High Levels of Genetic Diversity of Plasmodium falciparum Populations in Papua New Guinea despite Variable Infection Prevalence

Abstract

Abstract. High levels of genetic diversity in Plasmodium falciparum populations are an obstacle to malaria control. Here, we investigate the relationship between local variation in malaria epidemiology and parasite genetic diversity in Papua New Guinea (PNG). Cross-sectional malaria surveys were performed in 14 villages spanning four distinct malariaendemic areas on the north coast, including one area that was sampled during the dry season. High-resolution msp2 genotyping of 2,147 blood samples identified 761 P. falciparum infections containing a total of 1,392 clones whose genotypes were used to measure genetic diversity. Considerable variability in infection prevalence and mean multiplicity of infection was observed at all of the study sites, with the area sampled during the dry season showing particularly striking local variability. Genetic diversity was strongly associated with multiplicity of infection but not with infection prevalence. In highly endemic areas, differences in infection prevalence may not translate into a decrease in parasite population diversity.

High Genetic Diversity of Plasmodium vivax on the North Coast of Papua New Guinea

“…A similar finding has been observed for sympatric P. falciparum populations. 38 High levels of genetic diversity, despite a relatively low infection prevalence in the Wosera, which was sampled during the dry season, show that P. vivax and P. falciparum parasite populations are well-equipped to adapt to a changing local environment and that a significant reduction in transmission intensity will be required to reduce population genetic diversity in highly endemic areas such as PNG. The results of the present study highlight the enormous challenges facing malaria elimination efforts in countries of high malaria endemicity such as PNG.…”

“…Indeed, sympatric populations of P. falciparum surveyed in the same study showed a wider range of infection prevalence among villages of the Wosera (range = 1.7-43.5%). 38 Additionally, the villages comprising the three Madang catchments are distributed over a broader geographical area ( 50 km) than those villages of the Wosera ( 10 km). 8 Therefore, although likely due to higher coverage of insecticidetreated bed nets, local differences in vector abundance and ecology may also have contributed to differences in relative P. vivax prevalence 19 and warrant future investigation.…”

“…A similar observation was recently reported after analysis of P. falciparum infections from the Peruvian Amazon 39 and the same areas analyzed in this study. 38 For P. vivax, high genetic diversity may be maintained in the face of reduced transmission as a result of the latent hypnozoite stage of the lifecycle, which can remain in the liver for several months and even years. 33 Infection with different clones is thought to increase population genetic diversity through meiotic recombination in the mosquito midgut.…”

“…5,40 Thus, although the implementation of malaria prevention measures seem to have reduced P. vivax prevalence in East Sepik, an even greater reduction in prevalence may be required to decrease population genetic diversity for both P. vivax and P. falciparum. 38 The genetic complexity and unique biology of P. vivax infections, coupled with the enormous burden of both species, will present major challenges for malaria elimination in PNG.…”

High Levels of Asymptomatic and Subpatent Plasmodium falciparum Parasite Carriage at Health Facilities in an Area of Heterogeneous Malaria Transmission Intensity in the Kenyan Highlands

“…Allelic richness (Rs), a metric for allelic diversity, was calculated using FSTAT, version 2.9.3.2, software as previously described. 32 Random effects logistic regression was used to assess factors associated with having subpatent as well as asymptomatic malaria infection. Explanatory variables tested included year, sex, age, whether the individual was a patient or an accompanying person, reported taking an antimalarial drug in the past 2 weeks, reported taking an antipyretic drug, reported using a bed net the previous night, reported living in a household where indoor residual spraying had taken place in the previous 6 months, and number of infecting parasite clones.…”