A dreaded brood disease, American Foulbrood can devastate a hive and is easily spread
Brood diseases are numerous and nasty, but one of the nastiest has to be American Foulbrood. Caused by a bacterium that multiplies and spreads via some very tenacious spores, it’s one of the least pleasant surprises a beekeeper can find in their beehive.
American Foulbrood: What is it and why is it a problem?
- American Foulbrood (AFB) is a highly infectious, bacterial honey bee brood disease
- All Australian states report the presence of American Foulbrood, except the Northern Territory
- It can infect both weak and strong colonies, hive stress is not a factor
- AFB kills honey bee larvae and pupae but not adult bees
- AFB does not affect humans. Honey that contains AFB spores is safe for humans to eat
- Infection of bee larvae happens when they ingest spores of the bacterium Paenibacillus larvae
- Usually the larva dies immediately after adult bees cap the brood cell. Occasionally it dies later, at the pupal stage
- The bacterium begins to multiply rapidly after capping. Spores germinate to form vegetative ‘rods’
- It reaches the final stage of its lifecycle when the rods form into many new spores
- Through this process dead larva becomes a dried scale that sticks to the side of its cell
- There about 2,500 million American Foulbrood spores in the remains of a single infected bee larva
- Through rapidly infecting and killing brood, especially during the spring build up, AFB can significantly weaken or even destroy a honeybee colony
How is American Foulbrood Spread?
- American Foulbrood spores remain active for about 50 years or longer
- They are resistant to heat, freezing, direct sunlight, dehydration, fermentation, many chemical disinfectants and therapeutic drugs
- Infections start when nurse bees spread spores on their mouthparts to larvae when feeding
- A bee larva less than 24 hours old is most susceptible, as few as 10 spores cause an infection
- The disease cycle of AFB means that once spores reach the brood the bacteria can multiply very fast
- Inside the hive, nurse bees continue to spread spores when they clean infected cells and attempt to remove dead pupae
- Field bees can also spread spores within and between hives through robbing and drifting behaviour
- As AFB weakens infected colonies, these hives become easy targets for robbing bees
- Beekeepers can spread the bacterial spores if they place infected combs or hive components in non-infected hives
- Spread of spores can also occur on tools and equipment
- Re-feeding infected honey and pollen to bees will of course spread infection too
- Swarms and absconding colonies may also spread the disease between areas, but this is less common
Next week on The Buzz we take a look at identifying (diagnosing) and managing Amercan Foulbrood in your hive.