What are a horses enemies?

Natural enemies of a horse include bears, wolves, big wild cats like mountain lions, coyotes, foxes, vultures, feral/stray dogs (or any dog for that matter), humans (yes, horses DO consider us predators, especially by wild horses), parasites, biting insects like horse flies, and abiotic things like flood waters, thunderstorms, fire, wind (horses hate wind), and even the sun especially on really hot, sunny days when a horse has to spend his time in the shade and not out grazing.

Of course what a horse fears or considers an enemy really depends on the individual horse and what he has or has not been habituated to. Any object that is out of place is considered a threat, or something new that a trainer does to a horse is regarded by the horse with high suspicion.

Other answers:A horse has many natural enemies. A horse is a prey animal, which puts it on a lower rung of the food chain. Most any predator could kill a horse that was singled out. Though horses are very strong and fast animals a pack of wolves or even wild dogs could easily kill a lone horse. Horses traveling in herds are much less likely to be picked off by predatory animals.

Flies. But otherwise it depends on the horse some horses may not like dogs or cats or even other horses. They can also be afraid of flags or a certain object.

The domestic horse has very few natural enemies but one of the most dangerous things our horses face is barbed wire Fencing or inadequate fencing. Barbed wire fencing should never be used with horses. And broken or rundown fences that allow horses to get out into traffic claims horse and human lives every day.
The enemies of feral horses in the United States are cougars or mountain lions, lack of food and water, and humans. There are very few areas left in the world where horses run wild.