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By Zoe Davidson, DVM, MRCVS While we are all still reveling in the glorious months of summer, this time of year can bring a number of health issues to our equine friends. One of the most common conditions is Insect Bite Hypersensitivity. Insect Bite Hypersensitivity (IBH, Queensland itch, sweet itch, equine summer eczema) is the most common pruritic ( itchy) disease of horses. Definitely a common topic of discussion within the equine world, but yet not fully understood and frequently mismanaged. The goal of this article is to provide a quick simple run down of the cause, classic symptoms, and what we can do as vets and owners to keep our horses happy and healthy! Cause Allergic sensitivity to the saliva of Culicoides spp., biting midges; and a variety of insect species. There is a genetic component that does predispose some breeds to a more severe reaction than others. Your horse can develop hypersensitivity and associated symptoms even if you do not see your horse being actively bitten. There is much more than meets the eye going on below the skin surface. Simply put, the severity of the clinical signs is not always correlated with the number and frequency of insect bites, but rather the severity of their individual immune mediated reaction. Certain horses develop a much stronger reaction to the saliva than others, and once their system is primed, worse the clinical signs are. Classic Itchy Horse Symptoms IBH can look different in each horse. Most commonly the symptoms include urticaria “hives”, generalized pruritis (“itchiness”) leading to lesions associated with self trauma (e.g skin thickening, lesions, scaling, crusting, hives, and hair loss, which can result in extreme discomfort.) In severe cases the secondary lesions induced by self -mutilation cause open sores and become infected. Lesions in horses are usually found on the trunk, face, mane, tail, and ears, with locations varying depending on the biting characteristics of the particular insect(s). The external signs can be accompanied by a dull, depressed, lethargic temperament. Luckily, it is one of the most well understood of the allergic skin diseases of the horse which means we have developed very effective management practices to help keep our horses happy and healthy this season! TOP MANAGEMENT TIPS: 1. Catch Early - prevention is always the best cure! Monitor your horse twice daily for the signs mentioned above! 2. Fly Control - prevent the flies from biting! Effective fly spray applied 2X/day Routine sheath cleanings Comprehensive fly mask and fly sheet Clean out stalls 2X/day; place manure piles far from barn Place a fan on your horse's stall door! Fun Fact: Flies are actually pretty weak fliers! 3. Supplements: Platinum Performance Skin and Allergy as well as Kinetic Vet Equishield (Skin and Allergy) have been proven to be effective! Omega-3 fatty acids can aid in reducing skin inflammation. When to call a Vet? Hives accompanied by agitation, elevated respiratory rate, effort and/ or depressed lethargic demeanor, Lesions on the head, neck, mane, tail and or belly (ventral midline) that are being rubbed raw, swollen, runny eyes cough. Sometimes your horse may be reacting to a variety of different stimuli, and in this case a thorough examination and further testing is indicated in order to diagnose and effectively treat. Medical Treatments At this time, there are only a few effective treatments once your horse has developed more extensive IBHS. Our options include antihistamines and corticosteroids, both of which are variably effective and do not come without their own potential side effects. In more severe cases, your vet may discuss drawing your horse's blood for an allergy panel. Subsequently, the exact cause of the allergy can be identified, and a specific immunomodulator developed to help reduce their symptoms. A pricey, length and often not always effective option! With this in view, prevention and management are by far the best methods of keeping your horse comfortable, happy and healthy! If you are concerned about your horse, and eager to discuss any of the above information further, please do not hesitate to reach out. We would love to hear from you! Download a PDF of this article... Related resources you may also be interested in: “Equine Allergies” (Video) by Amanda Hedges, DVM, cVA, CVSMT “Equine Allergies” (Article) by Amanda Hedges, DVM, cVA, CVSMT

