I spend a lot of time worrying about Melissococcus plutonius and Paenibacillus larvae, the bacteria that cause European foulbrood (EFB) and American foulbrood (AFB) diseases, respectively. Both are rare compared to that insidious parasitic varroa mite, but they can cause major problems if they rear their heads in my apiaries.
I also teach veterinarians about these diseases because the 2017 Veterinary Feed Directive requires that beekeepers obtain antibiotic prescriptions from a veterinarian to treat EFB or AFB. So, we’d better have plenty of vets trained in honey bee biology and disease diagnosis/treatment!
But more broadly, the entire beekeeping industry needs to worry about EFB and AFB. Both diseases are highly contagious, and AFB in particular has had a devastating history in the USA. The reason this disease is called “American foulbrood” is because it was first described in the USA in 1907. In the 1920s, before effective monitoring programs and quarantine protocols were in place, AFB nearly wiped out the beekeeping industry in many areas, including several counties in upstate New York where the Dyce Lab currently exists (Morse, 1967).
Thankfully, we now have a vigilant network of state apiary inspectors throughout the USA who keep close tabs on EFB and AFB. We also have a national testing lab, the USDA ARS Beltsville Bee Disease Diagnostic Service Lab, which diagnoses these diseases and tests for antibiotic resistance. Thank you, state and federal government folks!
So, what’s the current status of EFB and AFB in the USA? Which disease is more common? Are there regional hotspots? Have these diseases increased or decreased since 2015? And what about resistance to antibiotics? Are the two main antibiotics used to treat AFB still effective? These are the topics for the seventy-seventh Notes from the Lab, where I summarize “Occurrence and distribution of two bacterial brood diseases (American and European foulbrood) in US honey bee colonies and resistance to antibiotics from 2015 to 2022,” published in the Journal of Apicultural Research [2024] and written by Mohamed Alburaki and colleagues at the USDA ARS Bee Lab in Beltsville, MD.
For their study, Alburaki and colleagues summarized the data from all brood comb samples submitted to the USDA ARS Beltsville Bee Disease Diagnostic Service Lab for AFB and EFB analysis between 2015 and 2022. During this period, 4790 samples were sent to the lab from 49 states across the USA.
For each sample, swabs of symptomatic brood were taken (see Photo 1) and transferred to sterile tubes containing water to create brood cell suspensions. From these suspensions, two tests were conducted.
First, a drop of the suspension was placed on a microscope slide, dried, stained, and examined using a compound microscope at 1000x magnification. Paenibacillus larvae and Melissococcus plutonius were identified…
