Because of the annual incidence of the dis- 

 ease, as well as the fact that the immunizing 

 agent itself was capable of introducing infec- 

 tion on premises, no State or Federal programs 

 were proposed for the eradication of the dis- 

 ease. Its control, consequently, remained with 

 the owner and the practicing veterinarian. 



In 1951, modified live virus vaccines were 

 perfected, which considerably reduced the haz- 

 ard of virus introduction from immunization. 

 The trend since then has been reduction in the 

 use of virulent virus and its replacement with 

 modified live virus and serum. Also in 1951, 

 the United States Livestock Sanitary Associ- 

 ation outlined procedures in a recommended 

 hog cholera eradication program. 



Status and stimulus 



Increased use of newer immunizing agents 

 and the prohibition against feeding raw gar- 

 bage, now imposed by all the States, have stim- 

 ulated the drive for eradication. 



Additional impetus has come from Livestock 

 Conservation Incorporated, which represents 

 various segments of the swine indu.stry. At its 

 annual meeting in February 1960, the organi- 

 zation noted that losses and damage from hog 

 cholera justified an all-out eradication effort. 

 It recommended an educational approach and 

 regional meetings by the U.S. Department of 

 Agriculture to urge States to start eradication 

 programs. 



Following that suggestion, the Division and 

 the Federal Extension Service held meetings 

 in Chicago, New Orleans, and New York dur- 

 ing March and May. Industry reaction was 

 enthusiastic. A fourth regional meeting was 

 held in Denver, Colo., in August. 



The future of hog cholera 



Additional regional and State meetings will 

 be held to acquaint the various interests with 

 the factors and problems involved in an eradi- 

 cation program. 



If industry then is still sufficiently interested 

 to give its support, it is expected that State 

 programs for the eradication of hog cholera 

 will be started. 



VIRAL ENCEPHALITIS 



Like many other diseases, the encephalitides 

 were present and inflicting widespread spo- 

 radic damage for many years before they were 

 identified. From Boston in 1854, Texas in 1882 

 and 1897, North Carolina in 1902, and Louisi- 

 ana in 1906 and 1907, came reports of a neu- 

 rologic disea.se in horses. It was variously 

 called "forage poisoning," "blind staggers," 

 and "brain fever." 



The disease was differentiated from a num- 

 ber of others and established, in 1930, as a 

 definite clinical entity called equine encephalo- 

 myelitis. The identification of its viral nature 

 came as the result of an investigation in Cali- 

 fornia that year of G.OOO affected horses and 

 mules, half of which died. 



Serological distinction of the disease into 

 two types. Eastern and Western, was made in 

 1933. The Eastern type has remained localized 

 along the Atlantic Seaboard and the Gulf of 

 Mexico, with isolated occurrences in Tennessee, 

 Mi.ssouri, Michigan, and Wisconsin. The West- 

 ern type has occurred in every State west of 

 the Mississippi. 



EQUINE ENCEPHALOMYELITIS 



Reported During Calendar Year 1959 



From 1935 through 1959, the total number 

 of horses reported affected with eastern and 

 western encephalitides in the United States 

 was 503,725. Of this number, 38,258 died. 



Considerable difference of opinion still exists 

 concerning the natural history of the virus. 

 There is general agreement, however, that 

 neither humans nor horses are necessary to the 

 life cycle of the disease. Both are accidental 



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