654 MICROBIOLOGY OF THE DISEASES OF MAN AND ANIMALS. 



contagious and is characterized by the eruption of vesicles in the mouths, 

 on the udders and on the skin surrounding the hoofs of cattle. It is very 

 prevalent in European countries. There have been two outbreaks in the 

 United States both of which were promptly eradicated by vigorous re- 

 pressive measures instituted by the Federal authorities. 



The cause of this disease is an invisible microorganism which exists 

 in the lymph from the vesicles which form in the mouths and on the feet 

 of cattle. This virus has never been cultivated artificially. It passes 

 through the Berkefeld cylinder but not through the finer-pored Kitasato 

 filters; it is quickly destroyed by formaldehyde, carbolic acid and similar 

 disinfectants. 



The disease is readily transmitted from one animal to another by 

 contact and the contagion may persist for some time in the manure, or 

 straw from infected stables. The milk of infected cows has been known 

 to produce the disease in children. 



Animals which recover from an attack remain immune for a short time 

 only; it is therefore not surprising that no satisfactory means of artificial 

 immunization has been devised. 



HOG CHOLERA.* 



The first recorded outbreak of hog cholera in the United States occurred 

 in Ohio in the year 1833 and it now exists in practically all sections of 

 this country. Hog cholera is most prevalent in the late summer and fall, 

 although outbreaks are reported at all seasons of the year. All races of 

 hogs are susceptible and the average mortality is about 80 per cent. In 

 the United States alone the losses from hog cholera are estimated to 

 average at least $15,000,000 annually. Hogs only are attacked. This 

 disease is supposed to have been introduced into the United States through 

 the importation of hogs from Europe, where it is known under the names 

 "swine fever" (Br.), " schweinepest " (Ger.), and "peste du pore" (Fr.). 



The essential features of hog cholera may be briefly summarized as 

 follows: Extreme contagiousness. Symptoms of severe illness accom- 

 panied by fever, loss of appetite, weakness and diarrhoea Hem- 

 orrhagic lesions in the various organs and lymphatic glands and 

 round button-like ulcers in the large intestine. Immunity in hogs 

 which recover. 



* Prepared by M. Dorset. 



