30 BULLETIN 810, U. S. DEPARTMENT OF AGRICULTURE. 



By one or more of these colony symptoms manifested by larvae 

 sick or only recently dead of the disease the experienced can diagnose 

 European foulbrood definitely without a microscopic examination. 

 The methods not only give definite results, but are also easy of 

 application. They have been indispensable in much of the writer's 

 experimental work and it is believed that the beekeeper will find 

 them to be valuable in practical apiculture where other gross meth- 

 ods fail. 



BACTERIOLOGICAL EXAMINATION 



The findings from microscopic examinations and from cultures 

 have been set forth in an earlier publication (10). These are always 

 adequate for a definite diagnosis when a suitable sample is at hand. 

 Bacillus alvei (p. 11) (fig. 2; PL VII, D, F) frequently overshadows 

 all other species. In larvae sick of the disease BacHlMs pluton (PL 

 "VTI, A, B) overshadows all others. With experience one learns to 

 recognize this species in stained preparations. The individuals are 

 seen frequently in groups. They are more or less lancet shaped, and 

 a variation in size is often sufficient to be noticeable (fig. 1).^ In 

 larvae nearly dead and in those only recently dead Bacterium eurydice 

 (p. 13) (fig. 4; PL VII, C) is frequently encountered. Streptococ- 

 cus apis (p. 12) (fig. 3; PL VII, E) occurs in a small number of 

 cases. Bacillus orpheus (p. 14) (fig. 5; PL VII, H), B. vulgatus^ 

 and B. mesenteHcus are occasionally encountered. While B. pluton 

 is present in all cases of European foulbrood, not infrequently in 

 routine examinations it is so masked by the secondary invaders that 

 the microscopic examination fails to reveal it. In many cases B, 

 alvei and B. orpheus are recognized microscopically. Cultures are 

 necessary for the differentiation of B. vulgatus and B. mesentericus. 

 In many cases cultures are needed to differentiate Strep, apis and 

 B. pluton. Strep, apis grows on the ordinary media, B. pluton 

 does not. 



DIFFERENTIAL DIAGNOSIS 



AMERICAN FOULBEOOD 



American foulbrood is recognized by the death of larvae in capped 

 cells and of pupae soon after transformation, the viscidity of the decay- 

 ing remains of the brood, and the " foulbrood " odor which is fre- 

 quently present. The presence of the spores of Bacillus larvae in 

 large numbers and the absence of other species is conclusive proof 

 of American foulbrood. 



1 Smears made from larvse sick of European foulbrood and quite early in the course of 

 the disease were selected in making a study of the morphology of B. pluton. These were 

 stained with iron hematoxylin. In smears made from dead larvae and stained with carbol 

 fuchsin, as is usually done, the pointed ends and the more or less rod-shaped forms are 

 less prominent than illustrated in iigure 1. 



