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Viagra Could Help Stop The Spread of Malaria, New Study Suggests

14 MAY 2015

The world's favourite little blue pill doesn't just treat erectile dysfunction, new research suggests that Viagra may also help stop the spread of malaria. By causing the parasite behind the disease, Plasmodium falciparum, to, well, stiffen, Viagra makes infected red blood cells less flexible, and encourages the spleen to filter them out of the blood stream.

 

While this doesn't stop someone from being infected with malaria, it does stop uninfected mosquitoes from picking up the parasite-carrying red blood cells when they bite these patients, and therefore prevents the disease from spreading to other people.

This isn't the first time Viagra has been shown to go above and beyond the call of duty. Previous research has shown that the drug, also known as sildenafil citrate, can help treat hypertension, altitude sickness and even some types of heart disease. But it's the first time that the drug has been used against malaria, and the results, which have been published in PLOS Pathogens, suggest that this work could lead to a whole new class of antimalarial drugs.

Normally when a malaria-infected mosquito bites a human, an immature form of the Plasmodium parasite enters their blood stream and quickly goes into hiding in the red blood cells found in the bone marrow.

By the time these cells enter the blood stream, the parasites have matured enough to disguise themselves, an their cells stay nice and squishy, just like healthy red blood cells. This means they pass easily through the body's blood filter - the spleen - without being cleared out, and are readily available to be sucked up by any uninfected mosquitoes that bite their host.

A team of researchers from France, England and Italy figured that if they wanted to take these infected cells out of circulation, they needed to find a way to keep the parasites and their cells stiff, like they are in their juvenile stage. Using an artificial spleen, they found that Viagra increased the presence of a messenger molecule known as cyclic adenosine monophosphate, or cAMP, and this made the parasite-infected red blood cells to stiffen, and become more likely to be filtered out of the blood. Alternatively, decreasing the levels of cAMP had the opposite effect.

This suggests that Viagra could help stop the parasite's life cycle and effectively lock it in its host, stopping it from spreading to anyone else.

Of course, the next step is to test whether this works as well in humans as it does in the lab, but the fact that Viagra has been so widely tested makes this process a lot easier and quicker. "Our observations provide an opportunistic approach towards the discovery of new malaria transmission-blocking drugs, by taking advantage of the wealth of clinical data available for sildenafil," the authors, led by Ghania Ramdani from Paris Descartes University in France, write in PLOS Pathogens.

 And before you say anything, don't worry - Medical Daily reports that the researchers will alter the drug before trials, to prevent the drug's erectile effect.

Current malaria treatments, including the new vaccine against the disease, work with varying success to target the juvenile form of Plasmodium, which causes the disease's symptoms. But this is one of the first treatment options that instead focusses on stopping the mature parasite, after the damage has already been done.

"In opposition to the Ehrlich’s 'magic bullet' which consists of targeting pathways that are essential for parasites, but absent in humans, this strategy, referred to as 'inverted silver bullet', open new avenues towards the design of novel interventions to halt the spread of malaria to humans," the authors write.

With 198 million cases of malaria worldwide each year and 500,000 deaths, it's about time we find a new strategy for stopping the spread of this terrible disease.