Ascaridia bonasae is a large, whitish nematode normally located in the small intestine of ruffed grouse. Hunters may find this roundworm in the body cavity when it escapes through holes in the small intestine created by pellets of shot.
In Ontario, A. bonasae is one of the most common parasites of ruffed grouse and can be found in birds throughout their range. Clarke (1936) found A. bonasae in 21 % of 124 grouse.
The life cycle of A. bonasae is direct, i.e., no intermediate host is necessary. Eggs are laid by adult female worms in the intestine of the host and are eliminated with the droppings. These eggs are in turn picked up by susceptible birds in feed and water. Development to adult worms then takes place within both the lumen and tissues of the wall of the small intestine.
Adult female worms measure up to about 50 millimetres and males to approximately 35 millimetres in length. There are usually only a few worms present in each grouse although more than 75 worms have been reported from a single bird. Dorney and Kabat (1960) reported that the extent of infection of young grouse with A. bonasae during the summer is directly related to the abundance of grouse during the latter months of the previous winter.
A. bonasae is not considered a serious pathogen of ruffed grouse and does not affect the edibility of the birds.
Selected References:
Bump, G., R.W. Darrow, F.C. Edminster and W.F. Crissey. 1947. The ruffed grouse-life history, propagation, management. The Holling Press, Inc., Buffalo.
Clarke, C.H.D. 1936. Fluctuations in numbers of ruffed grouse, Bonasa umbellus (Linnč), with special reference to Ontario. University of Toronto Biological Series No. 41. The University of Toronto Press, Toronto.
Dorney, R.S. and C. Kabat. 1960. Relation of weather, parasitic disease and hunting to Wisconsin ruffed grouse populations. Tech. Bull. No. 20, Wisconsin Conservation Department, Madison.
