Hive Medical Spotlight: Nosema
This week on our Hive Medical Spotlight we are discussing Nosema. What it is, and how to manage it if you find it in your beehives. This disease is caused by microsporidian parasites named aptly Nosema apis and Nosema ceranae. It is found on all continents that Apis Mellifera is found, which means every continent except Antarctica. The disease was first described by German researcher Enoch Zander in the year 1909.
A notation from our research source notes that N. apis has been replaced as the dominant species by N. ceranae due to climate. N. apis shows up dominant in temperate climates where there are long winters and fewer flight opportunities. N. ceranae shows up in more warmer regions.
This parasite is apparent in adult Honeybees of every caste in the hive with a hive becoming infected with fewer than 100 spores of N. apis. When these spores are ingested by the Honeybee it enters the mid-gut on its path through digestion. There it germinates and discharges a hollow filament which penetrates the gut epithelial cell allowing a sporoplasm to pass from the spore body into the cytoplasm of the mid-gut cell. This parasite will then replicate itself in 48-60 hours from the time ingested.
The parasite's prodigy grow inside a cell to the point that it ruptures to infect new cells in the same bee or to be passed in their feces into the hive or the environment where they are cold shock resistant and remain viable for over a year.
N. apis than is transmissible when other bees come into contact with it and ingest it from grooming after walking over contaminated comb, walls, floor, food or by transfer of food from one bee to another.
The greatest number of these spores are noted in older Honeybees of a colony. Light infections of bees are usually indicated by hundreds of thousands of spores in the mid-gut while more severe cases may have as many as 50 million spores. Research further noted that bees unable to make cleansing flights may hold as many as 200 million spores. You could imagine what this means to a colony with this many spores coming from individual bees.
A colony can become infected quickly, and it is also noted that bees may be co-infected by both varieties of Nosema. It usually appears in autumn and spring. Infection means that the bees soon start to become unable to process their food as their epithelial cells and may die an earlier death.
Inflammation of the digestive tract is noted by diarrhea and constipation by obstruction of the gut by released spores. As the gut becomes compromised nutrient uptake is reduced. Furthermore the epithelial cells degenerate and lesions form which through other process's lead to a reduction in RNA synthesis that alters the secretion of proteins and enzymes which increase further effects.
Colony organization begins to change for unknown reasons, but is mostly noted in wintering outbreaks of this disease. If egg laying by the queen or brood rearing changes take place that reduce the amount of brood the colony could be lacking a new generation at the onset of available forage leading to further weakening or possible collapse of the colony.
Factors involved become complicated as this parasite is related to infections of Black Queen Cell Virus, Bee Virus Y and Filamentous virus from N. apis. As a colony dwindles they start to see patterns in reduced juvenile hormone production, honey and pollen production drops and brood food starts to dip. Colonies with high rates of infection do not typically survive the winter and build up poorly in the spring.
In the Queen, Nosema becomes very serious. Infected queens start to lay less viable eggs as her ovaries start to degenerate due to proper nutrition. Oocytes have been observed to be reabsorbed (her unmature eggs). She will continue to lay normally and then may suddenly stop. She may then become sluggish to the observant hive watcher and may observe the Queens death if the hive workers do not carry her outside the hive to die.
N. apis is a little tricky to diagnose as even though we can show pictures of Nosema infections of the trade mark dysentery discharges, these discharges can also be associated with other diseases of honeybees. A true diagnosis of Nosema means a lab test to look for the spores in the mid-gut of the honeybee. A sample consists usually of 60-150 bees. The collected bees are then crushed in water after being preserved by alcohol or freezing beforehand. A part of this mixture is then placed on a slide for microscopy viewing under 400x magnification.
IPM strategy's to handle this disease usually include being mindful of a healthy diet for your bees, making sure that during a dearth you are providing supplemental feeding at the appropriate times. Being observant to having strong colonies going into winter with the proper stores of food. Replacing old combs, ensuring adequate insulation and ventilation of wintering colonies.
Chemical controls are available when an individual bees reach a threshold of 1 million spores. Once this threshold is reached with N. apis the colony can be treated with Fumagilin-B which is a trademarked Antibiotic. The treatment has no affect on the spores but rather suppresses the active growing spores. Mixing the antibiotic with hot syrup or long exposure to sunlight can reduce the effectiveness of this antibiotic.
The same controls exist for N. ceranae.
The prognosis of Nosema is difficult to determine depending on the level of the outbreak. If good beekeeping is practiced the prognosis is usually good for attentive beekeepers, the more lazy you are about managing your colonies, the more grim the picture will be. It's always best to be mindful of good hygienic procedures when dealing with any beehive to prevent the spread of infection, especially in today's hive health conditions and the ease of diseases spreading from gloves, hive tools and other items that come in contact with multiple hives. Bigger changes may be seen coming soon to commercial apiaries, and then to hobbyists.
Commercial apiaries obviously have a greater stake in being more attentive to their hives as it is their livelihood and critical component to their operations and their clients of pollination contracts. They usually will be the first to implement strategies that dictate how to handle highly contagious diseases, although it may take them a while to catch on to the world of microbiology.
Nosema is not to be taken lightly, please be mindful of your actions and how diseases can transfer from one place to another, a single gram of prevention is worth the hundreds of dollars and efforts expended for a cure with possible further losses. It pays for both hobbyists and commercial apiaries to take note of changing conditions in the world today as honeybee diseases become more prevalent.