Why do horses get warts

Equine Sarcoids - Detecting Skin Tumors in Horses

Equine sarcoids are the most common type of tumor found in horses. Even if they are not directly fatal to the affected horses, they can make life very difficult for them.

Equine sarcoids are becoming more common in horses. These skin tumors affect horses (and equine species such as donkeys, mules and zebras) of all races and ages, although it has been found that geldings, young horses and breeds such as quarter horses, appaloosas and Arabs are more likely to be affected. There is also evidence that there is a genetic predisposition to develop sarcoids.

What are equine sarcoids?

Equine sarcoids are connective tissue tumors that can generally appear on the entire horse's body. However, they are particularly common on the head, legs and stomach.
This is because the viruses are transmitted by stinging insects that prefer areas of the body that are not very hairy. The name sarcoid comes from the word sarco (from the Greek sarx, genitive sarkos = meat) due to its sometimes fleshy appearance. However, there are also equine sarcoids that look like skin fungus, warts, or nodules and lumps in the subcutaneous tissue.

Sarcoids are generally benign because they do not metastasize and do not spread to internal organs. Even so, they can be very aggressive locally, grow quickly and also have a strong tendency to come back after being removed. Depending on where the equine sarcoid is (e.g. in the belt position or on the head), the horse can become unusable as a mount, even if the sarcoid as such is not life-threatening. It's actually not painful either, as there are no nerves running through it. But anyone who has ever dealt with a horse that is affected by a fibroblastic sarcoid (one with a cauliflower-like, oozing surface) knows that the horse is very uncomfortable to touch.

Different types of equine sarcoids

The number of equine sarcoids varies. Some horses only have a single affected area that remains unchanged for years. Others have hundreds of sarcoids of different types. Apparently the malignancy of the tumors is different and recognizable by the shape of the sarcoid. Equine sarcoids, which look like skin fungus, so-called occult (hidden) sarcoids, have the lowest viral load and are therefore the most benign. Wart-like sarcoids can also stagnate for years or go away on their own through the immune system. This course is rare in the nodes. The sarcoid, which resembles wild flesh, is the most vicious variety.

Occult sarcoidsThis equine sarcoid is hidden under the skin. Often only a round, hairless area can be seen on the surface, which can expand. Sometimes the skin on the bald area changes, becomes scaly, rough, horny, or develops wart-like lumps. They are found more frequently around the eyes, around the mouth, neck, chest and other rather hairless areas of the body. Occult sarcoids usually grow very slowly and can remain unchanged for years.
Verrucous sarcoidsVerrucous sarcoids can also develop from occult sarcoids. This shape is often found in the ears, armpits, groin and vaginal area. As the name suggests, they look like knobbly warts, are irregular, and can affect a considerable area of ​​the skin. Usually they grow slowly. But if they are injured, they can quickly turn into the fibroblastic type.
Nodular sarcoidSometimes nodular tumors also form on the bald spots of the occult sarcoids: nodular sarcoids. Most of the time, however, they appear alone and sit encapsulated under the skin, where they can be pushed back and forth. They can also be stalked and are often found in the groin, chest, or vagina. The skin over the nodular sarcoids is initially still intact. However, when the tumor begins to grow underneath, the skin thins, bursts, and the fibroblastic sarcoid develops.
Fibroblastic SarcoidFibroblastic (fiber-forming) sarcoids are strikingly red, fleshy, and ulcer-like. They bleed profusely if injured. They usually appear on the eyelid and groin area. They can develop as primary tumors or through injury to other forms of sarcoid.
Malevolent sarcoidThe most aggressive, albeit rare, equine sarcoid found primarily on the head, neck, elbows and thighs. The malevolent sarcoid usually develops from the injury of a fibroblastic sarcoid, from which it then radiates out. Unlike the other sarcoids, the malevolent sarcoid attaches to fascia and muscle tissue. The skin can appear normal over most of a malevolent sarcoid. However, since these affect the local lymphatic system, they finally become visible to the outside through a tumor cord.
Mixed sarcoidsAll of the above forms can also appear in combination, mostly on the face, eyelid, groin, elbow, and thigh. The mixed sarcoid is often the result of unsuccessful tumor treatment.

Equine sarcoids differ in their appearance and degree of aggressiveness. (© www.slawik.com)

The cause of equine sarcoids

Bovine papillomaviruses (BPV) types 1 and 2 have now been identified as the main triggers for equine sarcoids. Papillomaviruses occur in many animals just as they do in humans and create tumors in the skin and mucous membrane. Genetic traces of these viruses could be detected in almost all patients and tests have shown that these viruses play a decisive role in the progression of the disease. They are not only found in the affected areas of the skin, but in the entire skin, just like in certain blood cells.

This becomes a problem especially when the horse has a wound. The healing process goes hand in hand with accelerated cell division in order to “plug the hole.” The BPV genetic information in the cells responsible for the equine sarcoids also multiply much faster than usual and this is how skin tumors develop.

