Abstract

Onchocerciasis, commonly known as river blindness, is a neglected tropical disease caused by the parasitic worm Onchocerca volvulus and transmitted through the bites of infected blackflies that breed near fast-flowing rivers and streams. The disease remains a public health concern in some endemic communities in Nigeria and can cause persistent itching, skin changes, visual impairment, and irreversible blindness in severe cases. The disease may also have social and economic consequences through reduced productivity, disability, and decreased quality of life among affected individuals and communities. Mass Drug Administration (MDA) is a major public health intervention for controlling and eliminating onchocerciasis and involves the periodic distribution of ivermectin to eligible populations in endemic communities. The objective of MDA is to reduce the burden of infection and interrupt transmission by reducing the number of microfilariae in infected individuals and limiting the availability of parasites to transmitting blackflies. Onchocerciasis prevalence refers to the proportion of individuals within a defined population who have evidence of onchocerciasis infection at a specified period. Sustained and adequately implemented MDA programmes are therefore important for reducing infection levels and supporting onchocerciasis elimination efforts in Nigeria. Against this background, this study investigates the effect of onchocerciasis mass drug administration on onchocerciasis prevalence among residents of endemic communities in Nigeria. The study will be anchored on the Health Belief Model, the Health Systems Framework, and the Social Ecological Model. The Health Belief Model explains preventive health behaviour through perceived susceptibility, perceived severity, perceived benefits, perceived barriers, and cues to action and provides a framework for understanding community participation in onchocerciasis MDA. The Health Systems Framework emphasizes service delivery, health workforce, health information, essential medicines, financing, and accessibility as important components of effective disease-control programmes. The Social Ecological Model recognizes that disease transmission and preventive behaviour are influenced by interacting individual, household, community, environmental, and health-system factors. Collectively, these theoretical perspectives provide a suitable framework for explaining how onchocerciasis MDA may influence onchocerciasis prevalence in endemic Nigerian communities. The study will adopt a quantitative quasi-experimental, cohort, or repeated cross-sectional research design, depending on the availability of programme and surveillance data. Data will be collected from residents of selected communities identified as endemic for onchocerciasis in Nigeria. A multistage sampling technique will be used to select states, local government areas, endemic communities, households, and eligible participants. Onchocerciasis MDA will be assessed using indicators such as MDA coverage, number of treatment rounds received, frequency of ivermectin distribution, proportion of eligible residents treated, treatment adherence, availability of ivermectin, availability of trained community drug distributors, community mobilization, health education, supervision, and programme continuity. Onchocerciasis prevalence will be assessed using appropriate parasitological or approved diagnostic methods and relevant programme surveillance procedures to determine the proportion of residents with evidence of infection. Data will be obtained from structured questionnaires, MDA registers, community drug-distributor records, health facility records, programme reports, and laboratory or surveillance records where available. Descriptive statistics will be used to summarize participants' characteristics, MDA coverage, and onchocerciasis prevalence patterns. Inferential statistical techniques, including chi-square tests, prevalence comparisons, correlation analysis, and regression analysis, will be used to determine the effect of MDA on onchocerciasis prevalence. Where baseline and follow-up data are available, changes in prevalence over time and before and after MDA implementation will be examined. Diagnostic tests will also be conducted to assess the reliability and robustness of the findings. The study is expected to find that effective onchocerciasis MDA has a significant negative effect on onchocerciasis prevalence among residents of endemic communities in Nigeria. Communities with high and sustained MDA coverage are expected to demonstrate lower levels of onchocerciasis infection than communities with inadequate or inconsistent treatment coverage. Repeated administration of ivermectin may reduce the microfilarial burden among infected individuals and consequently reduce transmission through infected blackflies. Effective community mobilization and health education may increase participation in MDA and improve treatment coverage. Regular programme supervision and monitoring may further improve the identification of individuals missed during previous treatment rounds and strengthen programme implementation. Conversely, low MDA coverage, refusal or non-acceptance of ivermectin, medicine distribution challenges, inadequate community awareness, insufficient numbers of trained drug distributors, weak supervision, and difficulties reaching remote populations may reduce programme effectiveness. However, MDA alone may not completely determine onchocerciasis prevalence because blackfly breeding conditions, environmental characteristics, population mobility, proximity to rivers and streams, individual participation in MDA, and other vector-control measures may also influence transmission. The study is expected to contribute to the literature on onchocerciasis MDA, onchocerciasis prevalence, neglected tropical disease elimination, community health, infectious disease control, epidemiology, and public health in Nigeria. The findings will provide useful information to the Federal Ministry of Health and Social Welfare, National Primary Health Care Development Agency, neglected tropical disease programme authorities, state ministries of health, local government health authorities, community health workers, community drug distributors, development partners, and policymakers regarding strategies for strengthening onchocerciasis elimination programmes. The study will also provide evidence-based recommendations for improving MDA coverage, strengthening community mobilization, ensuring consistent availability and distribution of ivermectin, improving training and supervision of community drug distributors, strengthening programme monitoring and surveillance, identifying populations missed during treatment rounds, and integrating onchocerciasis MDA with other neglected tropical disease control, community health, and vector-control interventions across endemic communities in Nigeria.

Keywords: Onchocerciasis mass drug administration, onchocerciasis prevalence, endemic communities, Nigeria, river blindness, ivermectin, neglected tropical diseases, disease elimination, MDA coverage, community health, infectious disease control, epidemiology, public health.