250 THE GROUSE IN HEALTH AND IN DISEASE 



External Effects. — The chief external evidence of Coccidiosis is the pale colour 

 and great fluidity of the csecal (soft) droppings of the Grouse, the pale tint being 

 due to myriads of oocysts and the condition being that of diarrhoea. A similar 

 disease in fowls is known among poultry-men as " white-diarrhoea." As the 

 coccidian parasites cause great denudation of the intestinal epithelium, digestive 

 derangements are brought about, and consequent on this, malnutrition occurs and 

 the bird becomes very emaciated and " anfemic." Feathering also is poor and 

 ragged, leg weakness is fairly common, and a peculiar bluish tint is sometimes 

 seen at the cere, ears, and other parts. 



Eimeria avium appears to be purely a parasite of the gut of the Grouse and 



does not affect such gut diverticula as the liver. The crop and gizzard of infected 



birds are rarely parasitised, though they may contain oc'icysts in the 



internal condition in which they have been ingested with food. Examination of 



organs. •' ° 



the duodenum shows that the sporocysts ingested with the food are 

 attacked by the pancreatic juice (as I have proved by pancreatic digestion ex- 

 periments, using both natural pancreatic juice and trypsin), and the sporozoites are 

 set free. These invade the tissue of the duodenum, rapidly become schizonts and 

 multiply, the result being that the duodenum is often riddled by the parasites, and 

 consequently inflamed. Both the villi and the crypts of Lieberkiihn are attacked, 

 and the parasites have also been found, though much more rarely, in the submucosa. 

 Great hypertrophy followed by atrophy of the epithelial host-cell occurs, and the 

 tissue attacked is often reduced to a finely granular, structureless mass. Desqua- 

 mation of the gut is common, and epithelium containing various developmental 

 stages of the parasite can be found floating free in the gut contents. 



Some of the merozoites formed in the duodenum pass down the gut, reach the 

 cseca and re-commence their life-cycle there. Active schizogony and sporogony go 

 on in the cseca,' chiefly in the epithelium, very rarely in the submucosa. Often the 

 cfeca are as heavily parasitised as the duodenum, whole areas being completely 

 denuded of the epithelium, especially when the fertilised oocysts pass outwards into 

 the csecal contents. The walls of the cseca are often rendered very thin and tender 

 by the action, direct and indirect, of the parasite. Ripe oocysts and sporocysts 

 occur in the lumen of the cseca of dying chicks. 



Podwyssozki (1890) stated that he found coccidian oocysts in the vitellus of 

 eggs of fowls, especially in summer. He considered it possible that the cysts 



' Coccidiosis may sometimes occur along the entire lengtli of tlie small intestine, and gametes may be 

 formed far forward, in the duodenum. 



