16 



of another breed from untested sources after the negative test. Since 

 these additions Mere not tested, it was impossible to determine whether 

 or not they were the cause of the flock becoming re-infected. One flock, 

 tested and negative in 1926-27, had infection in 1928-29. This again 

 sliows the importance of annual 100 per cent testing. 



Over Fifteen Per Cent Infection 



The problems presented bj' the flocks having above 15 per cent infec- 

 tion are similar, and will be discussed under one head and not as class- 

 ified in Table V. 



Of the 40 flocks having over 15 per cent infection, 25 were tested for 

 the first time during the 1928-29 season. In a study of these flocks tested 

 for the first time, it was revealed that none originated entirely from dis- 

 ease-free sources. One flock having 33.89 per cent infection was used in 

 1927-28 as a source of eggs for a hatchery which supplied stock to two 

 other flock owners in this group. One of the flocks originating from this 

 hatchery had 44.53 per cent, and the other 17.87 per cent infection. 



Seven of the 25 flock owners purchased at least part of their original 

 stock from states other than Massachusetts. Several of these out-of- 

 state sources, are known to have infected flocks, because every lot of 

 their chicks sent to this laboratory has been diagnosed as having pullorum 

 disease. 



Nine flock owners, in addition to the seven mentioned, purchased at 

 least part of the original stock from known infected sources in Mass- 

 achusetts. The remainder of the flocks came from sources within the 

 State, the histories of which are unknown. 



Most of these 25 flock owners made a very common mistake. They 

 purchased stock from several sources, paying little attention to the status 

 as regards pullorum disease. Many of them bought part of the stock 

 from tested sources known to be infected, part from untested sources, and 

 part from tested and non-reacting sources. The result of such a procedure 

 is always the same: the status of the flock as far as pullorum disease is 

 concerned becomes the status of the poorest stock purchased. In other 

 words, if infected stock is purchased and raised with disease-free stock, 

 the latter will very likely become infected. Poultrymen must learn that 

 the only safe source of stock, from the standpoint of freedom from pull- 

 orum disease, is flocks known to be free of the disease, as determined by 

 100 per cent annual testing. 



Fifteen of the 40 flocks having over 15 per cent infection have been 

 tested at some previous time. With four exceptions, these flocks have 

 never been without infection. One flock of 47 birds was non-reacting in 

 1927-28 and had 28.13 per cent infection in 64 birds in 1928-29. No visit 

 has been made to this farm and no definite information as to the cause of 

 the break has been found. 



Another of this group has not been tested since 1925-26 when 260 

 birds were tested and found non-reacting. In 1928-29, 324 birds were 

 tested and 17.28 per cent infection found. No definite cause for the in- 

 fection has been determined, but here is a striking example of what may 

 happen when every bird on the premises is not tested annually. If this 

 flock OM'ner had followed a program of annual total flock testing, a small 

 percentage of infection might have been determined at an earlier date, and 

 removed before so much damage had been done. 



