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FOOT-AND-MOUTH DISEASE 347 



cars, stockyards, cattle pens, manure, hides, wool, milk, 

 veterinarians, butchers, cattle dealers, herders, etc., are also ' 

 carriers of the contagion. Hay, straw, feed and the like 

 imported from infected districts often spread the disease. In 

 1908, as noted, foot-and-mouth disease was introduced into 

 the United States by some calves used for the propagation of 

 vaccine virus, which had been inoculated with contaminated 

 lymph imported from Japan. It is very probable that re- 

 covered animals ("germ carriers") may harbor the virus for 

 an indefinite period, which accounts for sporadic outbreaks of 

 the disease in uninfected districts. 



While cattle are most predisposed, the disorder also attacks 

 sheep, swine, goats and buffalo. It is rare in horses, dogs and 

 cats. 



One attack produces immunity for only a short period 

 (usually not over one year). In certain individuals no 

 immunity is conferred, the animal suffering within a few 

 months repeated attacks. Calves born of cows attacked in 

 advanced pregnancy are sometimes (not always) highly re- 

 sistant to either natural infection or artificial inoculation. 



Symptoms. — The period of incubation is two to seven days, 

 although it may be longer. 



The prodromal symptoms are those of fever, the tempera- 

 ture reaching 106° F., lasting one or two, days, and falling to 

 normal as soon as the vesicles appear. Unless complications 

 arise from secondary infection, no further rise in temperature 

 occurs during the course of the disease. 



With the fever there is a 'period of loss of appetite, sup- 

 pressed rumination and languor. The mouths of the patients 

 become sore, causing N them to masticate slowly and in an 

 interrupted fashion. The mouth is usually held closed, saliva 

 hanging from the commissures in long strands. When opened 

 a peculiar smacking sound is made. Where a number of 

 affected cattle are housed together the noise produced is 

 marked. 



On examining the mouth one or two days after the begin- 

 ning of the attack, the mucous membrane, especially of the 

 lips, gums, dental pad and tongue, shows a vesicular eruption, 

 the individual vesicles varying in size from a pea to a walnut. 



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