STATE HYGIENE 601 



The primary microbe may vegetate as a saprophyte 

 outside the body in forage, manure, soils, and in the sur- 

 roundings of animals; under unknown conditions it be- 

 comes pathogenic. The organism has been found in the 

 nostrils of healthy horses, but in them it has a low degree 

 of virulence. 



It has been proved by experiment that cultures of the 

 pasteurella of the horse which have become ' exalted,' if 

 injected subcutaneously cause acute influenza, pneumonia, 

 pleurisy, or peritonitis. If the cultures be introduced into 

 a vein they may cause enteritis or acute influenza. 



Climatic and meteorological conditions, a collection of 

 young horses, bad hygienic surroundings especially as 

 regards ventilation, even food, have all been blamed as 

 causes in exciting the saprophyte to become pathogenic. 

 Certainly the majority of these causes fit in with clinical 

 experience, influenza is more virulent in hot, close, badly 

 ventilated stables, and very fat or young horses are common 

 victims. 



In the light of these researches we can explain that very 

 common and nearly always fatal pneumonia met with on 

 board ship ; also those cases seen at sea which cannot be 

 distinguished from influenza ashore. 



Under the influence of board ship life, with its over- 

 crowding, defective ventilation, and impure atmosphere 

 charged with excreta, all the conditions are present for the 

 generation of the disease, assuming, as we think we must, 

 that the organism can be found in healthy horses, and only 

 needs adverse surroundings to stimulate its pathogenic 

 activity. 



Once the activity of the influenza microbe is established, 

 it is quite clear that it can be conveyed from animal to 

 animal by actual contact, by infection of water or food, and, 

 as experience shows, by stallions during coitus. 



Clinical records furnish abundant evidence on these 

 points ; the newly purchased horse may introduce influenza 

 into a clean stud, or a ship load of affected animals may 

 bring it into a town apparently previously free from the 



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