Warmer, drier weather is approaching quickly. As we come out of our winter hibernation and eagerly make plans with our horses, so too are flies, ticks, and mosquitoes making plans to be a nuisance. The unseasonably warm weather this past winter means insect populations will be returning in full force even earlier. Although small, flies, mosquitos, and ticks, each present unique threats to your horse’s health.
Perhaps, the most ubiquitous pest of horses, the flies can be categorized into ‘nonbiting’ and ‘biting’. The face fly is the most commonly seen nonbiting fly around horses. As its name implies, the face fly tends to hang out on a horse’s head. Nonbiting flies transmit infectious agents and intestinal parasites. Good care and management of open wounds and proper application of fly repellents are the best defense against face flies and other nonbiting flies, like house flies.
Several species of biting flies harass our unfortunate steeds, including, in this area, Tabanids, Stable flies, and Horn flies. Tabanids include horse flies and deer flies. In addition to imparting a hefty bite, Tabanids are able to transmit Equine Infectious Anemia due to their large size. Although smaller than Tabanids, Stable flies still produce a painful bite, leaving a grouping of 3-4 bites that are capable of transmitting dermatophilosis (rain rot) and dermatophytosis (ringworm). Like Face flies, they also are drawn to wounds where they can deposit larvae of the stomach worm. Horn flies are more typically seen on cattle, however, if horses are nearby they will land on them as well. They too can spread infectious diseases with their bites. Although more commonly, Horn flies cause ventral midline dermatitis (hair loss and crusting of the belly) in horses. Control of biting flies is best accomplished by eliminating their breeding sites, by removing decaying vegetation and fecal matter and creating a vegetation barrier of ~ 6 feet. Fly repellents are helpful against Horn flies, however, they are more effective if the local cows are treated as well.
Similar to flies are the biting midges, properly known as Culicoides. Also called “no-see-ums,” these insects are best known for causing fly bite hypersensitivity, an allergic reaction to fly saliva that causes itching, hair loss, and thickening of the skin from repeated self-trauma. Rubbing of the mane and tail are the most common symptoms, however, the head, ears, rump, and belly can be affected as well. As with all allergies, minimizing exposure is key to treatment. This involves keeping horses in from dusk to dawn when the midges are feeding and eliminating wet areas that can serve as breeding grounds. Traditional treatment of the itching is addressed in multiple ways, including topical therapies and oral medications.
Next up, are the mosquitos, notorious for spreading a range of neurologic diseases.
Given their predilection for human blood as well as equine, most of us are aware that they favor morning and evening feedings and that standing water is often their home base and breeding ground. In horses, mosquitos are the major vectors of West Nile Virus, Eastern Equine Encephalitis (EEE), Western Equine Encephalitis, and Venezuelan Equine Encephalitis. At this time, there is no evidence that the newly emerged Zika virus affects horses. Eliminating areas of standing water and applying fly repellents a minimum of twice daily will help reduce the incidence of bites. Nonetheless, given their prevalence and the severity of disease they can cause, vaccination against these viruses is especially important in protecting your horse.
Last, but not least, are the ticks. In horses, we worry primarily about the spread of Lymes Disease and Anaplasma. For some horses, the Brown Dog Tick bites cause an intense hypersensitivity reaction with itching and hives. Ear infections can result from infestations of other tick species in the ear canal. With severe infestations, particularly in ponies and foals, significant blood loss can occur resulting in anemia or Tick Paralysis can occur with exposure to a neurotoxin in certain tick’s saliva. Just as with ourselves, prevention of tick-borne diseases starts with avoiding areas where ticks are likely to be and following that up with topical tick repellents. Tick repellents are available for horses and come in wipes, sprays, and spot-ons.
While small, these pesky parasites can pack a big punch in your horse’s health. As the winter weather fades into the past, don’t forget to protect your horses from these potent disease vectors. Make sure to manage trails and pastures to limit overgrown vegetation, keep vaccinations up-to-date, and be sure to have plenty of insect repellent on hand!