302 DISEASES OF CATTLE, SHEEP, GOATS, ETC. 



BLACKLEG. 



Blackleg, blackquarter, quarter-ill, symptomatic anthrax, char- 

 bon symptomatique of the French, Rauschbrand of the Germans, is 

 a rapidly fatal infectious disease of young cattle, associated with ex- 

 ternal swellings which emit a crackling sound when handled. This 

 disease was formerly regarded identical with anthrax, but investiga- 

 tions carried out by various scientists in recent times have definitely 

 proved the entire dissimilarity of the two affections, both from a 

 clinical and causal standpoint. The disease is produced by a specific 

 bacillus, readily distinguishable from that causing anthrax. Cattle 

 between 6 months and 2 years of age are the most susceptible. Suck- 

 ing calves under 6 months are rarely attacked, nor are they as 

 susceptible to inoculation as older animals. Cattle over 2 years of 

 age may become affected, but such cases are infrequent. Sheep and 

 goats may also contract this disease, but man, horses, hogs, dogs, cats, 

 and fowls appear to be immune. 



Like anthrax, blackbleg is more or less restricted to definite 

 localities. There are certain pastures upon which the disease regu- 

 larly appears in the summer and fall of the year. As to any pecu- 

 liarities of the soil nothing is definitely known. Some authors are 

 inclined to regard moist, undrained, and swampy pastures favorable 

 to this disease, but these theories will hardly hold, as it is found in 

 all kinds of soils, in all altitudes, at all seasons of the year, and under 

 various climatic conditions. It occurs in this country from the At- 

 lantic to the Pacific and from Mexico to Canada, but it is more pre- 

 valent in Western and Southwestern States. Cattle in Cuba and 

 Australia also suffer. 



The cause of the disease is a bacillus resembling in some minor 

 respects the anthrax bacillus and differing but little from it in size. 

 It also possesses the power of forming within itself a spore. What 

 has already been stated concerning the significance of the spore of 

 the anthrax bacillus applies equally well to these bodies. They 

 resist destructive agents for a considerable length of time, and may 

 still produce disease when inoculated after several years of drying. 

 This fact may account for the occasional appearance of blackleg in 

 stables. In order to meet the requirements for the development of 

 the spores, which only takes place in the absence of the atmosphere, 

 it is necessary that the wound be very small and deep enough to 

 penetrate the subcutaneous tissue. 



Several observers have found this organism in the mud of 

 swamps. By placing a little of this mud under the skin the disease 

 has been called forth. 



-Since the disease may be produced by placing under the skin 

 material containing the specific bacilli and spores, it has been as- 

 sumed that cattle contract the disease through wounds, principally 

 of the skin, or very rarely of the mouth, tongue, and throat. Slight 

 wounds into which the virus may find access may be caused by 

 barbed wire, stubbles, thorns, briers, grass burs, and sharp or pointed 

 parts of food. 



