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

Year: 2025

Type: article

Abstract: Stonebrood (Aspergillus sp.) is a rare, poorly described disease of the Western honey bee (Apis mellifera) that can affect adult bees and brood. This study describes the pathogenesis using artificially reared pathogen-free Apis mellifera larvae, experimentally infected (5 × 102 spores/larva) with Aspergillus flavus. Between days 1 and 5 p.i. (larval age 4 until 8 days), five uninfected control larvae, up to five infected living larvae, and up to five infected dead larvae were examined macroscopically. Subsequently, the larvae were photographed, fixed (4% formaldehyde), and processed for histological examination (hematoxylin–eosin stain, Grocott silvering). Sections were digitized, measured (area, thickness), and statistically analyzed. In total, 19 of the 43 collected infected larvae showed signs of infection (germinating spores/fungal mycelium): dead larvae (from day 2 p.i.) showed clear histological and macroscopic signs of infection, while larvae collected alive (from day 1 p.i.) were only locally affected. Infected larvae were significantly smaller (day 2 p.i.: p < 0.001, 4 p.i.: p < 0.01, 5 p.i.: p < 0.01) than uninfected larvae (control group). Our study shows that the pathogenesis of stonebrood is characterized by a short period between Aspergillus germination and the onset of disease (about one day), and a rapid larval death.

Source: Veterinary Sciences

DOI: 10.3390/vetsci12020124

Authors: Tammo von Knoblauch, Annette B. Jensen, Christoph K. W. Mülling, Anton Heusinger, Heike Aupperle-Lellbach, Elke Genersch