Determinants of malaria in irrigated and non-irrigated villages of Mwea: a comparative assessment

Abstract

Today, approx:imately40% of the world's population, mostly those living in the poorest countries,are at risk of malaria.l-' 'which causes more than 300 million acute illnesses and at least one million deaths annually. Ninety per cent of deaths due to malaria occur in sub- SaharanAfrica, mostly among young children. The importance of malaria cannot be overemphasized. A project, (Agro-ecosystem Management for Community-Based Integrated Malaria Control in East African Irrigation Schemes) is currently underway in Mwea Division,Kirinyaga District, Kenya, under the auspices of the International Development Research Centre (IDRC) Canada and the International Centre of Insect Physiology and Ecology (lCIPE) in conjunction with the International Water Management Institute (IWMI). The overall aim of this ICIPE-IWMI Project is to improve the health and wellbeing of communities in irrigation schemes through the development of sustainable strategiesfor reduction of malaria and other health risks based on improved agro-ecosystem management. In Kenya, a considerable part of the area under irrigation is for rice production. The choice of Mwea is appropriate since it provides an ideal setting in which humanhealth can be factored into agro-ecosystem .research, thereby meeting the objectives of the ICIPE-IWMI Project. This cross-sectional descriptive study was part of the larger ICIPE-IWMI Project. Its main objectivewas to compare malaria prevalence and to assess the potential environmental and socio-economicdeterminants of the disease in irrigated (Ciagi-ini and Mbui Njeru) and non- irrigated(Kagio and Murinduko) villages of Mwea. Quantitative data was obtained from one cycleof malaria prevalence su.:rveys,undertaken in two villages within the irrigated area thatwere matched with two control villages in the non-irrigated area beyond the flight range of mosquitoes. This collective Malaria Prevalence Survey was carried out on 213 children aged 9 years and under, in December 2001 and February 2002. The response rate was 74.5%. Qualitative data was obtained through participatory methodologies carried out within the four villages and involved selected stakeholders and other target groups from Mwea. In addition, a Community Diagnosis was carried out in 420 households within the fourvillages. Malariawas ranked as the major health problem in all the four study villages (except at the Stakeholders'Consultative Workshop where it was ranked second). Within the irrigated villages,malaria, alcoholism, and lack of clean water were the predominant problems. Within the non-irrigated villages, the predominant problems were poor nutrition, HIV/AIDS, lack of sewerage systems, poverty, and ignorance. Poverty was not perceived asa problem at allwithin the irrigated villages but was a problem in Murinduko village in the non-irrigated area. Kagio, also in the non-irrigated area, was perceived to be relatively wealthy. Community Diagnosis generated inclusive quantitative household data on health, incomes,and the environment. A comparison of results from quantitative and qualitative data showed a high degree of consistency. However, an inconsistency occurred in Mbui Njeruvillagewhere the qualitative data ranked malaria as the major health problem whereas the quantitative data from the Malaria Prevalence Survey, which was conducted during the wetseason,showed no positive cases of malaria. The Malaria Prevalence Survey results showed that the overall prevalence for the four villageswas 23.5 per 100. Within the irrigated villages, the prevalence was 6.7 per 100, while in the non-irrigated villages it was 36 per 100, indicating that malaria prevalence was higher within the non-irrigated villages than within the irrigated villages. Relatively more males (68%)than females (32%) were positive for malaria parasites despite the roughly equal distribution of the sexes. Malaria prevalence was significantly related to the age and occupation of the household head, with those household heads that were that were in the 41-50year age group and those that were unemployed/reti:red having the highest p:roportion of children with a positive blood slide. In addition,there was a significant relationship between malaria prevalence and type of house. The majority (78%) of child:ren with a positive blood slide lived in temporary structu:res. There was no significant relationship between use of bed nets and a positive blood slide. However, there were significant differencesin reported use of bed nets between irrigated and non-irrigated villages. More respondents in the irrigated villages reported that all household members used bed nets as compared to the non-irrigated villages. More respondents in the non-irrigated villages reportedthat they did not use bed nets at all. Therewas a significant relationship between the use of anti-malarial drugs in the preceding three days and a positive blood slide. Most of the children who had used an anti-malarial drughad a negative blood slide. The averagenumber of Anopheles arabiensis mosquitoes in a house was significandy related to irrigationand to a positive blood slide. There was also a significant difference in the average number of Anopheles arabiensis mosquitoes in a house between irrigated and non-irrigated villages. Houses that had a lower average number of Anopheles arabiensis mosquitoes had a higherproportion of positive blood slides. This cross-sectional survey only revealed the malaria situation at one point ill time. Therefore, study that is more extensive is required in order to p:rovide a wider pictu:re of malariain Mwea throughout the year. More research is necessary to explain the unusual differencein malaria prevalence between irrigated and non-irrigated villages. More work: is alsoneeded to investigate other findin~ such as the difference in prevalence between the sexes,and between villages with a predominance of cattle and those with a predominance of other types of livestock. The symptoms of malaria are similar to those of other illnesses, notably typhoid, and this may partly explain the apparent mconsistency between qualitative and quantitative data on malariaprevalence observed in Mbui Njeru village. Ecologicaldevelopment may have important effects on the epidemiology of vector borne diseasessuch as malaria. This may be particularly significant where disease transmission is unstablefor example, in highland areas. Intersectional partnership is necessary, such as was the case in this study, in order to reduce the disease burden in Mwea. Understanding communityperceptions of aetiology, symptom identification, and treatment of malaria is an important step towards control of the disease. Moredetailed and ongoing research is vital if lasting solutions are to be found. Research projects should of necessity be participatory at all stages, such as was the case with the ICIPE-IWMI Project, and even more importantly, continuous, because of the need for monitoring,evaluation, and sharing of new information among concerned parties. The residents of Mwea require empowerment in terms of acquisition of relevant health education and sound economic and business principles in order to improve their socioeconomicstatus and therefore be able to adopt malaria-prevention measures.