Pollen as a potential vector for Nosema microsporidia

Abstract

In recent years, pollinators have been experiencing a significant decline. Of particular note are bees such as honeybees (Apis spp.) and bumblebees (Bombus spp.) which provide essential pollination as both natural and managed pollinators. Among other suggested causes for the decline, such as tracheal mites, microsporidia may be responsible for the increased colony loss seen in bees. Microsporidia are eukaryotic intracellular parasites that are known to infect many invertebrates including bees, in which the pathogen causes many detrimental effects. Nosema microsporidia, a genus that includes bee-specific species like Nosema apis and Nosema cerenae may be of increased importance to the decline of these pollinators. Microsporidia can be transmitted between individuals by direct contact or indirectly via infected feces. In addition to these transmission routes, the collection of raw pollen from flowers by foraging bees may be a further means of transmission. Unpasteurized pollen samples from three sources were examined for the presence of Nosema microsporidia. Samples were boiled to release the genetic material from the spores, which was then amplified using primers targeting a ~1230bp region of the SSU rRNA genes of the microsporidia. Amplification of the DNA was inconsistent, with 1/9 of the infected larvae and 5/9 of the infected larvae in pollen giving a band for the presence of Nosema microsporidia. Although no extractions from the pollen tested positive for Nosema microsporidia, due to the inconsistency of the extraction the presence of the pathogen cannot be determined conclusively. Other extraction methods such as the use of enzymes or chemical treatments may provide more precise results, and thus would allow for the status of pollen as a vector of microsporidia to be known.