194 Influenza of Horses. 



from fever should be used for work. The infected stable should 

 be thoroughly disinfected, and scrupulous cleanliness, as well 

 as free ventilation of the stable, should be carried out. 



As the development of the disease is favored by influences 

 which have a weakening effect on the animals, the protection 

 of the horses from such influences, and especially from taking 

 colds, should be given due consideration. 



Animals which have passed through the disease may, in 

 the majority of cases, and usually in the catarrhal form of 

 influenza, be considered as recovered and free from the in- 

 fection two weeks after cessation of the fever, and the dis- 

 appearance of all the symptoms. Convalescent patients from 

 the pectoral form of influenza if the changes in the lungs have 

 not entirely disappeared, and especially if in the meanwhile 

 relapses have occurred, are for a much longer time capable 

 of infecting other animals. 



Immunization. Shortly after the discovery of Schiitz' diplo- 

 coccus, Hell undertook the inoculation of over 1000 animals, with 

 bouillon cultures of this bacterium. Healthy animals were injected 

 S or 4 times with 40 cc. of the culture into the trachea, and some of 

 the animals were given in addition subcutaneous injections of 5 to 

 10 cc. The injection was followed by a fever lasting from one to two 

 days, whether the animals had had the disease or not. The subcutaneous 

 inoculation was also followed by abscess formation. Further observa- 

 tion showed that animals immunized against the Schiitz diplococcus 

 did not withstand the influenza infection, and therefore this method 

 of immunization was later entirely abandoned. 



Immunizations with blood serum from horses which had shortly 

 before recovered from the pectoral form of influenza have not given 

 uniform results. Although Hell, at first, reported favorable results, 

 the continued experiments among the horses of the German army 

 showed that the serum treatment of affected animals was entirely 

 unsuccessful and moreover produced such contradictory and even 

 unfavorable results, that this method has also been gradually aban- 

 doned. According to the tabulation of Christiani, in the years of 

 1892 to 1898 the results of 17 inoculation tests showed that in 9 cases 

 they were favorable, and in 8 they were unfavorable. In opposition 

 to the advocates of immunization (Eichhorn, Toepper, Garrey, Giancola 

 and especially Friis, Jensen & Nielsen), others (Pilz, Neusse, Wittich, 

 Zschokke, Troester, Mieckley) found it ineffective. The contradictory 

 results may be explained to some extent by the fact that the effective- 

 ness of the serum varies in accordance M'ith the intensity of the disease, 

 and also Math the time which has elapsed since the recovery of the 

 animal. 



At best serum inoculation affords the animals a passive immunity 

 which lasts but a few weeks. Such results do not meet the require- 

 ments of practice, even when the serious difficulties encountered during 

 the execution of the inoculations are not taken into consideration. 

 It would therefore be indicated only M^hen it appears desirable to protect 

 the animals, even for a short time, against a threatening infection, such 

 as immediately before or during cavalry maneuvers. 



Vaccination Technique. For the serum inoeulations blood is taken under 

 strictly aseptic precautions from a horse which has recovered from the pectoral form 

 of influenza not more than six weeks previously. The quantity of blood drawn 



