316 VETERINARY HYGIENE 



run on sheep at the same time. Many infected ticks will then be 

 diverted from their natural hosts, and the number of cases of red- 

 water will be likely to decrease.* 



One may get rid of large numbers of ticks by dipping the cattle 

 or sheep in arsenical solutions, and the best time to do this is April 

 and May and October and November, i.e., at periods when adult 

 ticks are attached. The reasons why it is preferable to dip at these 

 times is (a) on account of the fact that one is thus catching the tick 

 before it lays eggs; (&) owing to the fact that the period of attach- 

 ment is longer in the adult stage than in any other. Cattle may 

 be solidly protected by inoculation with blood from a recovered 

 adult or from an experimentally infected calf which has passed 

 through an attack. The operation is practically without danger 

 for animals under one year old, and even in those older is not so 

 serious as a natural attack. The difficulty is to fix a suitable dose 

 of infective blood, and the method cannot be considered safe for 

 valuable animals over two years of age or for animals which are 

 not in a good state of health. Animals should be kept indoors 

 for a fortnight or three weeks after they have been inoculated. 



COCCIDIOSIS. 



Coccidiosis (psorospermosis) is a disease which affects several 

 different species of domesticated animals and is due to protozoan 

 parasites known as coccidia. The life-cycle of these parasites is 

 somewhat complex, but so far as is known no intermediate host is 

 necessary. In common with many other classes of protozoan para- 

 sites coccidia have their own particular hosts, i.e., they are patho- 

 genic only for one species of animal or for an allied species. Thus 

 rabbit coccidia are capable of producing disease in hares, the fowl 

 coccidium is capable of infecting pheasants. On the other hand 

 the rabbit coccidium does not produce disease in the ox. The para- 

 sites multiply enormously in the intestinal epithelium and in the 

 case of some animals in the parenchymatous cells of the liver. The 

 chief symptoms of coccidiosis, therefore, are diarrhoea and 

 emaciation. 



Coccidia are known to be parasitic in cattle, rabbits, sheep and 

 birds. No authentic case has been described in the horse. The 

 disease has been recorded in other mammals, including the goat, 

 dog, cat, mouse, and also in man. The young of all animals are 

 more liable to attack than are adults. 



Coccidiosis of the Rabbit. The coccidium is known as Cocci- 

 * Annual Report, C.V.O., Bd. of Agric., 1908. 



