in the number of flocks and samples tested. One flock was infected, but the in- 

 fection was eliminated through retesting before the termination of the season. 

 The average number of birds to a flock in this group was 4,537. 



For all four groups 269 flocks were tested, representing 1,008,750 birds and 

 1,017,113 samples, of which 0.0009 percent were positive. The 260 flocks that 

 were 100 percent tested and nonreacting contained 996,782 birds of 98.81 percent 

 of the total birds tested. All tested breeding flocks were classified as negative at 

 the termination of the season. 



During the past year 64 or 23.53 percent of the flocks tested in 1956-57 were 

 not tested. Annual testing of flocks is required by the National Poultry Improve- 

 ment Plan. However, if flock owners find it necessary to omit testing for a year or 

 more, they should procure replacement stock from officially recognized pullorum- 

 passed and pullorum-clean flocks. Adequate precautions should be taken against 

 the introduction of infection. 



APPEARANCE OF INFECTION IN FLOCKS PREVIOUSLY NEGATIVE 



Pullorum infection was detected in one breeding flock that was classified as 

 negative the previous season. However, in 1956-57 this flock did reveal infection 

 which was eliminated through retesting. It is possible that all of the infection was 

 not eliminated which would explain the reappearance of infection in the 1957-58 

 testing season. On the first complete test of the flock, only two doubtful reactors 

 were detected (one hen and one pullet). Only the pullet which gave the stronger 

 reaction was called to the laboratory for examination. Gross pathological and bac- 

 teriological findings were negative. Serological results suggested pullorum infec- 

 tion quite strongly. The two pens (hens and pullets) were retested approximately 

 four weeks after the first test. Five reactors were detected among the hens, two of 

 which were submitted to the laboratory and S. pullorum was isolated. The birds in 

 the pullet pen revealed only one doubtful reactor which was not examined but re- 

 moved from the premises. Interestingly, the pullet and hen pens were in the same 

 building but on two different floors. After discovery of definite infection the bal- 

 ance of the flock was retested and another group of pullets, in another building, 

 revealed one reactor that yielded the organism on necropsy. The entire flock was 

 subjected to two additional retests, two weeks apart, and no additional reactors 

 were detected. Special attention will be given to this flock during the next six 

 months. 



Table 3 lists the incidence of "breaks" among Massachusetts tested flocks 

 during the past 17 years. Flock owners and hatcherymen should observe constantly 

 the strictest vigilance against the introduction and spread of the disease. 



The following measures have been 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 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 report. 



4. Offal from all birds dressed for market or home consumption as well as 

 dead birds that are not fit for consumption should be burned. 



