94 DISEASES OF SWINE 



frequently through the agency of some human being, animal, 

 or bird which goes from one farm to another. 



(11) Infectious material may be transmitted from one farm to 

 another through the agency of winds carrying infected dust. 

 This, however, is rather uncommon. 



(12) The virus itself is also present in the exhaled air from a 

 sick animal, but is carried in the air but a very short distance, 

 probably not over 10 feet. 



(13) Animals which are kept closely housed together in in- 

 sanitary quarters may transmit the infection directly from one 

 to another through the breathed air. 



VITALITY OF HOG-CHOLERA VIRUS 

 This is a question which is open to a great deal of discussion 

 and which is also of vast importance. Depending in large part 

 upon this question depends the length of time which must elapse 

 before a feed lot in which hogs have died of cholera becomes safe 

 for other hogs. 



We are handicapped in a large measure in determining these 

 facts on account of the ultramicroscopic character of the virus 

 with which we have to deal. Being unable to see the germ, even 

 with the aid of microscopes, we are in a poor position to say much 

 definitely upon the subject of the length of time during which the 

 germ persists after its introduction. 



Numerous experiments along this line have been carried out, 

 however, in which clinical evidence alone has been used in arriving 

 at conclusions, and the following facts have been determined: 



(1) The virus of cholera will remain for several months in feed 

 lots which have once been infected from the discharges of sick 

 animals. Remember that all the discharges of a sick animal are 

 infective — the feces, the urine, the saliva, the blood. 



(2) The length of time during which this infection will persist 

 is made much longer if the hog lots are shut off from the direct 

 sunlight. The direct rays of the sun are among the best germ- 

 destroying agencies that we possess. 



(3) Corn cobs, manure and dirt, and refuse of all kinds harbor 

 the infectious material and make it more persistent. If you desire 

 to free a hog lot from the disease germs it is necessary after all 



