Effect of seasonal variability on the incidence and transmission patterns of malaria in Urban, Peri-urban and Rural Communities around Kumasi, Ghana

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Changes in temperature, rainfall and relative humidity are expected to influence malaria directly, by modifying the behaviour and geographical distribution of malaria vectors and by increasing or decreasing the length of the life cycle of the parasite. This study was aimed at investigating the impact of these changes on malaria incidence in the Kumasi metropolis and a rural district in the Ashanti region, Ghana. Data on climatic variables from December 2009- November 2011 were obtained from the Owabi, Emena and Airport weather stations. Data on malaria cases from December 2009- November 2011 were obtained from Nkawie hospital (near Owabi weather station), Aninwaa Medical Centre (near the KNUST Weather station) and Manhyia hospital (near Airport weather station) from December 2009- November 2011. Based on malaria morbidity data, three communities were selected and sprayed for mosquitoes using the pyrethrum spray catch method. Data analysis was conducted with Microsoft Excel and Statistical Software Package, SPSS version (16.0). Pearson’s correlation analysis was done to establish the relationship between climatic variables and malaria transmission. In all the communities, Anopheles gambiae was the highest mosquito vector caught with few or no Anopheles funestus over 60% of which were fed with the dry season recording the highest percentage of fed mosquitoes. Over 90% of the fed mosquitoes had fed on human blood. Sporozoite rates for Nkawie were 6% between April and July 2011, 5.6% between August and November 2011 and 2.6% between December 2010 and March 2011. In Emena, the rates were 4.0%, 5.0% and 3.0% between April and July 2011, August and November 2011 and December 2010 and March 2011 respectively while Asawasi had 6.6%, 4.8% and 5% April and July 2011, August and November 2011 and December 2010 and March 2011 respectively. The annual Entomological inoculation rates (EIR) for Nkawie were 245.6, 203.6 and 52.4ib/p/yr April and July, August and November and December 2010 and March 2011. In Emena, August to November recorded the highest annual EIR of 182.5ib/p/yr, followed by April to July with a value of 175.2ib/p/yr and then December 2010 to March 2011with 94.9ib/p/yr. In Asawasi, April to July recorded the highest annual EIR of 245.4ib/p/yr followed by August to November and December 2010 and March 2011with 229.9ib/p/yr and 109.5ib/p/yr respectively. There were direct xii relationships between minimum temperature and human bite rate, maximum temperature and sporozoite rates, rainfall and number of mosquitoes caught during the study period and between malaria incidence and the entomological inoculation rate. There were also indirect relationship between maximum temperature and the number of mosquitoes caught. This research shows that malaria transmission is caused by a multiplicity of factors including climatic, environmental and socioeconomic factors. These factors play diverse roles on malaria vector biology as well as on the parasite.
A thesis submitted to the Department of Clinical Microbiology, College of Health Sciences, Kwame Nkrumah University of Science and Technology in fulfilment of the requirements for the award of Master of Philosophy in Clinical Microbiology, 2014