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- A Brief Review of EHV-1 Neurological Disease: EHV-1 Myeloencephalopathy
About EHV-1 Equine herpesviruses (EHV) are found in the majority of horses. Most horses have been exposed to the virus and have had no clinical signs or side effects. There are nine EHVs that we have been able to identify worldwide, but EHV 1, 3, and 4 are the strains that have caused clinical disease in horses. EHV-1 specifically has multiple manifestations of disease in horses: neurological form, respiratory form, and can cause abortion and neonatal death. There is also some evidence that it may cause chorioretinopathy (a disease process in the eye). Research has shown that greater than 80% of horses may be latently infected with the EHV-1 virus, but not all horses will develop clinical signs. The Science Behind EHM EHV-1 myeloencephalopathy (EHM) is still being studied today and we are constantly acquiring new information. There are multiple reports of theories describing how the virus causes neurological disease. A single point mutation in the DNA polymerase gene has been associated with neurological disease, causing the presence of aspartic acid (D) or asparagine (N) at position 752. AAEP reports that 80-90% of neurological disease cases are caused by D752 isolates, and 10-20% by N752 isolates. Recently, there has also been a proven association with a single nucleotide polymorphism at position 2254 in the DNA polymerase gene and the occurrence of EHM. The virus can become reactivated and furthers cell-associated viremia delivering the virus to endothelial cells in the uterus and central nervous system. Clinical signs occur due to the vasculitis and cellular damage caused by the virus. Infection of Horses Horses are affected through contact with respiratory secretion, aborted fetuses/placentas, or by fomites (infected objects, such as grooming tack). Following infection, a viremia is established as the virus circulates the body in infected cells. Following this, virus-infected cells are latently infected. Horses can shed virus in nasal secretions as early as day 1 of infection, and can continue to shed the virus for approximately 28 days. The virus can cause disease in infected horses or can re-activate from latency causing clinical disease in the horse. The virus can typically survive in the environment for up to 7 days, but this can vary based on the environmental conditions. Signs of EHM The incubation period of EHV is typically 4-6 days, but has the potential to be longer. Some clinical signs associated with the neurological disease may include: Fever Nasal discharge Hindlimb weakness Incoordination Loss of tail tone Lethargy Urine dribbling Head tilt Inability to rise Diagnosing EHM Clinical signs (neurological signs and fever) and isolation of the virus are how we confirm EHM. Isolation of the virus can be done using quantitative polymerase chain reaction (qPCR) from nasal swabs and blood collection. Treating and Preventing EHM After confirming EHM, implementing a strict quarantine and biosecurity measures under supervision of local and state veterinarians is key. Treatment options include anti-inflammatories and supportive care. Vaccination and biosecurity protection are the two ways to help avoid disease outbreak. No current EHV-1 vaccine has a claim to prevent EHM. Some EHV-1 vaccines can reduce nasal shedding and possibly viremia. By vaccinating your horses, you induce a strong immune response to the virus without inducing clinical disease. It is important to clean tack, equipment and the environment to inactivate the virus. Cleaning first with a detergent or soap to allow for removal of organic material (such as soil) is recommended in order to prevent disinfectants becoming inactive when they make contact with organic material. There are multiple effective disinfectants that will kill the virus, including 1:10 dilution of bleach to water. Other key points for understanding EHM prevention include: Immunity following infection or vaccination offers limited protection Boosting (routine vaccination) contributes to herd immunity to help protect individual horses It is difficult for the body to establish immunity due to “evasion” properties of this virus Early recognition and diagnosis is key Quarantine and close monitoring of suspected cases is important Exposed horses should have their temperature taken twice daily Please note that this virus is still being investigated and new research is constantly being release as we try to better understand EHM. Additional resources: AAEP: Equine Herpesvirus Resources California Department of Food and Agriculture: Equine Herpes Virus References: Allen GP. Risk factors for development of neurologic disease after experimental exposure to equine herpesvirus-1 in horses. American Journal of Veterinary Research 69, 1595–600, 2008 Diallo IS, Hewitson G, Wright L, Rodwell BJ, Corney BG. Detection of equine herpesvirus type 1 using a real-time polymerase chain reaction. Journal of Virological Methods 131, 92–8, 2006 Diallo IS, Hewitson G, Wright LL, Kelly MA, Rodwell BJ, Corney BG. Multiplex real-time PCR for the detection and differentiation of equid herpes- virus 1 (EHV-1) and equid herpesvirus 4 (EHV-4). Veterinary Microbiology 123, 93–103, 2007 Dunowska M. A review of equid herpesvirus 1 for the veterinary practitioner. Part A: Clinical presentation, diagnosis and treatment. New Zealand Veterinary Journal, 62, 171–78, 2014a Dunowska M. A review of equid herpesvirus 1 for the veterinary practitioner. Part B: Pathogenesis and epidemiology. New Zealand Veterinary Journal, 62, 179– 88, 2014b Equine Herpesvirus (Rhinopneumonitis). (n.d.) Retrieved March 7 2016, from http://www.aaep.org/-i-173.html Goodman LB, Loregian A, Perkins GA, Nugent J, Buckles EL, Mercorelli B, Kydd JH, Palu G, Smith KC, Osterrieder N, Davis-Poynter N. A point mutation in a herpesvirus polymerase determines neuropathogenicity. PLoS Pathogens 3, e160, 2007 Pusterla, N., & Hussey, G. (2014). Equine Herpesvirus 1 Myeloencephalopathy. Veterinary Clinics of North America: Equine Practice, 30(3), 489-506.
