Reprinted from the Journal of Economic Entomology, Vol. 14, February, 1921, No. i 



MIXED INFECTION IN THE BROOD DISEASES OF BEES 



By Arnold P. Sturtevant. Specialist in the Bacteriology of Bee Diseases, Bureau of 

 — — "^^ ' tlntomoTogy, United States Department of Agriculture 



The two principal brood diseases of bees, European foulbrood and 

 American foulbrood, heretofore have not been found associated together 

 conunonly in the same colony. The generally accepted belief has been 

 that it is indeed a rare occurrence to find both diseases under these 

 conditions. Sacbrood, on the other hand, is much more often found in 

 greater or less quantity associated with either European foulbrood or 

 American foulbrood, but seldom assuming dangerous proportions, 

 either alone or in conjunction with the others. Statistics for the past 

 few years, however, show that these cases of what may be called mixed 

 infection are probably more common than was previously supposed and 

 may account for some of the puzzling instances where colonies have not 

 responded to treatment in the customary manner, thereby causing 

 beekeepers to believe they have some new form of brood disease, or that 

 the disease is showing some new unheard of characteristics. 



Cases of so-called mixed infections are not at all imcommon among 

 human diseases. Where this condition occurs, such as when a person 

 afifected with typhoid fever develops pneiraionia at the same time, it is 

 always the individual to whom the term mixed infection is applied. 

 It is a somewhat different matter in the case of the brood diseases of 

 bees. In the first place, so far as is known, the organisms causing these 

 two diseases. Bacillus larvae of American foulbrood and Bacillus pluton 

 of European foulbrood, have never been found together in the same 

 individual larva. It is, therefore, the colony as whole which is to 



