ceranae

Nosema ceranae is a microsporidian parasite that infects the digestive tract of honey bees, primarily Apis mellifera. Originally described in Apis cerana, it has since become widespread and is a major cause of nosemosis in many honey bee populations around the world. It is distinguished from Nosema apis by genetics and, in some cases, by its epidemiology and pathogenesis.

Transmission and life cycle: N. ceranae produces spores that contaminate food, water, and hive surfaces. Bees ingest these spores, which germinate in the midgut and release infective sporoplasms that invade epithelial cells. The parasite replicates within these cells, causing cellular damage and disrupted gut function. New spores are released into the gut lumen and excreted in feces, enabling horizontal transmission within and between colonies. Infections can be chronic and may persist across seasons, often interacting with other stressors such as nutrition, temperature, and other pathogens.

Clinical signs and impact: In many cases, N. ceranae infections are subclinical, but they can contribute to reduced bee longevity, diminished foraging efficiency, and lower colony performance, especially under stressful environmental conditions. Colony decline or collapse has been observed in some contexts, though the exact contribution of N. ceranae relative to other stressors varies. External signs are not always evident, making diagnosis challenging without laboratory testing.

Diagnosis and management: Diagnosis typically relies on laboratory methods, including microscopy to detect spores in bee gut samples and molecular techniques such as PCR to distinguish N. ceranae from other Nosema species. There is no universally effective treatment; fumagillin has been used in some regions with varying success and regulatory status. Beekeeping management focuses on improving nutrition, reducing stress, maintaining strong colonies, and practicing good hive hygiene. Ongoing research explores disease dynamics, host resistance, and strategies to mitigate impacts on pollination services.