484 VETERINARY B ACTERIOLC >< ; V 



Immunization against the disease may be brought about by the 

 use of serum from hyperimmunized animals. Koch hyperim- 

 munized horses that had recovered from the disease by three to four 

 injections of virulent blood at intervals of a week, as much as two 

 liters being used for the last injection. Serum simultaneous 

 injections of this hyperimmunized serum and virulent blood 

 into susceptible animals in correctly proportioned doses will 

 immunize. 



The disease has been found to be contracted generally at night, 

 and the first frost puts an end to the epizootic for the year. Con- 

 siderable quantities of the virus must be fed before an infection 

 is produced, showing that natural infection is probably in some 

 other manner than by ingestion. It is probable that mosquitos, 

 possibly flies, act as carriers. The disease cannot be regarded, 

 therefore, in the strictest sense as contagious. 



Virus of Infectious Anemia of the Horse 



Disease Produced. Infectious anemia, pernicious anemia, mud 

 fever, swamp fever of the horse. 



This disease has been known as a clinical entity in Europe for 

 three-quarters of a century. Carre and Villee (1904-1906) and 

 Ostertag and Marek (1907) have demonstrated the disease to bo 

 due to a filterable virus. The disease has been studied in North 

 America by several investigators, and the ultramicroscopic nature 

 of the virus has been independently demonstrated. It is not 

 certain that all the infections described under this name are iden- 

 tical, but there is considerable evidence tending to establish such 

 as a fact. 



Distribution. The disease is probably wide-spread, but has not 

 always been clearly differentiated. It is known from Germany, 

 France, Hungary, Switzerland, and Sweden in Europe, and from 

 Saskatchewan, Manitoba, Minnesota, the Dakotas, Nebraska, 

 Kansas, Colorado, Wyoming, Montana, Texas, and Nevada in the 

 United States. 



Nature of the Virus. The causal organism is an ultramicro- 

 scopic, filterable virus that cannot be difTon-ntiatod by staii ing 

 methods and has not boon cultivated. It is found in tho blood, 

 the urine, and the feces of infected animals. It is destroyed at a 



