*Article* **Propolis Extract and Chitosan Improve Health of** *Nosema ceranae* **Infected Giant Honey Bees,** *Apis dorsata* **Fabricius, 1793**

**Sanchai Naree 1, Rujira Ponkit 1, Evada Chotiaroonrat 1, Christopher L. Mayack <sup>2</sup> and Guntima Suwannapong 1,\***


**\*** Correspondence: guntima@buu.ac.th; Tel.: +66-3810-3088

**Abstract:** *Nosema ceranae* is a large contributing factor to the most recent decline in honey bee health worldwide. Developing new alternative treatments against *N. ceranae* is particularly pressing because there are few treatment options available and therefore the risk of increased antibiotic resistance is quite high. Recently, natural products have demonstrated to be a promising avenue for finding new effective treatments against *N. ceranae*. We evaluated the effects of propolis extract of stingless bee, *Tetrigona apicalis* and chito-oligosaccharide (COS) on giant honey bees, *Apis dorsata*, experimentally infected with *N. ceranae* to determine if these treatments could improve the health of the infected individuals. Newly emerged *Nosema*-free bees were individually inoculated with 106*N. ceranae* spores per bee. We fed infected and control bees the following treatments consisting of 0%, 50%, propolis extracts, 0 ppm and 0.5 ppm COS in honey solution (*w/v*). Propolis extracts and COS caused a significant increase in trehalose levels in hemolymph, protein contents, survival rates and acini diameters of the hypopharyngeal glands in infected bees. Our results suggest that propolis and COS could improve the health of infected bees. Further research is needed to determine the underlying mechanisms responsible for the improved health of the infected bees.

**Keywords:** *Apis dorsata*; chito-oligosaccharide; *Nosema ceranae*; propolis
