The use of geographic information systems to identify the winter breeding sites of the Anopheles mosquitoes in Northern KwaZulu-Natal.
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Date
2001
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Abstract
Malaria incidence in the province of KwaZulu-Natal is influenced by seasonal climatic variations,
drug and insecticide resistance, and population mobility within the region. Current control
methods are directed at the malaria vector, the Anopheles arabiensis mosquito, through indoor
residual spraying. Control of the dominant malaria parasite, Plasmodium falciparum, is done by
treatmenting the symptomatic and asymptomatic parasite carriers with prophylactic medications
of. A ceiling of effectiveness with current control efforts have been reached, necessitating the
search for supplementary methods.
The study area is located in the Ingwavuma District of northern of KwaZulu-Natal which adjoins
the Mozambique border to the north, and includes the malaria areas of Ndumu and Makanisdrift.
Homestead location coordinates were obtained with Global Positioning System (GPS) receivers
and linked to malaria case records through homestead numbers which have been allocated to all
homes in the area. The study includes the cases reported during 1993 and 1994 as this was the
only data available when the project commenced in 1995.
A geographic information system was used to undertake the spatial analysis to test the hypothesis
that the malaria vector, Anopheles arabiensis, is localised to certain breeding sites during the
winter months in northern KwaZulu-Natal. Identification of these winter 'seed point' breeding
sites from which the onset of transmission spreads during the following malaria season, will allow
them to be targeted for winter larval control measures. This will contribute to limiting the
distribution and lowering the levels of malaria intensity in the region as a whole. The analysis
also provided evidence of the maximum likely flight distance of the female mosquito given an
adequate host supply in close proximity, thereby identifying those areas requiring additional
prevention and control activities. Understanding the local epidemiology of the disease was
necessary to determine which monthly malaria cases to include in order to identify the winter
breeding sites, due to seasonal variations in the length of the mosquitoes life cycle.
Medical geography, as a sub-discipline of geography, combines investigating spatial patterns with
the epidemiological principles of medicine and zoology through scientific methods. It is
traditionally divided into two approaches, the first being the geography of disease, under which
this research falls, and the second being the geography of health care. The integration of the two disciplines allowed the results of the analysis to be presented in maps, graphs and tables in order
to describe, interpret, test and explain possible associations between the location of the potential
breeding sites and the homesteads at which the malaria cases were reported. The potential
breeding sites consisted of the perennial pans, non-perennial pans and dams. Zones were created
in the GIS at one kilometre intervals from these sites up to a distance of four kilometres, and the
number of cases within each zone determined and corrected for the population at risk per 1000
people for comparative purposes. This spatial analysis was followed by the statistical analysis of
the results to verify the findings.
The results of the spatial and statistical analysis indicated that the perennial pans were used as the
winter 'seed point' breeding sites, and that the maximum likely flight distance of the female
mosquito, given an adequate host supply in close proximity, is 4 kilometres. The results will be
made available to the local malaria research and control community who will assess the feasibility
of implementing supplementary control measures.
Description
Thesis (M.Sc.)-University of Natal, Durban, 2001.
Keywords
Mosquito control., Anopheles., Malaria--KwaZulu-Natal--Prevention., Geographic Information Systems., Theses--Geography.