There are many types of mite that can affect horses; some more common than others. But all species of horse mite can cause a lot of irritation and distress, both to the horse and their owner. The reaction seen in the horse’s skin and hair is often referred to as ‘mange’. The sooner the mites are treated after diagnosis the better, as left for too long they can cause secondary infection from open sores, with very extreme cases potentially resulting in lameness.

What are mites?

Mites are microscopic arthropods that are closely related to ticks. Their tiny size makes them very tricky to spot with the naked eye, and therefore easy to miss. These parasitic mites make their homes in both the skin and hair of their hosts and feed on the protein-rich structures of the skill cells by piercing or burrowing into the skin.

Where do mites come from and how do horses get them?

Mites can live in numerous places, but in an equine environment are most commonly found in (and transmitted by) straw and hay, the wings of birds, and other infected horses. Mites can also be passed on from horse to horse via rugs, bedding, and even cleaning and grooming products, therefore it is important to ensure that any second-hand products purchased for your horse are washed and fully disinfected before use. This goes for their living environment too. If you are moving your horse to a new stable, make sure any old bedding is removed and the stable is properly disinfected.

What are the different types of mites that can affect horses?

There are many types of mite, but there are four main species that affect horses; Chorioptes bovis (formerly Chorioptes equi), Demodex equi (or Demodex caballi), Psoroptes ovis (formerly Psoroptes equi), and Sarcoptes scabiei var equi. They can affect different areas of the body, including (but not limited to) the ears, fetlocks, pasterns, and between the legs.

Chorioptes bovis (formerly Chorioptes equi);

These are the most common types of mite to be found on horses in the UK, and affect the legs, usually below the knee, and mainly the hind legs. These leg mites are also known as ‘feather mites’, as they tend to be more common in heavily feathered breeds. The reaction they cause in the skin is also sometimes referred to as ‘heel mange’ due to its location on the leg.

These mites are incredibly small, around 0.4mm to 0.6mm in size, and need to be identified under the microscope. They irritate the horse by biting the outer layers of skin to feed on the skin debris, fat, or sore that they create. The condition can initially look a bit like eczema, but if left untreated can result in crusty scabs or even large calluses and warts. Although they can cause incredible discomfort in horses, these mites are less dangerous than some of the other types of mite, with few cases resulting in severe harm, and while itching will be present, the reactions in infected horses are usually less pronounced than in other cases. However, they are very persistent and can be difficult to fully eradicate.

Demodex equi (or Demodex caballi);

These mites affect horses all over the world by getting into the hair follicles, which can then become infected with secondary bacteria. These tiny mites are even smaller than the other types of horse mite, at about 0.25mm long, and can survive for as long as 4 months off their host.

Demodex mites are more common in herds of horses and are very rarely seen in horses kept individually. Infected horses will often have a scaly texture to the affected skin, with lesions appearing most commonly around the head and eyes, progressing later on to the shoulders and sometimes the entire body.

Psoroptes ovis (formerly Psoroptes equi);

Psoroptes mites are 0.5 - 0.6mm long and, like other mites, need to be identified via skin scrapings examined under the microscope. Again, these mites can affect horses and mules worldwide, but are not often found in horses. They are commonly known as ‘scab mites’ due to the reaction they produce on the skin. It was originally thought that they created the reaction by piercing the skin, but it is now believed that it’s actually the faeces of the mites creating an allergic reaction. This causes the skin to exude, making it thicker and harder, resulting in crusts and sometimes hair loss.

These mites favour areas of the body with thicker hair growth, such as the neck, mane or base of the tail, but it is possible for them to affect the whole body. They can only be transmitted to other horses via close contact, however, they can survive off the host for 2 to 3 weeks in the surrounding environment and therefore be passively transmitted from horse to horse via tools and equipment in the stable.

Sarcoptes scabiei var equi;

These mites cause Sarcoptic mange in horses, donkeys and mules all over the world. Despite not being that common in horses, especially in the UK, when an infestation takes hold, they can be the most harmful of all mite infestations. As with the other species of horse mites, they are very small (0.3 to 0.5mm) and can only be diagnosed by examination under the microscope. 

Sarcoptic mites do not suck blood; they tunnel beneath the skin and feed on the liquids produced by the potent digestive enzymes in their saliva dissolving the skin tissue. The burrowing causes skin irritation, which is then exacerbated by an allergic reaction to the saliva that develops a few weeks later. The initial infestation displays itself as pimples on the affected skin that eventually become crusty, and creates huge amounts of hair loss, hardening and thickening of the skin, and the development of large folds. It often starts on the head and progresses down to the neck and shoulders.

