What are Seasonal Recurrent Dermatitis?
This condition has a high incident rate in Australia, only because sand flies are more prevalent and there are fewer preventative measures available to keep these biting insects at bay. Once the sand fly bites, a hypersensitive response can occur leading to severe itching.
This severe itching will cause your horse to rub or bite the area that is itching. Rubbing or biting can lead to hair loss or more importantly, damage to the skin, causing open sores that are susceptible to infection.
Seasonal recurrent dermatitis is known by several names including Queensland Itch, summer eczema, summer itch and sweet itch. It is the result of a reaction to the saliva of Culicoides midges, also referred to as sand flies and no see’ms.
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Symptoms of Seasonal Recurrent Dermatitis in Horses
Anytime your horse is uncomfortable, they can act unpredictably. If you notice that your horse is acting odd, do a cursory physical examination, observe their behavior. Check for these symptoms and contact your veterinarian for an appointment.
- Blisters at the site where the biting insects bite
- Open sores that are scabbing, scaling or crusting
- Intense itching
- Lesions around the head and ears
- Loss of hair, generally in patches, from rubbing or biting
- Thickening skin
- Loss of pigmentation in the hair
- Secondary infections
Causes of Seasonal Recurrent Dermatitis in Horses
Seasonal recurrent dermatitis is caused by an allergic reaction to the protein molecules within the saliva of certain insects. The most common insect that causes seasonal recurrent dermatitis is the Culicoides midge.
The allergic reaction is the result of an antibody that is produced by your horse’s immune system. It grabs onto the allergens, in this case the protein molecules, causing the overproduction of histamines and cytokines. These will cause inflammation in your horse’s skin, making your horse feel an extreme itch.
Diagnosis of Seasonal Recurrent Dermatitis in Horses
Your veterinarian will complete a full physical examination. They will ask about your horse’s medical history as well as what symptoms you have witnessed. A skin scraping may be taken of the lesions to rule out possible mites as a cause.
Blood tests and other allergy tests may also be given to try and determine the exact cause of the reaction. Diagnosing seasonal recurrent dermatitis can be difficult since it can present similar symptoms to other allergens and skin parasites. The presence of Culicoides midges will give your veterinarian a large clue as to what is causing the allergic reaction.
Treatments for various allergic reactions are treated very similar and preventing the insects from biting is important to stopping your horse from being affected. Move your horse at least ½ mile away from the breeding areas of the Culicoides midges and keep your horse sprayed with an insect repellent. Culicoides midges are usually found near water sources such as ponds, bogs and other slow moving water sources.
Treatment of Seasonal Recurrent Dermatitis in Horses
Your veterinarian will develop a treatment plan that will work best for your horse. Be sure to discuss any concerns you may have with the medications provided or the care that you need to be giving your horse during treatment.
Antihistamines have been used with some success to control the symptoms of the allergic reaction. There can be side effects of antihistamines that can cause your horse to become drowsy or not eat, if this occurs contact your veterinarian.
Antibiotics are also prescribed in most cases. These will help prevent a secondary infection from forming from the open sores. If there is already a secondary infection present, then more aggressive antibiotics will probably be described.
Medicated creams or topical ointments have been used to offer immediate relief of the itching. These are especially useful when sores develop.
There are research companies that are working to develop immunotherapy drugs that will successfully combat seasonal recurrent dermatitis. Vaccines that reduce or modify the histamine response within the horse are also in the development phases.
Recovery of Seasonal Recurrent Dermatitis in Horses
Once your horse has been afflicted with seasonal recurrent dermatitis, they will always be susceptible to flare ups. When you notice your horse beginning to itch, contact your veterinarian for an appointment and to begin treatments to slow the allergic reaction.
Keeping your horse’s stable and pasture treated for insects is a good way to help prevent your horse from ever developing seasonal recurrent dermatitis. Fly masks, blankets and insect repellant sprays will help keep insects from biting.
You can take steps to modify your stables to prevent biting insects from entering the stables such as placing fine screening on the doors and windows. Stabling your horse during peak insect times, usually dawn and dusk, can also help.