If you purchase an independently reviewed item through our site, we earn an affiliate commission. Read our affiliate disclosure.
American Foulbrood (AFB) is a devastating bacterial disease affecting honey bee brood, caused by Paenibacillus larvae. The disease, which is not stress-related, can strike even the strongest colonies, leading to their eventual collapse. This article provides an in-depth look at the treatment and management of AFB, emphasizing the importance of beekeepers taking necessary actions to combat the disease.
AFB spreads through spores, which can be transferred between hives via equipment or contaminated comb. The disease is globally distributed and can be identified by a sulfurous smell akin to rotten eggs, although this is not a reliable diagnostic tool. Symptoms include irregular brood patterns, sunken and darkened cell caps, and a semi-liquid, brown mass of decomposed larvae.
Early detection is crucial and involves inspecting brood comb at least twice a year, particularly in spring and autumn. The ‘Ropiness’ test is a field diagnostic method used to differentiate AFB from other diseases, but it should be followed by laboratory confirmation.
Treatment options include antibiotics like Oxytetracycline Hydrochloride and Tylosin Tartrate, although their use is controversial due to resistance concerns and potential contamination of hive products. Hygienic behavior in bees can help control the spread, but it’s not a fail-safe solution.
For infected hives, options include irradiation to kill bacteria and spores, though it’s often inaccessible for many beekeepers. Alternatively, burning and burying the affected hive and bees is recommended. Preventive measures include good apiary management, regular comb replacement, equipment sterilization, and adopting barrier management systems.
Emerging treatments like phage therapy and biological control show promise but are still under research. Cleanliness, proper hygiene, and vigilance are paramount in preventing and managing AFB to avoid significant losses in beekeeping operations.
About American Foulbrood
American foulbrood (AFB) is a fatal disease of honey bee brood. It is caused by the bacterium, Paenibacillus larvae. Brood that has been infected by the American foulbrood disease, dies at the pupal or pre-pupal stage. Serious infections that spread over a lot of the brood in a beehive, cause weakening of the colony and its eventual death.
How American Foulbrood Spreads
This disease of honey bee brood is not stress-related. It can infect even the strongest honey bee colonies in your apiary. Beehive management and prevention of robbing and drifting help prevent the spread of American foulbrood disease. While this disease is not very contagious, spores of the bacteria can however spread between beehives in an apiary. Exchanging equipment in beehives and erroneous use of infected comb in uninfected beehives, are common causes of American foulbrood spread between beehives in an apiary. Beekeeping equipment used in an infected beehive and not properly cleaned before subsequent use, can also transmit spores of the bacteria from one beehive to another.
How Common is American Foulbrood Disease?
American foulbrood disease is widely distributed over the American continent. Globally, the honey bee disease is found in all beekeeping regions of the world. It is not uncommon to hear beekeepers that have lost entire apiaries to this disease. Identification and diagnosis of the disease requires you to report it to beekeeping and agriculture regulation authorities for proper assistance.
What Does American Foulbrood Smell Like?
The disease gives off an unpleasant sulfurous smell. It is akin to the smell given off by rotten eggs. The smell is a result of honey bee larvae dying and decomposing in the beehive. This distinctive scent is easily detected by beekeepers with a keen sense of smell. It is however not a reliable indicator of the presence of the disease. Its absence is also not an indicator that the beehive does not have the disease.
American Foulbrood Disease Symptoms and Diagnosis
Beehive inspections are opportunities to look out for the symptoms and signs of bee diseases. The American foulbrood disease causes a range of changes in the beehive. They include an irregular brood pattern or a sketchy brood pattern. This is because the disease causes the death and decomposition of brood in capped cells. The cap appears sunken into the cell of the infected brood. In comparison to other brood cells, the one infected by Paenibacillus larvae is darker-colored or greasy-looking. Due to the death of larvae in the capped cells, it turns into a semi-liquid mass that takes on a brown color of various shades.
In some instances, you will notice that bees have perforated the afflicted bee brood cells and tried to remove the dead larvae from inside it. The remains of this brood are infectious. When opening up the beehive, you should pay some attention to the smell coming from inside it. In the event that there is an infection of American foulbrood plaguing your honey bee colony, you will smell a sulfurous odor emanating from the beehive. This foul odor should alert you to death and decomposition in the beehive caused by some problem. Even if the odor is not a product of an infection, it should alert you to give the beehive a thorough investigation for the presence of various other bee diseases, pests, and parasite infestations. Dead larval remains turn tough but brittle, and they are difficult to remove from the afflicted brood cell.
