Solving sheep’s can of worms

Breeding for high-value production traits has increased the susceptibility of sheep to a range of diseases, including worms.

Tiny worms in sheep and goats cause one of the biggest problems in the meat and wool industries. Affecting the health, reproduction rates and wool production of livestock, worm infestations can cripple a farming enterprise.

The main control methods used are anthelmintics/drenches, but the historic over-reliance on these chemical solutions has seen worm resistance increase, and the treatments become less effective.

Research undertaken at Federation University is helping to understand worm infections and find solutions. Dr Sarah Preston, who has published more than 30 scientific papers on immune responses to parasitic worms and tracking anthelmintic resistance, is currently looking for more farmers to become involved in her ground-breaking research, particularly on developing a quick test that can be applied in the field to determine whether an animal is resistant to worms.

“We still can’t diagnose worm infections very accurately without killing the animal, cutting it open and seeing how many worms they have,” she says. A small number of sheep producers will look at faeces under a microscope to look for worm eggs. “It’s a very small percentage that does that because they don’t have the time or the experience. But worm egg detection often doesn’t correlate with the number of worms in the animal, as the eggs are not equally distributed throughout faeces.”

Instead, having received funding from the Victoria Government, Dr Preston is looking for other ways to determine worm resistance in sheep – ideally a quick test similar to the COVID rapid antigen test that could be done on-site, such as in sheep yards. She says animals with worms will have an immune response to the parasites.

“We’re seeing if we can use markers of that immune response rather than markers of infection. We’re looking at blood tests, but also saliva, because then you wouldn’t need a vet – the farmer could do it themselves. There is a saliva-based test that has been developed in New Zealand, but it can’t be done on-farm and is not readily available in Australia.”

Dr Preston says breeding for high-value production traits, such as fine wool or meat quality, has increased the susceptibility of modern sheep to a range of diseases, including worms. “It’s a balancing act – you don’t want to breed really resistant sheep because, in the long run, you’re not going to make really good money off them.”

Her research and other studies have shown that some sheep more susceptible to worm infections are heavier and have finer wool. “It’s generally found that only a small percentage of the flock will have the biggest worm burden, but some of them will be the most highly productive animals,” she says.

“We think it’s related to the immune response. They’re able to convert energy from the food they’re eating to increase production traits, even though they have a heavy worm infestation. But others convert the energy into an immune response against the worm, rather than putting it into production traits.”

Providing farmers with on-farm tests to easily identify worm-resistant animals will give them the opportunity to balance animal selection based on production traits and immunity. This will allow them to be less reliant on drenches in the future to control worms.

Dr Preston is also fitting accelerometers to sheep and using a machine-learning algorithm to understand how worm infection affects the behaviour of sheep. The collar accelerometers can pick up behaviours such as movement, idling, head movement and ruminating.

“Previous work has shown some there are differences in the ways sheep with worms behave – they tend to travel to water sources more often, so they’re thirstier. But results in other tests have been inconclusive.”

Anyone who would like more information or become involved in the research should contact Dr Preston.

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