The transmission of European foulbrood (Melissococcus plutonius) to artificially reared honey bee larvae (Apis mellifera)

SUMMARY

The transmission of European foulbrood (EFB) was investigated by feeding larvae raised in vitro with a diet containing Melissococcus plutonius that had been artificially cultured or extracted from diseased larvae. EFB did not develop in larvae fed 1.1 × 10⁹ artificially cultured M. plutonius organisms/ml. However, the use of M. plutonius extracted from diseased material effectively transmitted EFB to larvae at a minimum concentration of 200 M. plutonius organisms/ml. The method used to raise and infect larvae in vitro had an associated larval survival of 81.2–100% (mean 91.9%). A strong correlation (r² = 0.96) was established between the mortality of larvae that died from EFB and the dose of M. plutonius organisms. A clear linear relationship exists between the time duration of feeding M. plutonius inoculated basic larval diet (2 × 10⁵ organisms/ml) and larval mortality (r² = 0.92).

Keywords:

• honey bees
• Apis mellifera
• larvae
• European foulbrood
• Melissococcus plutonius
• mortality