18 ANNUAL KEPORTS OF DEPARTMENT OF AGRICULTURE. 



hibited from leaving the building until they had been thoroughly 

 disinfected. No dogs, cats, poultry, or birds could gain access to the 

 building. Apparently the animals made a complete recovery and 

 were released from quarantine May 31, 1915, after very thorough tests 

 had demonstrated that the herd did not harbor infection. 



Recurrence ^of the disease. — On August 8, 1915, the local inspector 

 in charge of field work at Chicago telephoned to Washington 

 that a case of foot-and-mouth disease had been discovered among 

 119 hogs and 4 cattle at Wheeling, Cook County, 111., 22 miles 

 north of Chicago. It seems certain that this infection was pro- 

 duced by contaminated hog-cholera serum prepared in Chicago in 

 October, 1914, at an establishment where the disease had not been 

 known to exist at any time. This material had been kept in cold stor- 

 age and was not used until the quarantine restrictions had been re- 

 moved in July, 1915, and after negative tests on hogs had been made. 

 Pending investigation, all shipments of serum from Chicago were 

 prohibited. It was found that some of the product of the establish- 

 ment had been used on 11 herds of hogs, 8 of which were in Illinois 

 and 1 each in Minnesota, Michigan, and Indiana. A few infected hogs 

 were found in 8 of the herds, and all these herds, as well as the three 

 in which no disease was found, were slaughtered at once. 



A portion of the serum actually used was procured from the owners 

 of the hogs, together with samples of the remaining stock of the 

 company. Pigs and calves, the animals most susceptible to the dis- 

 ease, were inoculated with these. The results again were negative, 

 and after two series of tests had been made the Federal Public Health 

 Service was asked to conduct a third series. This also was negative. 



Up to this time, therefore, four series of tests had been made, in 

 which a total of 52 animals had been used, none of which developed 

 foot-and-mouth disease. The inoculations afforded no evidence that 

 the serum in any way was contaminated. Each series apparently 

 only confirmed the test made before the material was permitted to be 

 placed upon the market. The fact remained, however, that the hogs 

 treated by the owners had developed the disease. A fifth test there- 

 fore was made, and 10 days after inoculation a calf, which was the 

 sixty-second animal used in the tests, developed characteristic lesions. 

 The diagnosis of foot-and-mouth disease subsequently was confirmed 

 by the inoculation of other animals with material from the infected 

 calf. 