- Overview of Ringbone in Horses
By Timothy G. Eastman, DVM, DACVS, MPVM Published in Bay Area Equestrian Network March 2008 The pastern joint, also known as the proximal interphalangeal joint, is a relatively common source of lameness in horses (Figure 1: Note the smooth borders of the bones along the front of the pastern joint of this normal horse). Degenerative joint disease/arthritis of this joint is commonly referred to as high ringbone. Low ringbone refers to the same type of degenerative joint disease of the coffin joint and is much less common. Horses afflicted with high ringbone are difficult to keep sound. The area is similar to the lower hock joints in that it is a “high-load/low motion” joint, meaning the joint is subjected to a lot of pressure but undergoes very little movement. Unlike the lower hock joints, the pastern joint does not respond consistently to intra-articular injections. The diagnosis of high ringbone is based on localizing the source of the lameness to the pastern joint with nerve and/or joint blocks. Lameness can be classified as minor and only apparent with extreme exercise or severe enough to cause lameness at a walk. Radiographs and ultrasound are useful in confirming the diagnosis and determining the severity of the disease. Radiographically you see new bony growth along the front and the sides of the joint (Figure 2: Compare the new bony growth along the front of this arthritic pastern joint to the normal one in Figure 1). These bony prominences can sometimes be seen and felt prior to radiographs during the physical examination. If the disease was traumatic in origin, ultrasound can be particularly useful in identifying any concurrent soft-tissue injuries complicating the prognosis. A complete series of radiographs is necessary to determine the severity of the disease as the sides of the joint can only be seen on oblique views. Quarter Horses are predisposed to ringbone due to the rotational forces they exert on their lower limbs during the sudden stopping and turning common in Western Performance. Treatment of ringbone can be divided into medical and surgical options. Medical management of ringbone is aimed at slowing down the progression of cartilage degeneration and reducing pain and inflammation associated with the condition. Helping to “ease the breakover” of the foot will decrease the forces subjected to the front of the joint and can be accomplished by a farrier “squaring” the toe and “rolling” the shoe. Like any lameness condition, there are many ways to shoe for the same problem. Anti-inflammatories like Phenylbutazone (“bute”) are used to decrease inflammation associated with acute flare-ups of the condition and to manage horses on a long-term basis. Many horses with ringbone can be sound enough for light use by giving bute before and after exercise. Oral joint supplements alone are unlikely to be sufficient to provide relief but are thought by some to slow down the progression of the disease. More aggressive joint supplementation would include Legend? and/or Adequan?. Legend is an intravenous form of hyaluronic acid which is important in lubrication of joints and is an essential component of joint fluid. Some horses with ringbone will be sound enough for athletic use with Legend therapy alone. Adequan is an intra-muscular injection and is thought to delay the progression of cartilage degeneration. Injecting the pastern joint is not rewarding as consistently as some other joints but should be attempted to evaluate an individual horse’s response. There is tremendous variability with regards to how long an individual horse will respond to pastern joint injections. If controlling the disease with anti-inflammatories, shoeing changes and joint therapy is not sufficient to allow pain free performance, surgically fusing the joint may be the only option to provide pain free performance. While this procedure involves a major surgery, it offers the possibility of complete return to work and relief from pain for many horses. Research has shown that 2 out of 3 horses with ringbone of the forelimbs and greater than 4 out of 5 horses with hindlimbs affected will be sound enough for athletic use with surgical fusion. This joint is fused with a combination of plates and screws (Figure 3). Typically horses are maintained in a cast for several weeks, then a bandage and stall rest for several months prior to returning to full work. As with any lameness condition, your veterinarian and farrier need to work together to provide your horse with the highest level of soundness possible and to help you determine the best course of action for your particular horse.
