RELATION OF ETIOLOGY OF BEE DISEASES TO TREATMENT. 37 



caused by bacteria. Above all, you should understand that the death 

 of the brood is due to one species of bacteria growing in the larvse. 



Protozoa. — In contrast to bacteria, the protozoa belong to the ani- 

 mal kingdom. They are very small unicellular animals. Many 

 species are harmless, as are many species of bacteria, while some 

 species have the power to produce disease. They produce disease 

 and death in a manner very similar to bacteria ; that is, by growing 

 in the body of a living animal. As far as we know., none of the bee 

 diseases is due to protozoa. One investigator described what he 

 thought was a protozoon and named it Spirochceta apis. It was 

 shown* that he made an error in his observations. Therefore there is 

 no Spirochceta apis and no protozoon, as far as we know, which is 

 pathogenic to bees. 



Fungi. — The term " fungi " is a rather broad one, but in the dis- 

 eases of animals we usually refer, in speaking of fungi, to those 

 forms of plant life which are higher than bacteria. They are usually 

 made up of branching mycelial threads, and have a variety of meth- 

 ods for producing spores. One writer described one species, Aspergil- 

 lus polling which he was supposed to have proved to be the cause of 

 pickled brood, but he had not done so. 



To the above groups belong the known exciting causes. There are 

 also unknown exciting causes. When the unknown causes become 

 known they may be found to belong to the groups mentioned above. 



There is a very important classification of diseases into those which 

 are infectious and those which are noninfectious. From what has 

 been said, this classification becomes clear to us. An infectious bee 

 disease is one which may be transmitted from one colony to another 

 through the natural processes in the apiary. American foul brood 

 and European foul brood are examples of this class of disease. What 

 is transmitted in an infectious disease ? It is the exciting cause of that 

 disease. In American foul brood it is one species of bacteria, Bacillus 

 larvce. In European foul brood we do not know what is transmitted. 

 Since we do not know the exciting cause it must be classed under the 

 unknown exciting causes. When the cause is determined it will prob- 

 ably be found to belong to one of the three groups of micro-organisms 

 mentioned under the known causes. A noninfectious disease is one 

 which is not transmitted from one colony to another. The so-called 

 " pickled brood " and paralysis, as far as we know, illustrate this class 

 of diseases. 



This brief discussion of the etiology of disease is given in order 

 that you may get a clearer idea of the nature of disease and what is 

 meant by etiology. We shall now consider the treatment of disease 

 and illustrate with bee diseases. 



