....here is some evidence to support the theory that terramycin in the hive will negatively affect some of the bacillus that inhibits chalkbrood...leading to an increased infection.  not proof, but pretty strong evidence....any thoughts?

http://www3.acadlib.lv/greydoc/Jakobsona_disertacija/Jakobsons_ang.doc

Boriss Jākobsons 

Bišu kaļķu peru bioloģiskā apkarošana

Biological teratment of chalkbrood in honey bees
Promocijas darba
KOPSAVILKUMS
Dr. med.vet. zinātniskā grāda iegūšanai

Jelgava, 2005

"2.	Excessive treatment with antibiotics increases susceptibility of bee larvae to A. apis and therefore must be reduced."

[OT is oxytetracyclen...or terramycin]
"5.3.5.2. Effect of tetracycline treatment on the susceptibility of Apis mellifera to infection by A. apis
Mortality was highest in group b) (spores+OT): 25%-36%, followed by group a) (spores alone):   12%-26.7%. Mortality in all control groups was bellow 10%. The detailed results of this experiment are presented in Table 24. Statistical analysis of the results (chi-square) indicate highly significant differences (P<0.0001) between the group given spores alone and the group given spores and OT. Moreover, significant (P<0.0001) differences were found between these two groups and the control groups."

"Another factor to be considered is the wide use of acaricides and antibiotics to combat these mites, protozoa and bacterial brood diseases. This results in a significantly higher larval susceptibility towards chalkbrood infestations as shown in the experiments 
carried out in Thailand"

"Treatment of larvae of Apis melifera with oxytetracycline in vitro enhanced their susceptibility to an experimental infection with A. apis. "


"6.	The Bacillus sp. isolated and used in this research was shown to be susceptible to two of the most widely used antibiotic drugs in apiculture, i.e. streptomycin and tetracycline, strengthening our assumption that higher levels of chalkbrood infestation are related to an altered microbial balance in the hive."

"In vivo, the Bacillus sp. was found to be harmless to the bees while significantly reducing the levels of infestation with the fungus to levels low enough to permit the restoration of the natural host-parasite balance. Positive results were obtained both by applying the Bacillus sp. by spray or in the feed (in a 50% sugar solution). The most effective result was obtained by the feeding treatment with Bacillus sp. and the results were confirmed in Israel, Thailand and Germany in repeated trails over a three year period"

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