Ominous sounding name, huh?
This little sucker (literally) is one of the many pests which can affect the health and well being of a hive. Varoa is a mite which latches onto the honeybee and sucks the hemolymph from the bee. You can think of hemolymph as being like our own blood though it doesn't serve exactly the same purpose in the bee as blood does in humans. For one thing, bees don't need to have oxygen circulated throughout their bodies because they respirate (breathe) directly through the spiracles on their sides. Another type of mite, the tracheal mite, sets up home inside the bee's trachea and block the airways. You can't see those with your naked eye.
There's a Varoa mite prominently displayed right in the center of the picture behind that center bee's eyes. If you closely under the left wing of the second bee from the left on the bottom, you can see another Varoa mite. Without my reading glasses (yes, I'm getting old and my eyesight stinks) I can't see these mites, so I generally need to rely upon examining the pictures I take when inspecting my hive. I saw other Varoa mites in other pictures but not a lot of them. I will be treating for these in the next week using powdered sugar. Essentially you dust the bees with it and it helps to dislodge some of the mites as part of the process. The bees don't mind the powered sugar but it does actually result in some of the mites falling off.
Varoa reduces the life of a honeybee and so it is important to treat for these pests to keep them in check. Hives will have them - in fact most every hive is going to have Varoa mites. But the presence of these mites doesn't mean that your hive is doomed. A simple method for checking them is to treat with powered sugar and stick a slide-in card in your screened bottom board. The mites will fall off - at least many will - and you can count them to gauge how your hive is doing. It would be nearly impossible to prevent Varoa since bees don't live in a closed system - they are out and about and likely to pick up Varoa and bring it back to the hive. Our job as beekeepers is to treat for and keep account of the Varoa population rather than attempt to eliminate them - that's not going to happen. Varoa poses no direct threat to humans or animals as far as I know. It doesn't affect the honey either. It is simply a pest that affects the life of the bee directly.
Matt (twitter @MattInTheGarden) is not a fan of seersucker suits, NASCAR or zydeco music. He prefers sausage over bacon and bacon over Canadian bacon. His favorite pizza topping is black olives, at least today. Matt thinks right now is a great time for a nap.