14 DISEASES OF BEES 



which have been recently infected with B. pluton. Thus B. para- 

 alvei, B. orpheus, " S. apis," and another spore forming bacillus 

 which was recently described, have all been introduced into recently 

 infected colonies, and have been foimd in large numbers in the 

 decaying larvae. The modification induced by spraying B. para- 

 alvei was, as might be expected, similar to the " Parafoulbrood " 

 disease described by Bumside. This would seem to prove fairly 

 conclusively that this disease is merely one modification of 

 European foul brood and not a distinct disease. A peculiar 

 modification noticed in the laboratory was one in which a yeast 

 or torula was the principal secondary invader, and the combs gave 

 off a pronounced smell of fermentation. When B. alvei and B. 

 para-alvei are the active putrefactive agents the odour emitted 

 by the decaying larvae is particularly foul, but it is not nearly so 

 unpleasant when "S. apis," B. orpheus, or the other spore-forming 

 bacillus mentioned above, constitute the secondary invaders. 



Numerous attempts to cultivate B. pluton have been made, but 

 so far all have failed. The usual media employed in the cultivation 

 of other brood disease bacteria and a number of specially prepared 

 media (made from whole larvae, intestines of larvae, or royal jelly) 

 have not supported growth, when used aerobically, anaerobically 

 or at different pH values. Curiously enough attempts to cultivate 

 B. pluton in the stomachs of 3-4 day old larvae which were fed 

 this organism and subsequently starved several days at 33°C. 

 (hive temperature), have also failed. B. pluton cells could readily 

 be demonstrated in the stomachs of recently fed larvae, but these 

 rapidly decreased in number, and in most cases practically dis- 

 appeared, the larvae dying and autolysing, occasionally with no 

 visible bacteria, but more frequently with some rod-shaped bacteria 

 like Bacterium eurydice. All available evidence points to the fact 

 that B. pluton is a strict parasite which will multiply only in the 

 guts of young developing larvae. It seems probable that the parasite 

 is introduced by the bee into the larva when it is very young, 

 perhaps at the time of hatching, and that once established it 

 rapidly multiplies in the intestine, probably being localised in the 

 peritrophic membrane (White) where a delicate balance of nutrients 

 favouring its growth is reached. It is possible that B. pluton will 

 grow on living animal tissues in vitro, and it is hoped that this 

 possibility may be tested. Conclusive proof regarding the cause of 

 European foul brood can only be obtained when B. pluton has been 

 cultivated, has been shown to cause the disease, and has been 

 isolated from larvae thus infected. 



Several attempts have been made to determine how European 

 foul brood is carried by the bee. Bees usually remove larvae sick 

 or dead of this disease by sucking the infected material from the 

 cells, hence one would expect to find large numbers of disease 

 bacteria in the intestinal tracts of mu-se and house cleaning bees 

 from infected colonies. This has been found to be the case, for 



