Abstract
Background: This serological study conducted between March and July 2015 investigated the status of onchocerciasis in Ogun State, Nigeria after a decade of mass drug administration (MDA) with ivermectin. Baseline information from the rapid epidemiological mapping of onchocerciasis (REMO) prior to MDA had indicated that Ogun State was meso-endemic to onchocerciasis. Following years of treatment with ivermectin, it has become important to investigate the current status of the disease using more sensitive diagnostic methods.Methods: The study was conducted in 32 communities in eight onchocerciasis-endemic local government areas (LGAs). Using the Ov16 rapid diagnostic test (Ov16 RDT), finger-prick whole blood was obtained from 3 895 consented participants from age five and above. Skin snips were obtained from a subset of 481 corresponding participants as the majority of community members did not consent to skin snipping.Results: Study revealed a cumulative seroprevalence of 9.3% (CI 9.29–9.31%) by RDT and 17.3% (CI 16.73–18.34%) microfilaridermia prevalence by the skin snip subset. Seroprevalence among children between the ages of five and nine was 2.9% (CI 1.74–3.53%) across all LGAs. A community microfilaria load (CMFL) between 0 and 1.21 MF/skin snip was recorded in the different communities studied. Among the studied LGAs, children in Odeda LGA recorded the highest seroprevalence by RDT (14.9%) followed by Abeokuta North (5.1%), Abeokuta South (4.8%) and Imeko-Afon (0.6%), while Ewekoro, Ifo, Obafemi-Owode and Yewa North LGAs recorded zero prevalence.Conclusion: It appears that the elimination of onchocerciasis in some LGAs is possible considering the lack of new infection among children and the hypo-endemicity among the adult population. However, the microfilaria prevalence observed among adults is of concern as it may imply that mass treatment has not been effective. Increased therapeutic coverage is advised to fully maximise the potential of ivermectin treatment to achieve the disease elimination.
Highlights
OA Surakata*, SO Sam-Woboa, T De Los Santosb, D Faulxb, A Goldenb, K Ademolua, L Yokobeb, MA Adelekec, SO Bankolea, ON Adekunled, WA Abimbolad and CF Mafianae aDepartment of Pure and Applied Zoology, College of Biosciences, Federal University of Agriculture, Abeokuta, Nigeria bProgramme for Appropriate Technology in Health (PATH), Seattle, WA, USA cDepartment of Biological Sciences, Osun State University, Osogbo, Nigeria dDepartment of Plant Science and Applied Zoology, Olabisi Onabanjo University, Ago-Iwoye, Nigeria eDeputy Executive Secretary’s Office, National University Commission, Abuja, Nigeria ‡Part of the work had been presented as a poster at the European and Developing Countries Clinical Trial Partnership (EDCTP) summit in Lusaka, Zambia between 5-9 November, 2016. *Corresponding author, email: banjisurakat@gmail.com. This serological study conducted between March and July 2015 investigated the status of onchocerciasis in Ogun State, Nigeria after a decade of mass drug administration (MDA) with ivermectin
It appears that the elimination of onchocerciasis in some local government areas (LGAs) is possible considering the lack of new infection among children and the hypo-endemicity among the adult population
Control of onchocerciasis is anchored on annual mass drug administration (MDA) of ivermectin (Mectizan®, donated by Merck & Co., Inc., NJ, USA) a freely distributed potent microfilaricide which kills the O. volvulus microfilaria in the human host and reduces greatly the disease burden
Summary
This serological study conducted between March and July 2015 investigated the status of onchocerciasis in Ogun State, Nigeria after a decade of mass drug administration (MDA) with ivermectin. Onchocerciasis is an irreversible blinding disease associated with infection with the parasite Onchocerca volvulus, which is transmitted by insect vectors of the Simulium species It is distributed mostly along communities with fast-flowing rivers with rocky vegetation, which serves as suitable breeding ecology for the vectors.[1,2,3] The disease is of global concern as it is found in 31 African countries, Yemen and South America with confirmed elimination in Mexico, Ecuador, Guatemala and Colombia.[4,5,6,7,8] Nigeria ranks among those countries with the highest burden of the disease in the world, accounting for about a third of the global prevalence.[9,10,11,12]. While this model is exhaustive, factors such as baseline infection rate, endemicity (intensity of transmission) and numerous programmatic issues e.g. (85% therapeutic coverage and adherence) have suggested that 5–15 years of mass treatment with ivermectin could interrupt transmission.[4,5,6,7,8,9,10,11,12,13,14,15] As a result of long-term treatment with ivermectin, elimination of onchocerciasis in certain foci in Africa appears to be possible.[16,17,18] Successes recorded in MDA and increased global efforts to eliminate onchocerciasis and other neglected tropical diseases (NTDs) as a public health concern by the World Health Organization has called for a need for fielddeployable sensitive diagnosis and disease surveillance tools.[19,20]
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