Nosema disease, often described as a fungus, is one of the most intriguing honey bee diseases because it now comes in two very different “flavors.” The traditional form is Nosema apis, which has been associated with European honey bees for many centuries, and considered a classic disease enhanced by stressful conditions on a bee colony. Contributor Dave Cushman provides rather complete information on this organism.
Reports at bee meetings and elsewhere over the years have described Nosema as continuing to take its toll on bee colonies and most authorities agreed that it should not be ignored. Often, however, beekeepers were apathetic about this disease, caused by two persistent myths.
One is that Nosema apis could be discounted because it doesn’t kill a colony outright. Without concrete evidence of damage to colonies, many beekeepers don’t take the disease seriously. They haven’t accepted it for what it really is, a malady responsible for untold beekeeping losses each year. It is present in all bee colonies, but only when the infestation reaches high levels does it present an economic problem. Unfortunately, the economic threshold level was often not determined for many areas of the country.
The other myth is that controlling Nosema apis is expensive. The one chemical shown to be effective and labelled for Nosema treatment, fumagillin, was considered by many too costly, in spite of evidence that Nosema control could result in up to a 30% increase in honey production in some areas. Effective, chemical use should not be considered a panacea for Nosema apis. It is considered only part of a comprehensive control program for the disease, which must be coupled with good management technique that minimizes environmental stress.
Much of this has now been turned on its head. It appears that the a brand new disease is now replacing Nosema apis. This is Nosema ceranea which has a different etiology and biology. It was first reported in 2006. Since then it has taken the world of honey bees and beekeeping by storm. It is worth keeping up with research in this important area as time goes on. See a rather comprehensive presentation by Dr. Jamie Ellis at the University of Florida.
A recent paper updates much of the information we know about the disease:
“The microsporidia Nosema apis (Zander) and Nosema ceranae (Fries) are common intestinal parasites in honey bee (Apis mellifera L.) colonies. Though globally prevalent, there are mixed reports of Nosema infection costs, with some regions reporting high parasite virulence and colony losses, while others report high Nosema prevalence but few costs.
“Basic and applied studies are urgently needed to help beekeepers effectively manage Nosema spp., ideally through an integrated pest management approach that allows beekeepers to deploy multiple strategies to control Nosema when Nosema is likely to cause damage to the colonies, rather than using prophylactic treatments.
“Beekeepers need practical and affordable technologies that facilitate disease diagnosis and science-backed guidelines that recommend when, if at all, to treat infections. In addition, new treatment methods are needed, as there are several problems associated with the chemical use of fumagillin (the only currently extensively studied, but not globally available treatment) to control Nosema parasites.
“Though selective breeding of Nosema-resistant or tolerant bees may offer a long-term, sustainable solution to Nosema management, other treatments are needed in the interim. Furthermore, the validation of alternative treatment efficacy in field settings is needed along with toxicology assays to ensure that treatments do not have unintended, adverse effects on honey bees or humans.
“Finally, given variation in Nosema virulence, development of regional management guidelines, rather than universal guidelines, may provide optimal and cost-effective Nosema management, though more research is needed before regional plans can be developed. Read the full paper, which is quite extensive.“