Sweet Itch in Horses

Posted by Wormers-Direct on 19th Dec 2019

Sweet Itch in Horses

Flies and midges can be both a nuisance and a health issue for horses and certainly an annoyance to the rider. Midges cause sweet itch, and mosquitoes and other flying insects can carry diseases and flies can irritate the eyes and skin whilst at the same time causing stress for horses.

Sweet itch is a ‘disease’ caused by midges as their saliva is their weapon of choice to soften the horse’s skin, which enables them to chew their way through the outer layers of skin thereby causing inflammation, discomfort and pain. The horse then has an allergic reaction or suffers hypersensitivity. The midge saliva contains enzymes and proteins to soften the skin as well as agents that encourage blood flow and prevent clotting.

It is the female midge that lands on the horse and her aim is get her feed of blood for her eggs to develop fully. This tiny pool of blood is just under the surface of the skin and is sucked up by the female midges. The reaction of the horse is to release a defence mechanism from the white blood cells which is mainly histamine, which in turn leads to more itching and discomfort. Lesions occur around the head, ears, mane and tail; the horse may then start rubbing and even biting the affected areas which can cause bacterial infections.

Our UK midges are called Culicoides and are tiny, most no more than 1.5mm across the wingspan. The females can spend over 15 minutes on their egg laying and bloodsucking process but on a summers evening, a single horse can be bitten up to a thousand times and each time Culicoides are injecting foreign proteins from their saliva.

Midges inhabit marshy areas and areas with standing water but even rivers and streams will pose extra risk to horses. They are also partial to rotten horse manure and dirty stable bedding so like so many other issues regarding horse health, cleanliness and bio-security are the first lines of defence. In addition, feeding herbs such as Super Skin may have beneficial effects. Dusk and dawn are the period’s midges favour for their annoying endeavours so those would be the best times to physically protect your horse. Midges are poor fliers so the use of fans is also an option.