PARASITES OF WILD GROUSE 419 



determined whether the bird was infected before or after arrival. 



Incidence and Importance. An incidence of 0.2 per cent gapeworm infection in wild adults 

 and an incidence of 0.9 per cent in young chicks would not indicate this parasitism to be of 

 particular importance in grouse populations, even if there were evidence to show that it caused 

 serious lesions. 



In the Digestive Tract 



It is in the digestive system that the greatest numbers and variety of parasites are found. 

 The roundworms, tapeworms and coccidia which occur there are discussed below. They are 

 arranged according to the organs in which they are found, starting with the crop worm and 

 ])roceeding through a discussion of stomach and gizzard worms to the parasites of the intestine. 

 The relative positions of the various organs is shown in figure 80. 



Crop Worm (CapiUaria annulata) 



Dislrihulion. This parasite has been reported from grouse in New York. Michigan, south- 

 ern New England, from pheasants in New York, from quail in Virginia. Turkeys and chickens 

 throughout the East and the South, and other gallinaceous birds in Europe, Brazil and the 

 I'hili])|>incs are likewise susceptible. In New York, the birds found to be infected with this 

 worm were all taken in the Hudson River Valley. It was nol fomul in cilln r |iarl> of llir Skili-. 



Description. The crop worm is a long, thread-like form that is frequeiitb found imbedded 

 in the lining of the crop and esophagus of wilfl grouse. The niaics measure up to I inch long 

 and the females up to 2Vi inches. Though it is fairly long, it is so narrow that it is very 

 difTicult to observe. 



IJfe Cycle and Dissemination. Wehr'™ has found that earthworms act as intermediate hosts. 

 Apparently the larvae undergo a period of develoi)mcnl in the earthworm iiefore infection 

 of the avian hosi <an take place. 



Little is known witli regard lo the spread of this parasite under natural conditions. It is 

 probable that earthworms harboring the larvae may be infective over long periods of lime, as 

 has been demonstrated with the gape worm. Since the great majority of the cases encountered 

 in grouse were light infections with no noticeable gross changes, it does not seem likely that 

 conditions for massive infections of birds exist in areas frequented by grouse. 



Pathogenicity. Crop worm infection due to C. annulata has been found to l)e pathogenic 

 for many species of domesticated and wild birds. The literature is well reviewed by Cram"'. 

 Allen and Gross" have described a severe anemia in ruffed grouse when heavily infected. The 

 nature of the lesions produced is quite similar to those found in other species. There is a 

 marked thickening of the crop lining with an extensive wrinkling of the surface, giving the 

 organ a corrugated or washboard-like appearance. A false membrane is formed on the inside 

 which sloughs off in patches. If the croj) is stretched tightly between the bands and held up to 

 a strong light, the wavy outline of the parasites can be seen in the wall. Light infections with 

 this worm in grouse produce a thickening of the crop lining and cause an exudation of mucus. 



Incidence and Importance. The incidence of infection in birds of three months or older 

 was slightly more than one per cent. The average number of crop worms found was seven. 

 Most of the birds having the parasites were only lightly infected and suffered no marked gross 

 injury. The low incidence and degree of infection and the restricted area in which the para- 

 sitized birds are found eliminate this disease from serious consideration as an important factor 

 in grouse abundance. 



