Foot-and-Mouth Disease. 329 



History. The cause of the disease was attributed previous to the 

 middle of hist century, to various atmospheric influences, as well as to 

 spoiled food, although Sagar recognized its contagious nature during 

 his observations in Norway in 1764. In the second half of the last 

 century, especially since Bollinger reached his definite conclusions, it 

 has been generally recognized that the disease develops exclusively as 

 the result of a specific infection, but its causative agent is even at the 

 present time not clearly established. While various authors described 

 certain bacteria, or protozoa, as the cause of the disease (Siegel, Schot- 

 telius, Kurth, Behla and others), Loffler & Frosch (1897-1900) and 

 Hecker (1899) showed that the virus passes the ordinary porcelain 

 filter, and the first authors, with Nocard, and recently also Poels, con- 

 tributed valuable information relative to the eradication of the disease 

 with serum inoculations. 



Occurrence. From time to time foot-and-mouth disease 

 spreads rapidly over extensive territories, as a severe disease, 

 affecting principally cattle, in a lesser degree hogs and sheep. 

 Its spread was especially rapid in former times, when, spreading 

 from the east westward it swept unchecked during a period of 2 

 to 4 years, passing over the entire European continent, where- 

 upon a period of freedom from the disease followed its disap- 

 pearance which lasted for several years. In recent times the 

 disease usually spreads more slowly, since its dissemination is 

 more or less controlled by veterinary police measures. In the 

 course of the various historical outbreaks, recurrences were 

 repeatedly observed, but uniformity between the appearance 

 of outbreaks, and the periods of freedom from the disease is 

 not very regular. Formerly almost all the susceptible animals 

 of large territories became affected within a short time by tli^' 

 rapidly spreading disease, and therefore the disease disap- 

 peared of itself, when there were no longer any susceptible ani- 

 mals left, while in recent times the growing young stock con- 

 tinually affords suitable material for the perpetuation of the 

 virus, so that infective herds remain, even after the apparent 

 disappearance of the disease, from which in a short time new 

 outbreaks may develop. 



The disease spreads with particular rapidity during warm 

 weather, while in the winter it does not occur so extensively. 

 With the appearance of warm weather, however, it frequently 

 gains a wide prevalence, as a result of the greater traffic in 

 cattle. 



The economic importance of foot-and-mouth disease lies 

 in the severe losses, which the owners sustain from the long 

 period of inactivity of the affected animals, from the loss in 

 body weight, and from the diminished milk production, also 

 by the considerable limitation of the traffic in cattle, and through 

 the loss of calves and young stock, sometimes also of mature 

 cattle. These losses caused the inauguration of measures for 

 the eradication of the disease by the government, and the efforts 

 thus made have in recent times brought gratifying results in 

 many places. 