These mentioned symptoms are what you use to determine the presence of American foulbrood disease that has spread and is causing the death of bee brood. Between infection and death, there are some indicators you can use to detect the disease. Seeing these symptoms early on in the infection helps you prevent further spread of the disease and control it. The symptoms include:
- Infected brood changes from pearly white color to darker colors such as brown and black. The ‘Ropiness’ test (more on that later) for detection of American foulbrood disease can be carried out at this stage of infection.
- When older larvae are infected, their ‘tongues’ often become stuck to the upper walls of the brood cells.
Both weak and strong honey bee colonies are susceptible to American foulbrood infections. You should examine the comb for the disease at least twice a year. Constant vigilance is advised. Your vigilance for the disease should be heightened in the spring and autumn seasons. When inspecting the comb for the disease, each frame is removed and inspected on its two faces. Individual cells on the frame are also closely examined for signs of the disease. This includes capped brood cells and uncapped brood cells.
Detection of an early infection might involve spotting just two or three infected brood cells. That is why you should pay close attention to the deformities in the brood and the symptoms of the disease. Early detection allows you to manage the disease with a viable population of adult honey bees in the colony.
Advanced infection stages of American foulbrood disease, are an indicator that you will have a problem with the honey bee population in the beehive if you do not already have it. The death of the brood as a result of the infection, causes a rapid decline in adult bee numbers and kills the colony if left untreated. A sulfurous smell coming from the beehive indicates a very advanced spread of the disease and extensive damage to the health of the entire honey bee colony.
Ropiness Test for American Foulbrood Detection
Suspected cases of American foulbrood disease are subjected to a test to ascertain that the infection is not any other disease of bee brood. The Ropiness test is the best for the task. It allows for easy distinguishing of the disease from others. The test can even differentiate between American and European Foulbrood disease.
To conduct the Ropiness test, you will need access to the comb you suspect is affected. Prepare to open up the beehive and extract a frame of comb. This includes wearing protective clothing if there are bees in the hive. You should also have your hive tool ready for prying frames from the beehive. Proper handling of the beehive frames you test and the comb they hold should be practiced. Even if the comb is afflicted by disease, you do not want to break it and cause poor hive hygiene.
Conducting the American Foulbrood Ropiness Test
Honeycomb cells on which to conduct the test are those that have not yet reached the ‘scale’ stage. Identify the suspect cell push a matchstick into it, and then slowly withdraw the matchstick.
The semi-fluid remains of the dead brood leave a residue of varying lengths attached to the matchstick. If they make a thread that is between 3 and 5 centimeters long, the problem could be American foulbrood. The fluid should be dark brown in color for more certainty that it is in fact the disease.
After conducting the Ropiness test, you may check for the death of brood in the beehive and use it to further distinguish between European and American foulbrood diseases. The larvae infected by the disease, tend to die after the capping of their cells has been done. European Foulbrood often kills brood before their cells are capped.
Other Applications of the Ropiness Test
There are other honey bee diseases that you can test for using the Ropiness test. They include the European Foulbrood disease. In an infection of European Foulbrood caused by Melisococcus plutonius, the thread resulting from the dead mass of bee larvae is short. It stretches about 1.5 to 2 centimeters only. An infection of European Foulbrood caused by Paenibacillus alvei may give long threads that can be interpreted erroneously as American foulbrood caused by Paenibacillus larvae.
Is the Ropiness Test Final?
The Ropiness test is not 100% definitive. The performance of the test should be followed by laboratory tests that confirm the diagnosis of American foulbrood disease. In some jurisdictions, the disease must be reported to local authorities.
You should also let other beekeepers near you, know that you have had an incident of American foulbrood disease so they can increase their vigilance in their apiaries. Conversely, you should increase vigilance for the disease if another beekeeper near you reports having had an infection of the disease in their beekeeping operation.
American Foulbrood Treatment
Managing the American foulbrood disease in beehives involves adopting preventive measures and controlling it if it infects a beehive. When prevention fails, you have to treat the beehive to ensure the colony is restored to good health and strength.
