The effect of Trichostrongylus tenuis on the caecal mucosa of young, old and anthelmintic-treated wild red grouse, Lagopus lagopus scoticus.

The caecal mucosa of wild young and adult grouse infected naturally with Trichostrongylus tenuis was examined by means of scanning electron microscopy and compared with adult grouse which had been treated with an anthelmintic. The caecal mucosa of young red grouse with low worm burdens possessed longitudinal plicae and exhibited little damage. The caeca from adult grouse, most of which carried high worm burdens, showed a localized depression of plicae and atrophy and cell disruption in areas of nematode aggregation. Caeca from adult birds treated with an anthelmintic showed a similar caecal structure to lightly infected caeca from young birds. It is concluded that the normal functioning of the caeca is probably affected by heavy infections of T. tenuis.