IMPORTANCE OF ANTIBODIES IN DIAGNOSIS 387 



carrier detection studies. In the study of the agglutination reac- 

 tion with suspensions of those organisms, as well as with the Widal, 

 it is reeoni 111 ended that an incubation of three to twelve hours at 

 55° C. as suggested by Weil (1905) bo employed, and that readings 

 be made again after the tubes have boon standing in the refrigera- 

 tor overnight. 



Undulant Fever. — -In undulant fever one has to bear in mind 

 that there are at least three strains of Brucella : the caprine 

 strain, the porcine strain and the bovine strain. While they 

 differ in virulence for man, the caprine and porcine being quite 

 virulent and the bovine strain less virulent, they are fortunately 

 very similar antigenically. There are four la1)oratory procedures 

 employed as aids in the diagnosis of Brucellosis. One of these 

 is similar to the tuberculin test except that nueleoprotein obtained 

 from Brucella organisms is sulistituted for tuberculin. A second 

 test is based ui)on the phagocytic activity of the patient's leuco- 

 cytes; this is called the opsonocytophagic test; a third test is based 

 upon the isolation of Brucella organisms from the patient ; and the 

 fourth diagnostic laboratory procedure is a tost for specific 

 agglutinins. There is also frequently observed in undulant fever, 

 an increase in agglutinins for P. tularensis just as the converse 

 has been noted in tularemia ; this will be discussed later in the 

 chapter. Fairly high diagnostic titers are not exceptional. High 

 normal titers might be expected if the ingestion of milk containing 

 Br. ahortus can occasionally produce unrecognized or mild infec- 

 tions as is claimed by many. 



Heathman (1933) and others have shown that individuals em- 

 ployed in certain divisions of the meat industry show evidence of 

 latent or unrecognized infection as evidenced either by positive 

 skin reactions when tested with extracts of Br. ahortus or by the 

 presence of excessive amounts of agglutinins in their blood. She 

 found that those working in the beef departments showed a 

 high percentage of skin reactors, while agglutinin titers Avere high 

 among those employed in the pork dej^artments. Carpenter and 

 Boak (1930) have also discussed the significance of antibodies in 

 the diagnosis of undulant fever. 



In the agglutination test employed in susj^ectod Brucella infec- 

 tion of man and the lower animals two apparently equally reliable 

 methods are in use. One is the test tube method similar to the 



