12 



BULLETIN 671, TJ. S. DEPARTMENT OF AGRICULTURE. 



positive picture desired in the diagnosis of the disease. If, on cultur- 

 ing, the agar plates are free from Bacillus alvei the specimen is usu- 

 ally considered negative. 



Occasionally specimens are received resembling sacbrood that tend 

 to cause confusion. The head in some of these has a tendency to turn 

 upward, resembling sacbrood, but unless there is present the tough 

 body wall and watery granular contents, a diagnosis of sacbrood 

 should not be made. A resemblance to the disease is sometimes noted 

 after the brood dries down to form a scale, dark in color and sepa- 

 rating readily from the cell wall. The microscopic examination and 

 the cultures are often negative as in sacbrood. In such cases, when 

 there are only a few affected larvae, it is impossible to make a diag- 

 nosis. Samples of comb containing only pollen without brood or 

 scales have been received for diagnosis. Such specimens are always 

 unsatisfactory and insufficient for diagnosis. 



Table 1. — Differential features in the diagnosis of the brood diseases of bees by 



laboratory methods. 



European foulbrood. 



American foulbrood. 



Sacbrood. 



General appearance of 

 brood. 



Proportion of affected 

 brood. 



Position within cell 



Age of the larvae 



Coloration 



Odor 



Consistency 



Kind of brood affected. 

 Scales 



Microscopic findings . 



Cultures. 



Brood irregular. Large 

 amount of affected brood 

 unsealed. 



Varying number of young 



larvae affected, usually 



many. 

 Usually curled at bottom. 



Larvae soft, with melting 



appearance. 



Usually die before capping. 



Larvae yellow, gray, and 

 brown. 



Slight, inoffensive. 

 Soft, rather friable. 



Often considerable amount 

 of drone-brood as well as 

 worker-brood. 



Usually small and lie at bot- 

 tom of cell. Yellow, gray, 

 or brown in color. Some- 

 times a few larger, brown, 

 rubberlike scales. All 

 scales separate readily 

 from cell wall. 



Bacillus pluton always. 

 Bacillus alvei usually. 

 Streptococcus apis some- 

 times. Bacillus orpheus, 

 Bacterium eurydice, Bacil- 

 lus vulgatus, and Bacillus 

 mesentericus, occasionally. 



Any of the above organisms 

 except Bacillus pluton. 



Very irregular; affected 

 brood sealed, sunken 

 and perforated caps 

 present. 



Usually a large amount 

 of brood affected. 



Extension along lower 

 cell wall. Larvae soon 

 become a shapeless 

 mass. 



Usually die after capping 



Usuallv dark chocolate 



L'sually strong charac- 

 teristic odor. More or 

 less offensive. 



Viscid, can be "roped" 

 out a distance of 3 or 

 4 inches. 



Any considerable 

 amount of drone-brood 

 less likely to be seen. 



Extension along lower 

 cell wall dark 

 brown in color. Sur- 

 faces somewhat 

 smooth. Separate 



from cell with diffi- 

 culty. 



Usually only Bacillus 

 larvae. Occasionally 

 Bacillus vulgatus and 

 Bacillus mesentericus. 



Frequently negative. 

 Never Bacillus larvae 

 on common media. 



Broodless irregular, 

 perforated caps pres- 

 ent, dark sunken 

 caps not so pro- 

 nounced as in Ameri- 

 can foulbrood. 



Small amount of brood 

 affected. 



Extension along lower 

 cell wall. Head 

 turned upward. 

 Normal form main- 

 tained. 



Almost invariably die 

 after capping. 



Soon become dark 

 brown to almost 

 black. 



None. 



Contents watery and 

 granular. Larvae can 

 be removed from cell 

 without rupturing 

 body wall. 



Greatest ravages among 

 worker-brood. 



Extension along lower 

 cell wall. Dark in 

 color, often black. 

 Somewhat rough- 

 ened appearance. 

 Separate readily from 

 cell wall. 



Negative as a rule. 



Nearly always 

 negative. 



wholly 



