Efficacy of Gaseous Ozone Against Paenibacillus Larvae Spores on Hive Materials

Abstract

American Foulbrood (AFB) is a highly contagious bacterial honey bee disease caused by Paenibacillus larvae. The elimination of P. larvae spores from contaminated hives is a key factor to achieve the long-term success in AFB control. The purpose of this study was to evaluate the efficacy of gaseous ozone in inactivating the P. larvae spores on wooden and plastic hive materials. Untreated pinewood and polyvinyl chloride (PVC) were chosen as representatives for the hive materials. Pinewood and PVC sticks inoculated with a spore cocktail of three P. larvae strains were treated up to 120 min with two different constant concentrations of gaseous ozone (9.8 and 17.1 mg/L) at room temperature. Ozonation at 17.1 mg/L for 120 min yielded over the 4 log reduction in the counts of spores on PVC sticks. Whereas, reduction of 2.3 log was obtained on pinewood sticks under the same experimental conditions. Reductions achieved in the levels of P. larvae spores on PVC sticks after 90 and 120 min of ozonation were significantly (p<0.05) higher than those on pinewood sticks. Our results suggest that gaseous ozone treatment is a promising candidate for the sterilization of plastic hives contaminated with P. larvae spores.