- Enteroliths: A Rock and a Hard Place
By Timothy G. Eastman, DVM, DACVS, MPVM Published in Bay Area Equestrian Network March 2006 Enteroliths are one of the leading causes of severe colic in the state of California. The word enterolith is derived from the Greek terms “entero” meaning intestinal and “lith” meaning stone (Figure 1). The high incidence of enterolith formation in California is presumably due to the mineral content of our hay and water. Commonly referred to as stones, enteroliths are composed of struvite crystals that coalesce around some central object like a pebble or a small piece of wire ingested by the horse. When you cut an enterolith in half, you can frequently visualize a central body with rings of mineral deposits around it resembling rings in a tree trunk. The stones can be small and passed unnoticed in the manure or large enough to cause life threatening obstructions. The largest one I have seen was the size of a basketball. When they are round in shape, it usually means they are the only enterolith present, when several stones are adjacent to each other, they often become pyramid shaped by rubbing against each other. Enteroliths are a very important cause of colic in California and several other states. All the precursors of the struvite crystals (magnesium, ammonium and phosphate) are readily abundant in our water as well as our hay. It is widely recommended to limit alfalfa hay to 50% or less of a horse’s roughage because horses fed predominantly alfalfa hay are statistically more likely to develop stones than other horses. While enteroliths have been found in most breeds of horses, there is a breed predilection for Arabians and Morgans. The classic presentation for a horse with an enterolith in many practices would be a 10 year old Arabian horse fed predominantly alfalfa hay with a history of multiple colic episodes. Enteroliths take approximately 2 years to form a sufficient size to cause an obstruction. Therefore, horses with small enteroliths may or may not exhibit colic signs In many cases, there is a high index of suspicion based on breed and diet history. Because the stones can move within the large intestine, they can cause an obstruction with resultant build up of feed and gas causing pain, and then roll back out of the way allowing gas and feed to pass. When this happens, horses can have several episodes of mild to moderate colic over a relatively short period of time. In horses with suspected enterolithiasis, abdominal radiographs (x-rays) are the most likely route to a diagnosis. In a horse held off feed for 12-24 hours, enteroliths will be identified on abdominal radiographs greater than 80% of the time. Enteroliths too large to pass in the manure must be removed surgically. Almost every year, the most common cause of emergency abdominal surgery in California is stone removal. Counter-intuitively, the worst form of the disease is not the largest stones. A baseball sized stone that has passed from the large colon into the small colon causes more problems than their larger counterparts which are too large to leave the large colon. Baseball sized enteroliths can cause 100% obstruction and severe pain. If left untreated, the small colon can rupture causing peritonitis and resulting in death of the horse. Generally colic surgery for the removal of an enterolith has a very good prognosis. Greater than 90% of horses undergoing colic surgery for enterolith removal will survive and go back into full work. However, enteroliths that have moved into the small colon have a somewhat worse prognosis for surgical correction than their large colon counterparts. Unlike the small colon, almost the entire large colon can be exteriorized (lifted out of the abdomen) during surgery, allowing stone removal to be accomplished in an isolated area. This minimizes the chance of contamination of the abdomen with intestinal contents. Prevention of stone formation can be best accomplished by limiting the amount of alfalfa to less than 50% of the diet, housing horses in an area not known for stone formation, and attempting to acidify the diet. One cup of Apple Cider vinegar fed twice daily is commonly used in an effort to lower the pH of the large intestine to decrease the likelihood of stone formation. Additionally, a product called Restore® claims to be effective at reducing enterolith formation and possibly even an alternative to “dissolving” enteroliths in horses with stones not requiring immediate surgery.
