Understanding Nosemosis

Our guide to a common, contagious bee disease

Nosemosis – sometimes called Nosema – is a disease caused by a single-cell, fungal parasite. Highly contagious, it’s the most common disease found in adult bees.

The parasite causes serious intestinal problems for bees, which can lead to population loss and eventual colony collapse if left untreated. In New Zealand, outbreaks are most common in spring when bad weather and low pollen supplies can weaken colonies and leave them vulnerable to infection.

The origins of the disease

Nosema Apis and Nosema Ceranae are the single-cell, fungal organisms that cause Nosemosis. They are different varieties of sporozoan, which means they spread disease through microscopic spores.

A few tiny spores ingested while a bee is eating, drinking, or cleaning the hive, can be enough to lead to a serious infection in the hive.

Nosema Ceranae was originally discovered in the Eastern honeybee and spread to Western honeybees around 2005. Since then, it has spread through Europe, resulting in declining bee numbers and failed colonies. Spain is particularly affected by the disease.

Signs and symptoms

After a bee ingests Nosema spores, they enter the abdomen and cause serious damage to the intestines, reducing the bee’s ability to digest food. Long-term, the disease can lead to a shortened life span for adult bees, and a slow population decline in the hive.

Although both forms of the Nosema pathogen cause intestinal problems, they have slightly different symptoms. When a hive is infected with Nosema Apis, you will generally notice brown or yellow excrement stains inside the beehive. With Nosema Ceranae, the main sign of disease is a slow reduction in bee numbers.

How Nosemosis spreads – and how to stop it

Nosema infections can happen at any time of year, but they’re most common in early spring when colonies are at their weakest. Bad weather, low pollen supply, or a hive that’s placed in a damp, windy spot can all make infections more likely.

Transmission of Nosema spores can happen in several ways – bees feeding on flowers or drinking from watering holes that have been visited by infected bees, bees from other hives entering to rob honey, or beekeepers using contaminated equipment or transferring contaminated comb to feed the hive during spring. In a weakened hive, just a few tiny spores in the stomach of a single bee can lead to a full-blown infection spreading through the colony.

For beekeepers, disinfecting hives, hive tools, and honeycomb are the best ways to prevent the spread of Nosemosis. It’s also essential to feed colonies well through winter to keep them strong and resilient.

Want to know more about Nosema or other hive diseases? Talk to the team at Ecrotek for advice.