PARASITES OF WILD GROUSE 423 



question to be answered is whether this represents an age immunity or one acquired through 

 recovery from previous infection. The solution will require the infection of young birds held 

 in captivity and the following of the subsequent course of the disease. 



The overall incidence of infection in grouse over three months of age was 12.7 per cent. 

 Despite the fact that the stomach worm occurs half as often as the intestinal worm during 

 the same time period, the former possesses a much greater potentiality for damage to the 

 host. 



Where it occurs in New York, D. spiralis infection is the most important worm parasite 

 among wild ruffed grouse. The determination of its relative role in grouse population fluc- 

 tuation is not easy. No significant variation in occurrence from year to year and no relation 

 to cyclic diminution can be demonstrated. During the period of the Investigation, no epizootic 

 phase of the disease has been observed. The scope of this survey can only justify the conclu- 

 sion that this parasitic infection may be a cause of grouse mortality in certain areas. 



Gizzard Worm (Cheilospirura spinosa) 



Distribution. This parasite has been found in ruffed grouse from Michigan, New York, 

 Minnesota. Pennsylvania, New Jersey, Wisconsin, and Massachusetts, and in bolnvhitc quail 

 in Virginia and Tennessee. In New York it has been found to be widely distrilnitcd through- 

 out all the region. 



Description. Cheilospirura is a moderately slender pinkish worm found beneath the cor- 

 neus lining of ihe gizzard. The females measure up to T j inches, the males to ^'\ of an inch 

 in length. Cram gives a conii)lete description"". 



Lije Cycle and Dissemination. Embryonated eggs, discharged in the feces, are ingested by 

 grasshoppers. The worm larvae migrate from the digestive tracts of these insects and 

 become loosely encysted in their bodies. After 25 days, the infective larvae are developed. 

 Wlien susceptible birds eat infected grasshoppers, infection results. Maturity of the parasite 

 within the bird is reached in 45 days. 



Cross transmission of the parasite from ruffed grouse to quail was proven experimentally. 

 Aside from the fact that the life cycle of this jiarasite has been worked out, very few of the 

 factors that determine the spread and pathogenicity of this worm are known. Cram" noted 

 that with the gizzard worm infection in chickens (C. hamulosa) a certain proportion of the 

 invading nematodes failed to develop. She suggested the possibility that the health of the 

 individual fowl might play a role in explaining this phenomenon. It is likely that a similar 

 condition exists in grouse thus infected. The earliest date on which Cheilospirura was found 

 in grouse chicks was July 15 when it a|)peared in a female weighing 221 grams (almost 

 8 oz.). 



Pathogenicity. In experimental transmission experiments, Cram"" demonstrated the patho- 

 genicity of the gizzard worm for ruffed grouse and quail. Hemorrhage and necrosis of the 

 gizzard lining were noted, these changes being accompanied by flabbiness of the gizzard mus- 

 culature. Over a period of 84 days, an unnatural growth of this organ was produced in one 

 quail with a heavy infection. Fisher"" stated that in Michigan, where infection during 1935 

 and 1936 was over 50 per cent. "Many of the grouse were so heavily infected with these para- 

 sites that part of the lining of the gizzard had been destroyed and there was destruction of 

 the surrounding tissue." 



On the other hand, Boughton"" failed to find serious lesions in infected grouse in Minnesota. 



