16 CONTROL SERIES No. 58 



testing was resorted to and no reactors found, infection was frequently de- 

 tected later in the untested group. Untested birds should be regarded as a 

 potential source of infection even though the j^arent stock was tested and 

 found free of infection. 



Retest'mg of infected flocks. — Owners of infected flocks who wish to eradi- 

 cate the infection from their premises without disposing of the entire flock 

 may do so by retesting the flock at frequent intervals within the same season. 

 The first test should be applied at the beginning of the season, which will 

 permit ample time for subsequent retests. The number of tests required to 

 eliminate infection depends upon the size of flock, the amount of infection 

 present, and the management of the flock. According to observations at this 

 laboratory, the maximum number of tests required to eliminate the reactors 

 from a flock within one season has been five. Intensive retesting is the most 

 efl^ective and expedient means of eradicating infection from a flock, if the 

 owner observes proper eradication and sanitation measures. Retesting part 

 of the flock is not considered sound because experience has shown that in 

 most cases where a negative report was obtained through a retest of part 

 of the flock, infection would appear later in the portion that was not retested. 



Introduction of new stock. — The introduction of new stock has been a fre- 

 quent source of infection. During the past season, fifty flock owners intro- 

 duced stock from either infected or untested sources. Owners who introduce 

 stock should carefully and thoroughly investigate the source from which 

 stock is selected. The local county agent should be consulted since he is able 

 to furnish testing information about flocks in his county. 



Custom hatching.- — Owners who practice custom hatching as a source of in- 

 come may experience considerable trouble and loss if by chance eggs from 

 infected flocks are selected. Not only may the owner's flock be infected, but 

 also those of his customers. Custom hatching should not be practiced unless 

 the owner is certain that all eggs incubated are from pullorum disease-free 

 flocks. This likewise applies to owners who have their eggs hatched. 



Contest or show birds should be tested. — Birds that are returned from egg- 

 laying contests or shows should pass at least two consecutive negative tests 

 (four to six weeks apart) before they are re-admitted into the flock. This 

 measure should not be neglected, since flocks have been known to become in- 

 fected through birds returned from contests. The testing of the contest or 

 show birds is far less costly than retesting the entire flock. 



Necropsy of doubtful reactors. — In the testing of flocks that have been 

 negative for one or more years, one may encounter doubtful birds. Such birds 

 should not be regarded as free of disease. Since it is impossible to determine 

 definitely the true status of doubtful birds by only one agglutination test, one 

 must resort to retests and necropsy. When this additional service is neces- 

 sary, the laboratory will request that the doubtful birds be submitted for 

 further observation. If' the findings are negative the flock is considered nega- 

 tive. Some owners have failed to comply with the laboratory's request to 

 send in doubtful birds, and in that event the flock was considered positive. 

 The owner can better afford to sacrifice a few birds for further observation 

 than to have his flock considered positive when it might be negative. The 

 owner should not take a chance on the determination of his true flock status. 



Advertising. — Attention is called to the wide variation in the terminology 

 used in advertisements to describe the status of a flock as regards pullorum 

 disease infection. Such terms as "State Tested,'' "Officially Blood Tested,' 



