CHAPTER IX. 

 BLACKLEG. 



Blackleg, otherwise known as black quarter, quarter ill, or symp- 

 toinatis anthrax, is a disease found in cattle ranging from six months 

 to two years old. The losses from this disease in the dairying dis- 

 tricts of the colony make it at once an important disease of animals, 

 owing generally to the suddenness of its outbreak. As its geographical 

 distribution does not depend on climatic conditions, it may be found 

 wherever a previous case has existed. But as a rule it develops rapidly, 

 and if not checked it will quickly carry off all the calves in the flock. 



There have been repeated outbreaks of this disease in the Illawarra 

 and the Shoalhaven Valley districts, extending over a period of 

 seventy years (since 1834). But as soon as it made its appearance 

 inoculation with the correct species of garlic was resorted to, and 

 invariably the disease would disappear. At one time in these districts 

 no dairyman was without a supply of the common remedies necessary 

 for doctoring his stock ; and no neighbourhood was without its local 

 stock doctor. Microbes, ferments, and moulds were not studied in 

 those days ; nevertheless there were healthy herds and plenty to eat 

 and drink 'for man and beast. 



However, science had to be introduced as a means of exterminating 

 blackleg from the farms. Three French scientists Arloing, Cornevin, 

 and Thomas were the first to recommend preventive vaccination 

 against blackleg, and their method, which consists in injecting into 

 each animal two doses of highly attenuated blackleg virus, is still used 

 in many farming and dairying disricts. But the process requires that 

 each animal\ be treated twice, with an interval of ten days between 

 the two inoculations. It would appear that this system oi treatment 

 was very expensive, as the operation had to be exclusively performed 

 by veterinarians. It therefore became unpopular among the large 

 cattle owners of America, to whom we are indebted for the drastic 

 change that followed. The American authorities at once decided to pre- 

 pare a single vaccin, somewhat similar to the one used in France, 

 and to place it directly in the hands of the cattle owners, with such 

 instructions as would enable them to apply it without the assistance of 

 professional experts. This probably was the first time in the history 

 of preventive vaccination that the hypodermic syringe and attenuated 

 virus had been placed in the hands of a cattle raiser. The results, 

 however, prove that an intelligent cattleman can be trusted with the 

 most delicate experiments, provided the information for his guidance 

 is based on sound principles. 



Scientists tell us that the germ which causes blackleg much re- 

 sembles the malignant edema bacillus, but it is mo~e s!cnder, is ofte i 

 found in pairs, and never in chains like the latter. It frequently forms 

 illaments. It may be differentiated -from anthrax by the fact tliit in 

 animals dead from blackleg the spleen and other organs are not nDtice- 

 ably affected. There may be some reddening of the intestines, 1m. 

 the discn-r is usually located in the muscles and subcutaneous con- 

 nective tissm- of tin- thigh and inguinal regions. If the in-fecticr.i 

 takes place in the mouth or throat the disease will be localised in 

 the anterior portion of the body. The animal becomes suddenly lam . 

 usually in one leg. There is a rapid rise of temperature, and in the 

 respiratory speed. The animal ffCtS down, and dies in a few hours. 

 The aflYoted leg is much swollen. The abdomen contains much 



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