290 VETERINARY HYGIENE 



and a running stream may pass infection from one field to another 

 by carrying contaminated chaff or straw.* 



The period of incubation is from 1 to 10 days, generally 2 to 5 

 days. The rate of mortality which may be expected from this 

 disease is of little interest to the hygienist in this country, since 

 all infected and contact animals are slaughtered. Bangf pointed 

 out that the mortality in adults may be barely \ per cent. If, as 

 occasionally happens, the prevailing type of disease is of a more 

 virulent nature, the mortality may be much higher than this. For 

 unweaned stock the mortality is always high, but in older animals 

 as a rule symptoms have disappeared within ten days or a fortnight. 

 The disease is a serious one owing to its extremely infectious 

 nature and to the great economic loss resulting from trade disturb- 

 ance, abortion, diminished secretion of milk and falling off in 

 condition. 



According to Schiitz the saliva of infected cattle is no longer 

 dangerous for other animals after 10 days. Zschokke,$ however, 

 states that the virus may remain latent for a considerable time 

 in closed clefts in the horn of the hoof. He has noted outbreaks 

 arise after the horn of the claws of such cattle had been pared. 

 These cattle had shown symptoms of the disease three or four 

 months previously and no other source of contagion had been 

 possible. 



A Commission on the subject in Berlin which reported in 1897 

 and 1898 found the virus to be active after 14 days' exposure 

 in an ice chest. Its infective power was uncertain after 3 weeks, 

 though some samples conveyed the disease up to 8 or 9 weeks. They 

 further found that diluted lymph kept on ice was active up to 4 

 months. The virus was killed by 24 hours' desiccation at summer 

 temperature, by half an hour's exposure to heat at 70 C, or by one 

 hour at 60 C. According to Zschokke the virus when sealed in 

 glass tubes in sterile conditions and protected from light may 

 remain alive for 3 to 4 months. Evidence derived from the Edin- 

 burgh attack of 1908 also indicated that the virus might remain 

 active outside the body in certain circumstances for at least 3 

 months. 



PREVENTIVE MEASURES. Strict portal inspection and adherence 

 to the Orders restricting importation of cattle and fodder are the 

 most effective methods of preventing the appearance of the disease 

 in this country. Should it appear, early detection and notification 



* Annual Report, C.V.O., 1912, Cd, 6737-1. 

 fJourn. Comp. Path., 1912, Vol. XXV., p. 1., Trans. 

 %]ourn. Comp. Path., 1912, Vol. XXV., p. 355, Abs. 



