Haggis: the next victim of global warming?

Dr Sandy Clark, the vetinary centre manager at the Scottish Agricultural College in Thurso, said the parasite was thriving because it is able to survive in grazing all year round in the warmer climate.

Although lung worm will not necessarily show up in a healthy sheep or affect all the meat, it will make the lungs of the animal unfit for human consumption.

"Lung worm has been at a very low level and did not cause serious problems in sheep but with the changing climate and availability of the parasite it is becoming a problem," he said.

He also said lung worm has increased because new technologies mean farmers are only medicating animals that are shown to have traces of other diseases, rather than treating all animals on a regular basis.

"The sad fact is that the disease is causing the lungs to be condemned for human consumption because of the lung worm damage," he added.