Your horse only has neck threadworms, in which case they’re probably rubbing along the mane and particularly the base of mane, around the neck and face, under the chest and down the ventral line (under the belly), but not on the tail head – or at least, relatively little.Īre you by any chance now thinking other horses you know? If so, they might be suffering from Onchocerciasis.Your horse has neck threadworms and its inflammatory reaction to them has increased its sensitivity, so it’s now reacting to fly bites everywhere – in other words, Queensland/sweet itch has been triggered as a secondary response.(The point of this article certainly isn’t to try and say that all itch cases are due to neck threadworms. Your horse has the ‘regular’ itch (ie, Queensland, sweet, whatever it’s called in your region) and are reacting to midge spit – and nothing else.If your horse is itchy, something different could be happening to what you think is happening. It’s an unfortunate coincidence of environment that leads to many cases of neck threadworms being missed, because they’re assumed to be Itch.ĭoes your horse have “the itch” – or neck threadworms? The biting insect that serves as a carrier is the Culicoides fly, which is also connected to Queensland Itch (aka Sweet Itch, Summer Itch, etc.). Unfortunately for those of us who keep horses in warmer, humid climates, it’s more frequent here. The problem is global and horses in most countries have been found to have this parasite. It is the adult worm that later makes its home in the nuchal ligament. The microscopic larval form live in the horse’s skin, mostly around the head, neck, shoulders, chest and underside of the belly. One reason these worms get relatively little attention is that they never live in the intestines.

Onchocerca is what’s known as a parasitic filarial worm (nematode). All text and photographs (c) Jane Clothier. Original article by Jane Clothier, posted on, June 2013.

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