In the group tested for three or more consecutive years there were 291 flocks, 

 representing 1,012,916 tests, of which 0.01 percent were positive. Among the flocks 

 tested, 288 were nonreacting and three were positive. The average number of 

 birds per flock was 3,451. 



For the four groups as a whole, 371 flocks were tested, representing 1,155,359 

 birds and 1,168,739 samples, of which 0.04 percent were positive. The 357 flocks, 

 which were 100 percent tested and nonreacting, contained 1,135,436 birds or 98.28 

 percent of the total birds tested. Five flocks, representing 8,427 birds, were class- 

 ified as positive. The average percentage of reactors among these birds was 5.65. 



During the past year, 101 or 22.82 percent of the flocks tested in 1951-52 

 were not tested. 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 eff"ective in maintaining a pul- 

 lorum-clean flock. Annual testing of flocks is recognized as essential in the control 

 and eradication of pullorum disease. 



APPEARANCE OF INFECTION IN FLOCKS PREVIOUSLY NEGATIVE 



During the past year pullorum "breaks" were observed in seven flocks. Four 

 flocks revealed less than 0.5 percent infection. In one flock 6.19 percent reactors 

 were detected. 



The purchase of questionable stock appeared to be the source of infection in 

 four cases, whereas, in the other cases, the origin of infection could not be deter- 

 mined. Four flocks were retested and classified as nonreacting at the close of the 

 season. 



In Table 3 is given the incidence of "breaks" among Massachusetts tested 

 flocks during the past fourteen years. The percentage of "breaks" has decreased 

 slightly in comparison with that of the previous season. The incidence of "breaks" 

 can be reduced further, if flock owners will observe the preventive measures recom- 

 mended for pullorum disease. This past year several of the "breaks" could have 

 been avoided if the flock owners had been more cautious in the purchase of their 

 replacement stock. Thorough checking with the official state agency regarding the 

 status of breeding flocks is recommended. Too often flock owners consult "out- 

 dated" lists of approved flocks or they may take for granted that the source or 

 sources from which purchases are to be made appear satisfactory. Each "break" 

 may serve as an additional focus of infection for disseminating the disease to other 

 flocks. This was definitely true in one case this past year in which the flock revealed 

 6.19 percent reactors, and hatching eggs were being accepted from this flock by an 

 out-of-state hatchery before the flock was tested. Lax procedures of this type will 

 prolong our eff"orts to control and eradicate pullorum disease from our flocks. 

 Flock owners and hatcherymen are urged, therefore, to maintain strictest vigilance 

 against the introduction and spread of the disease. 



The following measures have been found to be effective in 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 justi- 

 fies 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. 



6 



