As in past years, the group tested for three or more consecutive years was by 

 far the largest of the four and showed the smallest percentage of positive tests. 

 A total of 353 non-reacting flocks was detected, which contained 99.01 percent 

 of the birds. These results showed that flocks which were tested annually have 

 made more progress in pullorum eradication than flocks tested in the other three 

 groups. The average flock size was 2,489 birds. 



For the four groups as a whole, 494 flocks were tested, representing 1,219,957 

 birds and 1,272,547 samples, of which 0.10 percent were positive. The 463 

 flocks which w^ere 100 percent tested and non-reacting contained 1,178,094 birds 

 or 96.51 percent of the total birds tested. Only 18 flocks were classified as 

 positive, representing 34,105 birds or 2.79 percent of the total birds tested. 



During the past year 137 or 24 percent of the flocks tested in 1946-47 did not 

 test this season. This is a larger percentage than dropped out the previous 

 season, suggesting the possibility that the production of hatching eggs and 

 chicks is reverting to the better-established poultry breeder. 



The above data show that annual testing is effective in establishing and main- 

 taining pullorum-clean flocks. Flock owners who adopt this program along with 

 other efl'ectiA'e measures are likely to succeed in developing a pullorum-clean 

 flock. 



APPEARANCE OF INFECTION IN FLOCKS PREVIOUSLY NEGATIVE 



During the past year reactors were found in 16 flocks which had been non- 

 reacting the previous year. Table 3 gives the testing results for these flocks. 

 The sixteen flocks had been negative for a varying nuirber of years as follows: 

 four for one year; two for two years; three for three years; three for four years; 

 one for six years; two for seven years; one for eleven j'ears. 



Thirteen flocks had less than 0.5 percent reactors on the original test. One 

 flock (No. 11) had 16.39 percent reactors. Eleven flocks obtained a negative 

 test through partial or 100 percent retests. Partial retesting is not recognized 

 if it is not followed by a complete retest. In most cases the first retest was 

 negative. Three flocks were not subjected to retesting. 



In 10 flocks the origin of the infection was unknown. In the remaining six 

 flocks the infection might be attributed to either the purchase of questionable 

 stock or inadequate disease prevention measures. 



While the number of "breaks" was less than the previous year, it is still evi- 

 dent that some flock owners are not as vigilant as they might be in keeping pul- 

 lorum disease out of their flocks. The following summary gives the incidence 

 of "breaks" among Massachusetts tested flocks for the past nine years. 



