EFFECT OF Nosema ceranae EXTRACTED FROM THAI HONEY BEES ON ENERGETIC STRESS OF Apis dorsata AND Apis mellifera

Abstract

Nosema ceranae is a microsporidian causing nosemosis in all Apis species. The ingested spores germinate and proliferate in gut epithelium causing detrimental impacts and inducing mortality of honey bees. The virulence of N. ceranae on Thai honey bees especially, A. dorsata, is not well understood. This study aimed to investigate the virulence of N. ceranae isolated from four Thai honey bee species on A. dorsata workers. The impact of N. ceranae isolated from A. mellifera on energetic stress of A. dorsata was then studied. Finally, alternative treatments using stingless bee propolis (Tretigona apicalis) and chito-oligosaccharide (COS) were tested to suppress the infection and promote honey bee health. The 100% infection was found when dosed with N. ceranae spores isolated from A. dorsata, A. florea, and A. mellifera at 5 × 105 spores per bee with the lowest survival was found in bees dosed with N. ceranae from A. mellifera. Moreover, N. ceranae from A. mellifera induced energetic stresses in A. dorsata workers by reducing trehalose levels, hypopharyngeal gland protein contents, and midgut proteolytic enzyme activities. Treating with 50% propolis extract and 0.5 ppm COS significantly reduced infectivity in A. dorsata and A. mellifera workers (p < 0.0001). Moreover, propolis and COS improved honey bee health by increasing trehalose levels, protein contents, and proteolytic enzyme activity in infected bees. The expression of apidaecin and hymenoptaecin increased in N. ceranae-infected A. dorsata and A. mellifera after treating with propolis, and only hymenoptaecin in A. mellifera increased after treating with COS. These results demonstrate that propolis extract can be used as an alternative antibiotic to control N. ceranae and improve honey bee health.

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