Submitted to: American Bee Journal
Publication Type: Popular Publication
Publication Acceptance Date: April 10, 2005
Publication Date: May 1, 2005
Citation: Cox, R.L., Eischen, F.A., Graham, R.H. 2005. American foulbrood survey in honey bees pollinating almonds, Part II: A disease equivalent number of spores. American Bee Journal. 145(5):390-391. Interpretive Summary: Not required for Popular Article.
Technical Abstract: In Part I of this series, we discussed a survey for American foulbrood (AFB) spores that we conducted in California during the 2003 almond pollination season (February). We found widespread incidence of AFB spores, but we wanted to determine how the number of spores correlated with the presence of AFB disease symptoms in the colony. Therefore, we set up an experiment in south Texas in May & June, 2003 to answer this question. We introduced a piece brood comb containing 1, 10, 48, or 141 dead, diseased larvae to five colonies each, in addition to five uninfected control colonies for a total of 25. We also introduced a piece of brood comb containing 50 AFB scales (dried-up diseased larvae) into only one colony. Then, 3, 6, 12, 24, 48, 72 and 168 hours after introduction we took samples of adult bees from the brood nest of the hives and analyzed them in the laboratory to determine the number of AFB spores. Colonies receiving only one diseased larva reached the peak number of spores at six hours after introduction (339 Colony Forming Units'CFU's) and had removed most of the pathogen by 24 hours later. However, when colonies received more than one diseased larva (10, 48 and 141) the peak number of spores in the bees did not occur until after 24, 48 or 72 hours, respectively. The highest average level of spores was detected in the group of colonies receiving 141 diseased larvae (65,565 CFUs). After one week (168 hours) the level of spores declined in most of the colonies. The colony containing 50 AFB scales had the highest level of spores (6,000 CFUs) after one week. If you calculate the average number of spores detected in 30 adult bees per diseased larvae introduced into the colony, a "disease equivalent" number of spores can be determined. For this calculation, about 400 CFUs equals one "disease equivalent". When this figure was applied to the number of spores detected in colonies in the California survey, 3.9% of the colonies contained at least one disease equivalent number of spores is quite large, especially in colonies originating in California (13,810) and the Rocky Mountain region (10,984). Losses in pollination and honey production due to the diseased condition of these colonies could be significant.