Equine dentistry is more than just floating teeth. It's much broader and examines the horse’s health more systemically, which is why it’s important to have your veterinarian perform annual dental exams. The general goals of equine dentistry include: Improving the chewing of food Relieving pain and treating or curing infection and disease Promoting general health, productivity, and longevity Preventing more painful and costly problems later According to the American Association of Equine Practitioners (AAEP), these 10 signs suggest that your horse needs a dental exam:

E.O.T.R.H. (Equine Odontoclastic Tooth Resorption and Hypercementosis) is a disease process of the incisor and canine teeth mostly seen in older horses. For reasons unknown, the body begins to resorb the bone and surrounding gum tissue. With increased loss, pockets will form causing feed to accumulate between the teeth and a subsequent infection occurs. The infection can further destroy the bone along with ligaments holding the teeth in place. Cementum (the hard covering of a horse’s tooth) proliferates near the gum line causing the incisors to take on a characteristic rounded and overgrown appearance. This disease process can be painful and cause the horse to become reluctant to eat. E.O.T.R.H. can be treated with partial or full removal of the incisor teeth. Many clients wonder, “How will my horse eat without front teeth?” But horses tend to do well and typically go back to normal feed within 24 hours after the procedure. Steinbeck Peninsula Equine Clinics Surgery Director and dental specialist Dr. Nick Carlson routinely performs this surgery and explains, “By the time the disease has progressed enough to warrant complete incisor removal, the horse has likely already adapted to using their tongue and cheeks to graze and chew.” This procedure can be done in the hospital and usually only requires a 1-night stay. The extractions are done with the horse standing, using intravenous sedation and local anesthesia. The horse is typically fed a wet pelleted mash that evening and begins back on normal feed the following day. Owners have reported significant improvements in behavior following extraction, such as increased energy, brightened attitude, eagerness to eat, and lessened facial sensitivity. If you believe your horse might be experiencing this or any other dental problem, please call to schedule an appointment with a member of our team.

Neurological form of Equine Herpesvirus-1 — Important information about EHV and EHM from the CEH Horse Report, a publication of the UC Davis Center for Equine Health, UC Davis School of Veterinary Medicine.

Your veterinarian may recommended a foot poultice to treat a sole bruise, foot abscess or other condition. (Note that if your horse is shod, the shoe will need to be removed to place the poultice. Your veterinarian will advise you regarding shoe removal.) Wrapping a bandage around your horse’s hoof to keep the poultice in place can be tricky. In this video, Dr. Jacquelyn Dietrich shows you how to place a foot poultice and securely wrap a bandage around the hoof. (Be sure to turn up your sound!)

In this video, Dr. Danielle Price shows you how to securely wrap a bandage around a horse’s lower leg. (Be sure to turn up your sound!)

In this video, Dr. Amanda Hedges shows you how to administer liquid medications, supplements and dewormers with a syringe. (Be sure to turn up your sound!) Related resources you may also be interested in: British Equine Veterinary Association (BEVA): Don’t Break Your Vet - Worry-free Deworming McKee-Pownall Equine Services: How To Give Oral Medications

In this video, Dr. Nora Grenager shows you how to take your horse's vital signs. (Be sure to turn up your sound!) Related resources you may also be interested in: “Emergency Horse Care” (PDF) “Emergency First Aid on the Trail” (PDF) Steinbeck Peninsula Equine Clinics Emergency Services

San Mateo County Large Animal Evac (SMLAEG) provides evacuation services and shelter for large/farm animals in the event of disaster, such as wildfire or flood, or in other emergencies. These efforts include the evacuation of animals, caring for the animals in holding areas after evacuation, and facilitating the return of animals to their owner/agent. SMCLAEG is activated by the San Mateo County Office of Emergency Services, or other first responders, and its efforts are staffed by SMCLAEG's core team members and volunteers. SMCLAEG is an all-volunteer 501c3. The group also provides preparedness workshops and site inspections upon request. HOW TO CONTACT SMCLAEG: In an emergency, call 911. Tell dispatch that you need the services of the San Mateo Large Animal Evacuation Group. BE PREPARED! Visit https://smclaeg.org/preparation to learn more... Steinbeck Equine Veterinary Clinics works with SMCLAEG as their primary veterinary contact to advise on planning evacuations and during emergency evacuations. LARGE ANIMAL EVACUATION RESOURCES: • Monterey County • Santa Clara County • Santa Cruz County • San Mateo County