Due to the discomfort caused by these mites, horses often cause themselves further injuries by vigorously biting, scratching and rubbing the affected area to try to relieve the severe irritation. These injuries can then become infected, creating an even bigger problem. All of this weakens the affected horse, resulting in weight loss and lowered immunity to other diseases.

As these horse-specific mites come from a wider strain of mites (Sarcoptes scabiei) that can also cause infestation in sheep, cattle, pigs, other livestock and even humans, these mites can be transmitted to any of these species, including humans. Unlike other species of mites, they cannot be transmitted via other external factors, such as birds, mice, rats, worms, insects etc. Adult Sarcoptic mites can live for 2 to 3 weeks on the host, and can be transmitted via close physical contact with other horses, as well as from factors in their immediate environment, including tools and equipment in the stable. However, they can only live for a few days off the host, so regular cleaning of the horse’s surroundings should be sufficient to stop them spreading in this way. 

What are the symptoms of mite infestation?

You may be lucky enough to spot some mites (or their eggs/larvae) yourself via visual inspection, however, their size makes this highly unlikely. You are much more likely to be alerted to the problem by your horse displaying some of the following classic symptoms of a localised skin irritation;

• Stamping of the feet
• Biting/chewing of the back legs
• Rubbing of the legs or body on walls, fences, or any other object
• Scabs, flakey scales, rashes or wounds on the skin
• Patchy hair loss
• Swollen or thickening of the legs (in severe cases)

It’s a good idea to check the condition of your horse’s skin and hair regularly for tell-tale signs of mites; this can be done most effectively during a thorough grooming session.

Diagnosis of horse mites

Mites are around all year, but the onset of horse mite infestation seems to be more of a problem during the colder months. It is thought that this is primarily due to the fact that the mites seek out the body heat of the horses, but there are also theories about the fluctuation in air temperature during the Autumn months, and the beginning of the moulting process, lowering resistance to mites in some horses. So these months are generally thought of as being a riskier time.

If your horse is displaying similar symptoms to those listed above, but during warmer weather, it’s possible your horse is suffering from a fly allergy called Sweet Itch, or a horse lice infestation.

More information on How To Diagnose, Prevent And Treat Sweet Itch >

More information on Diagnosing And Treating Horse Lice >

Whatever the time of year, if your horse is displaying any of the above symptoms and you suspect that they might have a mite infestation, you’ll need to get them checked out by a qualified veterinarian. They will be able to determine whether this is the case, including what type of mite infestation is present, by taking samples of the horse’s hair and skin for analysis under the microscope. No treatment for mites should be given without a visual clinical examination by your vet, at the very least. Ideally, your vet will give your horse a full and thorough physical examination to determine the condition of various elements, from measuring blood pressure and heart rate to studying their conformation and behavior, and may even conduct X-rays to rule out the possibility of any other underlying problems that could be causing the symptoms.

The best plan of action for tackling any mite infestation is to get a tailored treatment plan from a registered veterinarian, who can assess the situation on a horse by horse basis and recommend the treatments they deem most suitable for the circumstances.

Treating horse mites

When a horse has a mite infestation, it’s not just the adult mites that will be present at any one time, there will also be eggs and developing larvae. Eggs cannot be killed effectively with any form of treatment, so whatever method you choose will need to be repeated at least once (although it is recommended to do this several times) approximately 2 weeks apart, to allow the eggs to develop into adult mites before retreatment. 

Currently, there are no licensed veterinary products in the UK to treat horse mites, and these parasites are incredibly resilient, making them very difficult to get rid of. The nature of the infestation and the way the mites are passed between horses make it very tricky to get a handle on, especially in situations where horses are stabled or turned out together, as they will be transmitted from horse to horse via close contact or the surrounding environment. In some cases, it will be almost impossible to get rid of altogether and will be more about managing the ‘flare-ups’ than about full eradication.

While there are plenty of products out there designed to help treat mite infestations, many of them are based on chemical components, which ectoparasites like mites can become resistant to over time. This means that these types of treatments are only likely to work a few times before they build up a tolerance.

The other issue with using chemical agents is that they are often only external treatments, meaning they are highly unlikely to reach all the mites present on the horse. Natural and unavoidable factors, like rain and sweating, can also reduce the effectiveness of the treatment. The wide range of products available reflects the fact that no one treatment has proven effective for treating all cases of horse mites.

Internal treatments;

Dectomax (Doramectin);

In the case of severe infestations, a lot of vets will favour the use of Dectomax (Doramectin), administered via injection, as it has been proven to be safe to use and very good at reducing the number of mites present. It is effective at treating Psoroptic, Chorioptic and Sarcoptic mite infestations, and unlike some washes and powders, is able to reach the whole body. However, as the mites can live in the hair and surrounding environment of the horse (bedding, rugs etc) it is still possible for mites to go untreated by any injectable medication.

