Horse Mites 101

Horse Mites 101

What are mites?

Mites are parasitic arthropods, related to the tick family. They are microscopic and therefore are all too easy to be missed by the naked eye. They live in both the hair and the skin. “Mange” is a frequently used term that refers to the reaction on a horse's hair and skin to mites. They feed on the protein-rich structures of the skin cells by piercing the skin of a horse or burrowing in it, depending on the type of mite, and consuming the fluid.

How do horses get mites?

Mites live just about anywhere, i.e. in straw and hay, to name but two places they are commonly found. Birds carry certain species on the wing when they visit stables. Also, horses tend to pick them up when they come into contact with another horse that may already have them.

However, you may never know how your horse picked them up, but once they have you need to start a treatment as soon as you can to prevent a secondary infection taking hold in any open sores.

What mites affect horses?

Did you know that there are four important parasitic mite species that affect horses: Chorioptes equi, Demodex equi, Psoroptes equi and the Sarcoptes scabiei var. equi. They can affect the ears, fetlocks, pastern, between the legs or elsewhere on the body.

Chorioptes equi: the itchy leg mite which affects horses, donkey and mules worldwide. This is the mite that most commonly affects horses in the UK.

These mites are small, 0.4 to 0.6 mm, and can only be seen under the microscope. They have chewing mouth parts and neither suck blood, nor dig tunnels like sarcoptic mites, but bite the outer skin layers and feed on skin debris, fat, lymph or the sore that they create. 

Preferential sites are the hooves and the lower part of the legs, mainly on the hind legs. Horses with long hairs on the fetlocks are especially at risk. Initially, the condition looks more or less like eczema. If left untreated, scabs and crusts follow, possibly even large calluses and warts.

Itching is evident but usually not as intense as with psoroptic and sarcoptic mange, and the reactions of affected animals of biting, scratching, rubbing, etc, are also less vigorous. Harm is seldom severe, but infestations are difficult to heal and may persist for a long time.

These mites are less harmful than psoroptic or sarcoptic mites. They are not transmitted to humans.

A proper diagnosis has to be confirmed examining skin scrapings under the microscope in order to see the mites.

Demodex equi: the horse follicle mite which affects horses worldwide.

These mites have an elongated shape and are even smaller than psoroptic or sarcoptic mites, i.e. about 0.25 mm. They get into the hair follicles that can then become infected with secondary bacteria. Demodex mites can survive up to 4 months off the host.

Lesions often appear first on the forehead and around the eyes, and later on the shoulders. They may infest the whole body surface and the affected skin is often covered with scales.

It can develop year-round, not only during the cold season. It's rare in horses and is more common in large herds rather than in horses kept individually.

Psoroptes equi: the scab mite or equine body mite which again affects horses and mules worldwide.

Adult psoroptes mites are oval in shape, 0.5-0.6 mm long, usually only recognisable under the microscope. They produce typical scabs on the skin of affected animals, thus their common name - scab mites. In the past it was thought that they pierce the skin of their hosts. However, it’s now believed that they don’t pierce the skin, but that the mite faeces cause an allergic reaction of the horse’s skin, which reacts producing exudation and skin thickening and hardening, resulting in crusts and often hair loss.

As all mite species, psoroptes mites spend their whole life on the same host. Transmission from one animal to another is mostly by physical contact. The mites do not actively jump or crawl from one host to another, but are passively transmitted when animals come into close contact. Nevertheless, psoroptic mites and eggs can survive 2 to 3 weeks when off the host and in suitable conditions, i.e. animals can pick up mites or eggs from their environment, and they can also be passively transmitted by saddlery, tools or equipment in the stable.

This species is not very frequent in horses. It develops mainly in areas with thick hair, i.e. neck, mane, base of the tail, etc. but may affect the whole coat. Intense itching, vigorous scratching, biting, and rubbing against objects are common symptoms. All this leads to hair loss, weight loss, and general weakness, making them more susceptible to other diseases.

Psoroptic mites of horses are usually not infectious for humans.

A proper diagnosis has to be confirmed examining skin scrapings under the microscope in order to see the mites.

Sarcoptes scabiei var. equi: the common mange mite and the most serious that affects horses, donkeys and mules worldwide.

