170 SWINE DISEASES 



for the past thirty or forty years. The average annual 

 loss in the United States for the past four decades prob- 

 ably exceeds $50,000,000 annually, and in 1897 the losses 

 due to this disease alone approximated $100,000,000. 

 During the years 1912-13 a severe epizootic of hog 

 cholera extended throughout the principal hog-raising 

 section of the United States, the loss being excessive and 

 for the country at large amounting to over $100,000,000 

 each year. In 1913 there were 61,178,000 swine in the 

 United States, of which ten to fifteen percent died of 

 cholera. The losses from hog cholera in 191 in Iowa, 

 Nebraska, Kansas, and Missouri exceeded 3,000,000 

 hogs valued at $30,000,000. The losses in Iowa alone for 

 the years 1911-14 have exceeded $10,000,000 annually. 



Hog cholera is no doubt the most surely fatal disease 

 of swine in America, and at this time it is the most im- 

 portant disease economically in the United States. 



Etiology. The cause of hog cholera is attributed to 

 a filterable virus. The relation of a filterable virus to 

 hog cholera was first recognized by De Schweinitz and 

 Dorset in 1904, and similar investigations by Boxymeyer 

 of Michigan were also concluded in 1904. Other inves- 

 tigators have verified the findings by De Schweinitz and 

 Dorset. The virus of hog cholera occurs in the blood and 

 therefore in practically all the tissues of the body of an 

 infected swine. One to two cubic centimeters of filtered 

 blood serum from swine affected with hog cholera will 

 produce typical symptoms of this disease when injected 

 subcutaneously, intramuscularly, intraperitoneally, or 

 intravenously into a healthy, susceptible pig. The 

 symptoms become evident in from five to seven days after 

 the inoculation. 



The virus has not yet been successfully cultivated, but 

 very recent discoveries indicate that in the near future 

 the cultivation of it may become practicable in the pro- 

 duction of virus for the purpose of hyperimmunization of 

 swine for the production of anti-hog-cholera serum. 



Hog-cholera virus is ultramicroscopic and passes 

 through porcelain filters. The virus retains its virulence 