Chemical control of American foulbrood is one treatment method for an infestation. Some chemical control methods can also be incorporated into preventive practices to keep infestations from taking root in beehives. Some antibiotics have an effect on the American foulbrood disease. They are however not recommended and may be prohibited from use in your jurisdiction. It is important to check with agriculture authorities in your area to find out if antibiotics are allowed to be used in controlling American foulbrood in your area.
The antibiotics that are in use for the treatment of American foulbrood disease include Oxytetracycline Hydrochloride (Terramycin) and Tylosin Tartrate which was approved by the Food and Drug Administration body of the USA in the year 2005.
While the antibiotics are not effective in killing spores of Paenibacillus larvae, they can however slow down the spread of the disease in the affected beehive. However, antibiotics also cause problems due to their persistence in beehive products such as honey. Improper application and use of various antibiotics in beekeeping have led to the rise of American foulbrood disease strains that are resistant to antibiotics.
The hygienic behavior of honey bees contributes to the control of American foulbrood disease infections in beehives. It can also help when there is an outbreak of the disease in your locality. Some types of honey bees have shown limited tolerance to the disease when they have pronounced hygienic behavior. This involves the bees being active and efficient at uncapping infected brood cells and removing the dead brood from the hive. It prevents spores from the larvae from spreading into the beehive.
Even with the best hygienic behavior, however, the honey bee colony that is battling American foulbrood disease eventually collapses if you do not intervene. The beehive remains continually infected with many recurring re-infections that eventually exact a great toll on the honey bee colony.
Management of a Beehive with American Foulbrood Disease
In the event that you detect American foulbrood in a beehive, saving the honey bee colony is not always possible. Irradiation of the beehive and all its components kills the bacteria causing American foulbrood disease and spores too. Not many beekeepers can access or afford irradiation services. If the irradiation option is not available to you, it is recommended that you burn and bury the afflicted beehive, together with all its components and the honey bee colony. Before burning, close up the beehive entrance and be sure that all bees are inside. A deep pit should be dug and used to bury the ashes of the burnt honey bee colony and beehive.
To avoid loss of the entire beehive, partial burning and scorching can be used. The beehive infected by the American foulbrood disease is taken apart so that the frames and comb are burnt. The beehive boxes and other parts are scorched thoroughly to kill vegetative bacteria and spores. Exposure of the beehive to ethylene oxide gas for long periods of time damages the spores of Paenibacillus larvae such that they cannot cause a resurgence of the disease in the beehive. A closed chamber is great for gas sterilization. Other treatments you can explore include cleaning the beehive with 3% sodium hypochlorite, or dipping beehive parts in hot paraffin wax.
Emergent American Foulbrood Treatment Methods
Emergent technologies are contributing to beekeeping and the management of various aspects of beekeeping. In disease control, epidemiology and studies of organisms have given a few possible solutions to control American foulbrood disease. The two top advances are phage therapy and biological control.
Phage therapy makes use of bacteriophages. These are viruses that are harmful to bacteria. Introducing phages that are harmful to Paenibacillus larvae into the beehive can end an infestation if done well. Studies and fine-tuning of this method to control American foulbrood disease are ongoing.
Biological control for American foulbrood uses beneficial bacteria to antagonize Paenibacillus Larvae which causes the disease. Researchers are looking into various lactogenic bacteria that have shown great promise in competing with the Paenibacillus Larvae. They have successfully out-competed the bacteria in laboratory conditions. In field trials, the performance of the antagonistic bacteria has not yet proven its ability to reliably clear American foulbrood disease from an infected beehive.
Cleaning the Beehive after American Foulbrood Infection
After an infection of a beehive by the American foulbrood disease, you should make sure to clean the beehive and treat it. The spores of Paenibacillus larvae can remain viable for a very long time after the passing of the infection. Spores have been found viable after more than 50 years. They are resistant to freezing and heat treatment. A relapse of American foulbrood disease can come about as a result of such spores not being cleaned from the beehive. The best way to ensure there is no re-emergence of the disease is to adopt the best beekeeping management practices. Quick sanitization and cleaning of the beehive before the disease spreads to other hives are also commendable.
