Over the past 15 years, malaria infections have halved across Africa, yet in 2013 more than 3 billion people remained at risk of the disease globally. This year, the first vaccine against malaria – RTS,S – completed clinical trials and showed some level of protection, but will it be enough?
Meera Senthilingam investigates where a vaccine will fit into the current fight against malaria and explores what’s left to tackle the disease once and for all.
The buzz comes abruptly. A squealing buzz causing sensations across the surface of the skin, bringing with it anticipation of blood being drawn and skin being raised. For some, this buzz is merely a symbol of summertime, or warmer climates, or a mother trying to feed her young. But in 97 countries across the globe, this familiar sound strikes a nerve, many nerves. Here, this sound of a tiny mosquito hovering nearby hits nerves beyond the senses of sound or touch — it invokes fear.
These 97 countries and territories are endemic for malaria, a blood-borne parasitic infection spread only by the bite of a female Anopheles mosquito and killing almost 500,000 people each year. The saliva, not the bite, is what they truly fear. It’s the saliva from these female mosquitoes, which is filled with thousands of microscopic parasites, ready to infest any human within their reach. “One of these parasites alone could kill you,” says Sir Brian Greenwood, Professor of Clinical Tropical Medicine at the London School of Hygiene and Tropical Medicine, referring to the multiple parasites primed and waiting to invade the human bloodstream.With thousands lurking in the saliva, approximately ten injected in each bite, and just one plasmodium parasite needed to cause disease, the risk of infection is high.
An estimated 3.3 billion people are at risk of malaria, according to the World Health Organization (WHO), and 90% of them are in Africa. “Malaria is a very difficult disease to deal with,” says Prof Greenwood. Plasmodia have a complicated life cycle traversing both human and mosquito hosts and passing through varying reproductive stages within each host. In humans, just a few minutes is enough for parasites to get from the site of a bite, through the blood and into the liver. This is where the real damage begins.
“The parasite is quite vulnerable at that stage,” says Prof Greenwood making this point in time the perfect opportunity to stop the infection in its tracks — before thousands, and then billions, of parasites take over the blood. Over the past 30 years, hope has been emerging slowly with a potential vaccine on the horizon targeting this exact stage of infection – the RTS,S vaccine.
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