Bot flies lay hundreds of eggs on horses, which are most commonly found on the legs and are then ingested as the horse grooms or bites itself. Once ingested, the eggs will hatch in a few days. The larvae then migrate to the stomach and attach to its lining, where they will stay for up to a year to continue growing. Once fully mature, the larvae detach and are expelled in feces, where they develop into flies.

The adult bot fly does not have a mouth and cannot feed. Its main purpose is to reproduce before dying. Bot flies can be difficult to detect and even more challenging to deter and extinguish.

Face flies tend to be found on the face and around the eyes of a horse. This species of fly does not venture from paddocks and fields and can cause conjunctivitis and increased eye secretions. Fly masks and sprays can be used as a preventative.

House flies are considered nuisances and are usually present in unsanitary conditions. House flies may appear anywhere on the horse and can be found in barns, stalls, and tack rooms. The adult flies will consume and lay eggs in moist organic material. Proper sanitation and the use of traps and baits can help to eliminate these flies.

Stable flies are found on the lower legs of the horse because that is where they feed. Their bite is painful to horses. This species of fly is around a horse only to draw blood and will fly off and rest somewhere else to finish its meal. Eggs may be laid in decomposing hay and straw. Stable flies may transmit Equine Infectious Anemia. Proper sanitation may help to eliminate the population.

Horn flies are more prevalent in cattle but can become a problem to horses if cattle farms are nearby. These flies do not leave the host except to lay eggs in cow manure. Eggs cannot survive if laid in horse manure. Pesticides and repellants can be used as treatment.

Blow flies (Calliphoridae) are metallic in color with hues of blue, green, bronze or blue-black. This metallic appearance separates them from other species of flies. Blow flies are seen on dead tissue, garbage and organic materials. As such, they don’t often cause issues for horses, but may be attracted to open wounds, placenta, or an overflowing dumpster by a barn. In places where blow flies are present, they may linger year-round.

This species of fly is commonly referred to as green heads, yellow flies, deer flies, and horse flies. These flies will continuously feed on horses until full and with each feeding, an anticoagulant will be introduced which cause blood to drip from a feeding site once the fly leaves. These flies can transmit Equine Infectious Anemia and ringworm. Preventative measures aren’t often effective against this species.

Mange mites do not cause infectious disease but can be irritating to the horse. Mange mites can be found on the legs, ears, mane, and tail, as well as other areas of a horse. Mites will cause the horse to constantly rub and scratch the area so that the skin becomes dried and scabbed over. This can cause hair loss in infested areas. Infection is common, though full-blown systemic disease is rare. Topical medications can be used as treatment.

Mosquitoes can carry WEE/EEE/VEE, West Nile Virus, or malaria, which can be passed on to the horse if an infected horse is bitten first. Once bitten, there will be two puncture marks, one for the mosquito to allow the inhibition of blood coagulation, and the second to allow the mosquito to feed. Insecticides and repellants may be used to discourage mosquitos, and eliminating standing water is crucial.

Most ticks are active from the spring to the fall, however there are some species that can be active year round. Once a tick egg is laid, the tick hatches and must consume blood to continue to the next life cycle stage. Some ticks complete all stages of the life cycle on the same host, and others ticks require three hosts, with a different one needed at each stage of the life cycle. If ticks are found on the horse, it is important to remove the tick in its entirety. If the head remains lodged in the horse, it can cause disease and/or infection. The most common diseases associated with ticks are Lyme disease, equine piroplasmosis, equine granulocytic anaplasmosis, and tick paralysis. Topicals can be given, as well as oral deworming medication such as ivermectin to be effective as forms of treatment.

Lice will lay eggs in horses’ hair which will hatch 5 to 20 days after being laid. The lice will then breed in the coat, greatly increasing the population. Horse-to-horse contact and infected equipment can transmit lice from one horse to another. Infestations are more common in sick and immunosuppressed horses, but can be seen in large populations if transmission is high. Some lice may feed on the horse to the point of risking anemia so they should be eliminated whenever found.

Once lice have been detected on a horse, the horse’s coat should be washed immediately and thoroughly with an insecticide shampoo to remove dead skin and deter the bugs. The person treating lice on the horse should wear gloves to prevent spread. All infected equipment should be washed with insecticide, and blankets should be washed with hot water.