria, vector control has been successfully implemented in many malaria-endemic countries with indoor residual spraying (IRS) as an existing front-line measure. IRS has been implemented in some selected sites in Northern Ghana since 2009 and its effect on the members of An. funestus is poorly understood. Therefore, this study was aimed at investigating the species composition, malaria transmission and insecticide resistance status of An. funestus Giles group in three selected sites in Northern Ghana. Samples were collected using human landing catch (HLC) and pyrethrum spray collection (PSC) techniques from two IRS areas (Tolon and Savelugu Districts) and one non-IRS area (Tamale District). Archived samples (samples from 2010, 2013 and 2014) and newly collected samples (from 2015) were analysed. A total of 688 adult females morphologically identified as An. funestus mosquitoes were recorded in these districts across the years. The percentage abundance of these samples per site were 85.32 %, 3.20 % and 11.48 % for Tolon, Savelugu and Tamale Districts respectively across the years. Further identification using PCR revealed that An. funestus s.s was the only member of the group present in these study sites. The man-biting rates of the mosquitoes collected in Tolon district was significantly higher (P < 0.001) as compared with the other study sites. The heads and thoraces of individual An. funestus samples were tested for the presence of circumsporozoite proteins of P. falciparum using ELISA. Sporozoite infectivity rates of 2.98 %, 0 % and 1.43 % were recorded for Tolon, Savelugu and Tamale Districts respectively. There was no statistically significant difference (P > 0.05) in the sporozoite rates between the study sites. Blood meal analysis of the abdomen of these mosquitoes using ELISA revealed an overall human blood index of 31.50 %, 18.18 % and 32.86 % for Tolon, Savelugu and Tamale Districts across the years and a statistically significant difference (P < 0.001) between the study sites. PCR detection of kdr gene analysed in these mosquitoes showed 38.57 % possible mutation of the target site from samples collected in Tolon District. The results from this study indicate the importance of An. funestus s.s. as an effective malaria vector. Entomological monitoring and complementary vector control of the species are needed in order to control the species and preserve the efficacy of IRS.
