The sniffer dog joins the drive to pin the Corona virus down, says S.Ananthanarayanan.

As means of containing Covid-19, economic pressures are making it impractical to continue lockdown and meaningful isolation. And as long as people travel, and mix, spread of the disease is inevitable. Lockdown, in any case, is an onerous measure that mostly keeps healthy people away from other healthy people. Workable control needs to find and draw aside the infected ones. For this, having methods of rapid testing is the only way.

The ‘gold standard’ test for SARS-CoV2, the Covid-19 virus, is RT-PCR. As traces of the virus in sample fluids taken from patients are very sparse, RT-PCR works by getting these particles to multiply till they are easier to identify. The method, unfortunately, is time consuming and expensive.

An easier method is to look for the body’s immune reaction – the antibodies, which can signal the presence of the virus. The method, however, is not accurate, and healthy persons could be labelled as infected, or infected persons allowed to go free. The best efforts to locate where the infection is present are hence not good enough and the pandemic continues to rage.

As a measure to fill the gap, London School of Hygiene & Tropical Medicine (LSHTM), in collaboration with Medical Detection Dogs, an organisation that trains dogs to detect disease, and Durham University, which trained dogs to give early warning of malaria, have set out to see if dogs could step in. The study has received over half a million Pounds from the UK Government and If the study is successful, “the dogs could provide a fast and non-invasive detection method …. potentially screening up to 250 people per hour each,” a press release says.

Detection with the help of dogs is to leverage the amazing sensitivity of dogs to smell, and the fact that most organic entities exude some kind of odour. Nature, in fact, makes extensive use of odour for communication – this is both because odours are easily dispersed and that it is economical, as only infinitesimally low concentration is needed. Most animals declare their readiness to mate and reproduce by an odour – there are insects that can attract a mate many kilometres away – rodents and insects use smell to locate sources of food - the ability is found even in fish, in all creatures, from molluscs to mammals. In fact, even kinds of plants exude vapours when under stress, like grass when a lawn is mowed, to induce drooping or closing of leaves, or to discourage a predator.

The dog, among mammals, is again known for its acute sense of smell, and over centuries of domestication, this sense has been made to work in many ways. The dog, with its pack instinct, identifies closely with humans, and has been trained, as a watchdog, to tend sheep, to draw sleds, to lead the blind, for instance. And with its sense of smell, as a tracker and police dog. The odours of a missing person, or a fugitive, remain for a time at the place where she was last seen. A trained dog can then follow the scent to show its handlers the right places to look. Again, organic substances or chemicals, used as drugs, have odours that dogs have been trained to detect – and they are used to find contraband, even securely sealed in baggage.

In disease, also, the presence of bacteria, viruses, cause changes in the body and the body’s aura of chemical emissions. Detecting disease by analyses of the breath or body odours is now regularly practiced. While there are protocols and procedures, and devices like electronic noses, detection with the help of animals has been established, by dogs for lung or colorectal cancer, by rats for tuberculosis, for instance. Volatile compounds, or odours, from breath, blood, skin or urine are found as biomarkers of metabolic, genetic, or other disease, like diabetes, kidney or liver failure, multiple sclerosis, Parkinson’s disease, bacterial infections

In the case of malaria, it has been discovered that the mosquito, in taking a blood meal, selects infected persons over persons free of malaria. The reason appears to be that the blood of infected persons, which is depleted in red blood cells, is easier to feed on, and it may be an adaptive feature of the malaria parasite. As it looks like the medium of signalling the presence of malaria is through smell, researchers in the Durham University, UK, tried out using trained dogs to detect malaria through smell.

Dogs are readily trained by conditioning, by exposing the dogs to mixed stimuli, with a reward whenever they make a correct choice. This is the method used train dogs even in complex tasks like detecting drugs or explosives. In the same way, the Durham University team trained a pair of dogs to make out the scent of children infected with malaria from those who were not. The dogs were then presented with samples consisting of 175 used nylon socks of schoolchildren from West African Gambia, shipped to the UK. 30 of the 175 socks were of children infected with malaria. The dogs could successfully detect 70% of the socks of infected children and tell that 90% of the others were clean.

The same Durham University, and LSHTM, which was also part of the malaria trial, and Medical Detection Dogs, are now set to see if infection by SARS-CoV2 also gives rise to odours that dogs may be able to detect. As respiratory diseases are known to affect the body odour, it is felt that COVID-19 would have this effect. It really does not follow, as the early stages of the disease, which is when we are looking for a method of detection, have still not descended to the respiratory organs, but it is still quite likely that there is an odour.

The experiment is under way, with a team of six dogs, Labradors and Cocker Spaniels, undergoing training with samples collected from London hospitals. If the dogs are able to make out an odour that is unique to COVID-19, they can be trained to pick out infected individuals. They could then be stationed at places like airports, where every incoming traveller could be instantly screened, as she goes past.

The canine apparatus The insides of the canine nose consists of folds of skin, which contain 300 million smell-sensing nerve endings, compared to just 6 million that humans have. The area in the brain, dedicated to smell, is forty times larger than that of humans’, and the dog’s nose is said to be a hundred thousand times more sensitive. Research by Medical Detection Dogs shows that trained dogs can detect the odour of disease at the equivalent dilution of one teaspoon of sugar in two Olympic-sized swimming pools of water. This amounts to one part in six billion.

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