The worm in sheep’s clothing

Good news for sheep: scientists have moved a step closer to understanding how a disease-causing worm evades the sheep immune system.

Parasitic gastroenteritis (PGE) causes diarrhoea, weight loss and dehydration in sheep and can be fatal. The disease is commonly caused by a nematode worm, Teladorsagia circumcincta, which makes its home in the stomach of sheep. The infection is then spread throughout the rest of the flock as the worm’s eggs pass out with the faeces, hatch and develop into infective larvae in the grass, which is eaten by other sheep.

Due to its impact on the health of the sheep, PGE is estimated to cost UK farmers £80 million a year in lost revenue from their flocks. And new strategies to control the disease are urgently needed as the worm is developing resistance against current treatments, rendering them ineffective.

Now, researchers from the University of Edinburgh and the Moredun Research Institute in Scotland, have identified a molecule they believe the worm uses to confuse the sheep’s immune system.

They found that Tci-MIF-1, produced by the infecting worms, mimics the action of a natural chemical messenger in the sheep’s immune system. They suggest that this is one of a number of molecules designed to confuse the sheep immune system, so the worm can live in the gut for longer.

“The discovery of this molecule is an exciting step forward in our understanding of the way worms affect mammalian immune systems,” said Professor Jacqui Matthews from the University of Edinburgh, who led the research. “As our knowledge of these worms expands we come closer to finding new ways to control the diseases they cause.”

The study was funded by the Scottish Government Rural and Environmental Research and Analysis Directorate (RERAD) and the Wellcome Trust.

Part of this study was completed by Natasha Bell as part of a summer vacation scholarship funded by the Trust. This was part of the University of Edinburgh’s Research Track Programme.

Image credit: Wellcome Library, London