Intestinal helminth parasites have various effects on Finnish forest grouse


<p>The grouse species in Finnish forests - the capercaillie, black grouse, and hazel grouse - are hosts to several intestinal helminth parasite species. Helminth parasites are found commonly in the entire area of distribution of forest grouse. The most common intestinal helminth parasite in adult birds is Ascaridia compar. Findings suggestthat increased abundance of <em>Ascaridia compar</em> has a negative effect on the growth rate of grouse populations.</p>

Researcher Marja Isomursu from the Production Animal and Wildlife Research Unit at the Finnish Food Safety Authority Evira has in her thesis studied the effect of intestinal helminth parasites on grouse species in Finnish forests. The study was conducted in the University of Oulu in cooperation with the Finnish Game and Fisheries Research Institute and the Arctic Centre at the University of Lapland.

Forest grouse populations have fluctuated strongly in Finland and parasites have also been suspected to play a part in the fluctuations. The correlation between annual grouse populations and the abundance of parasites was analysed in the thesis. Ascaridia compar did indeed appear to have a reducing effect on the grouse population growth rate. The parasite was most common and most abundant in the years of grouse population decline.

The study material consisted of intestinal samples collected by hunters in five game management districts during the years 1995–2002. The most common parasite species in the samples was the nematode Ascaridia compar. Also, three species of cestodes (Skrjabinia cesticillus, Paroniella urogalli and Hymenolepis sp.) were found. Large size, male gender and age over 1 year were connected with an increased probability and intensity of A. compar infection.

Cestode infection seemed to make grouse more vulnerable to canine predation. Grouse infected by cestodes were significantly more common in bags hunted with a dog than in bags hunted without a dog. 

 Thesis in full Host–parasite interactions of boreal forest grouse and their intestinal helminth parasites (pdf, 733 kB)
English abstract (pdf 12 kB)

For more information, please contact:
Researcher Marja Isomursu,Production Animal and Wildlife Research Unit,
tel. +358 40 512 1248

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