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Stonebrood Disease—Histomorphological Changes in Honey Bee Larvae (Apis mellifera) Experimentally Infected with Aspergillus flavus

Summary

Stonebrood is a rare fungal disease of honey bees caused by Aspergillus flavus that can kill bee larvae very quickly. Researchers experimentally infected bee larvae with the fungus and tracked how the disease progressed, finding that larvae died within 48 hours of infection. The study revealed that the fungus likely kills bees by producing toxins rather than by physical damage, and poses a health risk to beekeepers who inhale the fungal spores.

Background

Stonebrood is a rare fungal disease of Western honey bees caused by Aspergillus species, affecting both adult bees and brood. Despite being the only zoonotic disease of honey bees, posing health risks to beekeepers, the pathogenesis remains poorly understood. Most information is based on a 1930 study by Burnside conducted under non-standardized conditions.

Objective

To describe the pathogenesis of stonebrood by examining artificially reared, pathogen-free Apis mellifera larvae experimentally infected with Aspergillus flavus through macroscopic and histological analysis. The study aimed to understand the course of disease and host-pathogen interactions under controlled and standardized conditions.

Results

Of 43 collected infected larvae, 19 showed histological signs of infection; significantly smaller than control larvae on days 2, 4, and 5 post-infection. Infection progressed through three phases: establishment (germination in midgut), spreading (mycelium penetration throughout larval body), and distribution (cuticle penetration and conidiophore formation). First infected larvae were detected at day 1 post-infection, with death occurring by day 2.

Conclusion

A. flavus establishes rapidly within 24 hours in experimentally infected bee larvae and causes death within 48 hours. The pathogenesis is characterized by a short incubation period and rapid progression, suggesting larvae likely die from mycotoxin exposure rather than mechanical damage. The study provides crucial understanding of stonebrood pathogenesis and highlights the disease’s aggressive nature.
  • Published in:Veterinary Sciences,
  • Study Type:Experimental Study,
  • Source: PMID: 40005884, DOI: 10.3390/vetsci12020124
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