QUANTITATIVE DEMONSTRATION OF THE PRESENCE 

 OF SPORES OF BACILLUS LARVAE IN HONEY CON- 



S^5!?i^^'^^° ^Y CONTACT WITH AMERICAN FOUL- 

 BROOD ^ 



By A. P. Sttjbtevant ' 

 Associate apiculturist, Division of Bee Culture, Bureau of Entomology and Plant 

 Quarantine, United States Department of Agriculture 



INTRODUCTION 



In a previous paper ^ the writer showed that it is possible to 

 demonstrate the presence of spores of Bacillus larvae, the cause of 

 American foulbrood, in samples of commercial honey that have had 

 contact with American foulbrood in the course of their production or 

 prepa,ration for the market. Siace this work was reported, 25 

 additional samples, making a total of 212 samples of commercial 

 honey, obtained on the open market from 28 States and 2 Territories 

 have been examined by the same method, and spores of B. larvae 

 have been found in 17, or 8 percent, of these samples.^ In most 

 cases the spores were present in relatively small numbers. 



The method of examiaation used in the work thus far reported 

 gave only a qualitative indication of the number of spores present, 

 the observations being recorded as showing "the presence of a suflfi- 

 cient number of spores resembling spores of B. larvae to be designated 

 as positive."* This araounted to from one or two definite spores to 

 a very few spores seen in numerous microscopic fields of each stained 

 sediment examined. The primary object was to demonstrate only 

 their presence or absence. It was assumed that iu most cases the 

 number of spores found was considerably smaller than would be 

 foimd in honey containing numbers comparable with the observed 

 minimum infective dose of 50,000,000 per Hter. 



The only way of demonstrating the accuracy of this assumption 

 has been to feed such "positive" samples of commercial honey to 

 healthy colonies of bees. This was done with 15 of the 16 samples 

 in which spores were demonstrated, and only 1 sample, or 6.7 per- 

 cent, was found to contain sufficient infection to produce the disease 

 in a healthy colony. These investigations indicate that the require- 

 ment of certification of honey, as has been proposed and even placed 

 in operation in certain States, is not a justifiable measure in the 

 control of American foulbrood under the present conditions of 

 inspection and control of disease in this country. 



To permit a more accurate, quantitative study of the infectivity 

 of honey that has been in contact with American foulbrood, on the 



' Beeeived for publication Jan. 27, 1936; issued June 1936. Tliis investigation was carried on at 

 the Intermountain States laboratory of the Division of Bee Culture, which is maintained cooperatively 

 by the University of Wyoming and the Bureau of Entomology and Plant Quarantine, XJ. S. Department 

 of Agriculture. 



' Acknowledgments are due to P. E. Hall, associate professor of commerce, University of Wyoming, for 

 advice and assistance in the statistical analysis of the data. 



' STOETEVANT, a. p. EELATION of COMMEBCIAL honey to the SPKEAD or AMEEICAN rOULBEOOD. 



Jour. Agr. Research 45: 257-285, illiu. 1932. 



* Stdetevant, a. p. honey or the inteemodntain eegion. Gleanings Bee Cult. 63: 463-468, illus. 

 1935. 



» Sttjetevant, a. p. See footnote 3. 



Journal of Agricultural Research, Vol. 62, no. 9 



Washington, D. O. May 1, 1936 



Key no. K:-269 

 57176—36 (697) 



