Abstract
This study predicts the ultimate probability of survival of a newly arisen drug resistant mutant in a population of malaria parasites, with a view to understanding what conditions favour the evolution of drug resistance. Using branching process theory and a population genetics transmission model, the probabilities of survival of one- and two-locus new mutants are calculated as functions of the degree of drug pressure, the mean and variation in transmission rate, and the degree of natural selection against the mutant. Probability of survival increases approximately linearly with drug pressure, the slope of the line increasing with mean transmission rate. Thus increased drug pressure, especially in combination with high transmission rates, strongly favours the evolution of drug resistance. These conclusions also hold for the case of multiple drug resistance where it is coded for by two unlinked loci: the greater effective recombination breakdown in high transmission areas is counteracted by greater effective selection so that the net effect of higher transmission rates is to favour the evolution of multiple drug resistance. High variability in transmission rate and natural selection against the mutants are unfavourable to mutant survival, though these are relatively weak forces.
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- Babiker H. A., Ranford-Cartwright L. C., Currie D., Charlwood J. D., Billingsley P., Teuscher T., Walliker D. Random mating in a natural population of the malaria parasite Plasmodium falciparum. Parasitology. 1994 Nov;109(Pt 4):413–421. doi: 10.1017/s0031182000080665. [DOI] [PubMed] [Google Scholar]
- Björkman A., Phillips-Howard P. A. The epidemiology of drug-resistant malaria. Trans R Soc Trop Med Hyg. 1990 Mar-Apr;84(2):177–180. doi: 10.1016/0035-9203(90)90246-b. [DOI] [PubMed] [Google Scholar]
- Carter R., McGregor I. A. Enzyme variation in Plasmodium falciparum in the Gambia. Trans R Soc Trop Med Hyg. 1973;67(6):830–837. doi: 10.1016/0035-9203(73)90011-4. [DOI] [PubMed] [Google Scholar]
- Conway D. J., Greenwood B. M., McBride J. S. The epidemiology of multiple-clone Plasmodium falciparum infections in Gambian patients. Parasitology. 1991 Aug;103(Pt 1):1–6. doi: 10.1017/s0031182000059217. [DOI] [PubMed] [Google Scholar]
- Curtis C. F., Otoo L. N. A simple model of the build-up of resistance to mixtures of anti-malarial drugs. Trans R Soc Trop Med Hyg. 1986;80(6):889–892. doi: 10.1016/0035-9203(86)90248-8. [DOI] [PubMed] [Google Scholar]
- Dye C. Population genetics of nonclonal, nonrandomly mating malaria parasites. Parasitol Today. 1991 Sep;7(9):236–240. doi: 10.1016/0169-4758(91)90236-h. [DOI] [PubMed] [Google Scholar]
- Dye C., Williams B. G. Multigenic drug resistance among inbred malaria parasites. Proc Biol Sci. 1997 Jan 22;264(1378):61–67. doi: 10.1098/rspb.1997.0009. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Gupta S., Swinton J., Anderson R. M. Theoretical studies of the effects of heterogeneity in the parasite population on the transmission dynamics of malaria. Proc Biol Sci. 1994 Jun 22;256(1347):231–238. doi: 10.1098/rspb.1994.0075. [DOI] [PubMed] [Google Scholar]
- Hill W. G., Babiker H. A. Estimation of numbers of malaria clones in blood samples. Proc Biol Sci. 1995 Dec 22;262(1365):249–257. doi: 10.1098/rspb.1995.0203. [DOI] [PubMed] [Google Scholar]
- Hill W. G., Babiker H. A., Ranford-Cartwright L. C., Walliker D. Estimation of inbreeding coefficients from genotypic data on multiple alleles, and application to estimation of clonality in malaria parasites. Genet Res. 1995 Feb;65(1):53–61. doi: 10.1017/s0016672300033000. [DOI] [PubMed] [Google Scholar]
- Koella J. C. On the use of mathematical models of malaria transmission. Acta Trop. 1991 Apr;49(1):1–25. doi: 10.1016/0001-706x(91)90026-g. [DOI] [PubMed] [Google Scholar]
- Ntoumi F., Contamin H., Rogier C., Bonnefoy S., Trape J. F., Mercereau-Puijalon O. Age-dependent carriage of multiple Plasmodium falciparum merozoite surface antigen-2 alleles in asymptomatic malaria infections. Am J Trop Med Hyg. 1995 Jan;52(1):81–88. doi: 10.4269/ajtmh.1995.52.81. [DOI] [PubMed] [Google Scholar]
- Paul R. E., Packer M. J., Walmsley M., Lagog M., Ranford-Cartwright L. C., Paru R., Day K. P. Mating patterns in malaria parasite populations of Papua New Guinea. Science. 1995 Sep 22;269(5231):1709–1711. doi: 10.1126/science.7569897. [DOI] [PubMed] [Google Scholar]
- Wernsdorfer W. H. The development and spread of drug-resistant malaria. Parasitol Today. 1991 Nov;7(11):297–303. doi: 10.1016/0169-4758(91)90262-m. [DOI] [PubMed] [Google Scholar]