Moose (Alces alces) with Boils on Hind Legs

Mike Brook writes,

This moose appeared to have 10 or more pink/red boils or bumps on its hind legs above the knee about an inch across give or take, similar to the size of a nickel to a half dollar coin. I don't recall seeing this on any moose around here in the past. I didn't notice any other skin conditions on the moose.

LEO says:

These spots may be the result of Moose Fly (Haematobosca alcis) bites. According to the ADF&G overview of parasites and diseases in Alaskan wildlife, "The flies bite the hindquarters of moose just above the hock. Hundreds of flies may attack a moose at one time. The numerous bites produce wet open sores, measuring up to 1 inch in diameter. The wounds are often bloody." These flies do not attack humans, or other members of the deer family such as deer, elk, or caribou. If Moose Fly (Haematobosca alcis) are seen on a harvested moose, the meat is still safe to eat. Source: Alaska Department of Fish and Game, Parasites and Diseases, Moose Fly. This observation has been shared with the ADF&G Division of Wildlife.

Alaska Department of Fish and Game Consult:

Kimberlee Beckman, Wildlife Veterinarian, writes: "These are Moose flies, (Haematobosca alcis) bites. They are an obligate parasite of moose, meaning they must live their entire life cycle on moose and can’t live without moose. The flies hang on to the back side of the moose at all times. To feed, they bite the area above the hocks and suck up the serum. When the moose gets up in the morning and defecates, the flies lay eggs on the fresh droppings. These flies are common throughout the moose range, virtually all adult moose have them from June through July and then the adults die. There isn’t a treatment for this, it is normal and doesn’t have a significant effect on the moose, although they do transmit a worm to moose that also is normal and typically has no adverse effect. The flies will be dead soon so the moose will no longer be bothered until the pupae become adults next June."