PARASITES OF WILD GROUSE 421 



scaber and Armadillidium vulgare, acted as intermediate hosts. The eggs laid by the female 

 worms pass out with the feces and are ingested by the sow bugs. After a period of develop- 

 ment of about 26 days, the larvae become infective. When infected sow bugs are eaten by sus- 

 ceptible birds, the larvae are liberated and invade the lining of the stomach. The worms reach 

 maturity in 27 days. 



It is not known how long the eggs of this worm remain viable or its larvae live in the in- 

 termediate host as a source of infection. It is significant that, in practically every instance, 

 grouse found to have severe lesions or to have died as a result of infection, were encountered 

 during the late fall and early winter. In fact, the incidence of the infection was highest during 

 that time of the year. 



Apparently the birds pick up stomach worms during the summer and fall. The effects of the 

 parasitism are seldom evidenced until the worms have matured. 



The smallest bird in which Dispharynx was found was a young male which weighed 144 

 grams (about S oz.) collected on July 27. The earliest record of occurrence was in a young 

 female collected on July 20. That she was in good flesh may be judged from her weight of 

 292 grams (about 10^2 oz.). at the time of collection. 



That infections with this worm may be quite localized was illustrated by collections made 

 on Connecticut Hill in 1934. Five birds out of 17 in one covert were infected while no stomach 

 worms were found in 13 birds taken in another covert 200 yards away. Each covert included 

 about 250 acres. They were separated by open land. 



PalliDficiiirilv. Dispharynx s/iiralis is |)robab!y the most ])athogenic parasite of wild grouse 

 in the more settled parts of the Northeast. Heavy infections with this worm result in a severe 

 inflammation of the glandular stomach or prevent riculus. This becomes filled with a thick, 

 white, shiny mucus. The proventriiular wall becomes tremendously thickened, sometimes to 

 three and four times its normal size. There is an extensive destruction of the glandular tissue 

 and of the muscular layers of this organ. This tissue destruction may progress to such an 

 extent that perforation of the glandular stomach may bring on peritonitis. 



Tissue necrosis quite often accompanies this parasitism. In many instances the proventri- 

 culus, due to destruction of its musculature, becomes quite flaccid and may telescope in its 

 entirety into the gizzard. Cases have been found where healing of the lesions resulted in the 

 production of masses of dense connective tissues resulting in a partial or complete closure of 

 the organ. 



Large numbers of worms may not always be found in spite of extensive tissue damage and 

 sometimes none are encountered. Undoubtedly many of the parasites pass out of the bird 

 with the sloughed off tissue or they may become detached during the time the bird is in a 

 dying state. On the other hand, 100 or more of the worms have been dissected out of a single 

 bird. Allen and Gross" have reported as many as 228 in one stomach. 



The invasion of the proventriculus by the stomach worm sometimes results in emaciation, 

 weakness and finally death. Hunters occasionally report that birds, later found to be seriously 

 infected, were sluggish in flight or that their dogs, unaided, ran down and caught the birds. 

 This is undoubtedlv due to weakness resulting from loss of function of the proventriculus 

 through tissue destruction and plugging of the stomach cavity. 



Light infections with this parasite have been encountered where no apparent ill effects on 

 the birds were noticeable. In these cases, however, the parasites were few in number and only 

 a small portion of the proventriculus was involved. 



