Microsporidiosis

Definition

A disease caused by infection with microsporidia, obligate intracellular fungal pathogens that replicate within host cells and disrupt tissue function. In humans, microsporidiosis typically presents as chronic diarrhea and wasting in immunocompromised individuals, but the disease is far more common and ecologically significant in arthropod populations, where microsporidia function as important regulators of insect and crustacean numbers. Infection occurs through environmentally resistant spores that germinate upon contact with host cells, extruding a polar filament to inject the sporoplasm directly into the cytoplasm.

Etymology

From Microsporidia (the pathogen group, from Greek mikros 'small' + sporos 'seed') + -osis 'disease condition'

Example

The microsporidium Nosema apis causes nosemosis in honey bees (Apis mellifera), a debilitating infection of the midgut epithelium that impairs digestion, reduces lifespan, and can lead to colony collapse; beekeepers manage the disease by administering fumagillin in syrup or by selecting hygienic stock.

Related Terms

• Microsporidia
• nosemosis
• Pathogen
• obligate intracellular parasite
• spore
• Polar filament
• immunocompromised host
• honey bee disease
• Biological control

Usage Notes

Microsporidiosis is a generic disease name; specific infections are often named after the host or pathogen (e.g., nosemosis in bees, pebrine in silkworms). The term is used in both medical and veterinary/entomological contexts, but specialists in insect pathology rarely use 'microsporidiosis' for invertebrate hosts, preferring pathogen-specific or host-specific names. Microsporidia were historically classified as protozoa and are still sometimes referenced that way in older literature.