A horse's tail punctuates his beauty and elegance with its carriage, thickness, and gloss. Owners go to great lengths to keep their horses' tails pristine. So when a horse rubs his tail into a frayed or hairless mess, there is motivation to get to the bottom of the problem as quickly as possible. When faced with a horse that persistently rubs his tail, one question to consider is the time of year this occurs. Is it seasonal or is it an incessant behavior that appears year-round?
Seasonal tail rubbing is often a result of a hypersensitivity response to certain insects. Christine Rees, DVM, Dipl. ACVD, a practitioner at Equine Allergy and Dermatology of Texas, has many occasions to evaluate horses with pruritus (itching). She notes, "Reactions to insects are caused by hypersensitivity to salivary antigens (proteins) in the insect bite. These proteins elicit release of inflammatory mediators that cause irritation and tail rubbing. The most common insects to cause tail rubbing are the Culicoides gnats."
Culicoides hypersensitivity in horses is also referred to as "sweet itch." In severe or advanced cases, itching is not just confined to the tail; the horse also rubs mane, neck, and chest in response to the systemic reaction generated by gnat bites. At times tail rubbing goes beyond just broken tail hairs; the tail might become completely denuded of hair, with self-inflicted trauma sufficient to create bleeding areas and a "rattail" appearance. Persistent, chronic tail rubbing of traumatized tissue exacerbates the dermatitis, referred to as tail pyoderma, making resolution of the problem that much more challenging.
Management Options for Insect Control
Rees explains that management is paramount when getting Culicoides hypersensitivity under control. She proposes a variety of environmental management options and preventive strategies:
- Culicoides tend to feed at dusk and dawn, so stable horses during these peak feeding periods.
- Place fans in stalls to deter gnats since they are poor fliers.
- Install time-operated spray mist insecticide delivery mechanisms to control insects in the barn.
- Culicoides require free-standing water to propagate. Therefore, avoid stabling a horse near ponds, marshes, or lakes. You might need to move extremely sensitive horses to another location free of gnat breeding grounds.
- Install fine mesh screens over stall openings to keep gnats out.
- Use insecticidal sprays on a regular basis--oil-based sprays tend to last longest. In one European study researchers determined that a permethrin and pyriproxifen product (KnockOut spray by Virbac) was effective. Another product some owners swear by is Skin So Soft (Avon) bath oil, mixed with water, although studies have shown only short-term protection against mosquitoes. Some veterinarians recommend attaching cattle ear tags impregnated with pyrethroid or organophosphate insecticides to halters or braiding them into the mane for insect control.
- Use fly sheets and fly masks to create a physical barrier so insects cannot feed as easily on your horse.
Insect Hypersensitivity Treatments
To treat Culicoides hypersensitivity reactions, Rees suggests, "The best approach is to try to control the insects and to treat the itch. Itch control may be achieved using topical oatmeal therapy with pramoxine (a topical anesthetic agent) or stero-ids, by feeding fatty acids, and/or by using systemic steroids."
Rees says MSM (methylsulfonylmethane, a derivative of dimethyl sulfoxide, or DMSO) might be helpful for controlling Culicoides hypersensitivity in horses. She continues, "I don't think horses traditionally hyposensitize very well to insects by themselves. In my experience, 20-30% will improve without therapeutic assistance. However, if the horse has other allergies, such as to pollen, then hyposensitization vaccines may be useful."
In addition, the veterinarian must rule out other external parasitic infestations, as, for example, irritation from lice or mange that is known to stimulate horses to develop tail rubbing behavior.
Internal parasites also play a role in tail rubbing. The most well-known culprit is the pinworm (Oxyuris equi), a common intestinal parasite that can cause external effects, such as irritation around the anus (perineal area, which includes the anal area, vulva in mares, and tissues between).
The adult female pinworm moves to the skin area around the anus to deposit eggs, which are encased in a gelatinous material that irritates the perineum. At times, female worms might rupture, amplifying the irritation. A horse affected by pinworms often lifts its tail to rub along the buttocks, leaving the dock of the tail unaffected, but many horses are so irritated that they'll rub their rear end in every imaginable way, making the dock of the tail raw.
Rees recommends, "The best way to tell if a horse has pinworms is to have the horse examined by a veterinarian. Diagnosis is made by pressing clear acetate tape to the skin around the anus and then placing the tape on a slide to look under a micro-scope for pinworm eggs."
The most effective treatment is a carefully applied deworming program. Many deworming medications treat the adult worms and some of the immature stages, but none of the eggs. Rees reports, "In difficult cases, I have used fenbendazole."
The horse inadvertently deposits pinworm eggs in the environment, such as on fence posts and feed or water troughs when rubbing his tail due to pinworms. Other horses become infected by accidentally ingesting the larvae. Pinworm eggs develop within three days and persist about one month in the environment. Rees suggests considering the life cycle of pinworms when formulating a treatment protocol, noting, "You can either deworm your horse, then vacate the area for five or six weeks, or if the horse remains in the same area, deworm three times at monthly intervals using antiparasitic drugs that target pinworms."
