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EQUINE HEALTH
To protect horses, use face masks, ear masks and topical repellents - sprays or, around wounds, ointments.
Composting done correctly generates enough heat to kill fly larvae as well as parasite eggs and larvae.
62 SPEEDHORSE July 2021
STABLE FLIES
These flies are often to blame for causing summer sores because they breed in rotting organic material that may contain manure and worm eggs - and are also attacking the horse to feed on blood, which provides opportunity to spread the tiny worm larvae.
The stable fly is similar in size and appear- ance to the housefly but has a long, slender proboscis that sticks up in front of its head. The stable fly rests on vertical surfaces such as fences, walls, trees, or structures near horses, and lands on horses only long enough to get a blood meal. Usually feeding on the lower legs, flank, and belly in early morning or late evening, stable flies cause great annoyance. Their bites are pain- ful, making the horse stomp and kick to get rid of them, licking at the bite wounds.
The stable fly lays eggs in rotting hay and straw and horse manure. Several genera- tions develop during summer and act as an intermediate host for Habronema micros- toma, one of the stomach worms that causes habronemiasis, aka summer sores.
To reduce stable fly populations, remove rotting organic matter that the flies use as breeding sites. Clean out manure and soiled bedding daily from stalls, along with piles of grass clippings or wet hay around the barnyard. Keep flies from multiplying in compost piles by covering the piles with black plastic. Use repellents to keep the flies away from horses. Spraying barns, stables, and foliage where the flies rest also reduces their numbers.
If a horse gets a summer sore, also treat his stablemates with ivermectin or moxidectin as a preventive measure. They’ve had contact with the same flies as the affected horse and may be harboring adult stomach worms.
Scientists are not sure why incidence of summer sores is increasing again, but it may be partly due to weather patterns. In recent years, warm weather has arrived earlier in the spring and may last longer in the fall. Warmer weather means a longer fly season, giving flies more opportunities to breed and produce offspring. Also, the past decades have brought changes in how horses are kept. More horses are concentrated in barns and stables, rather than out on pasture.
In these more crowded situations, inad- equate manure handling and lax fly control can give fly populations more chance to increase. If you have more flies, you could potentially have more summer sores. The good news is that a summer sore will heal with the right treatment, but also that these sores can be prevented in the first place with adequate fly control to reduce the popula- tion of house flies, face flies and stable flies that spread the worms.
FLY CONTROL IS IMPORTANT
Any open sore will attract flies, and flies will irritate the raw area and perhaps deposit more worm larvae. Fly-repellent sprays and ointments on the horse may discourage them, but farm-wide fly control is generally the best way to deal with these pests. The best practice is to remove or reduce the places where flies breed such as manure, wet feed, wet organic material, etc.
To reduce numbers of house flies, face flies and stable flies, pick up manure in horses’ stalls once or twice a day and clean all paddocks at least twice a week to get rid of manure, spilled feed, trampled hay and other materials that attract and provide feeding and breeding sites for flies. How you manage collected manure will depend on your farm setup. Composting done correctly gener-
ates enough heat to kill fly larvae as well as parasite eggs and larvae.
To protect horses, use face masks, ear masks and topical repellents - sprays or, around wounds, ointments. Stabling horses during the times of day when flies are most active, especially if the stable has fans or fly- proof screens can help protect them.
The stable fly lays eggs in rotting hay and straw and horse manure, and acts as an intermediate host for Habronema microstoma, one of the stomach worms that causes habronemiasis, aka summer sores.