American Foulbrood Disease
Beekeepers commonly worry about finding American Foulbrood Disease (AFB) in their hives. It is one of the most feared diseases that affect honey bee colonies. Caused by a spore-forming bacteria, this disease can spread quickly and often requires drastic action to control. How common is American Foulbrood today? Let’s break it down and cover some of the most important points that beekeepers need to know.
AFB is only one of several bee diseases that can harm colonies. Some are mild infections that affect productivity and overall health. But, this serious disease may harm not only your colonies but those of your neighbor as well.
What is American Foulbrood Disease?
American Foulbrood (also called AFB) is a bacterial disease caused by a spore forming bacterium (Paenibacillus larvae). It is a common widespread disease that affects honey bee brood (or young).
Only young developing bees are killed by this disease. Infected adults show no symptoms but can be carriers that spread the disease to other colonies.
For quite a while, the infected colony may not show a decline in population. From the outside, everything can appear normal and healthy.
However, American Foulbrood usually results in death of the colony. The survival time varies among hives. It may be months or even next year before the colony crashes.
During all this time, infected adults could be spreading the disease to other colonies in the area.
What AFB Looks Like in the Hive
Most brood that die as a result of AFB are in the late larval or capped brood stage of development. Death often occurs after the cell is capped and the larva has spun its pupal cocoon.
Once the larva dies, the capping sinks inward toward the bottom of the cell. Instead of protruding slightly above the surface of the comb, the capping appears sunken or concave.
Color Changes In Infected Larvae
A healthy honey bee larva is pearly white. When infected, it changes color- from white to caramel, then to very dark brown.
If death occurs in the pupal stage, you may notice the tongue protruding from the dead bee. However, itat is not always present and should not be relied on for a diagnosis of American Foulbrood.
The “Ropey” Test
At the mid-stage of decay, the contents of the brood cell become ropey. A common field test involves inserting a matchstick into the cell, stir and pull out the contents. If the brood goop stretches out ¾” (2cm) or more, you may have AFB.
Final Stage: Dry Scales
The decaying larva will continue to dry out and become a brown scale that is very difficult to remove from the cell.
Patchy Brood Pattern
Colonies infected with AFB often have a bad brood pattern that is patchy and uneven. This is due to infected and healthy brood being mixed on the comb.
However, there are many reasons for patchy brood patterns so that in itself is also not enough for a diagnosis.
How American Foulbrood Spreads
Having American Foulbrood is a hive is bad enough. But the true danger is the ease at which it can spread throught the apiary.
The Role of Bacterial Spores
American foulbrood spreads through spores that are produced by the bacterium Paenibacillus. These spores are extremely tough and can remain alive (though dormant) for years.
The spores can surivive in old equipment, wax comb and even in small traces in honey. Once inside the hive, they are easily passed from bee to bee.
How Bees Spread the Disease
Adult bees do not get sick from AFB – this may seem to be a good thing. However, they can carry spores on their bodies and in their digestive system.
As nurse bees feed developing larvae, they unknowingly pass the sprores along. Once the spores reach the larval intestines, they become active.
Germination and rapid multiplication continue in the gut of the bee larvae. Death usually results about the time the cell is capped.
As dead larvae break down into a gooey glue-like mass. New spores begin to form.
Drifting bees that move from hive to hive can distribute disease spores. And, when the infested colony’s population drops robber bees may attack the hive. They take the stored honey and the disease back to their own hive.
Beekeeping Practices That Spread AFB
Unfortunately, beekeepers often spread AFB without realizing it. Using contaminated equiupment – such as frames, boxes or tools can introduce spores into a healthy colony.
Hive tools or other pieces of equipment can harbor disease spores. (If you go to visit a beekeeper friend, don’t take your hive tool. Use theirs. 🙂
Swapping frames between colonies or feeding them unknown honey are common ways the disease is spread. This can happen when the beekeeper is making hive splits in the bee yard.
Even a small number of spores is enough to start an infection.
Why It is Hard to Control
The main read American foulbrood is so serious and hard to control of because of the spores. These long-lasting spores can remain viable for decades.
This makes it very difficult to completely eliminate from an apiary once present.
American Foulbrood Symptoms
How do you know if you have AFB in your colonies? The most fool proof way is to send a sample in for testing if you suspect the problem.
Various labs across the country are available for testing of bees and comb. Some states have strict regulations regarding dealing with this dangerous disease.
Common Symptoms:
- Rotting meat smell – dead animal
- Sunken cell cappings with off-center pinholes
- Dead larval contents rope out up to ¾ inch 2 cm
- Caramel color brood – may have pupal tongue extended
- Brown larval scale in cells that are hard to remove
- Spotty brood pattern – shot gun brood pattern
Another brood disease called European Foulbrood (EFB) is caused by bacteria. But, it does not form spores often clears up on its own when foraging conditions improve.
Ways to Reduce Risk
Despite any state regulations, every beekeeper has a responsibility to be a good citizen and protect the all hives in their region.
Practice Good Hive Hygiene
Good hive managment is one of the best defenses against American foulbrood. Keep your equipment clean and avoid using it in unknown hives and then in your hives without cleaning.
Regular hive inspections can help you spot problems early before they potentially spread to other colonies.
Avoid Using Contaminated Equipment
Be very cautious when buying used beekeeping equipment. There is always a risk of getting AFB spores – even if no bees have lived in that hive for years.
If the history is unknown, it is better to let that deal gone on by.
Be Careful When Feeding Bees
On occassion, beekeepers may feed honey to their bees. Honey from outside sources may contain foulbrood spores, even if it looks perfectly normal.
Buy Bees from Reputable Sources
The danger of bringing infected comb into my apiary is one of the reasons I prefer to buy package bees. Even this option is not completely safe – however I am not bringing comb, frames and wooden ware into my bee yard.
When purchasing bees (especially nuc colonies), buy from reputable sources who will stand behind their product.
Can American Foulbrood Be Treated?
Because AFB has 2 forms: vegetative (active) and spore (dormant) it is very difficult to eradicate. There is no cure. The spore form of AFB is very stable and can live on equipment for decades.
Researchers are looking for a way to prevent the spore form from becoming active. In most cases, infected colonies must be destroyed to prevent the spread of disease.
Chemical Treatments
Some states allow beekeepers to use antibiotics to suppress symptoms, but these do not kill the dorman spores. The disease may return later and continue to spread.
Other states will allow beekeepers to have the colony tested for the exact strain of AFB and possibly treat the hive with antibiotics such as -Terramycin (oxytetracycline hydrochloride).
I suggest checking with your state apiarist to get the latest recommendation
FAQs
AFB is not harmful to humans because it is not zoonotic. This means it has not made the jump from animal to human.
American Foulbrood is one of the most common and widespread bee diseases worldwide. But, most beekeepers will not see it every year and some never will.
This is a disease of honey bees caused by a highly contagious bacteria. One of the symptoms is dead brood (young bees) that have a very bad “dead animal” odor.
The definitive way to detect AFB in a hive is by using a lab test. Suspected colonies may be screened for some of the visual symptoms: sunken perforated cappings on brood cells, dead brood twisted in the cell that are very ropy, very bad odor.
Finally
How common is American Foulbrood in honey bees? While a serious contagious disease, AFB is more prevalent in some areas of the country. It is also a bigger problem in some years than others.
Most beekeepers don’t see it in their hives. I never have but that does not guarantee that there are no spores lurking somewhere. It can occur anywhere that honey bees live.