The Nosema disease is a parasitic disease of adult honey bees (Apis mellifera) caused by two species of microsporidia, Nosema apis and Nosema ceranae, which form spores in adverse living conditions.

Honeybees afflicted with nosemosis start to forge earlier, while pathological changes of their mid-gut epithelial cells, as well as digestive and metabolic disorders, cause malnutrition leading to premature deaths.

Spores enter the digestive tract of bees via infected food and drink or on the occasion of social food exchange with other bees. The most common sources of infection include unsanitary water supply, honeycomb marked with faeces of infected bees, and contaminated honey. After reaching the mid-gut, Nosema sp. spores germinate under the influence of diverse chemical stimuli and their vegetative form invades epithelial cells of the mid-gut where they multiply. A part of spores is expelled from destroyed epithelial cells of the gut via excrements and a part remains in the lumen where they take vegetative form and invade the previously healthy epithelial cells of the mid-gut. Consequently, bees are constantly hungry and take larger quantities of food which accumulates in their rectums as sweet faecal matter infected with spores.

New Nosema ceranae is highly pathogenic and there are usually no visible symptoms of diarrhoea or adult bee deaths and there is a total lack of seasonality in the diagnosis, and little is known about pathogenicity.

Factors favouring the spread of the disease include robbery in honeybee colonies and bad bee-keeping practices, as well as sudden temperature fluctuations, poor pasture, disturbance, and frequent movements of honeybee colonies.
Conditions which also influence spreading of the disease are the long-lasting impossibility of cleansing flights during winter and the honeydew honey which was brought by bees into the hive in autumn and the beekeeper could not extract on time.

  • “In 2008 I gave preventively Nozevit to my bees for the first time – in sugar syrup in August, September and in October, and I added it to pollen patty in January. In spring I detected no visible symptoms of Nosema in none of the beehives! Guided by good results I have continued this practice, and I have noticed no Nosema ever since.” — Hrvoje Domazetović, beekeper, Osijek, Croatia