I understand the distress and frustration with watching a horse mercilessly self mutilate. The only way to beat Queensland Itch is to live in a place that doesn't contain sandflies or midges (Culicoides species).
Sadly, it isn't always possible to move away from the coast to a drier environment that doesn't support the midge's favourite habitat. Queensland itch or sweet itch is more correctly known as Recurrent Seasonal Pruritus.
A vet explained to me many years ago that horses will rub themselves where they can, not necessarily where they are actually bitten. So if a horse is rubbing his head raw, the bites can be all over his body, the horse won't be getting bitten just at the head. Studies show that the majority of bites are along the topline region.
Unfortunately midges live and breed in still water, mud and wet grass, even manure, making it impossible to eradicate their favoured habitat.
An allergy is an exaggerated and imbalanced immune system response to something in the environment that normally shouldn't cause any detectable response. Queensland Itch, also known as 'Sweet Itch' is an allergic response to proteins in the saliva the midge inserts when it feeds, resulting in the skin becoming inflamed all over the body. So inflamed that a change of wind direction, a mosquito, anything can set the poor horse off itching. If you have ever owned a dog with flea allergy dermatitis then you'll know that the pooch doesn't need fleas to continue scratching.
For more detail on the science behind the allergic reaction occurs check out Dr Carl Eden's BVM&S MRCVS description.
Treatments consist of either keeping midges away or soothing the inflammation, especially where the horse is actively rubbing.
Keeping midges away:
Physical barrier like a rug. I know, sad to see a horse on a hot day with a rug on but the most effective means for preventing the buggers from biting your horse. Try to use a light but tough rug.
A layer of Vicks (Menthol 2.82% w/w and camphor 5.26% w/w), fly/mosquito repellents don't work with midges but are deterred by products containing camphor, menthol or thymol. [Incidentally listerine contains these active ingredients. Don't know how often you have to reapply.]
The product Brute is a wipe-on insecticide for horses, contains Permethrin. Swift is a bit too concentrated for sensitive skinned horses like Arabs.
Sulfur and olive oil or Vaseline or similar is effective, acts as a barrier but gee, I'd hate to saddle a horse covered in the stuff. Vaseline and sulfur is a greasy heel remedy.
Stable with insect screening and a fan as midges are not strong fliers. This is an option for early morning and late afternoon when the midges are at their most active.
Creams that contain neem oil or eucalyptus oil or lavender or calendular or combinations. These would sooth the inflamed skin but of course on their own won't prevent an itch problem.
In the US a product called Bactine is recommended, it contains 0.13% Benzalkonium chloride and 2.5% Lidocaine hydrochloride. We can't get it here as far as I know but it contains a local anaesthetic to take the pain away. This reminded me of an old recommendation from yonks ago - Friskies medicated dog wash contains triclosan and salicycate acid, is blue in colour and in the supermarkets. The salicycate acid is the aspirin type ingredient which when applied topically reduces the inflammation and eases the irritation and the triclosan has antifungal properties. Again I haven't tried this but could work. If you plan to try it do check with your vet if it is suitable and please email me with feedback.
Combination of soothing and a repellent/barrier to midges:
Dr Eleanor Kellon VMD in her book 'Horse Journal Guide to Equine Supplements and Neutraceuticals' recommends mixing 1/4 teaspoon of Campho-Phenique and 1/4 teaspoon of Calm Coat into a 13 oz or gram jar of Vaseline. The Vaseline provides a barrier while the Campho-Phenique is a barrier, repellent, anasthetic/disinfectant. Calm coat contains soothing essential oils and repellent. Apply generously 2-3 times per day.
The major bummer is that here in Australia we can't get either product (at least we can get Vaseline or similar!). I'm searching for equivalent products in Australia.
Home made treatment. Here is an example I haven't tried but I picked up years ago, the Calamine supposedly soothes the skin. Mix 200 m paraffin oil, 400 ml of 'oily' Calamine Lotion (make sure it is oily, not the ordinary), 20 ml of Oil of Citronella and 20 ml of Phenol (disinfectant).
