AFB or PMS – Beekeeping Diseases
Parasitic Mite Syndrome (PMS) is the destructive combination of mites, viruses, and general malaise that can overcome a colony with a high mite load. At first glance some of the symptoms of PMS can look a lot like foulbrood disease. I ran into this last week.
The hive in question started last spring as a 5 lb. package with Italian queen on drawn comb. This instant colony filled out two brood chambers and produced two and a half supers of honey last year. I felt that the mite load was acceptable all through the summer because I only saw a few mites on the screened bottom drop boards. As the weather cooled the mite drops increased a bit. I placed a formic acid pad on the colony in November and more mites came down, and I kept seeing heavy drops all through the fall.
Around this time I noticed lots of dying bees in front of the hive. Concerned about Nosema, I checked with the microscope but found no spores. The deaths tapered off – winter came – and now I find only about 3 frames of bees left with a small brood nest.
I observed several bees with deformed wings – signs of virus problems associated with Varroa. When I pulled a frame, the first thing I noticed were the perforated cappings on the brood cells. The thought of AFB immediately came to my mind. I tested for “rope-like” consistency of the dead larvae with a twig. Maybe – maybe not — What else could it be? I put a quart of sugar syrup with Terramycin on the hive and closed them up – dismayed with the prospect of burning yet another colony.
Today, armed with camera, toothpicks, and sample jar I took another look and collected a couple of samples for microscopic examination. If it is active American Foulbrood, there will be plenty of spores to see.
Last year I had to deal with AFB and took a few pictures of the spores through the microscope. The spores are small and numerous, and bounce around a lot because of Brownian motion. The picture above is what you don’t want to find!
Today the larvae that I probed did not rope much at all, so I’m quite convinced that I jumped the gun with the AFB fears. The microscope confirmed that no spores were present. (Sometimes its hard to know you are looking at in a “normal” sample. Digested pollen grains usually dominate bee gut microscopic images. Pollen comes in lots of shapes, so don’t expect all gut samples to look alike, even with normal healthy bees.)
So,although I found no foulbrood, I still have a very weak distressed colony that may not make it until spring. Now its time to reflect about what I should have done differently. Varroa mites and the trouble they cause are not going away any time soon.
I did run across a good reference on this subject which I’ll pass along: IPM_American_Foulbrood_and_Varroa_Mites_by_Simone.pdf