Los Angeles County West Vector & Vector-Borne Disease Control District
What is Sweet
Sweet Itch, or
Summer Seasonal Recurrent Dermatitis (SSRD), is a problem that affects
thousands of horses, ponies and donkeys worldwide. Within recent years, this
condition appears to have migrated into the Palos Verdes Peninsula as well
as other regions of Southern California. Virtually all breeds and types of
ponies and horses can be affected by Sweet Itch, from Shetland ponies to
heavyweight draught horses.
Sweet Itch is an allergic
condition that results when an animal develops a hypersensitive reaction to
a protein in the saliva of a biting midge. Sweet Itch can become quite
severe and unsightly, thereby reducing the suitability of the animal for
riding or show.
What are the signs of
dermatitis (weeping sores)
infection at site of sores
midline of the belly, top of the tail and mane are the areas that are most
commonly affected. The itching can become so severe that there can be a
marked change in temperament ranging from restlessness to lethargy and
increased agitation. Horses usually show signs of Sweet Itch between the
ages of one and five. It is probable that hereditary predisposition is a
factor in the development of Sweet Itch.
Biting midges, also known as ‘punkies’ or ‘no-see-ums’ are small, biting
flies with an average wing length of less than 2 mm.
the United States several species (of the 1,000 or so that exist) of the
biting midge (genus Culicoides) are responsible for Sweet Itch.
While both male and female adult biting midges feed on nectar, the females
require blood for egg production. The females possess piercing, sucking
mouthparts that are capable of obtaining blood meals from a variety of
hosts. Biting midges are most active at dawn and dusk but may feed at any
time during humid, cloudy days.
Where are biting
usually do not fly far from their breeding grounds. Biting midges dislike
hot, dry conditions, strong wind, heavy rain or bright sunshine. Breeding
sites include moist, decaying vegetation or wet soil (e.g. mud polluted by
animal excrement). Culicoides larvae are capable of surviving severe
frosts but do not survive prolonged drought conditions.
Diagnosis of Sweet
The symptoms and its seasonal nature are strong indicators of Sweet
Itch. However, symptoms can persist well into the winter months, with
severe cases barely having cleared up before the condition starts again in
late winter and early spring. If you suspect that your horse may have Sweet
Itch, please consult a veterinarian.
Is There a Cure
for Sweet Itch?
Unfortunately, there is no cure for Sweet Itch. Once an animal develops the
allergy, it generally faces a ‘life sentence’. The animal’s comfort and well
being are down to its owner’s management.
boggy fields. If possible, move horse to a more exposed, windy site
(e.g. bare hillside or a coastal site with strong onshore breezes).
is well drained and free from rotting vegetation (e.g. muck heaps, old
hay feeding areas, rotting leaves)
Stable at dusk
and dawn when midge feeding is at its peak. Close stable doors and
windows to prevent midges from entering.
large ceiling-mounted fan in the stable to create less favorable
conditions for the midge
Use an Insect
owners should use repellents approved for use on horses, but the
effectiveness of some formulations under certain conditions (e.g., rain,
perspiration) may be limited. Insect repellents can be effective for
humans and have some limited value for horses as well.
Products containing these active ingredients
typically provide longer-lasting protection than others:
Use an Insecticide
Use a Veterinary
veterinarian-prescribed corticosteroids to help reduce inflammation
caused by the immune response.
veterinarian-prescribed antihistamines may help to reduce allergic
lotions such as Calamine Cream, ‘Sudocrem’ or steroid creams may aid in
For Further Information:
information on Sweet Itch and suggestions from other horse owners, contact
your local veterinarian.