Watch this video of a presentation on EHM by Dr. Nora Grenager. (Be sure to turn up your sound!) Related resources you may also be interested in: California Department of Food and Agriculture (CDFA): Equine Herpes Myeloencephalopathy (EHM) Fact Sheet California Department of Food and Agriculture (CDFA): Equine Herpes Myeloencephalopathy (EHM) FAQ American Association of Equine Practitioners (AAEP): Equine Herpes Virus Resources American Association of Equine Practitioners (AAEP): Equine Herpes Virus FAQ

Watch this video of a presentation on equine allergies by Dr. Amanda Hedges. (Be sure to turn up your sound!) Related resources you may also be interested in: “Equine Allergies” (Article) by Amanda Hedges, DVM, cVA, CVSMT “Maximizing the Golden Years: Care for the Aging Horse” by Amanda Hedges, DVM, cVA, CVSMT and Nora Grenager, VMD, DACVIM

By Amanda Hedges, DVM, cVA, CVSMT, published in the San Mateo County Horsemen’s Association (SMCHA) Newsletter, Q1 2021 An Immune System Gone Awry Molecules that irritate our horse’s bodies are all around. One of the jobs of the immune system is to protect us from the harmful effects of these irritants, maintaining the balance between stimulus and an appropriate response that keeps a horse healthy. Equine allergies can occur when an irritant or combination of irritants disrupts or overwhelms the immune system’s balance. An allergic reaction may be severe and life-threatening (anaphylaxis), sudden (acute), or more slow/insidious in onset (chronic). Signs of an Allergic Reaction Signs of allergies often appear as an immune system overreaction, resulting in local or systemic inflammation. We see hives, itching, oozing, scabs, hair loss, tearing, coughing, breathing changes, nasal discharge, hair loss, poor performance, and even gastrointestinal upset. Anaphylaxis is a severe acute allergic reaction characterized by increased respiratory effort, rate, or noise, recumbency, and/or shock. Anaphylaxis is a medical emergency necessitating immediate veterinary intervention. Sometimes an allergic episode (e.g., hives) is a one-off and other times a horse has developed allergies to something in his/her environment. Restoring Balance To restore balance to the immune system in non-life threatening cases, we need a two-fold approach: 1) decrease the irritants 2) calm down the immune system. Let’s look at some common equine allergens and what we can do about them. Common Allergens Changes in the environment and the horse’s immune system can make it difficult to identify the cause of a horse’s allergic response. Some common equine allergens include: Insects: The most common culprit of chronic skin allergies is the saliva of the Culicoides fly (a.k.a. gnats, no-see-’ums). Other fly species, other insects, and even arachnids (spiders) can cause an allergic response. Environmental: Components of dust, different molds and mildews, different plants and pollens, and even some topical products can all cause allergies. Note that food allergies are not common or well-understood; it is more common for a horse to be allergic to the components of dust on hay than the hay itself. Treatment Strategies for Equine Allergies Treatment strategies focus on minimizing the presence of the allergen and influencing the immune system to restore balance. Common treatments include: Environmental management: if you know what your horse is allergic to from an allergy testing profile (see “Desensitization Injections” below), then you can minimize his/her exposure to specific irritants. General recommendations to decrease irritants revolve around fly control and dust control, both of which will add fuel to the fire of an overactive immune system. Fly control: Remove manure from the living area at least once daily. Make sure that your horse is stabled far from the manure collection area. Consider feed-through fly products, fly traps, automatic fly spray systems that use permethrin, overhead fans, fly sheets including belly coverage, fly masks including ears, fly boots, natural predators (bats, birds, wasps), and other fly control strategies. Dust: Consider wetting down your horse’s hay at each feeding. Stable your horse away from dusty arenas, and avoid riding during times of peak arena use. Good ventilation is also good. Diet change: While food allergies are not common, it is even more challenging to diagnose allergies due to dusts, molds, and contaminants in hay. A trial diet can help assess the contribution of diet to an allergy response. A