If anyone tries this and finds it successful please email me to let me know. Might be a sensible precaution to get this checked out by a vet to see if it is safe.
One reader recommended an Avon product called SSS Bath Oil. Her practice is to rub it on affected areas twice a week.
Some vets recommend drug treatment involving corticosteroids, this is my least favourite option. A vet explained to me that not all horses respond to drug treatment, some need multiple doses throughout the itch season and these drugs have nasty side effects and it can be expensive.
Internally the best approach is a more than adequate nutrient diet and minerals in the right proportions. This can make a difference by making sure our horses are provided with the correct level of nutrients which allows the immune system to produce counterbalancing responses.
A combination of chondroitin sulfate, spirulina and ground linseed has been very effective for a number of itch horses.
Chondroitin sulfate. On the Equine Cushings group some horse owners have reported success with feeding 2500 - 5000 mg chondroitin sulfate, twice a day. Dr Kellon advises it should be started before the itch season begins.
Spirulina - 20 grams twice a day. Spirulina has been successful in some cases on it's own or in combination with chondroitin sulfate. If spirulina does help, an improvement should be seen in a few days.
Ground linseed, also known as flax. A Canadian study found linseed can reduce the lesion size after intradermal injection of Culicoides midge extract, but large amounts of stabilised flax were fed (450 g/day for a 450 kg horse or 150 ml of linseed oil). To learn more about feeding linseed or linseed oil go to my page on 'Linseed, is it safe?'.
I've seen a lot of remedies recommended for Queensland Itch that do not work, mainly because there is nothing in it that deals with either soothing the inflammation or preventing the midges from biting. If you have a remedy that you are pretty sure does work I'd be interested in hearing about it.
Some people recommend the active worming ingredient ivermectin to be applied regularly along horse's topline but they are mistaken, ivermectin has nothing to do with Queensland Itch or midges, it deals with a worm called Onchocerca (neck threadworms) that can cause similar symptoms as Queensland Itch. These worms are so tiny, the midges are a carrier for them in their saliva. For me, that is incredible and even more reason to hate midges! The stage carried by the midge is late larval and travels to the nuchal ligament in the horse's neck. The stage that sets up house in the ventral midline and causes belly irritation is early larval and is coming from adults in the neck. Adults in the nuchal ligament of the neck can also cause irritation and make the horse rub. The adults live for about 5 years, producing microfilaria all that time but higher levels in the warm months. When they die, calcified nodules eventually form. Fortunately ivermectin and moxidectin easily kill the microflaria. Horses infected with Onchocerca generaly scratch along their manes and bellies but not the tails. The online Merck Veterinary Manual has an excellent summary on Onchocerca and treatment. Jane Clothier has an excellent explanation of Onchocerca on her page The Disturbing Truth About Neck Threadworms and Your Itchy Horse.
Dr Carl Eden's BVM&S MRCVS Queensland Itch
Equine Cushings group The Equine Cushings and Insulin Resistance group is the largest equine Yahoo list with over 8000 members. A place where experiences, veterinary knowledge and research, advice, and help can be shared to help deal more effectively with the diagnosis, symptoms, problems and emotions that occur. Dr Eleanor Kellon VMD contributes.
Jane Clothier The Disturbing Truth About Neck Threadworms and Your Itchy Horse
Herd RP and Donham JC (1983) Efficacy of ivermectin against Onchocerca cervicalis microfilarial dermatitis in horses.
Dr Eleanor Kellon VMD (2008) Horse Journal Guide to Equine Supplements and Neutraceuticals The Lyons Press, Guildford, Connecticut
Dr Eleanor Kellon VMD Nutrition and the Therapy course
Merck Veterinary Manual on Onchocerciasis
O'Neill W, McKee S and Clarke A.F (2002) Flaxseed (Linum usitatissimum) supplementation associated with reduced skin test lesional area in horses with Culicoides hypersensitivity