Entomological Assessment of the Impact of Long-term Mass Administration of Ivermectin in Onchocerciasis – Endemic Communities in Kaduna State, Nigeria.

Abstract Background: Onchocerciasis constitutes a major public health burden in endemic communities and areas because of its dermal and ocular manifestations. Nigeria accounts for the highest burden of the disease globally. Long term mass distribution of ivermectin has been recommended by the World Health Organization as a potent strategy in halting the transmission of the disease in endemic communities.Aim: The aim of this study was to evaluate the prevalence of infective blackflies after 17 years of community-based treatment with ivermectin in two onchocerciasis foci in Kaduna State, Nigeria.Method: Blood seeking female flies were collected using human landing capture from two breeding sites (River Galma and Gurara) in Lere and Kagarko LGAs of Kaduna State in 2010 and 2011. The fly heads and bodies, in pools of 100, were analysed using Polymerase Chain Reaction (PCR)-ELISA specific for O. volvulus DNA. Results: A total of 24,937 blackflies were caught during two-year catching period. The prevalence of infective flies reduced from 0.15% to 0% at River Galma and 0.08% to 0.04% at river Gurara in 2010 and 2011 catching period. Some pools containing the bodies of the flies were also positive for Onchocerca volvulus. Conclusion: The presence of O. volvulus in the heads and bodies of the black flies collected confirmed that there was ongoing transmission of onchocerciasis in Kaduna State, Nigeria during the period of survey. There is continued need for mass distribution of ivermectin in Kaduna in order to halt the transmission.