Do swarms carry diseases/parasites?

I set up a swarm trap for the first time this year and noticed a lot of scout bee activity around it yesterday! So I am really hoping it was to their liking and they will come back with all their friends soon.

But then it occurred to me for the first time, are there any precautions that one needs to take about swarms possibly carrying diseases or parasites? I have two other hives, not at this location. If I do get a swarm in the trap, they are far enough from my other bees to be effectively in quarantine. I would let them settle in for a week or two until I know for sure they are bringing pollen and have accepted their new home, and then move them to where my other hives are. Is there anything I should be doing in that week to confirm their health? On the other hand, I have read it is best not to disturb them in case they decide to move on.

I see some beekeepers, like one YouTube channel I watch, catch dozens of swarms every year. I don’t really hear them talking about disease in those swarms. Is the explanation that any colony that is strong enough to swarm is free of disease?

All swarms have the potential to carry both diseases and parasites. In practice, it seems to be rare that this is problematic.

Many beekeepers advise that a new swarm is not fed for at least a week, to use up any remaining stores in their honey stomachs. This minimises the risk of transferring EFB spores to the new nest.

All colonies carry varroa mites - but bees weakened by mites are unlikely to be able to fly strongly to stay with a swarm, and the number of phoretic mites being carried by bees is around 10% of the total population in the parent colony. Provided the swarm is not from a colony on the brink of collapse with mites, it should not be a problem.

The best safety precaution to protect your other hives is to quarantine them in situ for a month or so, then inspect and check for brood diseases and general colony health.

IN practice, I have been keeping bees for 20 years and never worry about this stuff. The only disease which would make me think twice is AFB, and it isn't in my area at present.

Thanks, Michael, that was very helpful!

I think what I will do is transfer the bees from the swarm trap (within the first two weeks or so, after they seem settled) into a proper hive body, inspecting them at that point; then inspect them again after two weeks and if all seems well I'd move them to their permanent location after that.

I hadn't planned to feed in the first week (or at all, unless we had a dearth which is possible, and maybe in the run-up to winter depending on their food stores), so allowing them that opportunity to clear out their systems should not be a problem.

Next time I will plan this a bit better and use a proper wooden hive body as the swarm trap to avoid that transfer. This time, I meant to do that but wasn't strong enough to lift it over my head into the fork of my first choice tree or climb a ladder with it, even using a rope over a limb to support some of the weight. And that tree was on the wrong side of a garden fence so I couldn't back the truck up to it and stand on the tailgate. So the trap I cobbled together is two waxed-cardboard nuc boxes that my nucs came in this year, taped together with big holes cut in the adjoining sides to make it look like one bigger cavity. I put my oldest frames in it, and a few drops of lemongrass essential oil.

Or perhaps that is actually a good thing as the initial quarantine period will take place in expendable equipment rather than possibly contaminating a hive body I'd want to keep.

I wondered if the scout bees had spent the night in it last night, as it was positively humming well into the evening and I found them crawling all over it and flying around it again at 6 AM this morning which seemed very early for bee activity. So maybe they stayed over? They seem to have all left now though. I don't know if that means they have decided against it, or if they've gone home to tell the rest.

Speaking of humming, at one point yesterday evening a hummingbird showed up and hovered briefly in front of the entrance, seemingly wondering what had attracted so many bees.