"GROUSE DISEASE " STRONGYLOSIS 235 



covered with Trichostrongylus pergracilis, but no evidence of 

 extravasation of blood into the lumen of the caeca was found 

 on the death of the bird. Apparently that seen in the first 

 case must have been associated in some way with the develop- 

 ment of the parasite before reaching maturity. 



These two experiments indicate in so far as such a limited 

 number may, that this parasite in very large numbers has a 

 marked pathogenic action upon Grouse, inducing loss of weight, 

 progressive wasting, and in extreme cases, death. 



If it be accepted that Trichostrongylus pergracilis is the Remedial 

 primary and essential factor in the production of the common n 

 form of " Grouse Disease " remedial measures must be directed 

 either to the destruction of the adult parasite within the bodies 

 of the birds, or of the young forms during their stay outside 

 the body. 



The impracticability of the former of these two methods is 

 obvious. The birds are unapproachable, and are spread over 

 a very wide area. Vermifuges or antihelminthics are expensive 

 and more or less poisonous substances, the dosage of which 

 has to be carefully estimated and controlled. The problem 

 therefore resolves itself into that of destroying the eggs and 

 larvae of the parasites during their existence outside the body 

 of the bird. 



The destruction of the eggs or embryos by surface dressing 

 with cheap chemical substances would appear at first sight to 

 be a hopeful line of action, but the occurrence of the caecal 

 droppings more or less all over the moor, and the enormous 

 area requiring treatment, render the suggestion of any such 

 method futile. Moreover, as we have shown, the larvae after a 

 brief period of development ascend the heather and can remain 

 hidden in the crevices of the leaves, in a quiescent, invisible, 

 and living state for a prolonged period. The only conditions 

 that could be inimical to these the infective forms would 

 be atmospheric conditions of marked severity, possibly a 

 prolonged frost or a prolonged drought, or destruction of the 

 infected heather by fire or cutting. The effect of extreme 



