Malaria in onchocerciasis-endemic populations: patterns in two districts in the Oti and Volta regions of Ghana

Background: In Ghana and many other sub-Saharan African countries, onchocerciasis and malaria are common infectious diseases that affect people of all ages. Their geographic overlap in specific areas could influence the diagnosis and management of both diseases. This study investigated the occurrence and patterns of malaria among individuals of various age groups diagnosed with onchocerciasis in two districts: Nkwanta North District in the Oti region and Adaklu District in the Volta region of Ghana. Methods: A retrospective case-control study of 345 participants was conducted using archived blood samples collected from a prior Onchocerciasis study in 2023. Samples were selected following a 1:2 ratio of onchocerciasis seropositives to seronegatives based on an Ov16 RDT. Demographic data, including age, sex, district, and onchocerciasis status, were recorded for each participant. Malaria detection was done with the OSCAR malaria P.f/Pan antigen test kit and conventional PCR. Results: The overall malaria prevalence was 42.6% (CI 37.5% – 47.8%), with 38.7% (CI 32.9% − 44.9%) in Adaklu and 53.26% (CI 43.1% − 63.1%) in Nkwanta North. Among participants from Nkwanta North, a higher proportion of onchocerciasis/malaria co-infection (81.7%) was observed. A weak correlation but significant association was observed between malaria and onchocerciasis, which increased when age and sex was adjusted in Adaklu (OR = 2.03 overall; OR = 3.52 in Adaklu). Rapid Diagnostic Test (RDT) results compared to Nested PCR (nPCR) results in a subset of 126 participants showed an RDT sensitivity of 89.2% (CI 75.3% − 95.7%) and specificity of 71.9% (CI 61.8% − 80.2%). Conclusion: Malaria prevalence in onchocerciasis-endemic populations in Adaklu and Nkwanta North is notably high, likely influenced by environmental and socio-economic factors rather than a direct disease correlation. Integrated control strategies, including vector management and strengthened healthcare systems, are essential to reducing transmission and improving public health outcomes.