THE CONSTANCY OF REPEATED AGGLUTINATION TESTS IN THE DIAGNOSIS OF PULLORUM DISEASE

Abstract

A high degree of consistency was secured in retests of five groups of birds from various sources and tested from 2 to 22 times. The results of repeated agglutination tests were, except in a few cases, confirmed by the macroscopic appearance of the ovary and by bacteriological examination.Data show that positive reactors consistently react positive to the test, and that they seldom recover from pullorum infection. This is especially true of birds that have completed the first laying year. With these very little variation can be expected in retests at short intervals. In the case of pullets that are just starting to lay, a small percentage of reactors may throw off the infection and subsequently react negatively.Non-reactors from an infected flock when left in contact with reactors in presence or absence of males, may in later tests react positively. This is generally due to infection through contact with infected birds, contaminated droppings, feed, water or litter. These non-reactors, if kept isolated from reactors, as a rule remain negative. When such birds become reactors at subsequent tests, the possibility of recent infection taking place just before or after the first test is not excluded. Hence, non-reactors from infected flocks should be retested at short intervals.Suspicious reactors as a rule do not show marked variations in titre from month to month. It is impossible to predict whether a suspicious reactor will in course of time become a distinctly positive or negative reactor. With these birds therefore diagnosis must be done with care and the general condition of the flock taken into consideration. In an eradication program the bird has to be sacrificed unless it is very valuable, in which case several retests would need to be conducted before a final diagnosis is made.Male birds do not as a rule react in as high dilutions as females, consequently fluctuations in reaction from test to test are not uncommon. Therefore, particular care must be exercised in diagnosis in the case of male birds.