Weekly Tips Mar. 08

Those Pesky Critters and other Signs of Spring

Ahhh . . . those wonderful signs of Spring! Birds chirping, buds popping, insects buzzing; the musk of damp earth and warm showers; the sweetness of early flowers. And then there are the other signs. Horses shedding, rain rot, lice, ringworm, scratches, and more. Where does all this stuff come from and why does it appear so suddenly?

Fungus Amongus

Fungus and bacteria are everywhere in the environment. Preventing your horse from coming in contact with them . . . no matter how clean he or his stall are . . . is impossible. Some parasites that attack the skin are carried by horses and only develop into a noticeable dermatitis when conditions are right. So, how do you know if your horse has a skin problem? And what are the differences between them? And how do you deal with these pesky invaders?

What Kinds of Dermatitis are Common in Horses?

The two most common skin problems seen in horses are "rain rot" and "ringworm". The first is not directly caused by the rain, but a bacteria; and the later is a fungus, not a worm.

Typical small lesions associated

with dermatitis.

Rain rot - also known as rain scald, dew poisoning and mud fever is caused by bacteria that can be harbored in the skin of all horses. The scientific name of the organism is Dermatophilus congolensis. Although a bacteria, it also has fungal characteristics, thus creating a misunderstanding that it should be treated with an anti-fungal medications. Rain rot presents itself as scab covered lesions - generally small patches anywhere from 1/4" long to approximately the size of a dime or nickel. Dry, scabs are either attached to a clump of hair and readily fall off, or are embedded with loose hair. Once the scabs are removed, the exposed skin is pink and generally oozes a clear or yellowish serum. If severely infected, there will be pus. It can be painful to pull or scrape the scabs off. In some cases, it can lead to raw, bleeding sores that are open to infection. In its early stages, you might discover many small raised lesions or raised tufts of hair. Scratches, greasy heel, or cracked heels are close relatives of rain rot and can be treated in a similar manner.

If all horses can harbor the bacteria, then why don't all horses get rain rot? And why do some horses seem to have severe cases that require weeks of treatment while others seem to rid themselves of it within several days?

For rain rot to establish itself, the skin must be compromised in some way. This could be through a cut or break in the skin. Insect bites and other irritations such as blanket rubs or persistent scratching also afford opportunities for invasion. The organism can be spread through shared equipment such as saddle pads, blankets, clippers, or brushes and curries. These should be disinfected to prevent spread or re-infection.

Two conditions must be present for the organism to become active - warm temperatures and moisture. Rain rot is most often seen in warmer climates or with the return of warm spring days in more northern regions. The lesions generally appear on the back and rump, but can be found on the lower legs. Many small lesions in close proximity will result in large patches of loose hair or bald spots.

Close-up of rain rot lesions.

Although the disease is generally self-limiting and will resolve itself within a couple of weeks, it is recommended that it be treated as soon as possible. Without treatment, it is possible that secondary staph and strep infections may occur. Recommended treatment generally consists of three steps:

2.Thorough cleansing of the infected area. There are many medicated shampoos with anti-bacterial additives. Other cleansing agents are povidine-iodine, Betadine, chlorhexidine, preparations containing tea tree oil, or any good anti-bacterial soap. In cold weather, when bathing is not advisable, the area can be cleaned with Excalibur Sheath Cleaner (contains tea tree oil) and rinsed off with warm water on a sponge or cloth. Dry the area with a blow dryer or clean towel. Be sure to disinfect cleaning equipment.

3.Application of a topical treatment may speed healing and deter further infection. There are several topical anti-bacterial sprays and ointments. Some owners apply concoctions made up of household cleaning agents. While these things are generally anti-bacterial, they are also caustic to living tissue and can cause damage to the area, thus defeating the purpose. Bacteria thrive on damaged and dead tissue. In some persistent cases - especially of leg dermatitis, application of a protective coating such as Desitin or Corona ointment will help keep the infected area dry during pasture turnout.

Typical ringworm lesion

Ringworm

Similar to rain rot, ringworm is a fungal dermatitis (Dermatophytosis) that is generally caused by direct contact with other infected animals or indirectly by sharing contaminated equipment. Unlike most other organisms that infect horses, ringworm is not species specific and will cross infect other animals and humans. Warning - The organism can be carried to others without infecting the host!

Ringworm usually appears as a rash leading to an ever outward growing lesion with a scab or rough center. The lesion may be circular, but isn't always. The center will heal, but often has a raised rim around the outer edge. Unlike rain rot, ringworm is very itchy. Rubbing and scratching of the lesions can promote secondary bacterial infections. Girth itch is a related fungal infection that results when the skin is irritated by the girth.

Ringworm establishes itself in the compromised skin when there is a break or abrasion. It is generally active during damp times of the year. Sunlight inhibits proliferation of the spores, therefore, the organism is most likely to be active during winter when days are shorter or on stalled horses that don't have much access to daylight. Because it is a fungus, ringworm is a parasitic spore that can be harbored for several months in clothing, blankets, and equipment until conditions are right for activation.

