294 VETERINARY HYGIENE 



incubation is 4 to 5 up to 20 days. The course varies from mild 

 types, in which mortality may be 8 or 10 per cent, and duration 

 about 3 or 4 weeks, to much more malignant types with higher 

 mortality. 



A lasting immunity is conferred by a natural attack. A method 

 of artificial vaccination (so-called " ovination ") consisting of a 

 subcutaneous injection of virulent lymph has been widely practised. 

 The immunity conferred is said to last about 12 months, but a 

 mortality of 1 or 2 per cent, of vaccinated animals is to be expected, 

 so the method is only practicable when the disease is already pre- 

 valent. Borrel* introduced a method of sero-vaccination which 

 gave excellent results when tried on large numbers of sheep. 

 Nevermann, Miessner and Weichelf described details of a procedure 

 as practised by them in Bulgaria. A sheep is inoculated with virus, 

 and from the resulting vesicles 100 to 150 cc. of lymph are collected. 

 This is diluted 2 to 6 times (depending on the virulence of the virus) 

 with boric solution. Vaccination is carried out by the injection 

 of a half to one drop subcutaneously in the ear. A mortality of 

 6 to -8 per cent, follows as against 5 to 50 per cent, in unvaccinated 

 animals. 



Cow-pox is a benign disease in which variolous lesions are 

 usually situated on the udder or teats of adult females and on the 

 lips or nostrils of calves. Any region of the body, however, may 

 be attacked. The disease is largely spread by the hands of the 

 milker. 



Horse-pox is benign in course, lesions being seen on the 

 heels or pasterns or on the muzzle and lips. As stated above, this 

 is considered by De Jong to be the same affection as the so-called 

 " contagious pustular stomatitis or dermatitis " since lesions occur 

 both on the mucous membrane of the lips and on the skin in 

 various parts of the body. The incubation period is said to be 

 4 to 6 days, and the virulence of the disease appears to diminish 

 as it progresses. Horse-pox is largely transmitted by means of 

 saliva. 



Swine-pox is said to occur in pigs not more than 10 weeks' old, 

 spreading among these by contagion. The mortality is variable, 

 depending partly on the virulence of the virus. The disease has 

 been said to occur in Hungary, and more recently Pcenaru $ has 

 described the existence of the disease in Roumania, mentioning an 

 outbreak which started in 2 pigs about 6 weeks' old and spread 

 * Hutyra and Marek, Spec. Path., Vol. I., p. 317, Trans. 



t Trap. Vet. Bull, 1917, Vol. V., p. 260. 

 $Journ. Comp, Path., 1907, Vol. XX., p. 158, Trans. 