Beekeeping tools used on beehives can spread the spores of American foulbrood. In normal working at an apiary with many beehives, normalize sanitizing of tools and equipment before using them on another beehive. It is the best first line of defense against the transmission of diseases, pests, and parasites between beehives. Bleach and other strong cleaning and sanitizing agents are used. They are safe for use with the tools and equipment used in beekeeping.
Preventing the American Foulbrood Disease
Prevention of disease outbreaks is emphasized in beekeeping. You should take steps to make sure you prevent the entry of American foulbrood disease spores into your beehives. Both experienced and beginner beekeepers should make sure they take prevention seriously and incorporate it in their apiary and beehive management routines and practices.
The number of spores that enter a beehive, has an effect on the speed with which an infection of the American foulbrood disease spreads throughout. Good colony management practices ensure that the disease will not get easy access into the beehive or spread too fast. Regular inspection of brood comb allows for early detection of the disease. You should check the entire comb in the beehive at least twice every year.
Old brood comb can act as a reservoir of American foulbrood disease spores and cause the presence of the disease at low levels over a long period of time. As a preventive measure, beekeepers remove the old comb from the beehive and allow honey bees to draw fresh comb. Every 3-4 years, the comb in the beehive should be removed from the brood boxes. You may use the comb for honey storage in beehive super boxes and then harvest the honey. After that, the comb can only be used in honey storage, harvested for beeswax, or discarded.
Limit Equipment Interchange
Interchange of materials and equipment between beehives should be limited in your apiary. It prevents the spread of diseases, parasites, and pests from one beehive to the next. When it is necessary and unavoidable to use equipment from one beehive in another, make sure to clean the equipment. Various treatments such as scorching and the use of washing soda and bleach to wash the equipment, help remove both macro and microorganisms from the equipment. Cleaning tools between use in beehives also help prevent the spread of honey bee diseases.
Barrier Management System for American Foulbrood Prevention
Implementing a barrier management system in large apiaries helps prevent the spread of various diseases, including American foulbrood. In the system, beehives are split into groups and managed as a unit. Equipment exchange can be done within the unit but not with the larger apiary. This confines disease, pest, and parasite outbreaks to a unit of beehives in the event of an outbreak or infestation. It improves biosecurity, traceability, and quality assurance. A barrier management system is a step towards the adoption and maintenance of best practices in beekeeping.
American Foulbrood Test Kit
Detection of the American foulbrood disease is aided and sped up by using a testing kit. It takes approximately 3 minutes for the results to show using these commercially sold test kits. The laboratory–level test results are accurate and can be taken as conclusive evidence that the beehive has the disease. You may also conduct further testing after using a testing kit on an infected beehive if you wish to. One test kit can be used on one beehive only and then discarded. When testing more than one beehive, purchase a test kit for each beehive you will be testing.
Vaccine and Cure
There is no known vaccine or cure for American foulbrood disease. There is however a lot of promising research that is hopefully set to give beekeepers a cure for the disease. Vaccination may also be possible in the future.
Research centered on blocking the Paenibacillus larvae spores from germinating, even if they gain access to the gut of honey bee brood is showing promising results. The researchers introduce a compound that is harmless to bees in the beehive and ensure that the bee larvae are fed the compound.
Honey bee brood that was treated this way in the research, were able to survive exposure to spores of the bacteria. Before it is rolled out, the researchers hope to perfect this method of preventing American foulbrood disease infections. They are working on a delivery method and still testing various compounds to determine the best compound for use.
Cleanliness and proper hygiene in the beehive and apiary keeps the chances of diseases such as American foulbrood, from taking root and spreading fast. Vigilance should be heightened in your apiary after an infection of the disease. Gradual and cyclic cleaning out of beehives in the apiary can also be done to ensure peace of mind. American foulbrood disease infections are contagious and can spread from one apiary to the next.
Both preventive and other control measures should be used to prevent losses in your beekeeping colony occasioned by infection with the disease. You have various methods and equipment available to you when carrying out American foulbrood treatment and management for honey bees. Beekeepers should therefore adopt the treatment and management method that gives them the best results, at the best financial cost that is not too injurious to the continuity of the beekeeping operation.
Have you ever dealt with the American Foulbrood disease in your beehives? Leave a comment below and let us know what your experience was like.