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Surprising discovery in human spleen could ‘redefine’ what we know about malaria

Scientists think the spleen is where the malaria parasite dies.

Now a team of researchers has discovered how many lives “Surprisingly very” Plasmodium A parasite that hides in the spleens of people with chronic malaria infection.

The discovery adds a new dimension to the multistage life cycle of the mosquito-borne malaria parasite. Some species may lurk in the liver before exploding into the bloodstream to multiply and spread.

It also helps explain why cases of chronic malaria fly under the radar in blood tests. But then it suddenly reappeared. and how some malaria parasites have adapted to survive.

Steven Kho, an infectious disease researcher at the Menzies School of Health Research in Darwin. “Our findings redefine the life cycle of malaria,”

; said Australia.

“Chronic malaria should be considered mainly as an infection of the spleen. with a small proportion circulating in the blood.”

In two papers, Kho and his colleagues report discovering two of five species of Plasmodium Parasites known to cause malaria in humans – P. falciparum and P. vivax – lurking in the spleens of the people living in Papua Indonesia where malaria is an endemic epidemic and chronic patients are common

although P. falciparum It is the most dangerous form of the malaria parasite. P. vivax poses greater challenges in eliminating the disease. The latter is widely spread around the world and causes repeated infections, hiding effectively without being easily detected during combat.

chronic cases P. vivax Malaria, which is still life-threatening, has also increased as disease control activities began to improve. P. falciparumThis is a sign that the disease is hindering our best efforts.

“The latest impetus to rid the world of malaria has brought P. vivax ahead,” explains parasitologist Georges Snounou in another paper from 2018, “acknowledging that exacerbations are a serious obstacle to erasure.”

The new research, led by Kho, describes a group of 15 adults showing no symptoms of malaria. and had surgery to remove the spleen for other medical reasons

Microscopy and cell staining to show the parasite in blood and spleen tissue samples. The researchers found that most of these people had a lot. Plasmodium parasites in the spleen

In expanding this first study By expanding the number of volunteers to 22, the researchers once again identified a significant number of spleen parasites. Even if the patient shows no symptoms of malaria.

Plasmodium vivax in the spleeninfected red blood cells P. vivax in the spleen (Kho et al. 2021).

The spleen is responsible for filtering our blood to remove old, damaged, or infected red blood cells. P. vivax The deposits in these people’s spleens may in some cases be hundreds of times higher than those found in the bloodstream.

The researchers calculated that this was more than you’d expect if the parasite was replicating in the red blood cells that the spleen blew out of circulation.

Therefore, the results suggest that the spleen is a previously unknown reservoir, where Plasmodium The parasite can hang out and reproduce.

“There is a large accumulation of parasites in the entire spleen. Plasmodium The kind that causes malaria but is particularly evident in P. vivaxwhere 98 percent of all parasites in the body hide in the spleen,” Kho explains.

Moreover Few people have malaria parasite blood levels that are undetectable. But their spleen was filled with cells infected with the parasite. This worried the researchers. but with few examples until now More large studies are needed to validate the findings.

“This is another factor that limits the success of malaria eradication programs based on mass blood testing and treatment of only those with detectable infections,” said infectious disease physician Nick Anstay, noting that this would How to thwart surveillance and elimination efforts?

but why P. vivax concentrated in the spleen good that still don’t know Researchers have a hunch that The spleen accumulates a large number of young red blood cells called reticulocytes. which is the only red blood cell that P. vivax can be infected

“This puts the spleen in the ideal position where the vivax malaria parasite can multiply,” Anstey said.

It may also stimulate research on malaria treatments and vaccines that attack different stages of malaria. Plasmodium Life Cycle As we know the spleen is an important part of the puzzle for P. vivax infection

Both are critically needed for the disease, which infects approximately 250 million people each year in the Asia-Pacific region alone, and for P. vivax which has long been overlooked in research

The study was published in New England Journal of Medicine and PLOS drug.

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