"GROUSE DISEASE "—STRONGYLOSIS 231 



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. 

 An examination of serial sections of the cfeca in heavily infected Grouse shows 

 that here and there the mucous membrane is penetrated by the anterior end of 

 the worm ; but no evidence was obtained from the sections that such penetration 

 led to the local invasion of the tissues by intestinal bacteria. The presence of 

 eosinoplulia in the blood as demonstrated by Dr Fantham indicates that 



• 1 Signifi- 



certain substances secreted or excreted by the parasite pass into the oanceof 

 circulation.' These, together with the loss of function of the cseca, 

 owing to the extensive decortication of the epithelial lining by the worms, seem^ 

 to me to sufficiently account for the resulting symptoms of the disease. The 

 final invasion of the general circulation by bacteria represents the terminal 

 phase in the progress of the disease, and not an essential factor in its causation. 

 Most adult Grouse suffer also from a slight degree of Coccidiosis. This parasite 

 to a much greater extent destroys the epithelial lining, so that were the 

 common disease amongst Grouse primarily the result of invasion by intestinal 

 bacteria, the coccidia should play a more important role than the Tricho- 

 strongylus in the causation of the symptoms of " Grouse Disease." Yet it is 

 well known that the droppings of adult birds may show evidence of considerable 

 infection with coccidia without any symptoms of disease being apparent. 

 Death of adults from Coccidiosis apparently only results from an intensity of 

 infection not met with on the moors, but only in the hand-reared birds or birds 

 experimentally infected. 



If it be accepted that Trichostrongylus jiergracilis is the primary and essential 

 factor in the production of the common form of "Grouse Disease" Remedial 

 remedial measures must be directed either to the destruction of the ™'^^s"'"'^s- 

 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 stay outside the body. 



The destruction of the eggs or embryos by surface dressing with cheap 



' Vide chap. xiii. p. 316. 