For best results, it is advisable to clip any feathers, especially on heavily feathered breeds, and wash/replace anything that could further increase the spread of the mites. We also recommend using a follow-up treatment roughly 2 weeks later, in the form of a topical wash that can be sponged on to the horse’s legs, and can be repeated a few times over the following weeks. The thorough cleaning of the horse’s surrounding environment should also be repeated after every treatment to drastically reduce the chance of re-infestation. 

Decotmax can, and will, only be prescribed by a veterinarian following a thorough examination, and will be administered via two injections (either under the skin or into the muscle), 10-14 days apart.

Ivermectin;

Ivermectin (the active ingredient in many wormers) administered via injection can also be an incredibly effective treatment, however, some horses can suffer from severe side effects and therefore it is not widely recommended. Ivermectin wormers can also be given by mouth to help reduce the number of mites, but many find that it doesn’t reach the skin in high enough levels to fully eliminate the problem and therefore is often not an effective treatment.

External treatments;

For milder cases of mites, topical washes, sprays and shampoos can prove effective treatments. A patch test should be performed prior to use of any external treatment, to ensure the horse does not suffer an allergic reaction to any of the ingredients.

Pig Oil;

Pig Oil has been used around the world, for hundreds of years, as a treatment for Chorioptic (leg or feather) mites. This inexpensive homemade treatment takes its name from when Edwardian pig farmers used to apply it to the skin of their pigs to get rid of mites.

Pig Oil is a mixture of white mineral oil (paraffin) and yellow sulphur powder, which has antiparasitic, antifungal, antibacterial, softening and soothing properties, all of which help to heal sores, reduce irritation and eliminate infestation.

To make Pig Oil, add half a cup of yellow sulphur into one litre of white mineral oil, and mix well until the powder has been dissolved into the oil. Start application from above the knee or hock and work your way down, ensuring the skin and hair is entirely covered. Massage well into lesions and areas of thickened skin. Repeat this treatment once a week for at least four weeks.

Lime Sulphur Dip;

This yellow concentrate is made from calcium hydroxide, sulphur and water, and has been proven an effective treatment for mites when repeated at least once a week for a minimum of four weeks. The colour of the solution means that it can stain, so this needs to be taken into account when using on light coloured horses.

Lime Sulphur Dip should be mixed well into water at a ratio of 1:40 (e.g. 100ml of Lime Sulphur Dip to 4 litres of water) and can then be poured, sponged or sprayed onto the coat, taking care to work it into the skin. Do not rinse after application, and repeat once every four weeks, or as advised by your vet. 

Fipronil;

Fipronil is the active ingredient found in Frontline spray, a product marketed for controlling fleas and ticks in dogs and cats. It has, however, been found to be generally safe to use on horses, and effective at reducing the irritation and number of mites present in cases of feather mite infestation, but doesn’t always resolve the problem entirely.

Fipronil can be found in various other products on the market, in either a spot-on or spray form. The spray is more easily applied, especially to horses who have sensitivities about their legs being touched, but you must ensure the product makes contact with the skin rather than just the hair. The spot-on gives you a more accurate application, however, it is only really effective when the feathers have been clipped.

Selenium Sulphide Shampoos;

Another effective treatment, which can be applied all over the body, is a shampoo containing Selenium Sulphide. This active ingredient, found in the likes of Head & Shoulders and Selsun shampoo, is an anti-infective agent that relieves itching and flaking of the skin, and removes the dry, scaly particles.

Use the wash all over the body (diluted in water as directed on the bottle), working it into the coat, then leave for 5 to 10 minutes before rinsing it off thoroughly. This should be repeated at least 3 times at intervals of approximately one week.

Tips for making treatment more effective

When treating horses for mites, there are a few things you can do that will help to make the treatment more effective and reduce the likelihood of reinfestation;

• Treat the whole horse, not just the affected area of the body.
• Treat all the horses on the property at the same time, thoroughly clean all stables and equipment, and rest any potentially affected pasture for a minimum of 12 weeks.
• Clean the horses’ skin with an antibacterial wash prior to any treatment, to remove dead skin cells from around sores and scabs. This will reduce the number of places mites could hide and interfere with their food source, whilst also making it easier for any treatment to be absorbed into the skin.
• Treat all horses multiple times and clean their surrounding environment thoroughly after each treatment, to reduce the chance of reinfestation.
• When treating leg mites, clip the feathers, especially on heavily feathered breeds, to increase the accuracy and penetration of external applications.

Please note: Feathers take a long time to grow back and are often not the same as they were before clipping. If preferred, feather mites can be treated effectively without the need for clipping, but you will need to be especially thorough and patient with your repeated treatments.