In the group tested for two consecutive years there were 61 flocks, representing 

 118,654 tests, of which 0.15 percent were positive. Sixty flocks were nonreacting, 

 representing 98.31 percent of the birds tested in this group. The average num- 

 ber of birds per flock was 1,929. 



In the group tested for three or more consecutive years there were 320 flocks, 

 representing 1,151,269 tests, of which 0.002 percent were positive. A total of 

 319 nonreacting flocks was detected, which contained 97.90 percent of the birds 

 tested in this group. One flock was positive. The average number of birds per 

 flock was 3.462. 



For the four groups, as a whole, 448 flocks were tested, representing 1,358,540 

 birds and 1,394,192 samples, of which 0.05 percent were positive. The 420 flocks 

 that were 100 percent tested and nonreacting contained 1,313,260 birds or 96.67 

 percent of the total birds tested. Six flocks were classified as positive. 



During the past year, 94, or 19.79 percent of the flocks tested in 1949-50, were 

 not tested. Annual testing of flocks is recognized as essential in the control and 

 eradication of pullorum disease. In flocks tested one year and not the next, in- 

 fection is more likely to become established among the birds than in flocks tested 

 annually. An effective program for maintaining pullorum clean flocks includes 

 the annual testing of flocks. 



APPEARANCE OF INFECTION IN FLOCKS PREVIOUSLY NEGATIVE 



During the past year pullorum "breaks" were observed in six flocks in com- 

 parison with 18 "breaks" the previous season. The percentage of reactors did 

 not exceed 0.20 for any of the flocks. In some instances only one reactor was 

 detected. 



Flock 1 had been negative for 14 consecutive years; the source of infection was 

 the introduction of questionable stock. 



Flock 2 had been negative for seven consecutive years; the infection appeared 

 to have originated from a hatchery. 



Flocks 3, 4, and 5 had been negative for two, three, and four consecutive years, 

 respectively; the source of infection for these three flocks was unknown. 



Flock 6 had been negative for one year; the source of infection was the intro- 

 duction of questionable stock. 



Four of the six flocks were retested and requalified for the official Pullorum 

 Clean grade. 



Table 3 gives information regarding "breaks" observed during the past 12 

 years. It is encouraging that the percentage of "breaks" was less than during 

 the previous season. Flock owners should exercise every possible precaution 

 against the introduction of infection. 



The following measures have been found to be efl^ective for establishing and 

 maintaining a pullorum-free flock: 



1. All the birds on the premises should be tested each year. 



2. If infection is present, the entire flock should be retested within four to six 

 weeks until a negative report is obtained, provided the value of the birds 

 justifies the expenditure. 



3. Every reactor, regardless of its value, should be removed from the premises 

 and sold for slaughter immediately upon receipt of the reports. 



