could not be accounted for in all cases. Custom hatching and the purchase of 

 questionable or infected stock were in most cases responsible for the infection. 

 This points out the fact that persons introducing new stock should make a very 

 thorough investigation of the disease status of the flock. Since purchases of 

 new blood lines are not apt to be made on the spur of the moment, as a rule, 

 there is ample opportunity to determine the true status of a flock from which 

 stock is desired. 



The value of annual testing is a-gain manifest in these 12 flocks. The fact 

 that the majority of the so-called "breaks" revealed less than 1 per cent re- 

 actors suggests that the infection had not had the opportunity to multiply, as 

 would have been the case if the infected birds had been permitted to remain in 

 the flock undetected to perpetuate and increase the amount of infection. 

 Generally when re-infection occurs, the smaller the amount the less difficult it is to 

 eradicate. 



The number of re-infected flocks can be reduced to a minimum only when 

 poultrymen conscientiously adopt measures that prevent the introduction of 

 infection. 



Non-Reacting and Positive Flocks Classified by Counties 



Table 4 shows that at the close of the testing season 229 non-reacting flocks, 

 representing 212,782 birds, were identified in 12 counties. Middlesex County 

 had the largest number (43) of non-reacting flocks, representing 45,183 birds. 

 A total of 33 positive flocks was detected in 10 counties. The number of birds 

 in these flocks was 50,459, approximately equal to one-fourth the number of 

 non-reacting flocks. No positive flocks were detected in Barnstable and SulTolk 

 Counties. Middlesex and Worcester Counties had the largest number of positive 

 flocks. 



It is, indeed, encouraging to observe that approximately four-fifths of the total 

 tested birds are found in non-reacting flocks. Having increased the ratio between 

 the number of birds in positive and non-reacting flocks in favor of the latter, one 

 is led to believe that the number of positive flocks will be reduced to a minimum 

 in the near future. The time may not be far distant when the testing program 

 can be so conducted that all flocks can be credited with at least one negative test. 

 This is entirely plausible since, as the number of positive flocks becomes less, more 

 attention and special consideration might be given to them in order to establish 

 non-reacting flocks. Furthermore, the owners of non-reacting flocks should 

 bear in mind that the number of positive flocks would also be less if they pre- 

 vented re-infection in their flocks. By following up the dift'erent avenues through 

 which infection is spread, and instituting the necessary preventive measures, the 

 foci of infection may be gradually eliminated. When a free flock is once estab- 

 lished there is no danger of re-infection, unless it be through uncontrollable and 

 unknown avenues which appear to play a very insignificant role, according to our 

 present knowledge. Therefore, it rests with the poultrymen to observe effective 

 preventive measures in an eradication program, since without this cooperation 

 the testing and control agencies can make little or no progress. 



