AgResearch scientists have confirmed a “clear timeline of changes” in livestock that could help in the early identification and management of the costly burden of intestinal parasites. Now the scientists want to test these potential early indicators of infection to prove they can be relied upon in any future diagnostic tools.

These parasites, or gastrointestinal nematodes, are a global problem impacting on livestock health, welfare and production. Infection can cause anorexia (reduced appetite), diarrhoea, anaemia, nutritional deficiencies and parasitic gastroenteritis, which can result in reduced liveweight gain, milk yield, or wool production. At worst, high burdens of these parasites can lead to death. These negative impacts contribute to financial losses estimated to be tens of billions of dollars for sheep, goat, cattle and pig production globally.
Adding to this challenge for livestock industries is the growing issue of parasites becoming resistant to drugs that have traditionally been used to control them. New diagnostic tools are now sought after to help farmers and industries manage the problem in New Zealand.
“We knew from previous studies that certain changes in animal behaviour and physiology can be early signs of disease,” says AgResearch scientist Melissa Hempstead.

Scientist Melissa Hempstead at work on the parasite research

“So, we set out to study changes in lambs infected with larvae, in an experiment that compared them with those that were free of infection. Thirty eight-month-old Romney-cross wethers were housed in pens where we could observe their behaviour from video camera recordings and we also attached sensors to them to continuously record their movements. We measured their liveweight and body condition throughout, as well as collecting blood, faecal, and saliva samples for the six weeks of the larvae treatment. All of this was done according to an animal ethics approval process.”
“We found that from week two, the infected lambs spent less time feeding and more time lying than the lambs free of infection, through to week five. At week three, elevated lipids (compounds including fats and oils), loose faeces and faecal soiling around the anus were observed in infected lambs. From week four, the faecal egg counts were elevated in the infected lambs and there was lower liveweight gain at four and five weeks compared with the uninfected lambs.”

While some of these changes have been previously documented as related to internal parasites, this may be the first research to show changes in lipids associated with worm infection in sheep and highlights a potential indicator of disease. Further Investigation is required to establish links between these increased lipids and animal health and wellbeing.

“A feature of this research was the use of metabolomics, an approach in which we can identify and quantify metabolites such as lipids and amino acids. To our knowledge, studies using metabolomics on sheep with intestinal parasites had not been performed before.”
“Overall, the results of this research show promise for future studies on early identification of parasitism in lambs. It provides a path to the development of diagnostic tools for use on farm to improve animal welfare and farm profitability.”

The published results of the study can be read in full here(external link)

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