ANTHRAX Control Has Been Aided by Results of Recent Experiments

In anthrax-infected districts immunization of susceptible animals plays an important role in control. At present there are several immunizing agents with which animals can be made resistant to the disease. Each has a particular field of usefulness and also definite limitations.

Much new information on the relative values and limitations of six of the available anthrax-immunizing agents was obtained by the Bureau of Animal Industry through recent experimental tests on sheep.  The animals used for study had had no previous contact with anthrax and carefully controlled conditions permitted the results to be evaluated on a comparative basis.

The products subjected to comparative tests were antianthrax serum, antianthrax serum and anthrax-spore vaccine in combination, anthrax-spore vaccine single injection, anthrax-spore vaccine intradermic, anthrax-spore vaccine in saponin solution, and anthrax bacterin (washed killed culture). In the tests each of these products produced definite protection against a subsequent exposure to virulent, anthrax. Some variation was found, however, in the rapidity with which full immunity was produced by the different products, as well as the length of time that, the respective immunities lasted.

In these tests the earliest complete protection was obtained with two of the products, namely, antianthrax serum alone and anthrax-spore vaccine intradermic, this being at 4 days after vaccination.  The longest duration of complete protection was produced by anthrax-spore vaccine single injection and anthrax-spore vaccine intradermic, complete immunity having endured for a period of a year.  The shortest duration of immunity was that produced by antianthrax serum alone. Definite evidence of waning of immunity was noted with this product at approximately 2 weeks after vaccination.

The results of these tests furnish sound experimental evidence indicating the particular field of usefulness of each of the products tested and add to the knowledge of the limitations to which each product is subject. This knowledge emphasizes the fact that immunization against anthrax is not merely a simple mechanical operation but a highly technical procedure that should be undertaken only by experts who are thoroughly qualified in this field. Veterinarians by reason of their special training are best fitted for controlling the disease.  Additional information on these comparative tests may be obtained on application to the Bureau of Animal Industry.

W. S. GOCHENOUR, Bureau of Animal Industry.