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Culicoides Hypersensitivity (view source)
Revision as of 19:36, 1 September 2010
, 19:36, 1 September 2010no edit summary
Culicoides hypersensitivity, commonly referred to as 'sweet itch' is an intensely pruritic dermatitis of horses caused by a hypersensitivity reaction to the saliva of biting insects. The most important causative agent is the ''Culicoides'' midge but other insects including ''Simulium''spp, ''Stomoxys'' spp and ''Haematobia'' may also have a role. In temperate climates, the condition occurs between spring and autumn (when midges are active) with a period of remission during the winter months.
Culicoides hypersensitivity, commonly referred to as 'sweet itch' is an intensely pruritic dermatitis of horses caused by a hypersensitivity reaction to the saliva of biting insects. The most important causative agent is the ''Culicoides'' midge but other insects including ''Simulium''spp, ''Stomoxys'' spp and ''Haematobia'' may also have a role. In temperate climates, the condition occurs between spring and autumn (when midges are active) with a period of remission during the winter months.
==Signalment==
==Signalment & risk factors==
Although sweet itch may occur in horses of all breeds and ages, the disease has a peak age of onset of between 2 and 4 years. Most breeds are affected although sweet itch is rare in Thoroughbreds. It has suggested that genetic factors may have a role in the pathogenesis of the disease as the prevalence of sweet itch in some breeds is higher, such as Icelandic ponies and German Shire horses. ''Culicoides'' require marshy areas or still water and horses kept in fields near streams or water may be at higher risk of developing sweet itch.
Although sweet itch may occur in horses of all breeds and ages, the disease has a peak age of onset of between 2 and 4 years. Most breeds are affected although sweet itch is rare in Thoroughbreds. It has suggested that genetic factors may have a role in the pathogenesis of the disease as the prevalence of sweet itch in some breeds is higher, such as Icelandic ponies and German Shire horses.
''Culicoides'' require marshy areas or still water and horses kept in fields near streams or water may be at higher risk of developing sweet itch. Additionally, in order to breed successfully the midges require decaying manure and bedding, therefore poor hygiene increases the risk of sweet itch.
==Pathogenesis==
==Pathogenesis==
==Treatment==
==Treatment==
The aims of treatment are to control pruritus, treat any secondary bacterial infections and reduce the number of midges coming into contact with the affected horse. In many cases, appropriate environmental changes are sufficient to ease clinical signs. Anti-midge rugs are available and prevent the insects from landing and feeding and are most effective when used in conjunction with an insect repellant containing citrus extract or DEET. Access to marshy pasture or fields near open water should be prevented and horses should be stabled at night when midges are most active. Fans and anti-fly mesh may be provided in the stable to provide additional protection from midges.
In severe cases, further treatment using corticosteroids to reduce inflammation and pruritus may be required. These should be used with caution in order to avoid possible side-effects including laminitis and iatrogenic hyperadrenocorticism. Antihistamines may be beneficial as a more long-term method of control but are only useful if administered before the onset of pruritus. Omega 3 and 6 fatty acids may aid in reducing pruritus and
==References==
==References==