12 



Intensive Retesting of Infected Flocks Expedites Eradication 



By the term intensive retesting is meant testing of a flock at intervals of 

 four to six weeks until one or two non-reacting reports are obtained. The 

 feasibility of intensive retesting has often been questioned by poultrymen, 

 their chief objection being the cost. It cannot be denied that more money 

 will have to be expended for intensive retesting if a clean flock is to be 

 established. However, the benefits and profits received from a non-reacting 

 flock must also be considered. These are based on increased egg production, 

 increased fertility and hatchability, and increased livability. The Virginia 

 Agricultural Experimental Station reports that in a flock of 100 birds with 12 

 reactors a loss of 5 to 10 dollars in egg production may be expected over a 

 period of eight months, when the average monthly egg price is 32 cents per 

 dozen. The losses experienced in maintaining an infected flock exceed the 

 costs of eradicating the infection from the premises. 



Figure 4 illustrates the results of retesting in contrast with results of an- 

 nual testing. Group I represents 30 flocks tested annually for two consecutive 

 years. Group II represents 30 flocks tested twice the first year and once the 

 second year. The 60 flocks considered had infection at the beginning of the 

 two-year period. The birds tested during the second year were progeny of 

 the stock tested the first year. In Group I, 9 flocks were tested 100 per cent 

 the first year and 12 the second year. In Group II, 17 flocks were tested 100 

 per cent the first test during the first year. In the second test of the first 

 year, some flock ovioiers retested only the birds in the pens where infection 

 had be€!n detected. The second j'ear 24 flocks were tested 100 per cent. In 

 Group I, 13 flocks received a negative report during the second year. In 

 Group II, 22 flocks received a negative report after the second test the first 

 year, and in the second year 28 flocks (93.33 per cent) received a negative 

 report. At the end of the second year, there were 50 per cent more non- 

 reacting flocks in the second group than in the first group. There were 15 

 more flock owners in the second group who profited by non-reacting flocks. 

 This was accomplished in a large measure through one additional test during 

 the two-year period. 



In comparing Groups III and IV, the results are similar to those in Groups 

 I and II. Group III represents 15 flocks tested annually for three consecutive 

 years. Group IV represents 15 flocks that were tested twice the first year, 

 once the second year, and once the third year. All flocks in both groups were 

 infected at the beginning of the three-year period. Not all flocks were 100 

 per cent tested on each test. In Group III, a negative report was issued on 

 eight flocks at the end of the second year. The third year nine received a 

 negative report. In Group IV a negative report was issued on twelve flocks 

 at the end of the first year. The second year the percentage remained the 

 same, but the flocks represented were not the same. Two of the three flocks 

 which were not negative at the end of the first year were negative the second 

 year. Of the three flocks found infected the second year, two had had only 

 the infected pens retested and one had not received a negative report during 

 the entire two-year period. The third year, infection was found in only one 

 flock, which had been positive on all previous tests. A comparison of the two 

 groups at the end of the second year shows that there were 26.67 per cent 

 more negative flocks in Group IV, and the third year a difference of 33.33 



