Dogs can detect malaria
Dogs have such exquisitely sensitive noses that they can detect bombs, drugs, citrus and other contraband in luggage or pockets.
Is it possible that they can sniff out even malaria? And when might that be useful?
A small pilot study has shown that dogs can accurately identify socks worn overnight by children infected with malaria parasites — even when the children had cases so mild that they were not feverish.
The study, a collaboration between British and Gambian scientists and the British charity Medical Detection Dogs, was released last week at the annual convention of the American Society of Tropical Medicine and Hygiene.
In itself, such canine prowess is not surprising. Since 2004, dogs have shown that they can detect bladder cancer in urine samples, lung cancer in breath samples and ovarian cancer in blood samples.
Trained dogs now warn owners with diabetes when their blood sugar has dropped dangerously low and owners with epilepsy when they are on the verge of a seizure. Other dogs are being taught to detect Parkinson’s disease years before symptoms appear.
The new study, its authors said, does not mean that dogs will replace laboratories. Inexpensive rapid tests for malaria have been available for over a decade; more than 200 million people in dozens of countries are infected each year.
But for sorting through crowds, malaria-sniffing dogs could be very useful.
Some countries and regions that have eliminated the disease share heavily trafficked borders with others that have not. For example, South Africa, Sri Lanka and the island of Zanzibar have no cases but get streams of visitors from Mozambique, India and mainland Tanzania.
And when a region is close to eliminating malaria, dogs could sweep through villages, nosing out silent carriers — people who are not ill but have parasites in their blood that mosquitoes could pass on to others.
Dog noses are 10,000 to 100,000 times as sensitive as human noses. Scientists are not sure exactly what dogs are smelling, but it is known that malaria parasites produce volatile aldehydes like those found in perfumes.
The parasites may have evolved the ability to exude odoriferous chemicals in order to attract mosquitoes to carry them to new hosts. Studies have shown that mosquitoes prefer to bite people who have malaria.
If just one chemical indicated cancer or malaria, “we’d have discovered it by now,” said Claire Guest, who founded Medical Detection Dogs in 2008 and oversaw dog training in the study. “It’s more like a tune of many notes, and the dogs can pick it up.”
Most breeds have good noses, she said, but the best for this task are dogs bred to hunt — pointers, spaniels and Labradors — and dogs with relaxed relationships with their owners.
The initial trials were just to prove that detection was feasible, said Steve Lindsay, an entomologist at Durham University in Britain who said he was inspired by a dog sniffing luggage for contraband food at Washington Dulles International Airport.
This preliminary study involved training just two dogs to sniff rows of jars containing bits of thin nylon socks that had been worn overnight by Gambian children.