11 



per cent) were flocks of over 1,000 birds; 11 (7.01 per cent) were flocks 

 of over 2,000 birds; and 5 (3.18 per cent) were flocks of over 3,000 birds. 



Tlie largest 100 per cent tested and non-reacting flock was one of 

 5,100 birds. This flock has been without infection for four years, and 

 has been the source of a large number of the non-reacting flocks in the 

 State. One other in the group of flocks composed of over 3,000 birds has 

 likewise been non-reacting for several years. Two have been on the in- 

 fected list, but have succeeded in eliminating the disease by an intensive 

 retesting program. The fifth flock in this group is one of 3,600 birds, which 

 was without infection two years ago, and was not tested in 19'37-28. Five 

 reactors were found on the original test in 1928-29 and the infected pens 

 were retested. No reactors were found on retest so a negative report was 

 given. 



The experience of the authors has been that it is very important to 

 test 100 per cent of the flock each year. The example given above is 

 an illustration of this need. If the flock had not been tested this year, 

 or if only a portion of it had been tested, there would be a strong possi- 

 bility of a much greater percentage of infection anotiier year, because of 

 the danger of leaving one or two reactors on the premises. 



Variation In Infection 



Table V summarizes the average variation in infection for the past six 

 testing seasons. 



The details regarding the source and other historical data given in the 

 following discussion are included as a matter of record. All these data, 

 refer only to the 1928-29 testing season, and emphasis is placed on such 

 examples as are illustrative of the need for annual 100 per cent testing,, 

 intensive retesting of infected flocks, etc. 



In 1928-29, the infection ranged from 0.00 to S4.43 per cent. There 

 were 228 non-reacting flocks, representing 153,334 birds in 1928-29, which 

 is an increase of 90 non-reacting flocks and 72,505 birds over 1927-28. 

 A more detailed discussion of the non-reacting flocks has been given in 

 the discussion of table III. 



Less Than One Per Cent Infection 



Of the 40 flocks having less than one per cent infection, 33 had pre- 

 vious testing histories, and seven were tested for the first time. One of 

 the seven tested for the first time, originated from a non-reacting source. 

 The one reactor in the flock was sent to the laboratory for autopsy and 

 bacteriological examination, and Salmonella pullorum^ the causative organ- 

 ism, was isolated. One of the flocks originated from a source having 5.22 

 per cent infection in 1927-28. Each of two flocks originated from two 

 sources, one reacting and the other a known non-reacting flock. Another 

 originated from one known non-infected, and one unknown source; and 

 one originated wholly from an unknown source. The flock which origin- 

 ated from a combination of the known non-reacting, and the unknown 

 sources, was composed of two breeds. The Rhode Island Reds originating 

 from a non-reacting source were without infection, while the Leghorns, 

 which came from another state, with no testing history had 4.44 per cent 

 infection. 



