Nosema disease is believed by some to be a significant stressor of honey bees. Nosema is contracted by honey bees by ingesting the spore through trophallaxis (food sharing) or by ingesting waste from an infected nest mate. Once ingested, the Nosema replicates inside the midgut (stomach) cells and essentially hijacks nutrition from the honey bee. As the spores replicate, the midgut membrane ruptures, which results in the release of more spores into the honey bee’s midgut, increasing the likelihood that the disease will be transmitted to others throughout the hive.
There are two species of Nosema known to impact honey bee health in the United States, although Nosema ceranae is more prevalent in Florida and throughout the country. Unfortunately, honey bee colonies typically do not show outward signs of infection when infected with Nosema ceranae until the colony is severely diminished. Luckily, Nosema is treatable. It is recommended that beekeepers ensure that their colonies have access to adequate nutrition. Adequate feeding may decrease the negative side-effects caused by Nosema. Some beekeepers also treat colonies with fumagillin (always follow label instructions). Fumagilin is an antibiotic administered to a hive typically in sugar syrup. In April 2018, the only registered fumagillin product was no longer commercially available. On October 2019, the commercially produced treatment will be available again for preventative use. Once treated, beekeepers should recheck spore counts in colonies 2-3 weeks after treatment. Always remember- the label is the law!
For information on monitoring Nosema in colonies, see How to Quantify Nosema Spores Infection Rate in a Honey Bee Colony (http://edis.ifas.ufl.edu/in1123) and visit http://entnemdept.ufl.edu/honey-bee/extension/beekeeper-resources/pests-and-diseases/nosema/