Sarcoptic mites of horses are a species-specific strain of Sarcoptes scabiei, a mite species that also infests sheep, cattle, pigs, other livestock, and humans. This means that it can be transmitted to humans.

Sarcoptic mites are very small, i.e. 0.3 to 0.5 mm, and can be seen only under the microscope. As with all mite species, sarcoptic mange mites spend their whole life on the same host. The mites do not actively jump or crawl from one host to another, but are passively transmitted when animals come into close physical contact. However, horses can pick up mites from the immediate environment and they can also be passively transmitted by saddlery or tools and equipment in the stable. But there are no external vectors that transmit the mites, e.g. insects, worms, rats, mices, birds, etc., as happens with many other parasites.

This mite does tunnel beneath the skin. Their saliva has potent digestive enzymes that dissolve the skin tissues. The mites feed on the resulting liquids. They do not suck blood. Adults live for 2 to 3 weeks. Off the host, the mites survive only a few days because they are very susceptible to dryness.

Sarcoptic mange is not very common in horses, but when it happens it is the most harmful of all mite infestations. It is more frequent in large herds than in animals kept individually. Mite digging causes skin irritation, which is enhanced by allergic reactions to the saliva that develop a few weeks after infestation. The affected skin develops pimples that become crusty, with massive hair loss, progressive hardening and thickening, and building of large folds. Infestations often start on the head, spreading to the neck and the shoulders.

Affected horses suffer intense itching and react by vigorously scratching, biting and rubbing the affected parts against whatever object. This causes injuries that can become infected. All this results in weight loss and general weakness that makes the affected horse more susceptible to other diseases.

Sarcoptic mange is also a typical winter pest in regions with a cold winter. Outbreaks usually peak in late winter and early spring.

A proper diagnosis has to be confirmed examining skin scrapings under the microscope in order to see the mites.

What time of the year are they a problem?

Mites are around all year, but a clear peak is seen in the winter months as the mites seek out the body heat of horses. The winter months are therefore also seen as the risk period for a mite infection. 

If your horse is very itchy during hot weather and you suspect that he has mites, he probably hasn’t, but the itching is due to Sweet Itch, an allergy to flies, or a scurfy coat that would improve with a bath using a good shampoo aimed at conditioning the coat.

Are some horses more susceptible than others?

In the autumn, a horse's resistance is running at full capacity. The extreme fluctuations in temperature along with the reduction in daylight hours, initiate the moulting process as well. This can result in a lower resistance in some horses, making them more susceptible to mites.

What’s the best treatment to get rid of mites?

Many products are based on chemical components. Mites can actually become resistant to them after a while. So, it may be that a treatment with a chemical product will only work so many times, i.e. after 3 or 4 times it will no longer work. In addition, chemical agents are often external. This has two disadvantages: it is impossible to reach all mites on the horse, plus sweat and rain dilute the effect. This is not the case with a natural nutritional supplement where sweating strengthens the effect.

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How can mites be treated and subsequently avoided?

Here are some hints and tips on how to treat and then avoid an infestation of mites:

* Treat the whole horse not just the problem area

* Wash and disinfect any rugs or other equipment once they have been identified

* Use shavings as bedding instead of straw

* Clean and disinfect your stable regularly or if you move to a new stable

* Consider using a supplement like Dodson and Horrell Itch Free

* Wash and disinfect bought or borrowed second-hand rugs or tack before using them on your own horse as mites can be passed via these

* If you are in any doubt if the condition of your horse is caused by mites, get a proper examination and diagnosis from your vet.

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Can horse mites live on humans?

The only mite that can be transmitted to a human is the Sarcoptes scabiei var. equi.

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Author

Kim Horton

Co-Founder of EQUUS and a keen equestrian, when Kim's not at her desk she's with her horse, Waldo.

Comments

  • Lyn Hannant posted on May 20 2020 at 12:05 PM

    Our heavily feathered cob got feather mites. He kept stamping on the ground and actually broke a bone in his foot. The first thing was to remove his feathers and keep the area clean and use mite powder. He had Dectomax injections twice a year because he also got dermatophilus congolensis. One point, are mites the same as what I’ve always called lice? One of our ponies developed them at the base of his tail and in his mane recently. I got rid of them with Decosomething I got from our vet.

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