Geneticists map the spread of a lesser-known malaria parasite across the world
Researchers mapped the genetics of one of the parasites that cause malaria to track how different variants may be spreading across the globe. They say the parasite, Plasmodium vivax, likely originated in Africa.
Researchers previously thought that rates of malaria caused by this parasite were low. But, it seems that cases are dramatically increasing in East Africa and other parts of the world.
Plasmodium vivax (PV) malaria cases are usually not severe, but recent studies show that PV can lie dormant in people and repeatedly reinfect them, causing them to miss work. This, along with the need for repeated treatment, can slow economies.
In this study, researchers wanted to analyse the genetics of PV parasites detected at various places globally. This genetic and geographical data can help health authorities to limit the spread of PV and better treat malaria.
The researchers extracted DNA from finger-prick blood samples collected from patients with PV malaria in New Halfa and Khartoum, both in Sudan. They also used data from samples collected in other parts of Africa, South America, and Asia. They compared the samples to find similarities and differences across the locations.
The researchers found that the genetics of PV samples were generally more similar to other samples from the same continent. This means they could potentially tell where a sample came from based on its genetics.
Interestingly, they saw that samples collected in Africa were more genetically diverse than samples from other continents. In other words, samples collected in Asia, for example, were more similar to other Asian samples than African samples were to other African samples.
The genetic diversity in Africa suggests that PV came from Africa. They also saw that African samples were more similar to Asian samples than South American samples. This means people or animals infected with PV probably recently moved between Africa and Asia. Mapping the genetics of a parasite in this way gives scientists insights into how the pathogen spreads to different locations.
The researchers say future studies could use this information to identify geographical characteristics, like mountains, that separate different PV variants.
The researchers that performed this study were based in Sudan, Eritrea, France, and the USA.
Plasmodium vivax malaria is a neglected tropical disease in Africa due to low occurrence rates and lack of accurate diagnosis. Recently, there has been a dramatic increase in P. vivax cases in East Africa and reportedly spreading to western countries. This study investigated the geographical origin and genetic diversity of P. vivax in Sudan by 14 microsatellite markers. A total of 113 clinical P. vivax samples were collected from two districts, New Halfa and Khartoum in Sudan. In addition, data from 841 geographical samples retrieved from the database for global genetic analysis were included in the analysis to further the genetic relationships among the P. vivax isolates at regional and worldwide scales. On a regional scale, we observed 91 unique and 8 shared haplotypes amongst the Sudan samples. Such a high genetic diversity compared to other geographical isolates lends support to hypothesis that P. vivax was originated from Africa. On a global scale, as already demonstrated, we observed distinct genetic clustering of P. vivax isolates from Africa, South America, and Asia (including Papua New Guinea and Solomon Island) with limited admixture in all three clusters. The principal component analysis and phylogenetic tree showed similar clustering patterns and highlighted the contribution of the African isolates to the genetic variation observed globally. The East African P. vivax showed similarity with some of the Asian isolates suggesting potential recent introductions. Our results show extensive genetic diversity co-occurring with significant multi-locus linkage disequilibrium, demonstrating the effectiveness of using microsatellite markers to implement effective control measures.
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