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Title: Effects of the caecal threadworm Trichostrongylus tenuis on red grouse
Author: Wilson, George R.
Awarding Body: University of Aberdeen
Current Institution: University of Aberdeen
Date of Award: 1979
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The reasons for the declines in red grouse numbers that occur periodically on the heather moors in the British Isles, have been uncertain for a long time. During some declines many grouse are found dead in poor condition, bearing thousands of tiny threadworms Trichostrongylus tenuis in their intestinal caeca. The purpose of my study has been to find whether threadworms alter the health of well-fed grouse. Although 90% of wild grouse that I examined carried threadworms, old birds had 30 times as many as young birds, and most of the worm population was carried by a few heavily infected grouse. This highly skewed distribution of parasites within hosts is common in parasite infections. Grouse become infected with threadworms when they eat worm larvae on heather. During the present study, adult worms were well tolerated by grouse and produced eggs which were passed in the birds' faeces for over a year. Nevertheless, the immune system of the birds seemed to be reacting to the presence of either larvae or worms, in that the numbers of circulating eosinophils and heterophils rose as did the concentration of alpha, beta and gamma globulin. The pathogenic effects of worms varied amongst individual grouse, and some grouse carrying 3000 - 4000 worms died while others survived with many times more. Infected grouse developed a mild anaemia and the levels of serum albumin in their blood fell. Body weight did not change but muscle masses shrank. These physiological changes were associated with a reduction in dominance of captive grouse at least in the short term, although two wild grouse dosed with trichostrongyles maintained their territories and breeding status. The idea of a link between trichostrongyles and either the dominance of grouse or their ability to hold territories should be retested. In conclusion, trichostrongyles reduce the condition of grouse and other physiological variables usually associated with good health, although they do not kill many well-fed grouse. In the wild, these effects might contribute to declines in population, especially if associated with poor nutrition.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available