Summer Sores On Horses – Prevention & Treatment Guide IN 2022

Summer Sores On Horses

Summer sores on horses sheath are a result of the placement of Habronema worm larvae in fresh wounds and moist areas of the sheath and horse eyes by infected stable and horse flies.

It is more frequent occurring from spring to autumn when flies “worry” wounds, the sheath, and the face.

The matured Habronema worms reside in nodules in the equine stomach wall.

Eggs travel through manure and are ingested by developing fly pupae.

Spread or re-infection is primarily by ingestion of dead or live flies in feed, or when horses lick wounds in which the larvae reside.

Symptoms Of Summer Sores On Horses

Generally, open wounds that have begun healing well with normal pink granulation tissue become infested with Habronema larvae introduced by stable or house flies.

The larvae move into the wounds to create hard nodules of raised red-brown tissue.

Similarly, you might notice these too on the conjunctiva of the eyes, the urethral opening of the pen!s, and the lining of the sheath.

summer sores on horses sheath

The lesions become big and spread progressively, and to relieve the irritation the horse will rub or bite the wounds.

Large nodules may bleed, ulcerate, and weep clear or yellowish tissue fluid.

The exudate attracts more flies, and if they are carrying Habronema larvae, the size of the lesions increases, and the degree of irritation worsens.

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Control and Treatment of Summer Sores

Larvae in present in the summer sore lesions, as well as adult worms in the stomach, can be controlled with a worming liquid or paste such as

  • Equest,
  • MecWorma,
  • Equimax or Amo,

Administered at regular worming intervals of 6-8 weeks during the high-risk period. See your vet for advice on a worming program.

The continuous control of flies is important to prevent wound infestation with larvae:

Keep wounds dry and clean to encourage healing and make them less attractive to flies.

Cetrigen Spray or Septicide Antiseptic Cream will repel flies from wounds that are starting to heal –

Also, apply each morning to the skin surrounding fresh open wounds to reduce fly swarming around and the chances of getting summer sores.

Yard and stable hygiene are important to controlling fly breeding. Environmental insect repellants are available that can be sprayed in bedding or stables.


To prevent Summer sores on horse’s sheath, apply fly repellent cream or spray to the front border of the sheath on a daily basis, particularly when flies are in plague proportions.

As soon as infection appears, veterinary treatment to remove large nodules, particularly around the sheath or eyes area, may become a necessity.

Seek your vet if any nodules are a thing of concern.