Vulnerability Mapping of Malaria Occurrences in the North-Central Region of Nigeria using Temperature Thresholds as an Indicator

ABSTRACT Health, water and food constitute the basic needs of man. However, resurgence of infectious disease poses threats to health, food and hence socio economic activities of man on planet earth. Malaria is the most common serious infectious disease worldwide. Although the problem is worldwide, Africa is most endemic of all continents. Out of between 1 million to 1.5 million malaria deaths recorded per year globally, 80% of the cases were from Africa (Bradley 1996). Based on the report of the American Association for the Advancement of Science (AAAS) Washington D.C of 1991 on malaria and development in Africa, pregnant women and children under the age of five are at high risk of malaria morbidity and mortality. Despite all the efforts of World Health Organization (WHO) to prevent malaria disease in Nigeria, it still maintains its status as one of the killer diseases affecting millions of people. Malaria has been ranked the second killer disease after measles in Nigeria (Iyun, 1987). WHO (2000) made a forecast of an increase of 16% growth in malaria annually. It has been identified as one of the leading health threats for the 21st Century as it kills in one year what the dreaded AIDS kills in 15 years. The most worrisome aspect of it is that all measures of control through the use of drugs seem ineffective as mosquitoes show resistance and become immune to the application of various antibodies and insecticides. Some malaria parasites have also developed resistance to most anti-malaria drugs (Epstein, 1977). Scott et al., (2000) in line with the above findings suggested that health should be pursued and not just focusing on curative medicines alone but as well on preventive measures which should include examination of vulnerability and risk factors as well as environmental factors. Thus this study attempts vulnerability mapping of North – Central Nigeria using temperature threshold values for egg hatching of Anopheles gambiae mosquito in order to understand current and possible future related risks of the region to malaria disease. Temperature threshold for hatching of egg is used because that is the first stage in the life cycle of mosquito. If this stage can be interrupted the entire system collapses and this will result in drastic reduction in the population of adult mosquito. Temperature has been identified as a critical factor that affect the rate at which the immature stages of mosquito insect develop into adults (Lassiter et al, 1995 cited in Bayoh and Lindsay 2004). Five out of eight states in the North – Central states of Nigeria were randomly selected for this study. These states are Kogi, Kwara, Kaduna, Plateau and Abuja-the Federal Capital Territories. Both minimum and maximum temperatures were collected from the selected stations for the period of thirty years which spanned between 1983 and 2012. The data was collected on monthly basis but later partitioned on annual basis and time series analysis was used to identify trend and relate to vulnerability of each state to global warming. Optimal temperature for Anopheles gambiae egg hatching ranges between 24 to 260C (Bayoh and Lindsay, 2004). This has a mean value of 250C. Decadal variations from mean on time series was calculated using the above threshold values. The results showed that Kogi State recorded both the highest maximum and minimum temperature while Plateau State observed the lowest maximum and minimum temperatures. All the states considered experienced a rise in temperature between the study period of 1983 and 2012. The temperature rise is in the following order ; Kaduna State by 0.021ᵒC, Abuja by 0.078ᵒC, Plateau State by 0.018ᵒC, Kwara State by 0.016ᵒC and Kogi State by 0.009ᵒC in the thirty year period of 1983 and 2012. The result also showed three states namely Kwara, Abuja and Kaduna were found vulnerable to high malaria occurrence during the first decade of 1983 to 1992, Kaduna State was the only State vulnerable during the second decade of 1993 to 2002 while Kwara and Kaduna were identified as endemic in the third decade of 2003 – 2012. Kaduna State was perpetually endemic throughout the period of study. Predicted mean annual temperature in the North Central Nigeria using five year moving average showed an increase of 0.03ᵒC. Temperature in the study area is expected to rise by 0.045ᵒC by year 2018 and 2.71ᵒC by year 2042. The predicted decadal vulnerability level of the selected states showed that Kwara, Kaduna and Plateau will be endemic to malaria disease through the three decades of 2013 to 2042. Thus various ways of mitigating and some forms of coping strategies are suggested to reduce this possible endemic vulnerability of the states. Useful and minimal cost malaria control to people in the third world region where mosquito is prevalent are clearing immediate surroundings of human habitation and reducing water collection in open containers after rainfall. This will help to reduce breeding places of mosquitoes. More general approaches would include reduction of aerosol ejection into the atmosphere by industries, bush burning by farmers and game hunters, fossil fuel combustion and the likes in order to minimize the anticipated increase in mean temperature. Immediate action could include increase in the distribution of treated mosquito nets. Key words: Mosquito, Malaria, Temperature, Health, Food