334 Foot-and-Mouth Disease. 



digestive tract, which at that age is sensitive, owing to its cover- 

 ing of loose epithelium. 



Susceptibility. Cattle are most susceptible to natural in- 

 fection, then follow hogs, sheep and goats. Differences are 

 observed in this regard in the various outbreaks, inasmuch as 

 the last named species of animals may become affected in the 

 same degree as cattle, or at least in considerable numbers. Buffa- 

 loes may also become affected, occasionally however they remain 

 healthy among affected cattle, while in other cases the cattle 

 may become affected through buffalo. Wild cloven-footed ani- 

 mals, including boars (Borzoni) are also susceptible to the dis- 

 ease, and sometimes it exists among these animals in an epi- 

 zootic form. Eeindeer and camels are also susceptible, and 

 very exceptionally horses, dogs and cats may become affected. 



Among the animals of a certain species a variation in susceptibility may be 

 observed in the various breeds, as under the same conditions a greater number of 

 animals of common breeds will resist the infection, than of the finer breeds. While 

 under conditions favorable to the infection, animals of the western European breeds 

 become affected in the proportion of 95-100%, among the common breeds only 

 40-50% contract the disease, and even after an energetic, artificial inoculation, 

 not infrequently 20-30% of the animals remain healthy (Kovacsy, Born). According 

 to Hartenstein hogs of the Mangalicza breed are more resistant than the Polish or 

 the German breeds. In Kobdnya hogs from the lower Danube region became more 

 severely affected than the native hogs. 



Recovery from the disease reduces the susceptibility for 

 a certain time. The immunity thus acquired lasts in the ma- 

 jority of cases longer than a year (according to Mazzini from 

 3 to 5, and according to Schwenck even up to 7 years). Excep- 

 tionally the same animal may become re-infected by the disease 

 within a short time. Strebel observed re-infection by the disease 

 in cattle after 6 to 10 weeks, Makoldy after 12 days, while 

 Kovacs observed a re-occurrence of the disease in a herd' of 

 hogs 10 days after the recovery of the animals. Warnesson 

 reports a case in which a cow became affected three times within 

 a year. Calves from cows which recovered from the disease at 

 an advanced stage of pregnancy are sometimes immune towards 

 the natural, as well as the artificial infection, while the feeding 

 of milk from immune cows does not reduce the susceptibility 

 of the calf (Frohner, Loffler & Frosch). 



Pathogenesis. Observations that the disease develops in 

 a typical form after intravenous inoculations of the virus, 'that 

 the development of vesicles is preceded by fever, and that the 

 blood is infections at the onset of the disease, indicate that 

 the virus, at least in some of the cases, reaches the tissues pre- 

 disposed for the development of the exanthema, by transmission 

 through the blood stream. As such should be considered the 

 deeper epithelial layers of the mucous membranes, and the finer 

 portions of the skin. The frequent affection of the mouth, 

 udder, and feet may possibly be associated with traumatic irri- 

 tation, or with superficial defects of these parts of the body.^ 



