Trichostrongylus tenuis

Trichostrongylus tenuis, also known as the strongyle worm, is a gut nematode found in the United Kingdom, sensitive to Pyrantel pamoate. Larvae have a short migration inside the mucosa of the intestine and return quickly to the digestive tract.

This endoparasite causes a condition often called strongylosis or 'grouse disease' and which can be the cause of regular crashes in grouse populations. When the adult worm burrows into the caeca walls it causes a lot of damage and internal bleeding which in itself is harmful to the grouse. The worms ultimately reduce the digestive efficiency thus affecting the condition of the grouse. The eggs of the strongyle worm found in the caecal droppings of Red Grouse, hatch out into a microscopic larvae stage. Living within the dropping they feed off bacteria and organic matter they develop through two moults reaching their third larval stage, 'L3'. The 'L3' larvae is now at its infective stage so it 'swims' up heather stalks, on a thin film of liquid, to the young shoots where it is most likely to be ingested by a host. Once in the body of a host they enter one of the two caecum in the intestine of the host where the larvae develop into adult worms. The adults mate within the caeca and the female can lay over 100 eggs a day which are passed out in the caecal dropping.