- Fractures in Horses: The Good, The Bad, and The Ugly
By Timothy G. Eastman, DVM, DACVS, MPVM Published in Bay Area Equestrian Network August 2007 After Kentucky Derby winner Barbaro underwent surgical repair of a severe fracture many equine veterinarians were hearing the same statement “I didn’t think you could fix a broken leg in a horse.” The truth is some you can and some you cannot. This article will describe recent advances in fracture fixation in horses and attempt to clarify why some fractures are considered “good” fractures and some are considered “bad.” The first sign of a fracture is generally a non-weight bearing lameness. The first thing to rule out is the most common cause of severe lameness in horses, the foot abscess. With foot abscesses the foot is frequently warm and the pulse to the foot is increased. Start at the hoof and work your way up the limb applying pressure every several inches around the limb to check for other sites of pain, heat or swelling. The horse should be confined and a veterinarian called immediately to help differentiate the two. Sometimes with fracture of major long bones the diagnosis is unfortunately very easy due to instability of the leg. With some fractures the goal will be returning a horse to full athletic soundness. In other instances you are attempting to save their life for “pasture” soundness. Which ones are good and which ones are bad can be very surprising and should be evaluated by someone specializing in fracture repair. The cost associated for repair of many fractures can vary tremendously depending on the duration of hospitalization, number of implants (plates and screws etc.), type of surgery needed etc (See Figure 1: Radiograph showing use of large number of implants). The biggest challenge facing equine surgeons with regards to fracture repair is the fact that horses for the most part need to remain weight bearing on all 4 limbs. This is true even in the case of a fracture. If a person has a serious fracture of a limb, we are generally confined to bed rest for long periods of time and then transitioned to a wheel chair or crutches and possible a walking cast if all goes well. Horses need to be able to put weight on a fractured limb immediately after surgery. Add in the fact that many of our equine patients weigh well over 1,000 pounds and are “fight or flight” animals and the challenges become obvious. Most fractures even in large horses could be repaired but the opposite (“good”) leg needs to be able to bear weight. If the good leg supports too much of the horses body weight for too long a period of time, the support structures of that leg start to break down frequently leading to laminitis. This is why it is better to have a fracture of the hind limb than of the forelimb. Forelimbs must also support the weight of the head and neck. Laminitis of the “good” leg is called “support limb” laminitis and represents one of the most serious forms of the disease (this is what ultimately led to the demise of Barbaro). Body weight is the primary reason that fractures in foals and ponies tend to carry a much more favorable prognosis than full sized horses. In general, most fractures in foals less than approximately 500-600 pounds are candidates for repair (see Figure 2: Radiographs showing cannon bone fracture in foal and repair). As body weight increases, the biggest determining factor for prognosis becomes the bone involved. In general, full sized horses with a fracture below the knee or hock may be candidates for surgical repair. Fractures above the knee or hock in full sized horses carry a poor prognosis unless the bones are not displaced at all. X-rays are generally needed to provide an accurate prognosis. Other factors include where in the bone the fracture occurred (i.e. how close to the middle), whether or not the fracture extends into a joint, the number of pieces involved, and whether or not the skin over the fracture is intact (a “closed” fracture) or has penetrated the skin (an “open” fracture). The first-aid applied can be of paramount importance in improving chances for survival. Equine veterinarians are trained in how to best prepare a horse with a fractured limb for transportation to a surgical facility. Improper first-aid can lead to a closed fracture becoming an open one. In general, open fractures have a much lower prognosis and a much higher cost associated with treatment. The reason for this is the next big challenge in fracture repair, infection of the implants can be a very serious complication and repair of open fractures have a higher incidence of infection. As bacteria gain access to the stainless steel implants they may secrete a “biofilm” that can prevent the access of antibiotics and lead to loosening of the screws and plates used in a repair. Antibiotics given intravenously or intramuscularly often are not sufficient to combat infected implants and a race may begin where the fractured bone hopefully heals before infected implants need to come out. Some of the biggest recent advances in fracture