29 



During the past two years careful observations have been made to 

 determine the reasons for failure in eradication of the disease in certain 

 flocks. Some of these reasons are discussed below. 



Failure to Test All Bir(1n an the Premises: — Great .stress has already been 

 placed on this subject, but much more emphasis is needed. Striking ex- 

 amples have been brought to our attention, but one of the best is that 

 of a flock owner who had 720 birds in his flock. In October, 1927, he had 

 180 birds tested, and they were non-reacting to the test. In December, he 

 had the remainder of his flock tested, and 3.75 per cent of the birds were 

 reactors. The first group was progeny from a tested non-reacting source 

 while the second M'as from an unknown source. If this man had not had 

 the second group tested, he probably would have considered his entire 

 flock non-reacting, and would have had infection among his chicks. His 

 flock was later retested, and no infection was found. Progeny of the birds 

 mentioned above have been tested during the past season, and no reactors 

 were found in his entire flock. 



Failure to Retest at Intervals Within the Season: — Experience has taught us 

 that only in rare cases can one hope to eradicate pullorum disease by a 

 single test in a season. The disease is of an infectious nature, and until 

 all of the infection has been completely removed from the premises, it is 

 only natural that some birds become infected after the first test has 

 been made. Furthermore, as long as much infection exists, a few birds 

 can always be expected to be in a stage of the disease where no reaction 

 will occur until time has been granted for anti-bodies, upon which the 

 test is dependent, to develop in the blood stream. 



Again, there is the problem of the non-reacting birds remaining in 

 contact with the reactors until the test has been completed, the reactors 

 removed, and the premises cleaned and disinfected. 



The poultryman who cannot afford to have his entire flock retested 

 should plan to buy hatching eggs, or day-old chicks from known clean 

 sources, after cleaning and disinfecting if much infection is found in his 

 flock. If he has stock that will warrant paying for retests, there is no 

 doubt but that he can successfully eliminate the disease after from two 

 to five retests, at intervals of one month to six weeks. The number of 

 tests which will be required to obtain a non-reacting flock depends largely 

 upon the virulency of the germ infecting the flock, and the general man- 

 agement of the flock following the test. 



A few flocks which had infection at the beginning of the season were 

 entirely free from the disease after on« retest. An outstanding example 

 was a flock of 1008 birds which was tested for the first time in 1927-28, 

 and 18.4.5 per cent infection recorded. The flock was retested in about 

 six weeks and no reactors were found. The progeny of that flock, con- 

 sisting of 959 birds, was tested during the past season, and no infection 

 was reported. During the 1928-29 season one flock having between two 

 and three hundred birds had over 30 per cent infection on the first test, 

 and no reactors on the first retest. These are, however, the unusual cases. 



As has been mentioned earlier, an average of 90.28 per cent of all 

 reactors can be removed by a single test. Furthermore, the disease can 

 be eliminated from the flock having a high percentage of infection as well 

 as from the flock having a low percentage of Infection, provided coopera- 

 tion from the poultryman is assured. In such cases, the entire flock should 

 be retested at intervals of from one month to six weeks. 



