DESPITE BEING ELIMINATED from southern and southeastern Brazil over 50 years ago, malaria is making a comeback in the region with humans being infected by it through a parasite that usually only affects monkeys.

Researchers writing in The Lancet Global Health said that analysis of 28 cases of malaria in humans found that they were infected, via a mosquito bite, with plasmodium simium which is a parasite usually only found in monkeys.

They said this discovery “poses a unique problem for malaria control efforts and may complicate the drive towards eventual elimination of the disease”.

Cases of malaria used to be widespread across Brazil, but now 99% of incidences occur in the northern Amazon region.

However, between 2006 and 2014, 43 cases of malaria were reported in the Atlantic Forest area in southern Brazil, and then an additional 49 occurred in 2015-16.

Samples from 33 cases were taken by researchers, and the monkey-affecting parasite was found in 28 cases rather than the human parasite plasmodium vivax.

Importantly, there is no evidence to suggest that this parasite can then be passed on from human to human.

Study author Dr Patrícia Brasil said: “In addition, there is no current threat to people in the city of Rio de Janeiro, or in other non-forest areas of the Rio de Janeiro state, where transmission of the disease does not exist.

Although benign and treatable, visitors should follow measures to avoid insect bites when going into the forest.

This form of contracting malaria – called zoonotic malaria – is common in southeast Asia but this is the first example in forest locations in a region considered to have eliminated the transmission of malaria 50 years ago.

As the researchers have only begun testing, they do not yet know the extent of the problem or if this ability for the monkey parasite to infect humans is a new phenomenon.

In an accompanying comment to the article, experts Matthew J Grigg and Georges Snounou said it is now “imperative” to establish if the parasite found in monkeys would “pose a substantial threat to malaria elimination throughout the continent and possibly beyond”.

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