exists in a breeding flock may be ascertained through testing. A flock once free 

 from the disease does not necessarily continue to remain free as will be discussed 

 in another part of this report. Pullorum infection may be introduced into a 

 flock through various channels. The introduction of infection may be more 

 difficult to prevent through certain avenues than through others. Considering 

 the widespread nature of the disease and the inadequate employment of disease 

 control and prevention measures against dissemination of the infection, poultry- 

 men cannot be assured from one year to the next that their flocks will remain 

 free from infection. 



In Table 2 are given comparative results on flocks tested for the first time, 

 flocks tested intermittently, flocks tested for two consecutive years, and flocks 

 tested for three or more consecutive years. 



The number of flocks tested for the first time was 84, representing 66,379 tests 

 of which 0.73 percent were positive. In this group there were 71 non-reacting 

 flocks, representing 54,925 birds, and 58 of these consisting of 47,694 birds were 

 100 percent tested. Among flocks tested for the first time, there was an increase 

 of 29 flocks and 25,586 birds over the previous season. It is encouraging to note 

 that in this group the average percentage of infection is less than 1 percent and 

 that most of the birds tested are found in 100 percent tested non-reacting flocks. 

 Such results strongly indicate what can be accomplished in establishing additional 

 pullorum-clean flocks through careful selection from a known nucleus of breeding 

 stock free from pullorum infection such as exists in Massachusetts. 



The number of flocks in the intermittent-tested group was 23, representing 

 34,750 tests of which 1.03 percent were positive. The number of flocks tested, 

 birds tested, and average percentage of infection varies but little from the results 

 of the last few years. 



The flocks tested for two consecutive years numbered 46 and represented 

 79,049 tests of which 0.92 percent were positive. This group revealed 38 non- 

 reacting flocks of which 33 were 100 percent teste. 1. 



The group of flocks tested for three or more consecutive years was the largest 

 of the four groups in number of tested flocks (202), tested birds (419,390), and 

 tests (435,027). The average percentage of infection (0.13) was the lowest. 

 Of the total birds (571,065) tested, 73.4 percent were in the group tested for three 

 or more consecutive years. Of the total negative flocks (327) detected, 197 or 

 60.2 percent were in the group tested for three or more consecutive years; and 

 184, representing 333,561 birds, were 100 percent tested. A large number of 

 flocks in this group have passed a negative test for several consecutive years. 

 Such flocks are by all means the safest sources in selecting pullorum-clean stock. 



Of the total birds tested (571,065), 82.2 percent were in flocks which passed a 

 negative test. Among the 355 flock owners who received service, 327 or 92.1 

 pe-cent obtained a negative report and 309 or 87.04 percent had all the birds on 

 the premises tested. 



Twenty-eight flocks were classified as positive, representing 101,931 birds. 

 The marked increase in the number of birds in this group is explained by a "break" 

 in one large flock. 



In Table 3 is listed the range of infection for the positive flocks. In the first- 

 year group, the range of infection for the flocks falls in higher levels than is the 

 case for the other groups. In comparing the percentages of positive flocks among 

 the four groups, it is noted that those percentages for the intermittent flocks and 

 for the flocks tested for three or more consecutive years are the lowest. The 

 percentages of infected flocks in the first three groups are subject to fluctuation 

 from year to year because the number of tested flocks is not very large. Few 

 flock owners test for three consecutive years or longer without completely eliminat- 



