THE WHOLE BLOOD TEST FOR PULLORUM DISEASE 23 



Lubbehusen and Beach have observed that agglutination may occur after a period 

 of 10 to 12 minutes. While the majority of positive reactions occur within a very 

 short time, yet some birds give delayed reactions which may be overlooked. 

 These delayed reactions consist of fine clumps, few in number, which are in most 

 cases impossible to distinguish from reactions obtained with birds that are non- 

 specific reactors. As to what factors have a direct or indirect influence on the 

 incubation period, our knowledge appears to be very limited. It is apparent, 

 however, that blood from high-titred birds as a rule produces immediate agglutina- 

 tion. By perfecting the whole blood-antigen dilution and improving the sen- 

 sitivity of the antigen, we may possibly anticipate encouraging results in the 

 detection of the delayed reactors. 



The adoption of the whole blood test as the sole diagnostic means for accredit- 

 ing flocks free from pullorum disease would seem an inexpedient procedure at 

 this time in certain sections of this country where considerable progress has been 

 made in the establishment of pullorum-clean flocks. In those sections where 

 flock owners have adopted and attained eradication as their goal, the livability 

 of the chicks is not the only benefit derived from a pullorum-disease-clean flock; 

 but the owners are relieved of the frequent retesting that is necessary in a flock 

 from which infection is not completely eliminated. In certain sections where 

 the whole blood test is employed extensively, the benefit claimed from it, and 

 justly so, is the reduced chick mortality. However, that does not mean that 

 pullorum infection is not present in those flocks, because occasionally infected 

 pullets are detected by the tube agglutination test when there has been no pre- 

 vious suspicion of the disease. With the presence of any infection in a breeding 

 flock, little control can be exercised over the amount transmitted to the progeny. 

 The amount of infection passed on to the progeny is influenced by factors such 

 as the number of infected eggs which hatch, effective incubator disinfection, 

 proper care and handling of baby chicks, the virulence of the organism, and the 

 natural resistance of the chicks. One or two infected birds in a breeding flock 

 may be responsible for acute outbreaks of pullorum diseasa in the progeny. 



Since the whole blood test has several desirable features, a concerted effort 

 should be made to improve its diagnostic efficiency, followed by standardization 

 of the different steps in the procedure of the test. 



SUMMARY 



The whole blood agglutination test was not as efficient as the standard tube 

 agglutination method. Factors such as proper and constant temperature, adequate 

 light, and an effective and constant whole blood-antigen dilution influence the 

 sensitivity and efficiency of the whole blood agglutination test. 



Great variation was observed in the whole blood-antigen dilution. The lack 

 of constancy in this dilution exerted a perceptible influence on the degree of 

 agglutination and played an important role in detecting low-titre birds. 



Delayed weak reactions occurred in a few instances with blood obtained from 

 birds that harbored S. pullorum. The standard tube test detected infected birds 

 which failed to react with the whole blood test. 



The adoption of the whole blood test as the sole diagnostic means for establish- 

 ing and identifying pullorum-disease-free flocks seems inexpedient at the present 

 time. 



