Summer Sores in Horses: Causes, Symptoms, Treatment & Prevention
When horse owners in Florida think about summer health concerns, flies, humidity, and skin irritation are often at the top of the list. One condition that can quickly become frustrating for both horses and riders is summer sores, also known as cutaneous habronemiasis or habronematidosis. These stubborn, itchy, non-healing lesions can interfere with comfort, performance, and overall health if left untreated.
At Steffee Showjumping, we know that proper horse care is just as important as elite training. As a premier hunter and jumper boarding, training, and sales facility in Wellington, FL, we help horse owners stay proactive with seasonal health issues like summer sores so their horses can remain comfortable and competition-ready.
Table of Contents
1. What Are Summer Sores?
2. What Causes Summer Sores?
3. Common Symptoms of Summer Sores
4. Why Summer Sores Return Every Year
5. Diagnosis and Treatment Options
6. How to Prevent Summer Sores in Florida
7. Why Fly Control Matters in Wellington, FL
8. Final Thoughts
9. FAQs
What Are Summer Sores?
Summer sores are parasitic skin lesions caused by the larvae of Habronema stomach worms. These parasites are linked to the normal life cycle of stomach worms in horses, but instead of being swallowed and developing in the stomach, the larvae are deposited by flies onto wounds or moist areas of the body.
This causes an intense inflammatory reaction in the skin, resulting in lesions that are often:
* Moist and ulcerated
* Red to reddish-brown
* Raised and proud-flesh-like
* Intensely itchy
* Slow to heal
* Containing yellow “sulfur-like” granules
These sores most commonly appear during spring and summer when fly populations rise, which is why they are called summer sores.
What Causes Summer Sores?
Summer sores are associated with three species of Habronema worms that infect horses:
* Habronema muscae
* Habronema microstoma
* Habronema megastoma
Adult worms live in the horse’s stomach and usually cause minimal problems there. Female worms lay eggs, and larvae are passed through manure.
From there, the cycle continues:
1. Fly maggots consume the larvae in manure.
2. Larvae develop inside the fly.
3. Adult flies land on horses.
4. Instead of depositing larvae near the mouth to be swallowed, flies leave them in wounds or moist tissue.
5. Larvae cannot mature in the skin, so they trigger inflammation instead.
This leads to the characteristic non-healing lesions horse owners dread each summer.
Common Symptoms of Summer Sores
Summer sores can develop anywhere flies are attracted, especially areas with moisture or existing irritation.
Most Common Locations:
* Corners of the eyes
* Lips and muzzle
* Sheath or genital region
* Lower legs
* Existing cuts or abrasions
* Belly line
Signs to Watch For:
* Persistent wounds that won’t heal
* Excessive itching or rubbing
* Swelling around the lesion
* Red, raw tissue
* Proud flesh formation
* Yellow granules within the wound
* Increased sensitivity or pain
Because these sores can resemble proud flesh, fungal infections, or even tumors, veterinary diagnosis is important.
Why Summer Sores Return Every Year
One frustrating characteristic of summer sores is recurrence. Once a horse develops habronemiasis, the condition often returns in future warm seasons.
Why?
* The horse may remain hypersensitive to larvae exposure.
* Florida’s long fly season increases reinfestation risk.
* Even minor skin injuries can attract flies carrying larvae.
* Warm temperatures allow flies to remain active much longer than northern climates.
Many cases improve during winter months when fly numbers drop, but the issue can reappear in spring if preventive steps are not taken.
Diagnosis and Treatment Options
If you suspect summer sores, contact your veterinarian promptly. Early treatment can reduce discomfort and minimize scar tissue.
Veterinary Diagnosis May Include:
* Physical examination
* History of seasonal recurrence
* Lesion appearance
* Biopsy or skin scraping in uncertain cases
Common Treatments:
1. Deworming Medication
Anthelmintics such as:
* Ivermectin
* Moxidectin
These help eliminate Habronema larvae and reduce ongoing exposure.
2. Anti-Inflammatory Therapy
Veterinarians often prescribe corticosteroids to reduce:
* Swelling
* Itching
* Granulation tissue formation
3. Topical Wound Care
Proper cleaning and medicated dressings can support healing.
4. Fly Control
This is essential. Without controlling flies, reinfection is likely.
5. Surgical Debridement
Severe proud flesh or chronic lesions may need trimming or advanced wound management.
With treatment, many horses improve significantly, especially when started early.
How to Prevent Summer Sores in Florida
At Steffee Showjumping in Wellington, FL, prevention is always better than treatment. Florida’s climate allows flies to thrive, so horse owners need a consistent management strategy.
Best Prevention Tips:
Keep Manure Removed Daily
Flies breed in manure, so regular stall cleaning and paddock maintenance dramatically reduce populations.
Use Fly Masks and Fly Sheets
Protect sensitive areas such as eyes, muzzle, and body from fly contact.
Treat Minor Cuts Immediately
Even small wounds attract flies. Clean and cover injuries promptly.
Use Effective Fly Sprays
Rotate products if needed to maintain effectiveness.
Stable Management
Fans in barns can reduce fly activity since flies are weak fliers.
Strategic Deworming
Work with your veterinarian on a parasite control plan tailored to your horse.
Why Fly Control Matters in Wellington, FL
Wellington is one of the premier equestrian destinations in the world, but our warm climate also means longer fly seasons than many other regions.
For hunter, jumper, and show horses, summer sores can cause:
* Irritation affecting performance
* Difficulty wearing tack if sores are near girth areas
* Cosmetic concerns for sale horses
* Time off from training
* Risk of secondary infection
At Steffee Showjumping, we emphasize elite horse care alongside world-class training. Managing flies, wounds, and seasonal skin conditions helps horses stay healthy and competition-ready year-round.
Final Thoughts
Summer sores may start as a minor irritation, but they can quickly become painful, persistent, and difficult to manage without intervention. Because they are caused by parasite larvae spread through flies, prevention focuses heavily on sanitation, wound care, and fly control.
If your horse develops a wound that seems unusually itchy, moist, or refuses to heal during warmer months, don’t ignore it. Early veterinary treatment can shorten recovery time and help prevent severe lesions.
At Steffee Showjumping, we believe top performance begins with top care. Whether your horse is competing, training, or enjoying life in Wellington, proper summer management is key to long-term wellness.
FAQs
1. Are summer sores contagious between horses?
No. Summer sores are not directly contagious. They result from fly transmission of Habronema larvae rather than horse-to-horse contact.
2. Do summer sores heal on their own?
Some lesions improve during winter when flies disappear, but many require veterinary treatment and often recur the following summer.
3. Can summer sores happen indoors?
Yes. If flies are present in barns or stalls, horses can still develop summer sores.
4. What is the best treatment for summer sores?
Treatment typically includes ivermectin or moxidectin, anti-inflammatory medications, wound care, and aggressive fly control.
5. How can I prevent summer sores in Wellington, FL?
Daily manure removal, fly masks, prompt wound care, strategic deworming, and strong fly management are the most effective prevention methods.









