A theoretical model of malaria populations is constructed in an attempt to reflect the important features of the human-mosquito-malaria system under the key assumption that strain-specific immunity occurs, and is controlled by alleles at a single locus (to be referred to as the immuno-allelic locus) in the parasite genome. The model is more realistic with regard to the nature of malaria than previous models of strain-structured malaria populations, and includes such features as a short period of immune memory and competition between parasites growing in hosts. The model is complex, and is thus designed to be examined through computer simulation. Both the epidemiological and genetic effects of strain structure on malaria populations are studied. For example, the effects of the number alleles at the immuno-allelic locus on the proportion of hosts infected are examined. Also, the degree of genetic heterogeneity of malaria parasites inside hosts compared to the total level of genetic heterogeneity of the parasite population is examined. This is done by calculating the value of the statistic G<SUB>ST</SUB> for a neutral locus in the parasite genome (referred to as G<SUB>ST</SUB>(n)). The degree of genetic heterogeneity in a parasite population is of interest as it determines the degree to which sexual recombination will lead to the generation of novel genotypes. The generation of such novel genotypes is important as it may allow evasion of a new vaccine, or the development of resistance to anti-malarial drug. In the simulations examined, G<SUB>ST(n)</SUB> is found to decrease (the degree of genetic heterogeneity increases) with increasing numbers of alleles at the immuno-allelic locus. It also decreases with increasing levels of transmission in the population. This latter result appears to agree qualitatively with the findings of recent population-genetic field studies. The importance of taking into account the epidemiology of a parasite population when examining its genetics is also highlighted. Finally, the importance of the effects of a strain structure on methods of control of malaria populations are discussed.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:663606 |
| Date | January 1997 |
| Creators | Wedgwood-Oppenheim, Bruce Andrew |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/13219 |
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