There are two honey bee foulbrood diseases. Often they are referred to a “stress diseases.”
The most problematic known as American foulbrood or AFB, is caused by the bacterium, Paenibacillus larvae larvae. It is feared because the pupal scales or deposits associated with severe cases are very difficult for bees to remove from combs, and the bacterium forms highly resistant spores that can tolerate harsh environmental conditions. Due to this, the most often recommended treatment is burning. Robbing by honey bees is the major way the disease is spread. It is this disease that is the historic reason for honey bee inspection services in the U.S. and around the world.
This has resulted in an association of inspectors that continues to meet occasionally to discuss honey bee health, which now has expanded much beyond earlier concerns like the foulbroods. Inspection continues to be controversial to some extent as its original mission has been somewhat compromised.
The only way to eliminate AFB spores is by fire. In many U.S. states inspection laws have been written to mandate burning of colonies, brood and honey that have been found to be infected. The disease is the reason most honey bee inspection services exist in state laws. The disease appears to be always present and so epidemics can take beekeepers by surprise. In New Zealand, there continues to be efforts to eradicate the disease.
AFB can be controlled by antibiotics, but this treatment option is falling out of favor due to resistance issues. Specific cases of this have been documented in Argentina and Florida. The use of sulfa drugs (no longer legal), later followed by antibiotics, to prevent American foulbrood has proved a boon to beekeeping. Unfortunately, antibiotics do not kill Bacillus larvae larvae. These substances only prevent the bacteria from multiplying; they thus suppress the symptoms of American foulbrood, but cannot rid a colony of the bacterium or its spores. This is not always well understood in beekeeping circles, but is a vital piece of information that must be taken into consideration before a drug-feeding program begins.
Recently the Food and Drug Administration (FDA) has declared both antibiotics beekeepers use for this treatment (oxytetracycline – Terramycin- and tylosine tartrate – Tylan) prescription drugs. An extensive list of antibiotics routinely used in domestic animals, therefore, will no longer be available over the counter as in the past. A new rule for beekeepers obtaining antibiotics is due to go into effect January 1, 2017, and demands that a relationship with a veterinarian be established via something called vetrinarian-client-patient relationship (VCPR). There is also growing evidence that exposure to antibiotics significantly alters the honey bee gut microbial community structure and leads to decreased survivorship in the hive, likely due to increased susceptibility to infection by opportunistic pathogens.
Once antibiotic treatment has begun to control American foulbrood, it is a long-range management decision that cannot be abandoned and every colony being fed must be treated as if the Bacillus were present. Only certain antibotic formulations are suitable for feeding honey bees and they must be fed according to the label accompanying the product. Again, these are on the chopping block and will no doubt simply not be available in the future.
Treatments are in constant flux and so beekeepers must continually be aware of new developments. One shows some promise is via competing bacteria, revealing a possible biological control of this important disease. Another is the potential use of “phages,” with at least one research project fully focused on this topic. A recent webinar by Dr. James E. Tew (49 minutes) is certainly worth a look and hearing. It contains valuable information, some taken from a classic work on the subject, American Foulbrood, by White, G. F. (Gershom Franklin) published in 1920 by the USDA.
European foulbrood or EHB is another bacterial disease considered less virulent because the causative bacterium does not form spores, Simply requeening will often rid a colony of EHB symptoms. This procedure provides two important things: (1) a break in the brood cycle which allows the bees to clean out infected larvae, and (2) the possibility that the replacement queen’s worker bees will be more resistant to the disease. Another way to achieve these conditions is replacing the combs, while saving the bees through what is called a “Shook Swarm.”
AFB is sometimes confused with EHB, named because most of the research was either done in America or Europe. The treatment and symptoms, however, are quite different.
