Monitoring of Paenibacillus larvae in Lower Austria through DNA-Based Detection without De-Sporulation: 2018 to 2022

Area of Science:

• Apiculture
• Veterinary Microbiology
• Molecular Diagnostics

Background:

• American foulbrood, caused by Paenibacillus larvae, severely impacts honey bee colonies, often detected too late for effective intervention.
• Early detection through active monitoring and hygiene measures is vital to control disease spread and protect apiaries.

Purpose of the Study:

• To compare the efficacy of culture-based detection versus RT-PCR for identifying Paenibacillus larvae spores.
• To evaluate the feasibility of using direct DNA detection from spores for rapid screening in voluntary monitoring programs.

Main Methods:

• A five-year voluntary monitoring program in Lower Austria utilized honey and brood cell samples.
• DNA was extracted directly from Paenibacillus larvae spores using chemical and enzymatic treatments followed by mechanical lysis.
• RT-PCR detection of P. larvae DNA was compared against traditional culture methods.

Main Results:

• RT-PCR provided comparable results to culture methods but with a substantial time saving.
• A high proportion of monitored bee colonies tested negative for P. larvae (ranging from 72.09% to 91.9% annually).
• Most positive colonies exhibited very low spore loads, though two apiaries required eradication due to clinical signs.

Conclusions:

• Direct DNA detection via RT-PCR is a rapid and effective tool for early American foulbrood screening in apiculture.
• Implementing rapid molecular diagnostics in monitoring programs can aid in timely interventions and disease management.
• Sustained monitoring efforts indicate a generally low prevalence of significant P. larvae infections in the studied region.