Dogs are trained to detect sheep infected with parasites. Now scientists are developing a device that mimics this detection, writes Dr Marina Murphy
It has to be a dog's dream job - sniffing sheep and their droppings. But it is not all about having fun. Canine sniffing skills which allow dogs to detect worm-infected sheep could pave the way for the development of a new electronic device able to identify the presence of parasites in sheep. Early detection could potentially save Irish farmers millions of euro in lost productivity.
A prototype of the handheld electronic "sniffer" device could be available in just five years, potentially replacing the faecal worm counts currently used to quantify infection.
Its development comes from the training of dogs to detect the signs of gastrointestinal worms in sheep droppings. Sheep pick up these parasitic worms on pasture or in water. If they become heavily infected, they can develop diarrhoea and lose their appetite. Growth rates are poorer and the quality of the wool is affected. Some animals die.
Drugs have been used for many years to treat infected animals, but many parasites have developed resistance to them. Resistance is a major problem in Irish sheep.
Recent studies by Barbara Good at Teagasc Sheep Research Centre in Athenry, Co Galway, found evidence for resistance to the antiparasitic drugs Benzimidazole and Levamisole in 80 per cent and 30 per cent, respectively, of flocks tested.
"It is unlikely that any new drugs will come on the market in the near future, and even if they do they will meet the same fate as the present products, ie develop resistance to them," says Good.
"Developing a tool that could quantify the level of infection and help farmers make treatment decisions would ultimately be important," she says.
Resistance is less likely to develop if farmers only treat the worst-affected animals and leave the sheep with low-level infections untreated. This ensures the survival of worms susceptible to drugs, while ensuring that the sickest animals are treated.
"At the moment, counting worms in fresh faeces under the microscope is the main tool available to farmers to identify the sickest animals," says Good.
Researchers at La Trobe in Australia wanted to try something different and hit on the idea of using dogs. Seb, a female German shepherd, was trained to detect parasite-infected sheep droppings in much the same way as dogs are trained to detect drugs.
The dog was repeatedly exposed to bags containing infested faeces that were placed among bags of non-infested faeces and trained to pick out the infested samples. Seb was 80-90 per cent accurate.
"This is actually too good for farm use as most sheep will have infections and we only want to detect those with clinically important infections," says Kate Richard, a scientist at La Trobe and the owner and handler of Seb.
But sheep across Ireland will no longer have to suffer the indignities of standing for faeces-sniffing dogs. The La Trobe scientists plan to identify the chemicals that the dog is picking up and use the information to develop an electronic handheld "sniffer" device. Farmers would hold the device near the sheep or near faeces to get an instant result. "This would save farmers substantial amounts of money from reduced drug usage, labour and time," explains Richard.
Good agrees that the approach is potentially important. "Irish consumer's desire for chemical-free food means it is important that we know why and when treatment is needed."
Gastrointestinal worms live in the intestinal tract, breed and lay eggs, which pass on to the pastures and hatch into larvae that develop and re-infect their hosts. The cycle can become very rapid in mild, moist conditions when animals are in confined areas.
Drugs are used in these cases to control diarrhoea. And as the larvae re-infect animals, treatment is repeated over and over again, which is how resistance develops.
Three major worm species were used in the trials. All the faeces came from experimental animals for which precise knowledge of their infections and disease were available. Richard admits that the presence of other diseases in the farm environment may complicate detection and says that further work is required to overcome any potential problems.