332 VETERINARY HYGIENE 



to show a greater degree of virulence for some species of birds than 

 for others. Thus outbreaks have been noted in which the disease 

 spreads more amongst one species of bird than amongst others, 

 and so the terms " duck cholera," " goose cholera/' &c., have come 

 into use. None of the domesticated mammals is susceptible. 

 Though bacteriological evidence indicates that the fowl cholera 

 bacillus may exist as a saprophyte on the earth's surface, in tem- 

 perate countries the organism can be looked upon as obligatory 

 and, in consequence, sporadic cases do not occur. During 1900 

 two outbreaks occurred simultaneously in this country on two 

 farms several miles apart, and it was thought that infection was 

 possibly introduced by foreign corn sweepings. The method of 

 infection is by ingestion of the virus, which is always present in 

 the diarrhceic faeces. The disease is chiefly spread in this way, 

 and virulent material may be transported by persons' boots, by dogs 

 and other animals, and by small birds. One cannot always discover 

 the cause of the first case in an outbreak, though infection is 

 frequently introduced by a newly purchased bird. The organism 

 remains alive in manure for at least 3 months (Gartner) also in 

 putrefying carcases and in garden soil (Kitt).* Desiccation and 

 light, however, have a rapid and destructive influence, e.g., in 

 exudate exposed to sunlight and air the virulence was lost in 48 

 hours. The period of incubation was found by Ostertag and 

 Ackermannf to be 4 to 9 days in chickens which had received one 

 meal from the organs of a fowl dead of cholera. The duration is 

 1 to 3 days in most acute cases, but exceptionally it may be 7 to 

 12 days. 



The mortality is very high, and the disease very quickly clears 

 out the poultry yard. Pasteur introduced a method of vaccination 

 which, however, has not been very largely practised partly because 

 at times it may be dangerous and partly on account of the rapid 

 spread of the disease. The method consists in the use of attenuated 

 cultures. 



FOWL PLAGUE. Fowl plague due to an ultravisible virus is 

 somewhat similar clinically to fowl cholera, though as a rule tend- 

 ing to run a rather more chronic course, the affected birds sometimes 

 showing nervous symptoms. Fowl plague was first described in 

 1878 in Italy by Perroncito, and the cause elucidated by Centanni 

 and Savonuzzi$ in 1901. Between 1894 and 1900 it existed in 

 various parts of Italy as an epizootic, but extensive outbreaks have 



* Hutyra and Marek, Spec. Path., Vol. I., p. 88, Trans. 



t Hutyra and Marek, Spec. Path., Vol. I., p. 92. 

 $ Journ. Cofnp. Path., 1918, Vol. XXL, p. 168, Ref. 



