Dogs sense malaria in new trial by smelling socks

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In 2016, there were 216 million cases of malaria worldwide, an increase of 5 million over the previous year.

Luckily, man's best friend is here to lend doctors a helping paw. In a small, proof-of-concept study, two trained dogs were able to distinguish between socks worn by children who had malaria and socks from the feet of those who did not. The study's results were presented at the annual scientific meeting of the American Society of Tropical Medicine and Hygiene in New Orleans on Monday. They wore them overnight while sleeping and turned them over to researchers the next day. The team noted that socks were only used from malaria-infected children if the they did not express symptoms of the disease. Steven Lindsay is a public health entomologist at the Department of Biosciences at Durham University in the United Kingdom.

In total, 175 sock samples were tested including those of all 30 malaria-positive children identified by the study and 145 from uninfected children. The pooches-a Labrador retriever and a Labrador mixed breed-would sniff each sample and freeze if they detected malaria, or move on if not. Currently, the only way to address the problem of "asymptomatic" carriers-who still can cause new infections by passing along their malaria parasites to the local mosquito population-is to test or treat an entire community.

There are some limitations to the work, however.

"The handlers think the scent is so strong that the dog may be able to pick out people from the crowd", Lindsay told Inside Science. If a dog's nose can sniff out malaria, then it's conceivable that a portable diagnostic device modeled off the canine olfactory system can be developed.

That makes it tricky to use dogs to scent-detect malaria.

However, Guest and her team don't believe the dogs were memorizing individuals. Using a standard finger-prick test, the researchers were able to determine which of these children had the malaria parasite Plasmodium falciparum in their blood. "What happened to the other sock?"

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Identifying people infected with the malaria parasite, but not presenting symptoms, is critical as they can be treated with antimalarial drugs and the spread of the disease can be prevented.

Although the research is still at an early stage, experts say the findings may even lead to new ways of testing for the disease. Indeed, diagnosing people with suspected infections is a laborious and time-consuming process.

"They are much faster than existing rapid diagnostic tests which can take up to 20 minutes and require a fully trained professional to do". Fifteen minutes later, a colored bar appears if an antigen produced by the malaria parasite is in the patient's blood. Besides, labs are not required and many samples can be tested in field like setting. A dog, in contrast, "could go down a line of people and be done in seconds", Logan says. This means journalists are losing the ability to hold the rich and powerful to account. However, forget the traditional signs, because dogs can apparently smell it on you.

One unknown piece of the puzzle is why, exactly, malaria-infected people smell differently. It could be from the parasite itself or perhaps the body's reaction to the parasite. "And it may be possible to pick someone out from a crowd that's infected with malaria parasites".

Now British and African scientists have used that trait to train dogs to sniff out malaria from a child's dirty sock.

"So for countries that have eliminated, it's a really interesting potential new way they could protect their borders and keep their countries malaria free".

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