repair in horses have been in the treatment and prevention of infections. There are very few implants used in fracture repair in horses that are designed specifically for horses, most are made for people. Although it seems intuitive that horses would just need much bigger plates, the laws of physics and the amount of skin present limit the size of the plates that may be used. Plates used in fracture repair are designed to compress the fractured bone ends together. Plates and screws are oftentimes not sufficient to allow a horse to bear weight after surgery so some type of cast is frequently needed. A “transfixation cast” is sometimes placed due to the fact that this type of cast can support the majority of the weight of the limb (see Figure 3: Transfixation cast). With transfixation casts, large pins are placed through the bone above the fractured bone and then incorporated into the cast. This transfers the weight of the limb through the pins to the cast. These casts are not without risk as additional fractures can occur through the holes used to place the pins. However, the added protection of a transfixation cast can sometimes be the difference between success and failure. One of the most stressful times in repair of a fracture is getting the horse from the operating table to back on their feet. Options to help minimize the chances of the repair falling apart include pool recovery systems like used on Barbaro at New Bolton Center, recovering in a sling, or using a system of ropes on the head and tail to assist in standing (see Figure 4: Horse recovering from anesthesia in a sling). In closing, surgical repair of fractures in horses will always remain a huge challenge for equine surgeons due to the above mentioned factors. However, many fractures that were once hopeless are now fixable. If you suspect your horse has a fracture work with your veterinarian to decide whether or not surgical repair should be attempted. Even though fracture repair has made huge advances in recent years, it can still be a major undertaking and the risks and benefits should be thoroughly weighed before choosing repair.
- Management of Wounds in Horses
By Timothy G. Eastman, DVM, DACVS, MPVM Published in Bay Area Equestrian Network October 2006 Horses are “fight or flight” animals and have a great propensity towards skin wounds which generally occur while avoiding a potential threat, are surprised, or by accident. Oftentimes horse owners are faced with the dilemma of examining a wound and determining whether or not a veterinarian needs to be contacted. The aim of this article is to clarify some differences between wound types with regards to severity and prognosis, as well as provide an overview of current concepts in wound management. Abrasions are wounds involving only the superficial layers of the skin. As they are generally not all the way through the skin, they can not be sutured. They may however be very painful and can cause a great degree of lameness. If severe, they should be closely evaluated to make certain that no portion of the abrasion goes full thickness into an important structure. Generally they respond well to hydrotherapy, sweat-wraps and anti-inflammatories (“bute”). Horses do get bruises or contusions, they are just more difficult to see than in humans because of their thick hair coat. These are treated according to severity. Puncture wounds typically create a lot of necrosis of deep muscle tissue and are generally treated by daily lavage (“flushing”) and antibiotics. Because of the degree of deeper trauma, oftentimes these are not closed primarily but are allowed to heal by second intention. One common puncture wound is nail punctures to the feet. Where the nail goes is of paramount importance and can be very difficult to determine once the nail is removed. For this reason, most veterinarians recommend leaving the nail in place until an x-ray can be taken to determine what structures are involved (see Figure 1: Radiograph (x-ray) showing a nail puncture to the foot that missed all vital structures). Most don’t involve vital tissues and are managed similarly to foot abscesses. Those that involve vital structures (primarily the navicular bursa) are very important and managed aggressively like infected joints discussed later in this article. The most common type of wound in horses is a laceration (“cut”) of the face or limbs. Most lacerations can be sutured if caught early enough and should be evaluated by a veterinarian. Most wounds if sutured will heal in 2 weeks with minimal scar formation. As in people, laceration repairs in horses sometimes fail. If this occurs contact the veterinarian who performed the repair as he or she may want to re-evaluate the wound and change game plans. When a laceration is Radiograph showing a nail puncture to the foot that missed all vital structures. sutured closed, it is said to heal by 1st intention or “direct” healing. A laceration allowed to heal on its own by heals by 2nd intention or “indirect” healing. Sometimes veterinarians allow a wound to