What beekeepers need to know

Recent testing by the Department of Primary Industries and Regional Development (DPIRD) has confirmed the presence of Nosema ceranae, a fungal parasite, in managed hives across Western Australia. The wide geographic spread among beekeepers suggests the pathogen is already well-established.

Words James Sheehan, Project Officer — Bees, Sustainability and Biosecurity, DPIRD

What is Nosema ceranae?

Nosemosis, or nosema disease, is caused by Nosema apis and Nosema ceranae. Nosema is a fungal parasite caused by a spore-forming microsporidian fungus — a microscopic parasite that invades the bee’s gut lining, negatively impacting bee health (see Figure 1).

FIGURE 1. Nosema spores on a gridded microscope slide for counting spore numbers, at 400x magnification.

Source: Shannon Holt

How it affects bees

The disease lives inside the stomach of honey bees, affecting their digestive systems. It reduces adult bee lifespan and weakens overall colony health and productivity. While the two strains are similar, infections may cause significant losses in adult bees. The impact is influenced by environmental conditions, colony health, genetics, and management practices.

Spread and detection

Nosema apis has long been endemic across WA, with impacts often isolated and seasonal. Nosema ceranae is present in all other Australian states, and its extension into WA is now considered part of its natural range expansion. Although newly identified in WA, it is likely to have been present for some time. Its spread can be gradual, and symptoms may take time to become apparent. Symptoms may resemble other bee health issues, complicating early detection.

Nosema can be identified by microscopic (400×) examination of adult bee abdomens to detect spores. Differentiation between strains requires molecular diagnostics.

Management strategies

Apiary management practices for both Nosema apis and Nosema ceranae are similar. Implementing effective strategies can help minimise their impact on bee health and colony productivity.

• Monitor and diagnose regularly — Conduct routine checks to detect early signs.

• Optimise hive management — Maintain strong, healthy colonies.

• Maintain hygiene — Clean equipment and hives to reduce spore spread.

• Adapt to seasons and environment — Adjust practices based on climate and stressors.

• Breed for resistance — Select bees with traits that resist Nosema.

• Keep detailed records — Track hive health and interventions.

Cleaning hives to reduce spore spread.