Climatic Determinants of Malaria Incidence in Bokkos Town, Plateau State, Nigeria

Background: Human health is significantly dependent on natural environmental factors, including air temperature, precipitation amount and relative humidity. Under global climate change, the variability of these parameters is increasing, leading to increased extreme weather events and altered seasonal disease patterns, particularly in countries with limited adaptive resources. One of the most climate-sensitive infectious diseases is malaria, a life-threatening disease caused by parasites of the genus Plasmodium, transmitted through the bites of infected female Anopheles mosquitoes. Recent research confirms that climate warming is shifting malaria risk zones to higher latitudes and altitudes, complicating disease forecasting and control. Understanding relationships of climatic factors and biological mechanisms is key to developing effective epidemiological surveillance strategies, climate-sensitive forecasting models, and resilient public health adaptation measures in the face of ongoing climate change. Despite compelling global and national evidence confirming the crucial role of temperature, precipitation, and relative humidity in controlling malaria transmission, detailed empirical studies quantifying the impact of these climatic factors on the seasonal and interannual dynamics of malaria incidence in Bokkos remain lacking. Objectives: Bokkos represents a unique natural-climatic laboratory for studying climate-driven changes in malaria epidemiology in the highlands of Nigeria. The objective of this study is to identify and quantify the relationships between climatic factors such as ambient temperature, precipitation, and relative humidity and malaria incidence dynamics in Bokkos from 2014 to 2023. Unlike previous studies, which have primarily focused on lowland or regionally aggregated data, this work aims to provide new empirical evidence reflecting the specificity of high-altitude conditions and their transformation under climate change. The study is based on the hypothesis that rising temperatures and changing precipitation patterns over the past decade have led to an extension of the malaria transmission season and an increase in seasonal peaks in Bokkos. Methods: The study was conducted in Bokkos Local Government Area located in the central part of Plateau State, Nigeria. Data on Plasmodium malaria cases were obtained from the medical registries of Bokkos Cottage Hospital, located in the study area. Records covered the period from March 1, 2014, to March 31, 2023, and included aggregated monthly data on the number of confirmed cases. All climate data were obtained from the Nigerian Meteorological Agency (NiMet) based on observations conducted at the Yakubu Gowon Airport weather station. The study had an observational design using retrospective medical and climate data, supplemented by questionnaire. The sample size for the socio-demographic component of the study was determined using the Cochran formula and there were 150 respondents. Quantitative data were analysed using SPSS and Microsoft Excel software. Inferential statistics, including the Pearson correlation coefficient, were used to assess the relationships between climate variables (temperature, precipitation, relative humidity) and malaria incidence. Research framework views malaria incidence in Bokkos as the result of complex interactions between climatic elements and the local ecosystem. Results: It was found that during the study period malaria was the most prevalent disease, accounting for 53% of all recorded cases. Typhoid fever ranked second (22%), followed by diarrhoeal diseases (14%), while respiratory diseases showed the lowest incidence (11%). The year-round persistence of malaria transmission with pronounced seasonal peaks is supported by the frequency of visits to medical canters: 44% of respondents visited more than three times per year, 31% visited two to three times, and 25% visited once per year. Precipitation showed a positive and statistically significant association with malaria incidence (r = 0.646, p < 0.05). Relative humidity was found to have an even stronger association with malaria incidence (r = 0.852, p < 0.01). Conclusion: This study confirmed that malaria remains the dominant infectious disease in Bokkos, affecting more than half of the residents surveyed between 2014 and 2023. The study supported the hypothesis that changes in rainfall patterns and high relative humidity contributed to the extension of the malaria transmission season and increased seasonal peaks of disease incidence. Relative humidity proved to be a key factor, increasing adult mosquito survival and bite frequency, while significant rainfall creates favourable conditions for vector breeding. It is shown for the first time that in a high-altitude tropical climate, humidity and precipitation are decisive factors determining the seasonality and intensity of malaria outbreaks, while temperature plays a secondary role. This fills a gap in knowledge about the local determinants of malaria transmission in the highlands of Nigeria, where only generalized regional models previously existed.