BLACKLEG 313 



the occurrence of outbreaks in stable-fed animals speak for 

 this mode of infection. The disease is miasmic and does not 

 spread from animal to animal. Blackleg carcasses, however, 

 if not rendered harmless by cremation or deep burial, con- 

 tribute toward the perpetuation of the infection by reinfect- 

 ing the soil. 



Symptoms. — Blackleg is seen almost exclusively in cattle. 

 Probable cases in sheep and swine have been recorded. Opin- 

 ions differ concerning its occurrence in horses, but no authen- 

 tic data in this regard are available. Blackleg is a disease of 

 young, full-blood, or high-grade cattle. It is rarely noted in 

 animals under six months or over two years of age. The 

 period of incubation is usually one to three days, occasionally 

 longer (five days). The symptoms are both (a) general and 

 (b) local. 



General Symptoms. — Fever, the temperature reaching 

 107° F. The temperature rises and drops early in the disease. 

 When the animals are down it is usually normal and just 

 before death subnormal (95°-96° F.). There are refusal of 

 food, suspended rumination, and great mental depression. 

 Quite often the first symptom noticed is lameness in one 

 limb. 



Local Symptoms. — Following or sometimes preceding the 

 general symptoms, external swellings appear in the region of 

 the thigh, croup, loins, shoulder, breast, and throat. While 

 at first small, the timiefactions rapidly increase in size until 

 a large portion of the body is involved. In rare cases the 

 swellings may be internal and located in the tongue, pharynx 

 or bowel (colic sj^mptoms). At first the tumors are firm, 

 hot, and tender, but later, provided the animals live long 

 enough, cooler, non-sensitive, the overlying skin hard and 

 dry, and on palpation marked crepitation is noted. When 

 the tumors are incis6d, a bloody, foamy fluid of a peculiar 

 sweetish, fetid odor is discharged. The periphery and 

 environment of the swelling are edematous. The lymph 

 glands are swollen, arid may be felt under the skin as firm 

 nodes, at times the size of a goose egg. As the swellings 

 enlarge the symptoms become more pronounced, the patient 

 shows marked dyspnea, is unable to rise, muscular tremors 



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