Studies on the helminth parasites of sheep in Southern Greenland.

The nematode population of sheep on Greenland is dominated by Ostertagia circumcincta and three Nematodirus species: N. spathiger, N. helvetianus and N. abnormalis. These results are compared with those for other Nordic countries. Great similarities exist with subarctic Norway but there is a lesser degree of correlation with Iceland and lowland Norway which tend to have a richer spectrum of species. N. helvetianus and N. abnormalis, however, have not been reported from sheep in these countries. The abomasal worm population was remarkable in that it contained specimens with an abomally large body size. The epidemiology of infection followed the pattern recognized throughout Europe with an early-season periparturient rise in the faecal egg-count of the ewe being followed by increasing levels of infection in lambs in late summer. The epidemiology of Nematodirus infections was quite distinct from that seen in most of Europe. Species differences and the cool summer climate were thought to account for this disparity and a hypothesis was advanced to explain the observed pattern of events. Levels of infection were apparently similar in undergrazed and fully-utilized grazing areas. Dosing ewes during the winter (between November to March) eliminated the periparturient egg rise. Lambs could be kept almost worm free by keeping them on clean rangeland and dosing at 3-5 week intervals. A clear weight-gain advantage over conventionally reared lambs was only recorded in one year of the study.