18 JOHNE^S DISEASE 



hauled in large quantities on to land that is used for 

 growing swedes or other roots, is capable of infecting 

 the roots, and so by this means the disease may be 

 spread, as housed cattle often receive thirty to forty 

 pounds of such roots daily. 



Under natural conditions it is improbable that the 

 majority of animals which ingest the specific bacillus 

 would die of Johne's disease, even if kept alive for a 

 sufficient time for the disease to develop. If this were 

 so, then in a byre containing one badly infected animal 

 among twenty healthy beasts, a much larger proportion 

 would contract the disease than usually happens. 

 According to statistics which we have been able to 

 gather from veterinary surgeons, as a rule, not more 

 than one or two cases occur on a farm in a year. The 

 number of abortive infections must play an important 

 part in determining the true infection of an animal, and 

 possibly some strains of bacilli are more virulent than 

 others, although inoculation experiments seem to show 

 that the disease is not so readily contracted as tuber- 

 culosis. 



Many authors are inclined to consider certain breeds 

 of cattle, notably the Jersey, more susceptible than 

 others to Johne's disease, while O. Bang states that the 

 future of the Jersey breed in Denmark depends upon 

 the possibility of eradicating pseudo-tuberculous 

 enteritis from the herds. 



M'Fadyean has recorded cases in Shorthorn, Sussex, 

 and Jersey cattle ; Angwin in Jerseys and Guernseys ; 

 Male in Jerseys and Devons. Chase has seen cases in 

 South Africa which occurred in imported Jerseys ; and 

 one of the first cases to be reported in North America 

 by L. Pearson occurred in a Jersey cow bred in that 

 country. Townsend has seen cases in pedigree red- 

 polled cattle, while M'Fadyean, Sheather, and Edwards 



