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Understanding Cutaneous Habronemiasis ("Summer Sores") in Horses

Summer is a time for outdoor activities and enjoyment, but for horse owners, it also brings about the potential risk of cutaneous habronemiasis, commonly known as "summer sores." These troublesome skin lesions can cause discomfort for horses and concern for their caregivers. In this blog, we will delve into the world of cutaneous habronemiasis, exploring its causes, symptoms, prevention, and treatment options.

What is Cutaneous Habronemiasis?

Cutaneous habronemiasis, often referred to as "summer sores," is a parasitic skin condition caused by the larvae of stomach worms, specifically Habronema spp. These worms are commonly found in the stomach of horses, and their eggs are passed through the feces. Flies, particularly those from the genus Musca and Stomoxys, play a crucial role in transmitting the larvae to horses. When these flies feed on the horse's wounds, they inadvertently deposit the larvae, initiating the infection.

Symptoms and Clinical Presentation

Summer sores can present with a variety of symptoms, including:

  1. Swelling and Nodules: Raised, swollen, and nodular skin lesions are often observed, with varying degrees of inflammation and soreness.

  2. Ulceration and Granulation Tissue: As the lesions progress, they may become ulcerated, causing the development of granulation tissue. These open wounds can be painful and prone to secondary infections.

  3. Itching and Scratching: Horses affected by summer sores may display signs of discomfort, including itching, scratching, and rubbing against objects to relieve the itchiness.

  4. Excessive Discharge: In some cases, the lesions may produce a serous or purulent discharge, further exacerbating the irritation.

Prevention Strategies

Preventing cutaneous habronemiasis involves addressing the factors that contribute to its development:

  1. Fly Control: Implement rigorous fly control measures to reduce the exposure of horses to the flies responsible for transmitting the larvae. This includes using fly sprays, fly sheets, and keeping the stable environment clean.

  2. Wound Management: Promptly treating any wounds or skin abrasions can prevent flies from depositing larvae in the first place. Regularly clean and dress wounds to promote quick healing.

  3. Stable Hygiene: Maintaining a clean and hygienic stable environment can reduce fly populations and the risk of larvae transmission.

Treatment Options

If summer sores do develop, timely treatment is crucial to prevent further complications. The approach to treatment may include:

  1. Deworming: Administering dewormers, especially those effective against stomach worms, can help control the internal parasite load and limit the availability of larvae for transmission.

  2. Topical Medications: Applying topical creams or ointments with anti-inflammatory and antiparasitic properties can help reduce inflammation, control the larvae, and promote wound healing.

  3. Surgical Removal: In severe cases, surgical removal of granulation tissue and necrotic tissue may be necessary to facilitate healing.

  4. Systemic Medications: In cases of widespread infection, your veterinarian may prescribe systemic medications to target the internal parasites.


As horse owners, being informed about cutaneous habronemiasis ("summer sores") and its prevention and treatment is essential for maintaining the health and well-being of our equine companions. By implementing effective fly control strategies, practicing proper wound management, and seeking prompt veterinary care when necessary, we can minimize the risk of summer sores and ensure a comfortable and enjoyable summer season for our horses. Always remember that consulting with a veterinarian is vital for accurate diagnosis and treatment planning.

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