MrViralNews (EUA)

Malaria parasite in the Americas is more genetically diverse than previously thought

Publicado em 29 outubro 2017

The populations discovered in the Americas of Plasmodium vivax, considered one of the major human malaria parasites, are as genetically diverse as these discovered in Southeast Asia, the place malaria transmission is a lot more frequent.

Because P. falciparum, the predominant species of malaria parasite, shows low genetic variety in the Americas in contrast with different areas, scientists believed the similar was true for P. vivax. This perception is mistaken, in keeping with a research by researchers at the University of São Paulo (USP) in Brazil, in collaboration with colleagues from Rio de Janeiro, Uruguay and the United Kingdom. The outcomes had been revealed in PLOS Neglected Tropical Diseases.

Principal investigator for the research, Marcelo Urbano Ferreira said that the research introduced stunning outcomes. “The discovery that populations of P. vivax in the Americas are more diverse than populations of P. falciparum was stunning. If we settle for the speculation that each P. falciparum and P. vivax got here to the Americas after European colonization, we’d look forward to finding comparable ranges of genetic variety in each species, as they’d have undergone an intense inhabitants squeeze throughout their ‘migration’ to the New World. However, this is merely not the case,” mentioned, the Brazilian scientist, a professor in the Parasitology Department of the Biomedical Science Institute at the University of Sao Paulo (ICB-USP).

The research of P. vivax‘s genetic variety in the Americas seeks clues to the origin of the many lineages or populations discovered on the continent.

Upon arriving in the Americas, P. vivax seems to have retained a lot more of its current variety, as in Africa for instance, than P. falciparum.

“A attainable rationalization is that the populations of P. vivax that got here to the Americas originated in a wider geographical space, together with Africa, Europe and maybe Asia, than the populations of P. falciparum that got here right here, as these had been predominantly African, however this has but to be demonstrated,” Urbano Ferreira mentioned. The investigator coordinates the Thematic Project intitled “Scientific bases for residual malaria elimination in the Brazilian Amazon,” supported by the São Paulo Research Foundation — FAPESP.

Ancient lineages might have come to the Americas, and relying on the magnitude of the migration (the variety of people concerned), they could have misplaced little variety on the manner.

Some lineages might have come to Brazil in the nineteenth century with immigrants from Italy and Spain, the place malaria was endemic till the mid-twentieth.

“The variety of P. vivax in Brazil is substantial, given more than 300 years of slave buying and selling, considered one of the methods the parasite migrated. However, it entered Brazil in some ways at completely different instances, not least in the nineteenth century with the first wave of immigrants,” mentioned Thaís Crippa de Oliveira, a PhD pupil at ICB-USP and first writer of the article revealed in PLOS Neglected Tropical Diseases.


Blood samples had been collected from sufferers in Northwest Brazil, more exactly in the cities of Acrelândia and Remansinho, close to the border with Peru and Bolivia. Brazil accounts for 37% of all malaria instances reported in the Americas. All 9 sufferers had been discovered to be contaminated with P. vivax.

The parasites in the samples had been separated, and their nuclear DNA was remoted and subjected to whole-genome sequencing. To place these sequences in a regional context, the researchers carried out complete genome sequencing of 75 different medical isolates of P. vivax from Brazil (2), Peru (23), Colombia (31) and Mexico (19) obtained through worldwide gene banks.

All this materials was analyzed in search of single-nucleotide polymorphisms (SNPs), extensively used as markers of differentiation and in this case able to establishing variety amongst the parasites sampled.

The research confirmed that the genetic variety discovered in Brazil’s P. vivax inhabitants is much like that discovered in different nations of the Americas.

The evaluation of P. vivax‘s nuclear genome sequence was carried out utilizing three populations from the Americas. “For now, we have genome data for parasites from only four countries in the Americas. Even within each country, we don’t have a representative sample,” Urban Ferreira mentioned. “Many lineages are undoubtedly circulating in the Americas, far more than three, but owing to the intense genetic recombination to which most of them are exposed these lineages aren’t stable. Genetic recombination quickly creates new ‘recombinant’ variants that circulate on the continent. It’s highly likely that clonal lineages aren’t being transmitted along several generations of parasites.”

“This research is a work in progress,” Urbano Ferreira mentioned. “So far, the available data, both ours and those of other research groups, suggests P. vivax came to the Americas from Africa, Europe and Asia. It’s also possible there was a contribution from Oceania, but this needs to be confirmed,” Urbano Ferreira mentioned. “Mitochondrial genomes are very useful in these studies, but we certainly need more complete nuclear genomes to make more definitive inferences.”

According to the researcher, it could simplistic to imagine that every one the genetic variety discovered in the populations of those parasites in the Americas at present has come about in the previous 500 years. This can be the case provided that the migration had concerned a “founder effect,” i.e., if just one or only a few lineages had come to the continent and all the parasites at present alive on the continent had been descendants of these first lineages.

“Mitochondrial genomes are very useful in these studies, but we certainly need more complete nuclear genomes to make more definitive inferences,” stresses Urbano Ferreira.

The researchers at the moment are engaged on a brand new pattern collected by Urbano Oliveira from a single neighborhood throughout 12 months of research.

Whole-genome sequencing of those parasites will allow them to guage the ranges of genetic variation in populations of P. vivax over time and infer a few of the mechanisms that contribute to such variation, together with migration and recombination.