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Preliminary studies on human lymphatic filariasis transmission control trials using Insecticide Treated Bednet (ITBN) in parts of Imo State, Nigeria


A.A. Amaechi
B.E.B. Nwoke
C.N. Ukaga
I.R. Keke
C.M.U. Ajero
J.I. Iwunze

Abstract

Human lymphatic filariasis (LF) is a significant public health problem in many tropical and sub tropical countries resulting in disfigurement and disability which warrants preventive action. The effectiveness of insecticide-treated bednet (ITBN) was compared in selected sentinel villages of Imo State, Nigeria, between February 2009 and December 2011, to evaluate their potential for LF control. Two cohorts were used; ITBN-full coverage/wide scale use and ITBN-vulnerable coverage/ selective use. Endophilic mosquitoes caught twice a month by pyrethrum spray catch (PSC) and day resting indoor collection (DRI) with aspirator were identified using standard morphological keys. Of 8,349 engorged female mosquitoes dissected/ examined for parity infection/infectivity status with Wuchereria bancrofti larvae, 60.88% (5,088/8,349) and 39.12% (3,266/8,349) represented ITBN-vulnerable and ITBN-full coverage catches respectively. Overall, ITBN-vulnerable cohorts collections were insignificantly higher than ITBN-full coverage cohorts (62.31% versus 37.69%, 59.22% versus 40.73%, 62.22% versus 37.78%) for 2009, 2010 and 2011 respectively. Five species present in both cohorts comprised Anopheles gambiae s.l., the most abundant (85.19% versus 74.04%), An. funestus s.l. (8.42% versus 12.19%) and Cx. quinquefasciatus (5.88% versus 3.83%) while Aedes aegypti and Mn. africana were rarely present. Village-specific vector densities/relative abundance from ITBN-vulnerable cohorts and ITBN-full cohorts showed no significant difference (p>0.05). Similarly, the physiological, infection (0.18% versus 0.49%) and infectivity status (0.00% versus 0.00%) were insignificant between the cohorts (p>0.05). The study highlights the importance of integrating vector borne disease interventions in the on-going plan to eliminate LF and the transmitting mosquito vectors in Nigeria.

Keywords: Lymphatic filariasis; ITBN-full household coverage; ITBN-vulnerable household coverage; W. bancrofti; vectors


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