"GROUSE DISEASE "—COCCIDIOSIS 263 



It may be of interest to note that houseflies {Musca domestica) have been 

 shown experimentally to ingest coccidian oocysts. 



To summarise, wind and rain acting on infected faeces are probably the principal 

 agents in dispersal, while the feeding habits of Scatophaga and other flies form 

 subsidiary means of spreading the disease. 



VII. Duration of Vitality of Coccidian Oocysts. 



(a) When the Oocysts are kept in Water or very moist. 



Much moisture is present on many moors, and faeces of infected chicks contain 

 coccidian spores which not only get washed into the soil, but also into tarns, etc., 

 at which Grouse drink. It was, therefore, of some importance to determine the time 

 required for the degeneration of the resistant spores of the parasite when in water. 



Coccidian oocysts with undifferentiated contents were placed in water, kept at 

 about 20 degrees C. (July temperature), the water being replaced as required, to 

 avoid evaporation effects. Ordinarily, the oocysts develop sporocysts very rapidly 

 — in two to three days. In the case of cysts kept in water, nine days elapsed 

 before much change was noted. At the end of that period, a few oocysts showed 

 differentiated protoplasmic masses, and still fewer showed four sporocysts. Two 

 days later many more oocysts contained four sporocysts, and this progressive 

 development continued for some days. Little signs of degeneration were seen until 

 about the fortieth day, when some showed signs of gas bubbles in their interiors. 

 Others, however, had completed their development, and their four sporocysts, 

 apparently unharmed, were set free into the liquid. By the fiftieth day practically 

 all oocysts had either matured or degenerated, and the sporocysts had begun to 

 degenerate. 



From the above experiment, the conclusion is that the development of oocysts 

 and sporocysts is delayed by the presence of much moisture, but that the power 

 of infection is retained for a long time by means of the sporocysts. 



Very damp air has similar eff"ects. 



(,8) When Fceces are merely kept and allowed to dry on the outside. 



AVhen freshly voided soft droppings of Grouse containing coccidian oocysts are 

 allowed to dry, the oocysts in the surface layers rapidly develop sporocysts, the 

 inner ones remaining unaffected. 



Faeces kept en masse in covered dishes for as long as twelve months have 



