Genetic Diversity of Plasmodium falciparum Shows Geographical Variation

Creasey, Alison M.; Fenton, Brian; Walker, A.; Thaithong, Sodsri; Oliveira, S. D. de; Mutambu, Susan; Walliker, David

doi:10.4269/ajtmh.1990.42.403

Cited by 99 publications

(44 citation statements)

References 2 publications

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“…Part of the answer may relate to the ecology of P. chabaudi in its natural host, hamnom s rutilans, where it is described as a persistent, chronic infection (Landau & Chabaud 1994) with many hosts harbouring more than one genotype (Beale et al 1978). Mixed infections of the human malaria, P. falciparum, are also common (Creasey et al 1990 ;Day et al 1992). It may be that malaria parasites have evolved to maximize transmission from mixed-genotype infections genotype infections.…”

Section: Discussionmentioning

confidence: 99%

Mixed–genotype infections of malaria parasites: within–host dynamics and transmission success of competing clones

Taylor

Walliker

Read

1997

Proc. R. Soc. Lond. B

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114

104

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SUMMARYMixed-genotype infections of microparasites are common, but almost nothing is known about how competitive interactions within hosts affect the subsequent transmission success of individual genotypes. We investigated changes in the composition of mixed-genotype infections of the rodent malaria Plasmodium chabaudi clones CR and ER by monoclonal antibody analysis of the asexual infection in mice, and by PCR amplification of clone-specific alleles in oocysts sampled from mosquitoes which had fed on these mice. Mixed-clone infections were initiated with a 9 : 1 ratio of the two clones, with ER as the minority in the first experiment and CR as the minority in the second experiment.When beginning as the majority, clones achieved parasite densities in mice comparable to those achieved in control (single-clone) infections. When they began as the minority, clones were suppressed to less than 10 % of control parasitaemias during the early part of the infections. However, in mosquitoes, the frequency of the initially rare clone was substantially greater than it was in mice at the start of the infection or four days prior to the feed. In both experiments, the minority clone in the inocula produced as many, or more, oocysts than it did as a single-clone infection. These experiments show that asexual dominance during most of the infection is poorly correlated to transmission probability, and therefore that the assumption that within-host population size correlates to transmission probability may not be warranted. They also raise the fundamental question of why transmission rates of individual genotypes are often higher from mixed than single-clone infections.

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Section: Discussionmentioning

confidence: 99%

Mixed–genotype infections of malaria parasites: within–host dynamics and transmission success of competing clones

Taylor

Walliker

Read

1997

Proc. R. Soc. Lond. B

Self Cite

114

104

View full text Add to dashboard Cite

show abstract

“…Since the first report of chloroquine resistance from eastern Africa in 1978, it spread rapidly all over the continent (Henry et al 1994). Today about 50% of African Plasmodium falciparum strains are resistant to chloroquine, but the pattern of resistance varies with geographical location (Creasey et al 1990). In Ifakara, Tanzania, where this trial took place, 20% of P. falciparum strains were reported to be resistant to chloroquine in 1988 (Koella et al 1990).…”

Section: Introductionmentioning

confidence: 99%

Distinction of recrudescences from new infections by pcr‐rflp analysis in a comparative trial of cgp 56 697 and chloroquine in Tanzanian children.

Irion

Felger

Abdulla

et al. 1998

Tropical Med Int Health

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SummaryOBJECTIVE To test the efficacy of a new compound drug (CGP 56 697) against acute, uncomplicated falciparum malaria. METHOD Reappearing parasites were analysed by PCR-RFLP within a randomized controlled trial. 130 patients received chloroquine and 130 patients were treated with CGP 56 697. Samples from 96 patients with parasitological failure were tested by PCR-RFLP for MSP2 of Plasmodium falciparum. Seven days after treatment 32 patients of the chloroquine control group with reappearing parasites were tested by PCR and one infection was unequivocally determined as a new infection. After 7 days, in the CGP 56 697 group, 6 samples were tested in which one new infection was identified. Similar observations were made one and three weeks later in both groups. RESULTS Although a high multiplicity of infections on admission was observed, there was no significant correlation between multiplicity and either recrudescence or new infection. Patients in both treatment groups with subsequent recrudescent parasites had higher initial mean parasite densities than patients who cleared. Those of the patients with recrudescent parasites who were treated with CGP 56 697 had higher initial parasite densities than those treated with chloroquine. The rate of re-infection increased with time as expected in holoendemic areas and appeared to be higher in chloroquine patients. Generally, CGP 56 697 showed a superior clearance rate, successfully cleared higher parasite densities and suppressed new infections over a longer period of time. CONCLUSION The PCR analysis confirmed that reinfections beyond day 7 are significant in areas highly endemic for malaria and showed the necessity of excluding these when estimating 14 day clearance rates. Provided new infections are excluded, the 28-day clearance rate can also be used to determine the efficacy of antimalarial drugs in highly endemic areas, and adds to our knowledge of drug resistance and dynamics of infections in people living in such areas. keywords malaria, Plasmodium falciparum, drug treatment, resistance, polymerase chain reaction, artemether, benflumetol correspondence Hans-Peter Beck, Swiss Tropical Institute,

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“…P. falciparum shows remarkable genetic diversity, which allows the parasite to adapt to drugs and the host's immune response. This genetic diversity has been manifested by isoenzyme and antigenic methods, drug tests, and gene sequencing (2)(3)(4)(5).…”

mentioning

confidence: 99%

Evidence for clonal propagation in natural isolates of Plasmodium falciparum from Venezuela

Urdaneta

Lal

Barnabé

et al. 2001

Proc. Natl. Acad. Sci. U.S.A.

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We have analyzed 75 isolates of Plasmodium falciparum, collected in Venezuela during both the dry (November) and rainy (May-July) seasons, with a range of genetic markers including antigen genes and 14 random amplified polymorphic DNA (RAPD) primers. Thirteen P. falciparum stocks from Kenya and four other Plasmodium species are included in the analysis for comparison. Cross-hybridization shows that the 14 RAPD primers reveal 14 separate regions of the parasite's genome. The P. falciparum isolates are a monophyletic clade, significantly different from the other Plasmodium species. We identify three RAPD characters that could be useful as ''tags'' for rapid species identification. The Venezuelan genotypes fall into two discrete genetic subdivisions associated with either the dry or the rainy season; the isolates collected in the rainy season exhibit greater genetic diversity. There is significant linkage disequilibrium in each seasonal subsample and in the full sample. In contrast, no linkage disequilibrium is detected in the African sample. These results support the hypothesis that the population structure of P. falciparum in Venezuela, but not in Africa, is predominantly clonal. However, the impact of genetic recombination on Venezuelan P. falciparum seems higher than in parasitic species with long-term clonal evolution like Trypanosoma cruzi, the agent of Chagas' disease. The genetic structure of the Venezuelan samples is similar to that of Escherichia coli, a bacterium that propagates clonally, with occasional genetic recombination.

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Genetic Diversity of Plasmodium falciparum Shows Geographical Variation

Cited by 99 publications

References 2 publications

Mixed–genotype infections of malaria parasites: within–host dynamics and transmission success of competing clones

Mixed–genotype infections of malaria parasites: within–host dynamics and transmission success of competing clones

Distinction of recrudescences from new infections by pcr‐rflp analysis in a comparative trial of cgp 56 697 and chloroquine in Tanzanian children.

Evidence for clonal propagation in natural isolates of Plasmodium falciparum from Venezuela

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