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A new study of entomologists from Iowa State University describes how mosquitoes fight the parasites that cause malaria, a disease that sickens millions of people each year.
The study, recently published in the scientific journal Proceedings of the National Academy of Sciences, shows how the immune system of mosquitoes fights malaria parasites in several stages of development. A better understanding of the immune response of mosquitoes could lay the groundwork for future research to combat malaria transmission, said Ryan Smith, badociate professor of entomology and senior author of the study.
About 219 million cases of malaria, a disease transmitted to humans by the bite of an infected mosquito, have occurred worldwide in 2017, according to the Centers for Disease Control and Prevention. Most cases are concentrated in tropical and subtropical climates such as sub-Saharan Africa and South Asia. The disease resulted in 435,000 deaths in 2017, according to the CDC.
Mosquitoes are required to transmit malaria, acquiring malaria parasites by pricking an infected person, and then transmitting the disease a few weeks later after the parasite has finished developing in the mosquito. The new study focuses on how the immune system of mosquitoes reacts to the parasite.
"Mosquitoes are usually pretty effective at eliminating the parasite," Smith said. "We wanted to understand the mechanisms and ways that make this possible."
The researchers treated the mosquitoes with a chemical that impoverishes their immune cells, which are needed to defend against pathogens. Experiments have shown that malaria parasites survive at a higher rate in mosquitoes when immune cells are depleted. The research also shed light on how these immune cells have promoted different "waves" of the mosquito's immune response targeting different phases of the malaria parasite in the host mosquito.
Smith, who also heads the ISU Medical Entomology Lab, said the findings provide insight into a complement-like pathway that intervenes in the initial recognition and destruction of parasites, similar to those found in mammals. The work also implies that phenoloxidases, an insect-specific immune response, elicit a secondary immune response to the later stages of the malaria parasite, he said.
Understanding these immune responses could help eliminate malaria parasites in the mosquito, thereby reducing malaria transmission. For example, Smith said scientists could use genetic approaches to make mosquitoes resistant to malaria parasites. The introduction of mosquitoes with enhanced immunity in endemic areas of malaria could significantly reduce cases of human malaria.
"More steps are needed to validate this type of approach, but we believe this study lays the groundwork for these future experiments," Smith said.
Hyeog Sun Kwon, scientific badistant in entomology, also contributed to the study.
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Material provided by University of Iowa State. Note: Content can be changed for style and length.
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