DEPARTMENT OF VETERINARY SCIENCE AND ANIMAL PATHOLOGY. 



CONTROL OF BACILLARY WHITE DIARRHCEA, 



1922-1923. 



BY G. E. GAGE AND O. S. FLINT. 



NATURE OF BACTERIUM PULLORUM INFECTION. 



The scientific results of the work of the last few years have proven bej^ond a doubt 

 that the nature of bacillary white diarrhoea is infectious. Bacterium puUonwi is 

 the causative agent. It is well known that chicks which survive the infection may 

 become permanent carriers, with the ovary as the important seat of infection. An 

 epidemic may be produced by the organism of the disease being transmitted to normal 

 chicks through infective droppings. These infective droppings come from chicks 

 hatched from eggs, the yolks of which are infected. Yolks of eggs thus contaminated 

 with Bad. pullorum are from diseased ovaries of hens, thus establishing them as dis- 

 ease carriers; and chicks that develop in these infected eggs may in turn become in- 

 fected and have the disease at time of hatching. 



The problem is to locate the disease carriers and eliminate them from the breeding 

 flock. To locate such carriers in any breeding flock, it is essential to find proof of the 

 infection. This is accomplished either by finding the organism Bacterium pullorum 

 itself, or evidence of antibodies (agglutinins) elaborated in the blood of the infected 

 hen. The macroscopic agglutination test is our most expeditious method for making 

 this determination, and the application of it, as a means of identifying the carriers, 

 has aided greatly in controlling the disease. 



The macroscopic agglutination test is based on the principle that in the blood serum 

 of infected hens a substance is produced as a reaction against Bacterium pullorum, 

 the organism causing bacillary white diarrhoea, known as an agglutinin. Under lab- 

 oratory manipulation this agglutinin causes the bacteria of bacillary white diarrhoea 

 to clump together and precipitate in the bottom of the test tube, as rolled up or 

 clumped masses of the organism. This process is known as agglutination. This 

 agglutination reaction may be seen with the unaided eye; hence the whole process 

 is known as the "macroscopic agglutination test," in order to differentiate it from 

 those other agglutination tests in which the microscope must be used to see the ag- 

 glutination. When, after proper laboratory manipulation, no agglutinin is found in 

 the blood, the bird is considered free from the infection of bacillary white diarrhoea, 



SERVICE RENDERED UNDER THE POULTRY DISEASE ELIMINATION 

 LAW FOR THE SEASON ENDING AUG. 1, 1923. 



During the present season, 1922-1923, 33,602 breeding birds have been examined 

 for bacillary white diarrhoea by the macroscopic agglutination test. The following 

 tables show the geographical distribution according to breeds, where the reactors 

 are located in Massachusetts, and the amount of infection among the various breeds 

 tested, a classification of the sizes of the flocks tested, and the number of flocks having 

 certain limits of infection. 



