In the Spring of 2019 I started noticing a poor brood pattern in three of the four hives at an apiary used for students of the New Mexico Beekeepers Association. Upon closer inspection, I saw uncapped brood that was sunken, twisted on its side, discolored (yellow and dark brown), and showing its tracheal outline. Some larva had dried up and scaled to the side of the cell. Bees were quickly removing this dead larva, so it wasn’t easy to recognize these sick larva at first glance. There was also no smell. The rope test showed that it wasn’t ropey, but had a watery texture.
I took a sample from Hive 4 and sent it to the USDA Beltsville Lab in Maryland. They soon confirmed that the comb sample (with brood) that I sent in had European Foulbrood. Hive 3 also had EFB and Hive 2 had a small amount. I tried supplementing the hives with sugar water and I cut out infected and old comb. The EFB persisted. As a last resort, all four hives were treated with Terramycin following these recommendations from the Ohio State Beekeepers Association:
“For feeding 1 colony, mix 1 teaspoon of TM plus 5 teaspoons of powdered sugar…dusting should be directed on the outside edge of the frame top bars in the brood area, avoiding direct contact between the brood and the Terramycin mixture.”
Dusting this mixture directly onto the brood can kill any brood it comes into contact with as it is a concentrated amount and needs to be fed to them by nurse bees. To accommodate a top bar hive, I placed the mixture on the bottom of the hive below the brood nest. I treated all four hives in the apiary to ensure that any and all EFB was treated.
The EFB seemed to clear up quickly and completely. All hives looked healthy and robust in the fall, ready for winter.
Early this spring I saw that the bees came through winter well. They were healthy, but on April 1st I noticed that Hives 4, 3, and part of Hive 2 had signs of EFB. Unfortunately, reoccurance is a common problem with EFB. Hive 1 was almost completely clear of any signs. I got another comb sample from Hive 3 and prepared to send it to the Beltsville Lab again; however, due to the COVID-19 restrictions the lab is not taking samples until further notice.
This was disappointing, but after comparing pictures to this year’s brood and last year’s, it’s apparent that the EFB is back.
I did some more research and found that shook swarms have been quite effective at preventing recurrence of EFB in the UK (please refer to the study in resources below). I decided to do a shook swarm on all three infected hives, requeen them, feed them sugar water and ensure that they had a good pollen supply. These hives had a lot of old comb, and now would be a great time to give these hives a fresh start (no students coming to the apiary due to COVID-19).
Brief description of the shook swarm method:
Step 1: Place new hive and new bars or frames next to infected colony
Step 2: Find the queen and cage her; place her and new uninfected comb into new hive box with a few other bars of uninfected comb
Caging the queen first makes it easier to find her, ensures that she is not harmed in this process, and when she is caged the colony gets a brood break. The bacteria that causes EFB (Melissococcus plutonius) lives in honey and wax, so the bees need to expend all of their resources on making new wax and not feeding new eggs and larva–the new wax is later cut out. In the photo above the opening of the queen cage is face down, you do not want to do this if attendants are in the queen cage with her. If an attendant dies they can block the opening, preventing the queen from leaving the queen cage.
Step 3: Cover most of the hive with top bars if using a top bar hive so that bees aren’t completely exposed when they are shaken into the new hive.
It’s also a good idea to keep the infected area of the hive covered as much as possible to limit robbing and exposing other colonies to bacteria laden comb and honey.
Step 4: Shake bees into the new hive one bar at a time, cutting the comb off of the old bar and placing it into a closed container. (The old bars will need to be disinfected along with the old hive)
Step 5: Once new hive is completely assembled-close off the old hive completely and move it out of the way.
Step 6: Place colony in its original hive location.
The hive will quickly focus it’s efforts on building new comb. This is just what we want, as it encourages the bees to empty their honey crop and stomach of nectar infected with EFB. Infected honey (in their gut) is also not fed to larva at this time.
Step 7: Make sure hive is fed sugar water
Feeding the hive sugar water ensures that they have a decent food source, and more quickly clears their gut of nectar infected with EFB.
Step 8: Come back in 3 days to ensure that queen is released and cut out all of the new comb they have built. You don’t want to leave this new comb as it may have remaining bacteria. Now is a good time to add more uninfected comb and resources (honey and pollen).
Step 9 (optional): Requeen.
I re-queened these hives as this gave us one more way of ensuring that the EFB doesn’t reoccur. The old queen showed that her offspring could easily succumb to EFB. So why did I go ahead and cage the old queen? I caged the old queen and left her in the hive briefly so that the colony was more intact after having all of their brood taken away. Doing a shook swarm causes a lot of stress temporarily. Taking away the queen would just be one more strain on the hive and another reason for them to not behave as a cohesive colony.
Outlook: After a week and a half (April 15th) the bees are showing no signs of EFB. The brood looks healthy and the bees are quickly expanding with new comb, brood, nectar and pollen.
Unfortunately, Hive 1 that was showing none and then very few signs of EFB also succumbed to this disease. This hive was also requeened and is being fed sugar water in hopes that the EFB will clear up without having to do a shook swarm. If possible, I’d like to move this hive to another area to place it in quarantine…
More on EFB:
European Foulbrood is known to be brought on by stressors such as poor nutrition. When the hive is weakened larva can succumb to the bacterium Melissococcus plutonius.
This bacteria is spread when tools or resources from one infected colony come into contact with another. Sometimes this bacteria is spread through natural bee movement. Bees carry bacteria in their gut with nectar that is then fed to larva and spread throughout a colony. It was no surprise that EFB seems to have affected most hives in the apiary. Hives are close together and students carry hive tools from one hive to the next. Its always important to wear gloves or wash hands, and disinfect hive tools when going from one hive to another.
CREDIT: Thank you Sarah Simms for giving hours of your time to this process and for taking the videos and many of the great photos above. This couldn’t have been done without you!
Information on Melissococcus plutonius: https://www.cabi.org/isc/datasheet/34446