novel food source, for example timothy pellets, is fed for 3 months, and the horse’s allergy signs are monitored. If allergy signs improve, then a food allergy is suspected. Other feeds can then be added to further identify the allergen. Often wetting down the feed is helpful to minimize the amount of inhaled aerosolized allergens. Medications: Steroids: Short- or long-acting steroids may be used to help suppress the immune system. Steroids can have some unwanted side effects, so use the lowest dose needed for the shortest amount of time. Combine with environmental management, antihistamine, and omega3 fatty acid supplementation for better effects. Antihistamines: A key molecule in the allergic response is histamine. Oral antihistamines, such as hydroxyzine, cetirizine, or diphenhydramine, can suppress the histamine response. Unlike steroids, these drugs are safer for long-term use though they can make some horses a bit sleepy. Your vet can advise on which drug may be the best for your horse, and the ideal duration of treatment. In horses these medications are better at preventing an allergic reaction than at treating a current one. Supplements: Some supplement ingredients can help support the body’s immune system. In addition to good quality hay or pellets and a vitamin/mineral supplement, horses with allergies may benefit from: Omega3 fatty acids: Research supports that horses fed a high dose of omega-3 fatty acids may have a decrease in allergy signs, possibly by decreasing the inflammatory response. This should be used long term as effects are not immediate. Equine-specific research is poor or lacking for other compounds reported to help with allergic reactions such as ashwagandha (found in some plants in the nightshade family), American ginseng (plant in the ivy family), astragalas (herb in the legume family), MSM (an organosulfur compound), quercetin (a plant flavanol), spirulina (a biomass of cyanobacteria), and turmeric (in the ginger family). Combinations of these ingredients can be found in brand-name supplements and in traditional Chinese herbal medicine formulations. Immunotherapy (aka allergy shots): For a personalized treatment, consider requesting an allergy test. Two test protocols are available to identify the specific allergens to which your horse is reacting. The most precise test for skin allergies is called intra-dermal skin testing. To perform this test, a veterinary dermatologist injects a small amount of different environmental irritants under the skin and then monitors the strength of the horse’s immune response at 30 min, 4 hours, and 24 hours. The second option is blood sample, while this is a more convenient way to test for allergens, it is thought to be less specific than intra-dermal testing. Following testing, a personalized allergy shot protocol is developed for your horse, with a dosing regimen to slowly introduce the allergens to your horse’s immune system without overwhelming it, resulting in a more appropriate response. Environmental management is again key to maximizing the success of this treatment plan. While the frequency of injection decreases over time, most horses require life-long treatment to keep allergy signs at bay. Allergy desensitization is a great way to manage skin allergies long-term; it greatly reduces the allergic response in most horses (though give it up to a year to work fully). There’s not much proof that allergy desensitization shots work very well for respiratory allergies. Allergies and Aging With time, both the environment and your horse’s immune system will change. New irritants can come in the form of new landscaping, new products, changes in air quality, etc. As horses age, there is some evidence that they can experience immunosenescence, or the gradual weakening of the immune system over time. Both of these factors may mean that your horse’s allergy status and immune system needs may change with time. If you notice any allergy signs, contact your veterinarian to discuss further options! Setting Expectations It may take weeks, months, or even years to find the perfect combination of immune-support and environmental control to rebalance your horse’s body. This plan may need to be regularly adjusted depending on the season. After establishing a treatment plan with your veterinarian, it may take weeks to see results. Complete resolution of all clinical signs may not be possible. With patience and persistence, almost every horse can find some degree of relief from allergies.