Proper prevention

As is common with viral infections, equine sarcoids are contagious in horses. There is now little doubt about that. But how the viruses are transmitted is not yet fully understood. The theory that BPV is transmitted from cattle to horses via insects has meanwhile been abandoned, partly because the genetic information of BPV on horses does not match that on cattle. It is more likely that the viruses are transmitted from horse to horse, which has also been confirmed in experiments. They can survive on surfaces outside the host body and have also been detected in insects in the vicinity of affected animals.

Nonetheless, they say at the University of Vienna that the risk of infection is very low if you follow a few rules. It is not necessary to isolate affected horses, but they should definitely have their own grooming and saddlery, blankets, gaiters, bandages, etc. Because skin particles contaminated with the viruses still adhere to it, which could be transmitted to healthy horses. The sick horses should also not exchange boxes with other horses.

Bovine papillomaviruses (from cattle) cause equine sarcoids. Nevertheless, according to the current state of knowledge, there is no possibility of infection. (© www.toffi-images.de)

Diagnosing Equine Sarcoids - Better Without a Biopsy

The diagnosis of an equine sarcoid should be made clinically by experienced veterinarians, because sarcoids can look like excess scar tissue and can therefore not always be reliably identified. In addition, there is a risk that they will overgrow more than before after a sample is taken. In Vienna, the BPV genetic information is the likely explanation for the fact that sarcoids usually return in a more aggressive form and often also in other parts of the body. Therefore, a biopsy to obtain a tissue sample is not recommended for diagnosis.

Since the different forms of sarcoid can be confused with other skin diseases, it is advisable to take dandruff or a hair sample from the affected area and analyze these samples for BPV. Incidentally, there is also a risk of aggravation in the event of an operation on the sarcoid.

Sarcoids in Horses - The Proper Treatment of Skin Tumors

We are now certain that injury to a tumor, on the one hand, promotes its spread and, on the other hand, promotes the change from a harmless to an aggressive form. Therefore, early diagnosis and treatment of sarcoids is critical, emphasizes Dr. Sabine Brandt from the University of Veterinary Medicine, Vienna. Unfortunately, the more attempts have failed, the worse the chances of recovery.

As a rule of thumb, it is said that equine sarcoids must be treated as early and as aggressively as possible. The main thing is to prevent it from returning. Surgical, chemotherapeutic and immunological measures are possible for treatment.

Equine sarcoids can be found all over the horse's body. A sarcoid on a horse's hose is not uncommon. (© St.Georg)

Wide range of treatment methods

The choice of treatment method depends on the clinical findings, the location and the type of equine sarcoids in the horse. Setting or freezing off can help, and ointments such as Aldara® or xx-Terra can also be used for sarcoids on horses. So-called BCG vaccines (Bacille Calmette-Guérin) are often vaccinated. This vaccine increases the local immune system at the site of the injection. This leads to a rejection reaction in the tissue, which the veterinarians use to fight the tumors in equine sarcoids. For reasons that have not yet been clarified, this works best with sarcoids on the head. However, the reaction is not specific; H. it is directed not only against the tumors produced by papillomaviruses, but also against the tissue into which it is injected.

Irradiation of the sarcoids is promising, but expensive and time-consuming. In the case of occult sarcoids in horses or those that are not yet taller than five millimeters, rubbing in acyclovir ointment, a means that specifically fights viruses, may be sufficient. Aloe vera gel can also be used to combat horses with sarcoids.

Another product that can help is the bee product propolis. In horses with sarcoids, it has more antibacterial and anti-inflammatory effects. The equine sarcoids are treated with honey, cream, paste or tinctures of this product and disappear in some horses.

Support through feed additives

The healing of equine sarcoids in horses can also be supported by the right horse feed. Among other things, oregano has an antioxidant effect in horses with sarcoids, which in some cases has led to the disappearance of the sarcoids. But also metabolism-stimulating or pain-relieving feed additives such as rose hips or beetroot can have a positive effect.

Possible cure through homeopathy

Alternatively, sarcoids in horses can also be combated with a treatment made from homeopathic remedies. Homeopathy focuses on supporting the immune system. Equine sarcoids in horses can be treated with thuja, for example, to strengthen the horse's metabolism and at the same time have a detoxifying effect.

Immunotherapy - New in Research

A research team from the University of Vienna is currently working on the development of a vaccine against papillomaviruses. However, it is not yet available and is not suitable for treating existing tumors. As in human medicine, where young girls can be vaccinated against papillomaviruses as protection against cervical cancer before their first sexual intercourse, the vaccination should also be carried out in horses before an infection with the virus has taken place.
That is why another method is currently being tested: treatment with interleukin 2. The tumors are treated with local injections, the IL-2 increases the function of the body's defenses and causes a local inflammatory reaction.

This type of tumor treatment is already used in different ways in humans and animals. The results obtained so far in horses with equine sarcoids are encouraging. All forms of sarcoids can be treated, even if other treatment options have not led to the desired result. It should be noted that the patient himself has to achieve the rejection reaction through inflammation of the tissue.

In some cases, the body's immunological reactions are so strong that the treatment has to be stopped because of immune reactions in the form of fever or severe swelling. In some cases, the treatment cannot be completed because the horses no longer allow the injections.

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