Horses are bothered by a variety of flies and midges. Each has it’s unique biology that contributes to its impact on horses. Here I will discuss some of the more common ones. I differentiate irritation from insect allergy, which I discuss elsewhere.
In most stabling situations, horses are frequently bothered by Stable Flies. While usually just an annoyance, stable flies cause some horses to develop hives (usually on the neck and chest).
Biting Midges (Culicoides and similar) tend to attack the ears, face and top-line, often at night. A percentage of horses bitten by these midges will develop allergic hypersensitivity which manifests as hair loss and skin irritation over the top-line and ears.
Horn Flies are small biting flies that feed on the back and underbelly of horses. They often draw blood in the areas in which they feed. They are usually found near cattle, their usual host. These flies can cause eye irritation and conjunctivitis.
Certain fly species carry disease. Following are a few examples of many: Stable flies can carry bacterial and viral disease agents, including those that cause Pigeon Breast and Vesicular Stomatitis. Horse flies are thought to transmit EIA and VS. Black Flies and Biting Midges may transmit certain viral disease, including the virus that causes Aural Plaques.
Other Diagnoses Considered
Prognosis & Relevant Factors
The prognosis depends on the situation. Most flies just irritate horses.
Horses that develop hypersensitivity may require special treatment and management. Disease transmission is rare and is most common when infestation is severe.
I Might ObserveRelated Observations
QUESTIONS TO ASK MY VET