120 



Biological Therapy 



RECOMMENDATIONS FOR USE 



Abortion vaccine should not be used until .after a posi- 

 tive agglutination test reveals the presence of infectious 

 abortion in the herd. As soon as possible after this diagnosis 

 has been established all non-pregnant females should receive 

 a subcutaneous injection of ten c.c. Such animals should 

 not be bred until two to three months after this prophylactic 

 treatment. Only one injection is required but this should be 

 repeated before subsequent pregnancies. For the treatment 

 of the sequelae which follows abortion in pregnant cattle 

 see Metritis on page 161. 



Blackleg 



Blackleg is an acute infectious and extremely fatal 

 disease of young cattle. On rare occasions other animals 

 are affected. The disease is characterized by high fever, 

 crepitant swellings in the heavily muscled parts of the body 

 and a heavy mortality. 



ETIOLOGY. The disease is caused by Bacillus gan- 

 graenae emphysematosae, an anaerobe which is found in the 

 soil and water of certain infected districts. The organism 

 is most prevalent in swampy pastures and land which be- 

 comes inundated from time to time. The ability of the 

 organism to remain alive in the soil by spore formation helps 

 it to retain its infectivity over long periods of time which 

 accounts for land remaining permanently contaminated. 



Infection generally occurs through the digestive sys- 

 tem when contaminated material is ingested but may also 

 occur through wounds obtained while on infected territory. 



SUSCEPTIBILITY. Calves between the ages of six 

 months and two years of age are most susceptible. The 

 disease is rarely observed in older cattle or in suckling 

 calves. Well bred and good conditioned animals are more 

 susceptible than scrubs or lean calves. The period of incu- 

 bation is from one to five days. 



SYMPTOMS. Ordinarily the temperature is very high 

 with a marked tendency to become subnormal just before 

 death. Localized lameness in one leg, marked depression 

 and complete suspension of rumination is followed by local- 

 ized swellings which appear on the thigh, loin, shoulder, 

 throat or breast. These are at first hot and painful, later 