be treated under a sweat wrap for 1 or more days prior to closure, this is “delayed primary closure”. Delayed primary closure is sometimes used when a laceration has passed the “golden period” which is the time (approximately 6 hours for the average wound) in which a wound is likely to be managed by suturing because contamination and/or infection has not become established. The BIG thing is that if the wound is over a synovial structure (a joint, tendon sheath or a bursa) it needs to be treated immediately as wounds involving these structures can be life threatening. Tendon sheaths occur in front of and behind most joints of the limbs of horses. They serve to provide fluid identical to joint fluid to lubricate tendons as they glide over bony prominences. A bursa is a synovial fluid filled sac which, like a tendon sheath, serves to facilitate tendons gliding over bony prominences. The navicular bursa is often treated in navicular disease, distension of the olecranon bursa is a “shoe boil”, and distension of the calcaneal bursa is a “capped hock”. It can be difficult to determine if a wound involves a synovial structure (joint, tendon sheath or bursa) but a good rule of thumb is if a wound is within a hands breadth of the middle of a joint, involvement of a synovial structure is more likely. More on this later. So, if you identify a laceration on a horse under your care, the following steps should be taken. First evaluate the degree of bleeding or hemorrhage. If you can “count the drops” as the wound bleeds, you have plenty of time to treat the wound. If however, there is a steady stream of blood shooting from the wound under pressure in veterinary school they preach “Don’t Panic, Apply Direct Pressure, Clamp, & Ligate”. The first two things, don’t panic and apply direct pressure should be performed by the caretaker. Direct pressure will decrease most hemorrhage to a safe level. This can be accomplished with a towel, gauze or even just a hand until a bandage can be applied. Bandage material should be a part of everyone’s first aid kit at the barn and in the trailer. A bandage of just good thick cotton material and “vet-wrap” is generally sufficient to maintain pressure on a lacerated vessel until a veterinarian arrives. If hemorrhage is minimal or it has been controlled the wound should be thoroughly cleaned. Betadyne or Nolvasan are the two anti-septics used most commonly in horses and both are very effective. Cold hosing a wound is a good first line of defense followed by thorough scrubbing with an anti-septic. Once the wound has been cleaned, it is generally safe to apply an antibiotic ointment (Furacin, Nolvasan, Silvadene etc) and a light bandage if possible. This is now the time to contact a veterinarian. You have assessed the wound location and can provide a reasonable description of the wounds proximity to the nearest joint, as well as the thickness of the wound and applied first-aid. It will be the call of the veterinarian whether or not a visit is indicated. If you can pull the skin edges apart, it is a full thickness laceration and most veterinarians will recommend an evaluation unless it’s very small and in a safe spot. Virtually any equine veterinarian can tell you horror stories of very small wounds in a bad spot that were not properly managed and led to the horse’s ultimate demise so they don’t mind being consulted. The vast majority of wounds are superficial and do not involve any vital structures. In general, they will be managed by having the surrounding hair clipped and being thoroughly cleaned, the edges of the skin around the wound “blocked” with a numbing agent (lidocaine or carbocaine) and primary closure will be attempted. Wounds of the lower limb may not be blocked directly but be desensitized by having their nerve supply temporarily deadened. Some wounds because of their location or the nature of the patient require general anesthesia. Oftentimes, wound edges will be “freshened up” by trimming the margins. This makes a traumatic wound more like a surgical incision which tends to do better. Whether or not they will need to be covered by a bandage generally depends on veterinarian’s preference as well as location (most wounds of the lower limb are bandaged). The same is true about indication for antibiotics. All wounds and circumstances are different and some don’t mandate antibiotics at all while others require several weeks of intravenous antibiotics. Most are managed with oral antibiotics administered by the owner under the guidance of the veterinarian. The lower legs and face are probably the most common sites for lacerations. Wounds around the face have a very good blood supply and usually heal very well with primary closure. In many instances, the same wound on a leg would be allowed to heal on its own but on the face closure is attempted. Typically the sutures will be removed from any of these wounds in 12-14 days. Wounds involving the foot, especially the heel bulbs are under a lot of tension while horses walk which is why they are frequently managed