A drug already widely used in massive campaigns to help control two parasitic diseases, river blindness and elephantiasis, could also reduce malaria, a new study has found. The compound, called ivermectin, shortens mosquito spans the lives and makes them less likely to transmit the malaria parasite.
Ivermectin is known worldwide primarily developed as a drug to treat head lice in children and heartworm in animals. It also kills several tropical parasites, including those transmitted by mosquitoes that cause lymphatic filariasis, a disease also known as elephantiasis for members horribly swollen suffered by patients and those worn by black flies that cause river blindness, blindness rivers.
many countries use ivermectin in a strategy called mass drug administration (MDA), which means that the entire population in an affected area is given the drug once or twice a year. Merck, which produces ivermectin under the brand name Mectizan, provides free to treat river blindness and elephantiasis; the company promised to do as long as necessary.
But Brian Foy, who studies insect vectors at Colorado State University in Fort Collins (and became a minor internet celebrity last year after the sexual transmission of the virus to his wife Zika and the publication of a study on this), is interested in another effect of ivermectin: it kills mosquitoes. Laboratory studies have shown that when mosquitoes bite a person recently treated with the drug, they swallow a dose which is sometimes fatal to them. To see if the drug could thwart malaria transmission, Foy and colleagues studied mosquito populations in a region in southern Senegal where ivermectin is used in annual MDAs to stop river blindness. In a study published last year, the team showed that MDA has greatly reduced the lifespan of mosquitoes that feed on treated.
In the new study, Foy and colleagues wanted to know if the insecticide effect of ivermectin translates into less infectious mosquitoes, which could slow the spread of malaria. In theory it should, because Plasmodium falciparum , the malaria parasite, takes about 2 weeks to develop inside the body of the mosquito, which is the life of the insect. So the team took the mosquitoes in three villages who participated in a MDA and three others nearby who do not. Indeed, they found that in treated villages, the proportion of mosquitoes with fully developed P. falciparum in their saliva fell by 79% in 2 weeks. But in the villages of control, the proportion increased by 246%, the ratio of online research today The American Journal of Tropical Medicine and Hygiene .
The discovery suggests the mass ivermectin treatment would be a new weapon against malaria, in addition to insecticide spraying, bed nets and other drugs, said Foy. But ivermectin should be given more often than once a year, he said, perhaps monthly, because the effect of the drug on the mosquito population will not last long. Merck will donate the extra amount needed Ivermectin is clear.
Brian Greenwood of the London School of Hygiene & Tropical Medicine paper called an "interesting pilot study," but he is "not very impressed" by the evidence in the document. He says the number of mosquitoes tested by researchers was small, and the paper leaves some unanswered questions such as why mosquitoes in treatment villages had much higher rates of malaria at the beginning of the study, or why rates rose in the control villages.
Peter Hotez, head of the Sabin Vaccine Institute in Washington, DC, and the current president of the American Society of Tropical Medicine and Hygiene in Deerfield, Illinois, agrees that much more study of the antimalarial activity ivermectin is necessary but calls the idea of Foy "exciting" and "potentially very important." Hotez helped create the global Network for neglected tropical diseases, advocating the widespread use of a set of cheap drugs, including ivermectin, to target the seven tropical diseases less well known. "Now we have the proof possible that this package can also have an impact on other infections, including malaria," says Hotez.
Hotez sees a pattern emerging. In 09, a study published in the Journal of the American Medical Association showed that the mass administration of antibiotics in Ethiopia to treat trachoma, a bacterial eye infection, had huge additional benefits. For reasons still under discussion, it has reduced infant mortality by half. "We are only beginning to understand the enormous potential impact of MDAs on diseases for which they are not intended," said Hotez.
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