Deworming against bots is also helpful in derailling tail rubbing stimulated by bot larvae irritation of the rectum as they exit the horse in the spring. If tail rubbing continues despite an aggressive deworming strategy, then you should look for other causes. It is important to be patient regarding return of your horse's lustrous tail, as it takes at least a month for hair to grow back once rubbing stops.
That Dry, Itchy Skin
"If a horse's skin becomes excessively dry and scaly," Rees says, "it can be pruritic, i.e., itchy." She recommends thoroughly washing the horse using appropriate shampoos, and apply sprays or lotions. She prefers products that contain moisturizing agents along with anti-itch medication such as pramoxine. Veterinary products containing pramoxine include Relief Shampoo and Relief Cream Rinse (DVM Pharmaceuticals) and Resiprox (Virbac). After shampooing your horse with a soapy lather, make sure you rinse well. Shampoo or soap residues that remain on skin or tail can also cause itching.
Ray Randall, DVM, of Bridger Veterinary Clinic in Montana, describes a buckskin Quarter Horse that presented with tail rubbing that he ended up attributing to photosensitization. He recalls, "During my exam, the gelding's hind white stocking looked odd. His blood work showed that one of his liver enzymes (GGT) was very high, typical of liver effects related to ingestion of photosensitizing plants, often found in pasture. Once we eliminated the noxious plants in his diet, no other treatment was necessary to solve the tail rubbing behavioral problem."
Randall has also seen general dermatitis or hives contribute to an odd case of tail rubbing. In these cases, he suggests, "Management changes should be addressed along with corticosteroid therapy when appropriate. For some horses, the gold standard of allergy skin testing may identify the allergen. This can then be followed with appropriate hyposensitization injections to control the allergic response."
Veterinarians in some areas of the country point out that just as common as tail hair loss due to itching is severe pruritis on the ventral abdomens of horses with fly allergies.
Randall notes that if enough debris accumulates in a gelding's prepuce (sheath), he'll demonstrate discomfort by rubbing his tail. He says, "I don't typically see this behavior in active breeding stallions since they usually express a lot of material during live cover or when cleaned prior to hand breeding or collection."
Randall also observes, "The amount of accumulated material in a horse's sheath depends on the ground he lives on, his ordinary secretions, oils, and waxes, and what he does for exercise."
Rees suggests, "There may be irritation from pollen or other foreign material in dirt accumulated in the sheath, or possibly an infection that causes inflammation, irritation, and pruritus."
Since the horse can't reach his sheath to scratch, his inclination is to back up to a solid object and persistently rub his tail. Randall additionally remarks, "It's possible that a mare with enough secretions and irritation between her udders might also display tail rubbing behavior." The solution is simple: have your veterinarian sedate your horse and do a thorough sheath (or udder) cleaning with attention to every nook and cranny.
Is Your Horse What He Eats?
"It is possible for a food allergy to cause tail or perianal pruritus in horses," says Rees. In horses, food allergies are not as com-mon as insect hypersensitivity or atopy (an inherited predisposition toward the development of allergy). She explains, "Several different foods or ingredients may cause food allergies, and there is not one particular food that causes an allergy in every horse. Each horse is individual, and must be evaluated as such. Examples of food ingredients that are reported to cause equine food allergies include alfalfa, wheat, oats, concentrates, bran, and tonics."
Horse owners have heard for years that feeding a small amount of oil (2 ounces) in the diet is good for the hair coat. Rees concurs, "Fatty acids may be beneficial for a pruritic horse. In recent times, the most popular supplement is flaxseed or flaxseed oil added to food at a dose of 2-3 ounces daily. Other fatty acid supplements used in horses include Derm Caps ("100's," DVM Pharmaceuticals), Glänzen 3 (HorseTech), and Platinum Performance Equine (Platinum Performance).
Behavior problems often appear subsequent to boredom or stall confinement, and some horses might develop a habit of backing up to a perimeter and scratching or rubbing the tail. Rees notes, "Some atopic horses have been reported to rub their tails; however, most of these horses have skin lesions on other areas of their bodies, as well."
Horses respond to physical or mental irritation with obvious behavioral quirks, sometimes inflicting harmful trauma on their own bodies.
While a variety of problems can cause itching, a horse might concentrate his itch behavior on tail rubbing. There might be a couple of health issues going on simultaneously, so your veterinarian should rule out all possibilities of tail rubbing behavior with a diligent exam.
Once he or she addresses the primary problem along with appropriate behavior modification, the horse's rubbing should rapidly resolve and his tail will return to its fullness and sheen.
About the Author
Nancy S. Loving, DVM, owns Loving Equine Clinic in Boulder, Colorado, and has a special interest in managing the care of sport horses. Her book, All Horse Systems Go, is a comprehensive veterinary care and conditioning resource in full color that covers all facets of horse care. She has also authored the books Go the Distance as a resource for endurance horse owners, Conformation and Performance, and First Aid for Horse and Rider in addition to many veterinary articles for both horse owner and professional audiences.
POLL: University Equine Hospitals