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Approaching the future management of sweet itch

02 March 2022
8 mins read
Volume 6 · Issue 2
Figure 1. a) The mane of a pony that has suffered from chronic insect bite hypersensitivity. Note the shortening of the hairs and the dull brittle nature of the hair ends. b) The tail of the same pony. The hairs are almost absent here, giving the pony a ‘rat-tail’ appearance.
Figure 1. a) The mane of a pony that has suffered from chronic insect bite hypersensitivity. Note the shortening of the hairs and the dull brittle nature of the hair ends. b) The tail of the same pony. The hairs are almost absent here, giving the pony a ‘rat-tail’ appearance.

Abstract

Insect bite hypersensitivity, commonly known as the ‘sweet itch’, continues to prove frustrating to manage in practice. Insect bite hypersensitivity is the most common allergic skin disease in horses, characterised as a hypersensitivity to the salivary proteins of the Culicodes genus of insects. The complex nature of this allergic disease means that no set of affected horses can be managed in the same way. Common approaches to sweet itch can be broken down into the categories of anti-inflammatories, allergen avoidance, skin conditioning and immunotherapy. Many effective management techniques focus on avoiding insect bites and regularly washing skin. Advances are currently being made towards effective immunotherapy, with varied results in clinical trials and in practice. As a result of this, a multimodal approach to the management of insect bite hypersensitivity is often recommended.

Insect bite hypersensitivity is the most common allergic skin disease in horses, causing a localised pruritus to the feeding sites of the biting midge (Scott and Miller, 2011; Schaffartzik et al, 2012) (Figures 1 and 2). The seasonal nature of this disease has been attributed to the biting insects of the genus Culicoides, which are traditionally associated with dry warm days between the spring and autumn in the UK (Meiswinkel et al, 2000; Van Grevenhof et al, 2007). Midges tend to congregate in breeding sites around densely wooded areas, or near stagnant water, leading to increased numbers of biting insects (Carpenter et al, 2008). However, the prevalence of insect bite hypersensitivity is also subject to considerable variations depending on the equine's breed and, even more so, on family lineage (Littlewood, 1998; Van Grevenhof et al, 2007).

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