Entomological Assessment Of Lymphatic Filariasis Transmission In Selected Communities In Ghana

Abstract

Resurgence of lymphatic filariasis (LF) infection after several rounds of Mass Drug Administration (MDA) has been the main reason behind constant monitoring of treatment. The MDA is designed to interrupt transmission by reducing microfilaraemia in a community to a threshold that local vectors may not be able to pick up microfilariae (MF) during a blood meal. The current study has been carried out to determine whether transmission had actually been interrupted following stoppage of MDA in the Anyakpor (Greater Accra region), Voggu Kpalsogo (Northern Region) and New Bakanta (Western region) communities, which had undergone several rounds of MDA treatment. Similar work was also done in Dwease in the Ashanti region, a site located within a non-endemic area to determine whether transmission is still absent there or not. This entomological assessment was done by collecting mosquitoes using the Pyrethrum spray collection (PSC), Human landing catches (HLC), and CDC light trap (LT) methods. In all, a total of 700 mosquitoes were collected with 251 (35.9%), 99 (14.1%), 97 (13.9%) and 253 (36.1%) obtained from Anyakpor, Dwease, Voggu Kpalsogo and New Bakanta respectively. The mosquitoes were dissected under a dissecting microscope and larval stages of Wuchereria bancrofti detected with the aid of a compound microscope. Following molecular identification of different species of mosquitoes, 10 mosquitoes of the same species were pooled together in a tube. A total of 74 pools were constituted, conventional polymerase chain reaction (PCR) and Real time PCR (RT-PCR) were performed on them for the detection of the parasite larvae. Microscopy revealed no larval stages of W. bancrofti, but 1 pool each from Anyakpor and New Bakanta communities revealed positives using the conventional PCR method. Using the RT-PCR method 17 (22.9%) of the pools were found to be positive. Of these 17 positive pools, 13 (76.5%), 3 (17.7%) and 1 (5.9%) belonged to the Anyakpor, Voggu Kpalsogo and New Bakanta communities respectively. The mosquito species in the positive pools consisted of An. gambiae ss, An. coluzzii and An. melas, all of which belong to the An. gambiae complex. In conclusion, this study has detected An. gambiae ss, An. coluzzii and An. melas and has revealed that active transmission of LF by them is ongoing in the Anyakpor, Voggu Kpalsogo and New Bakanta communities. The study also confirms the absence of transmission in Dwease notwithstanding the prevalence of An. gambiae ss and An. coluzzii there.