– People with malaria parasites produce specific smells in the skin. We found that dogs with a sensitive sense of smell can work out to detect these smells. It also applies to clothes used by infected persons, "said Steven Lindsay at the Biosciences Department at Durham University, UK, and lead researcher behind a new malaria study.
He recently presented his findings at the annual meeting of the American Society of Tropical Medicine and Hygiene.
Sniffed on socks
Several hundred Gambian schoolchildren participated in the new survey. First, they went through a general health check when tested for malaria parasites. Then they got a pair of socks that would be used overnight. The following day, the researchers collected the socks, and divided them into the status of children's malaria problems. They just collected socks for malaria infected children without symptoms and socks at the healthy kids. The socks were then sent to England. Here they were frozen while the sniffing dogs were trained.
The sniffing test was about to distinguish between socks for malaria-saturated and healthy children. They should cut each pair of socks and freeze if they thought they found malarimids. If they did not smell something they should proceed.
The result of the test showed that the dogs managed to identify 70 percent of the stockings of the malaria-affected children and 90 percent of the healthy ones.
Malaria parasite mutates
The researchers say that the impact of the impact is impressive and that the dogs could identify the socks for children with lower infectious status than required by the World Health Organization (WHO) rapid tests.
In general, malaria diagnostics are done by means of blood samples and microscopy. It can be time consuming and special skills are needed. You can also use quick blood samples, but it is quite expensive. They have a high level of accuracy.
The researchers were aware that this was a so-called proof of the conceptstudy, to show that malaria can be diagnosed by dogs. They further believe that sniffing the dog's accuracy can be as good as blood samples. Lindsey motivates this because the malaria parasites on the children are not always of the same type as they go through different stages of the disease. The smell they create in human skin changes then.
He points out that the tests used today can also be short, as the malaria parasites mutate. Thus, the parasites can not have the specific protein necessary for the clinical tests to show infection
In addition, researchers believe that the ability of the sniffing dogs to detect certain smells associated with malaria can be an inspiration for the development of new and artificial electronic noses that can smell diseases.
Malaria guard dogs at the borders
Lindsey believes that the sniffing dogs may be helpful when health authorities want to control villages for malaria carriers who do not have visible symptoms. By being a carrier, you can transfer malaria parasites to local mosquitoes. The only way we must prevent spreading today is to test or cure everyone in a city.
The researchers behind the survey therefore believe that the sniffing dogs would work well at border crossings, to countries where malaria is almost extinct. Lindsey draws on the eastern island of Zanzibar, where the removal of the malaria parasite has been difficult due to a steady stream of immigrants.
Too little correct
Gunnar Hasle is a specialist in infectious diseases and runs Reiseklinikken in Oslo. He says that the preliminary hit rate of 70 percent is too low.
"This means that the method is useless to find out if a fever has malaria, as it is not acceptable to quit a 30 percent error.
He also points to 90 percent of those healthy, and that 10 percent get an error message about malaria.
"It's an unacceptably high figure if the method is to be used to smell a large number of healthy people," he says.
Blood test at the clinic, dogs at the borders
Hasle also says that odor indications have been used for hundreds of years. It is possible, among other things, to succeed in diabetes by breathing odor of acetone or nail polish remover. In addition, it is possible to smell liver failure because the breath has a sweet smell.
"It has also been tried to make dogs diagnose lung cancer," says Hasle, referring to a survey from 2012. The result was about the same as in the malaria process.
He thinks it's completely impossible to use dogs to diagnose clinics and that it will still be difficult to train enough dogs to meet the need
– Every health unit in the tropics should have access to malaria diagnoses. Then it's much easier to get quick tests that you can use after minimal training than getting trained dogs.
However, he believes that in some cases they can help and support the researchers' thoughts of using the sniff dogs as malaria guards.
"Sniff dogs can be used for mass screening on immigration to an area that has eradicated malaria," he concluded.