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Transmission and Cross-Mating of High-Level Resistance Plasmodium falciparum Dihydrofolate Reductase Haplotypes in The Gambia
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
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2010 (English)In: American Journal of Tropical Medicine and Hygiene, ISSN 0002-9637, ISSN 20348495, Vol. 82, no 4, 535-541 p.Article in journal (Refereed) Published
Abstract [en]

A high-level pyrimethamine resistance Plasmodium falciparum lineage with triple dihydrofolate reductase (dhfr) mutations prevails across Africa. However, additional minority lineages were seen. We examined transmission success of mutant dhfr haplotypes among 22 children in The Gambia and 60 infected Anopheles gambiae mosquitoes fed on their blood. Additional polymorphic genes of the gametocyte-specific protein (pfg377) and merozoite surface protein-1 (MSP-1) were examined. Similarities were seen between pfg377 and MSP-1 alleles in children and mosquitoes and evidence of cross-mating between different parasite genotypes was seen in some infected mosquitoes, reflecting high transmission success of existing clones. With regard to dhfr, 16 haplotypes were seen among the children: 2 carried double mutations and 14 carried triple mutations. However, only nine haplotypes, all with triple mutations, were detected among mosquitoes. A single triple-mutant dhfr haplotype, similar to that in other countries in Africa, predominated among children (42%) and mosquitoes (60%), supporting the hypothesis of migration of this haplotype across Africa. However, evidence of cross-mating between the above haplotypes signifies the role of local evolution.

Place, publisher, year, edition, pages
2010. Vol. 82, no 4, 535-541 p.
National Category
Medical and Health Sciences Biological Sciences
URN: urn:nbn:se:uu:diva-137624DOI: 10.4269/ajtmh.2010.09-0378ISI: 000276219700006OAI: oai:DiVA.org:uu-137624DiVA: diva2:378576
Available from: 2010-12-15 Created: 2010-12-15 Last updated: 2011-06-28Bibliographically approved
In thesis
1. Factors Influencing Evolution to Antimalarial Drug Resistance in Plasmodium falciparum in Sudan and The Gambia
Open this publication in new window or tab >>Factors Influencing Evolution to Antimalarial Drug Resistance in Plasmodium falciparum in Sudan and The Gambia
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Drug resistance is a major obstacle to management and control of malaria and currently progressing at a rapid rate across Africa. This thesis has examined factors influencing evolution of resistant P. falciparum at two sites in Africa, including parasite migration, cross mating and fitness cost of resistance. In Asar village, eastern Sudan, the frequencies of drug sensitive and resistant parasites were monitored throughout the dry season in the absence of anti-malarial drug usage to examine whether persistence of resistant parasites is reduced in the absence of drug pressure. Two cohorts of P. falciparum infected patients were treated with chloroquine in the transmission season (Oct-Dec), and followed monthly in the dry season into the next transmission season. A large proportion of the cohort maintained sub-patent asymptomatic P. falciparum infections throughout the entire study period. Alleles of the chloroquine resistance transporter (Pfcrt) and multi-drug resistance protein (Pfmdr1) were examined. Mutant alleles of Pfcrt reached fixation following CQ treatment and remained high in the transmission season. However, at the start of the dry season, wild type alleles of both genes started to emerge and increased significantly in frequency as the season progressed. The mutant Pfcrt haplotype was invariably CVIET, indicating migration of CQ resistant parasites into an area; otherwise the CVMNK haplotype is normal. In addition, microsatellite haplotypes of dihydrofolate reductase (dhfr) gene and dihydropteroate synthase (dhps) genes, which control the parasite response to pyrimethamine and sulfadoxine respectively, were characterized. One major dhfr haplotype with double dhfr mutations and two major mutant dhps haplotypes were seen in eastern Sudan. These haplotypes are distinct from those prevailing in other African countries, suggesting the likely local origin of dhfr and dhps haplotypes conferring drug resistance.

Transmission capacities of different P. falciparum clones within a single infection in The Gambia have a high ability to produce gametocytes and infect Anopheles mosquitoes even when they exist at levels not detectable by microscopy and PCR. These findings emphasize the crucial role of gametocyte complexity and infectivity in generating the remarkable diversity of P. falciparum genotypes seen in infected people. Parasites with different resistant dihydrofolate reductase (dhfr) haplotypes have the ability to infect Anopheles mosquitoes following drug treatment, and cross-mating between parasites with different dhfr haplotypes was detected. Our results showed that the major dhfr haplotype in the Gambia is similar to the common one seen in other African countries, suggesting that parasite migration plays a major role in spread of resistance. Indeed, the dominant resistant haplotype seen in infected patients was readily transmitted to infect mosquitoes.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2011. 54 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 661
cross-mating, fitness, microsatellite haplotypes, mosquito infectivity
National Category
Infectious Medicine
Research subject
Molecular Genetics
urn:nbn:se:uu:diva-150254 (URN)978-91-554-8044-8 (ISBN)
Public defence
2011-05-12, C10:301, Biomedical Center (BMC), Husaratan 3, Uppsala, 09:15 (English)
Available from: 2011-04-20 Created: 2011-03-28 Last updated: 2011-05-05Bibliographically approved

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