258 THE GROUSE IN HEALTH AND IN DISEASE 



1909. In its caeca numbers of both coccidian oocysts and 

 Trichostrongylus pergracilis were found. The bird had prob- 

 ably survived an attack of Coccidiosis, and in its weakened 

 condition had fallen a victim to Strongylosis. Several other 

 birds in a similar condition were examined in September 1911. 



Though Coccidiosis is peculiarly fatal to Grouse chicks 

 during the first few weeks of their lives, adult Grouse also can 

 become infected, for an adult bird has been examined that 

 probably died of Coccidiosis. Old birds in the chronic condition 

 serve as reservoirs of oocysts, and so may form sources of new 

 infections on the moors. 



Coccidiosis outbreaks spread with fair rapidity, but though 

 many birds in one locality may become diseased, adjoining 

 districts may be free. Epizootics of Coccidiosis also disappear 

 very quickly, the disappearance often coinciding with a change 

 of weather. 



Infection has been shown experimentally to be due to the 

 ingestion of oocysts (cysts), either by way of the food or drink. 

 Coccidian cysts undoubtedly occur on the heather, and in the 

 tarns and pools from which the Grouse drink. 



The soft droppings of infected chicks are heavily loaded 

 with cysts, and not only do they foul the ground, heather and 

 water in their vicinity, but, when dried, the powdery material 

 produced is disseminated by the wind, and thus oocysts and 

 their contained sporocysts are scattered over comparatively 

 large tracts of country. Such cysts may remain infective from 

 season to season. 



Other methods of producing local infections may be due to 

 insects. The agency of insects, both larval and adult, such as 

 dung-flies, has been observed in nature, and demonstrated 

 experimentally. 



The conditions most favourable to the coccidian cyst, and 

 the duration of its vitality on the open moor, are two points of 

 the greatest practical importance, for without some knowledge 

 on these subjects it is impossible to suggest any preventive 

 measures. Some of these conditions may now be considered : 



