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The evolution of parasites makes it difficult to detect and treat malaria


Conceptual diagram of blood cells and Plasmodium parasites

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Inexpensive and quick inspection of malaria helped drive down Disease prevalence In many parts of Africa. However, only about 15 years after its introduction, the “stealth” malaria parasite has evolved and can no longer be detected by standard rapid tests.

“This is a big threat to malaria control,” he says. Jane Cunningham At the World Health Organization Global Malaria Program in Geneva.

In many African countries, only those who have a positive rapid test result are treated. However, in Eritrea around 2016, healthcare workers I really have malaria The test was negative. When doctors looked at blood samples under a microscope, they found that many children were actually infected.

“It was a crisis,” says Cunningham. “They thought there was something wrong with the test.”

Instead, her team found that up to 80% of malaria parasites in the area had mutations that stopped producing two proteins called pfhrp2 and pfhrp3 that were detected by rapid testing.

“Continuous use of these rapid tests [parasites without the two marker proteins] To proliferate, “says Cunningham.

Her team then conducted a survey in nearby Ethiopia. “It wasn’t as prevalent as Eritrea, but I was really worried about the level,” she says.

Evolution is often a trade-off, and mutations that provide some benefits are otherwise disadvantageous. However, parasites appear to propagate without the pfhrp protein, whose function is unknown.

Area with Mutant Plasmodium has switched to tests that detect other proteins, but these tests are still unreliable, for example, less thermostable. Switching to microscope detection is not an option in most places as it requires expensive equipment and skilled technicians.

Ideally, rapid testing looks for several biomolecular targets of the parasite and those that play an important role in the biology of the organism at once, so they are difficult to mutate, says Cunningham. However, this makes the test more complicated and expensive.

Commonly found in viruses, bacteria and parasites And cancer Evolving resistance to treatment, but much rarer to avoid testing-this may be the first clear example. Some hepatitis B viruses have mutations that mean they are missed on the test, but it is not clear if this is due to the choice as a result of the test.

Some countries are currently using rapid tests to detect the coronavirus SARS-CoV-2. This could theoretically evolve to avoid them.

Journal reference: Nature microbiology, DOI: 10.1038 / s41564-021-00962-4

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The evolution of parasites makes it difficult to detect and treat malaria

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