Sniffer dogs show we can sock it to malaria
Clever canines can pick up the disease in frozen socks even before symptoms start showing
Sniffer dogs Lexi and Sally can pick up malaria from socks worn overnight by children infected with the parasites, a pioneering study released on Monday shows.
The canine sleuths had a 78% success rate in detecting malaria even though the socks had been frozen for months while they were being trained.
This new and non-invasive way to detect malaria has the potential to save lives by picking up infections before people with the parasites show symptoms. Swift detection and treatment prevent fatal infections and limit malaria spreading.
Trained sniffer dogs at airports could also detect whether people were carrying malaria parasites when they entered countries where the disease had been wiped out or those that were close to eradicating it.
Labrador golden retriever cross Lexi and Labrador Sally were used for the research involving children in The Gambia, where the deadly disease is endemic.
“People with malaria parasites generate distinct odours on their skin and our study found dogs, which have an incredibly sensitive sense of smell, can be trained to detect these odours even when it’s just on an article of clothing,” said public health entomologist Steven Lindsay, from Durham University in the UK.
The British charity, Medical Detection Dogs, was one of their collaborators in the study. Its dogs have been trained to scent medical conditions, including prostate cancer and people at risk of slipping into a diabetic coma.
Lindsay said several hundred children from five to 14 years old, who seemed healthy, were sampled for malaria parasites and fitted for nylon socks in which they were asked to sleep for this research.
The socks were collected the next day and sorted according to the children’s malaria infection status. A finger-prick test was used to determine if the malaria parasite (Plasmodium falciparum) was in their blood.
Socks from children with malaria, but no fever, were selected, along with socks from uninfected children, and all of those were shipped to the UK and frozen. The dogs could have had better results with socks worn recently rather than put on ice.
Tests were done on 175 sock samples “including those of all 30 malaria-positive children identified by the study and 145 from uninfected children”.
The dogs had to “freeze” before socks in which they detected the malaria parasite, and keep moving if they did not, in this experiment. They identified 70% of the children with malaria and 90% of the uninfected children correctly from the socks.
“The dogs’ success rate actually might have been higher – up to 78% – if the children with malaria were all carrying the same type of parasites,” said Lindsay. “As malaria infections progress, the parasite goes through several stages of development.”
The parasites’ odour changes as it reaches “a certain stage of maturity”, he thinks. “Some of the children were carrying these more mature parasites, but the dogs were not trained to detect their odour.”
This research was intended to – and did – prove that dogs could detect. A third dog, Springer Spaniel Freya, has been trained to detect malaria since the initial study.
The only way to tackle malaria in people not showing symptoms is to test or treat a whole community, and the sniffer dogs could change this, scientists said.
Co-author Professor James Logan, head of Disease Control, at the London School of Hygiene & Tropical Medicine, said: “Our results show that sniffer dogs could be a serious way of making diagnoses of people who don’t show any symptoms, but are still infectious, quicker and easier.”
Next, the scientists are likely to test samples from people infected with malaria in different regions of Africa and other continents.
Another co-author and Medical Detection Dogs CEO, Dr Claire Guest, said: “This is the first time we have trained dogs to detect a parasite infection and we are delighted by these early results.”
The research was presented on Monday at the American Society of Tropical Medicine and Hygiene Annual Meeting in New Orleans.
The global fight against malaria has stalled recently. The most recent WHO World Malaria Report says malaria cases increased by five million in 2016 to 216 million cases, and deaths remained at about half a million (445,000).
The number of malaria cases in SA last year increased by nearly 50%, from 6,375 reported in 2016 to 9,478.
The need for greater resources, as well as delays and gaps in spraying, had contributed to this problem, and the most affected provinces were Limpopo, Mpumalanga and northern KwaZulu-Natal.