Ringworm is another dermatitis that is generally self-limiting and likely to resolve itself within a short period. However, without taking immediate steps of treatment, the spores are likely to spread and chances of re-infection or infection of stable mates, other animals, or humans is possible.

2. Clip the area around the infection (be sure to sanitize your clippers afterwards). This removes the fungus' source of nourishment - hair follicles. Use a #40 (surgical) blade and clip any remaining hair on the lesions and about 1/2 inch outward into non-affected areas.

3. Thorough cleansing of the infected area. Betadine or Nolvasan scrub is recommended as effective in killing the fungus. Let the application set for approximately 10 minutes to have time to work. Tea Tree oil is also considered an anti-fungal agent and there are anti-fungal shampoos for humans and horses that should be effective.

6. Keep the lesions dry and exposed to sunlight to help prevent re-infection and provide an unfriendly environment for remaining fungus. This means that you should avoid blanketing if possible and offer as much turnout as possible, especially on sunny days. Additionally, you should avoid grooming with metal curries or stiff brushes that may abrade sensitive skin and provide a foothold for new spores.

Both sucking (Haematopinus asini) and biting lice (Bovicola equi) infect horses. They are species specific and therefore will not infect other animals or humans. However, they will infect other equid such as donkeys and mules. Source of contamination are other infected horses. Unlike bacteria or fungus, the parasites cannot live without a host and die soon after removal.

Generally, the mane, tail, head, and neck are the only areas infected. However, if the problem is left untreated and lice populations grow beyond support range, then they will spread out to other areas of the body. Heavy infestation can affect the overall health of the horse and may predispose it to other diseases. The most noticeable symptom of lice infection is rubbing or scratching. Lice activity can be very itchy and increases as populations rise.

The sucking lice (image at top left) feed on the horse's blood and the biting lice (image at right) feed on shed skin or secretions from the skin. Both types reproduce throughout the year, however they generally become most noticeable during winter. Good grooming and adequate nutrition are important to maintain the health of the horse and reduce chances of infestation. Grooming provides an excellent opportunity to inspect your horse for lice. The most common treatment is lice dusting powder.

Several types of tiny mites cause skin conditions that are collectively referred to as mange. Generally the symptoms of mange include areas of cracked, dry skin and formation of scabs. Mite activity is extremely irritating and results in scratching, rubbing and licking infested areas. Secondary infections of the infested areas are possible. Mites most generally invade the inside of the ears, but can also be found in the mane and neck area. When the infestation is excessive, other areas of the body can become infested.

A sarcoptic mange mite, Sarcoptes scabiei equi, is shown above on the left. Confirmation of mite infestation usually requires microscopic examination of skin scrapings. Early detection is important in limiting the spread of the mites to other horses and to prevent severe mange. Mites spread through direct contact or by the use of common grooming tools and tack. Frequent grooming is important for early detection; when symptoms appear, consult a veterinarian for confirmation and treatment.

There are several triggers that provide just the right circumstances for proliferation of different dermatitis in horses. Climate and weather are factors that we have no control over, but are instrumental in activation of skin infections. Additionally, the horse becomes its own worst enemy by growing a wooly winter coat that traps body heat and moisture and conceals the work of active parasite colonies.

But, beyond the obvious and uncontrollable conditions, there are underlying hidden problems that can result not only in invasion of "critters", but other infections and diseases. Dermatitis is often found in younger and older horses that are not coping with winter stresses well. Their nutrition may be adequate for summer weather, but not for dealing with the excesses of winter. Especially in older or hard working horses, immune systems may be compromised.

Often owners unwittingly set their horses up for winter problems during the summer months. Many horses do well on pasture and often gain weight - sometimes in excess. Owners feel that it is important not to let their horse get overweight - and that is well intended. The horse generally looks so sleek and healthy, that little attention is paid to its nutritional intake. To compensate, feeds and supplements are often reduced or elminated from the feeding program, scheduled de-worming is passed over and work loads are increased. But what does all this lead to?

Nutrition is not just calories or amounts of feed or even shiny coats. Exercise and competition during hot weather often leads to mineral loss. Likewise, standing in stalls for long periods to avoid hot or cold weather results in mineral loss in growing horses. Feed manufacturers that claim to provide adequate amounts of vitamins and minerals also provide recommendations for feeding. If you are not providing the recommended amounts - generally 4-6 lbs/day - then you are also not providing the guaranteed levels listed on the tag.

Forage, whether grass or hay rarely meets even maintenance levels of necessary vitamins and minerals. While it is not important to provide other feeds during grazing periods, it is important to provide a quality equine vitamin/mineral supplement to fill the gaps, especially where grazing areas are limited in plant variety and by space. When horses do not have pastures and must be fed a continual diet of hay, even if the quality is supreme, it still cannot provide all the nutrients needed to keep your horse optimally healthy. Soon after harvest, the nutritional value of hay begins to deteriorate. Storing for six months results in the depletion of most vitamins and other nutrients. Some nutritionally beneficial elements such as essential omega-3 fatty acids and probiotics are provided in adequate amounts only through consumption of grass and other live plants.