For the four groups as a whole 475 flocks were tested, representing 1,360,865 

 birds and 1,444,364 samples, of which 0.06 percent were positive. The 454 

 flocks which were 100 percent tested and non-reacting contained 1,337,524 birds 

 or 98.28 percent of the total birds tested. Ten flocks, representing 16,005 birds, 

 were classified as positive. The average percentage of reactors among these 

 birds was 2.77. 



Annual testing of flocks is recognized as essential in the control and eradication 

 of pullorum disease. During the past year 85 or 17.53 percent of the flocks tested 

 in 1948-49 were not tested this season. This is a smaller number than dropped 

 out the previous season. In flocks tested one year and not the next, infection is 

 more likely to become established among the birds than in flocks tested annually. 

 Owners of breeding flocks should adopt a program that will be effective in main- 

 taining a pullorum-clean flock. 



APPEARANCE OF INFECTION IN FLOCKS PREVIOUSLY NEGATIVE 



During the past year an increase in pullorum "breaks" was observed among 

 the tested flocks. Table 3 shows that reactors were found in 18 flocks which 

 had been negative the previous season. Eleven flocks had been negative for 1 to 

 5 consecutive years, three flocks for 8 to 13 years, and four flocks for 21 to 25 

 years. In all but two of the flocks less than 0.5 percent reactors was found on 

 the initial test. 



In nine flocks, questionable or infected stock had been introduced for replace- 

 ment stock; in four flocks, incomplete or inadequate preventive measures were 

 observed ; and in five flocks the source of infection was classified as unknown. One 

 of the "break" flocks (No. 13) was responsible for the infection in Flocks 1,4,9, 

 and 10. A study of the testing results revealed that the infection apparently was 

 introduced into Flock 13 from an unknown source during March or April, some 

 months after the flock had been tested and received a pullorum-clean rating. 



Twelve flocks were retested and obtained a negative test. Flocks 9 and 13 

 were subjected to short-interval retesting. Flock 9 was subjected to seven re- 

 tests. The birds were tested five times before a negative test was obtained. 

 However, after two consecutive negative tests, one reactor was detected on the 

 seventh test. Flock 13 was tested five times before a negative test was obtained. 

 The entire flock passed three consecutive negative tests during a two and one-half 

 month period. Approximately two months after the date of the last negative 

 test, the flock was tested again and one infected bird was detected in a pen of 

 birds which had passed five consecutive negative tests, the first negative test 

 being obtained five months previously. 



These results show that flocks with a relatively high percentage of infection 

 may not respond favorably to an intensive testing program. A more expedient 

 and economical procedure for the eradication of the disease would be to dispose 

 of the infected flock and replace with pullorum-clean stock. However, it is 

 difficult to persuade owners of valuable breeding flocks to adopt such a program. 



