96 DISEASES OF SWINE 



them, and again produce the disease. In such cases the first ani- 

 mals attacked may show the chronic form of cholera, but, with the 

 passage through the body of living animals, the virus regains its 

 original virulence, and soon begins to produce again the acute type 

 of the disease. 



(8) Runty animals which are left after an epidemic of cholera 

 often carry in their intestines chronic cholera ulcers, and remain 

 for months discharging virulent cholera virus, which keeps the 

 pens constantly re-infected. These animals are a constant menace, 

 and should be gotten rid of at once, either by slaughter or sale to 

 butchers. In the latter case the animals usually show such lesions 

 of cholera as to be condemned at time of slaughter. 



(9) Animals which have apparently entirely recovered from 

 cholera often prove capable of distributing the infection. Such 

 animals should properly be classed as "cholera carriers," and often 

 cause an outbreak of the disease in healthy herds to which they may 

 be added. Be careful at all times in buying hogs at a public sale, 

 or from a distance, that you do not unknowingly bring the disease 

 upon your place. 



(10) The virus of cholera is especially persistent when kept in 

 contact with animal flesh in moist, damp places. This is one of 

 the strongest arguments against burying of cholera carcasses. The 

 virus will remain alive in such carcasses and in the soil in which they 

 are buried for a year or more. When brought to the surface by 

 burrowing squirrels, moles, skunks, or other small animals it 

 readily regains its virulence and attacks swine which may come 

 in contact with it. 



(11) The virus of hog-cholera is effectively destroyed by proper 

 heat, such as burning. It is for this reason that burning of dead 

 hog carcasses, especially those that have died from cholera, is so 

 strongly advocated. By all means it is the only efficient way of 

 destroying the carcass, and at the same time destroying all danger 

 of the infective virus. 



(12) As a general statement, it may be said that hog-cholera- 

 infected pens remain dangerous for a period of at least one year 

 after the occurrence of the last case of the disease therein. This 

 period of rlunger may in part be shortened by thoroughlj'^ cleaning 

 the pens, gathering up all corn cobs, old boards, litter, manure. 



