INFLUENZA OF THE HORSE 343 



(Dieckerhoff, Bang) have pronounced influenza not to be 

 a clinical entity. They assumed that under this head at 

 least two separate and distinct diseases existed which dif- 

 fered in their pathogenesis, period of incubation and symp- 

 tomatology. They were therefore given separate names. 

 In Germany the catarrhal form was known as "Staupe" 

 "(influenza), and the pectoral as " Brustseuche" ("chest 

 plague"). Dieckerhoff described a third disease, included 

 under the term influenza, which he called "Skalma." 



The recent experiments of Gaffky and Liihrs, which con- 

 cerned the etiological factor primarily, indicate that the term 

 "influenza" has been made too inclusive. Their results seem 

 to substantiate the work done by former authorities, espe- 

 cially Dieckerhoff and Bang. Two separate and distinct 

 diseases are therefore recognized in this work. 



Influenza of the Horse (Catarrhal Fever; Pink Eye; 

 Typhoid Fever) . — Definition. — Influenza is an acute, contagio- 

 infectious, usually enzootic, disease of the horse which is 

 characterized by inflammation of the mucous membranes, 

 subcutis, and tendons. It is due to a flltrable virus. 



•Occurrence. — ^The disease is very widespread, occiu-ring in 

 all countries. North America was visited by an epizootic 

 of influenza in 1776 and again in a still severer form in 1870-72 

 when it swept the Continent from Canada to the Ohio, and 

 westward to California. The disease is now permanent in 

 this country where it is kept alive by the unsanitary stables 

 of horse-dealers and in livery barns, whence it is from 

 time to time spread. It may also attack asses, mules and 

 zebras. 



Etiology. — The most recent investigations indicate that the 

 cause of influenza is a flltrable virus which appears in the 

 blood and probably other body fluids. Gaffky produced 

 influenza in healthy horses by subcutaneous injections (5 c.c.) 

 of defibrinated blood from natiwaUy infected horses. The 

 period of incubation is from five to six days. When the blood 

 was injected intravenously the period of incubation was only 

 four days. In artificially infected horses the characteristic 

 symptoms, were produced in forty hours. Similar experi- 

 ments made with filtered blood serum gave positive results. 



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