by a “foot cast” (see Figure 2: A foot cast extending up to the mid-pastern area). This is a cast that you can generally manage at your barn as it does not extend up above the fetlock. Heel bulb lacerations tend to heal much better in these casts and you actually probably save considerable money in the long run as several bandages typically cost more than one cast. These casts are typically removed in 2-3 weeks. Another way to manage wounds that are under tension, especially those further up the limb is the use of “stents”. Stents are just devices that distribute the pressure of the suture over a wider area. This can be accomplished with plastic tubing placed between the suture and skin, buttons, and a whole host of other ways. Lacerations involving joints are a whole different thing. Once a wound communicates with a synovial structure, it is assumed that the structure is infected, and it does not take very many bacteria at all to do this. Septic arthritis is the result of an infected joint and due to the damage the bacteria cause to the cartilage and surrounding structures as well as the amount of pressure exerted on the joint capsule as fluid pressure rises, horses can be as lame as if they had a fracture. The resultant arthritis can be severe enough to cause permanent lameness. Also, the “good leg” opposite the wound now has to bear more than its fair share of the horse’s weight which can lead to laminitis. Whether or not a synovial structure is involved is the first thing your veterinarian will try to determine. If that assessment cannot be made visually, further precautions are necessary. If a wound is near a joint for example, the surrounding area is typically cleaned very thoroughly and a sterile needle will be placed into the joint away from the wound (see Figure 3: Sterile fluid being injected into a fetlock joint to determine if the wound communicates with the joint). The joint is then distended with sterile saline and the wound is closely inspected for fluid leakage. If fluid injected from a syringe away from the wound comes out of the wound, you have communication from the wound to the joint and a life threatening condition. The good news is modern medicine has made huge advances in the management of infected joints. The bad news is it is not always successful and is very expensive to treat. Infected joints are generally treated by lavaging large volumes of sterile fluid through the joint to flush out the bacteria and the toxins the bacteria produce. This is typically done under general anesthesia. A regional limb perfusion is a procedure that can also be of tremendous value (see Figure 4: A regional limb perfusion of a horse with an infected joint). With a regional limb perfusion the target area of the limb is isolated by one or two tourniquets, and a large dose of a very potent antibiotic is placed in a vessel near the wound. The tourniquet holds the antibiotic near the wound for 20-30 minutes and allows the area to be “supersaturated” with the antibiotic. The levels of antibiotic achieved at the wound are not attainable by conventional routes. Systemic antibiotics will also be a big part of the management of these wounds and are typically given by the intravenous and or intramuscular route as these antibiotics are usually better suited than oral antibiotics. The prognosis for soundness varies tremendously with wounds involving infected joints and are determined on a case by case basis. Lacerations involving tendons are another major cause for concern. The tendons of the distal limb run directly in front and behind the legs. If while examining a wound you notice glistening white tendon like material in the wound, have a handler hold the horse still until a veterinarian can get there as soon as possible. The severity of tendon lacerations depends on location and extent of damage. In general, tendon lacerations of the front of the limb (“extensor tendons”) do well, lacerations involving the tendons of the back of the limb (“flexor tendons”) are serious. Full thickness involvement is obviously more serious than partial thickness ones as is multiple tendon involvement more serious than single tendon involvement. Hindlimbs have a better prognosis than forelimbs with tendon lacerations and infected joints because they don’t have to bear the weight of the head and neck. Flexor tendon lacerations are generally managed with some form of cast or splint and prognosis for full athletic soundness varies but is not typically great (see Figure 5: A splint supporting the back leg of a horse with a severe flexor tendon laceration). In summary, most wounds should involve at least a phone call to your veterinarian, especially if they are near a joint or tendon. Being familiar with basic anatomy will be of tremendous value in helping describe wound location and how serious they are. Have your veterinarian help put together a first-aid kit for your barn or trailer and become familiar with its contents. Doing all the initial steps right are the biggest keys to a successful outcome.
- What Does It Mean to Be a Specialist?
By Laramie Winfield, DVM, DACVIM, cVA, CVMMP Veterinary medicine has changed in recent years, with more practitioners choosing to become board certified in a specific area of practice. This allows us to have a more precise focus in one particular area like surgery or medicine. To best serve your horse's needs, Steinbeck Peninsula Equine Clinics provide veterinarians board certified in multiple different specialties including general equine practice, surgery, internal medicine, and sports medicine and rehabilitation. Learn more about what it means to be a specialist... Learn more about some of our specialtIes: Equiine Practice Internal Medicine Surgery Sports Medicine and Rehabilitation
- Ultrasound: An Invaluable Tool In Equine Medicine
By Wade Tenney, DVM Published in Bay Are Equestrian Network in June 2007 There was a time when the only practical use of ultrasound in equine medicine was to diagnose pregnancies and bowed tendons. With recent advancements in ultrasound technology, the image quality has improved tremendously. It is now possible to identify subtle injuries and to image parts of the horse that before now could not be seen. In fact, you may be surprised at the number of ways that ultrasound is being utilized in equine medicine. The cornerstone of ultrasound use in equine athletes still centers around the tendons and ligaments that course down the back of the front and hind limbs. These supporting structures are under a tremendous amount of stress during exercise, making them prone to injury. We are able to evaluate the cross-sectional area (size), echogenicity (density) and fiber pattern of these soft tissue structures. Once the injury is diagnosed, recheck ultrasounds (generally at 60 day intervals) allow the veterinarian to evaluate the healing and strength of the injured tendon/ligament. This information allows the veterinarian to constantly adjust and customize your horse's rehabilitation program to prevent re-injury. The evaluation of joints is another important use of ultrasound in our equine athletes. While radiographs (x-rays) give us important information regarding the bony changes within a joint, we need ultrasound to evaluate the soft tissue structures within the joint. Some of the structures we evaluate include the joint fluid, joint lining (synovium), collateral ligaments, menisci and articular cartilage. The joints that we commonly evaluate via ultrasound include the coffin joint, fetlock joint, hock, stifle, elbow, shoulder and even the temporomandibular joint. By combining the information from radiographs and ultrasound, your veterinarian can get a very thorough picture of the condition of the joint. Ultrasound guided procedures have allowed veterinarians to fine tune many diagnostic and therapeutic procedures. Once the target area is visualized with ultrasound, a needle or biopsy instrument can be introduced and visually guided directly to the target area. For instance, ultrasound can guide a needle into deep joints such as the neck or hip so that they may be blocked or treated with steroids. Ultrasound can aid in the biopsy of deep organs such as the lung, liver or spleen. It can also be used to obtain a sample from a deep fluid pocket or internal abscess. One increasingly popular treatment is ultrasound guided injection of stem cells into a core lesion within a tendon or ligament. Without this useful tool, many disease processes would go undiagnosed or untreated. Fortunately, heart problems are not that common in horses. However, if your veterinarian diagnoses a heart murmur in your horse, ultrasound is an invaluable tool to provide information regarding cause and prognosis of the murmur. Ultrasound can tell us which valve is affected and how severe the regurgitant blood flow is. Ultrasound may also help guide the treatment plan; for instance, the treatment will be very different for a heart valve with an infection versus a valve with a degenerative lesion. Some ultrasounds have specialized programs to determine the size of heart chambers, thickness of walls, and the speed of blood through a valve. This information can be used to give a prognosis and potentially help determine if your horse is safe to ride. Ultrasound of the equine abdomen is more commonly implemented, especially in cases of colic, diarrhea, weight loss and liver or kidney disease. On the right side of the horse, ultrasound can visualize the cecum, right kidney, right liver lobe and right dorsal colon. On the left side of the horse, we can evaluate the spleen, left kidney, stomach and left liver lobe. The small intestine and large colon can be seen throughout the abdomen and can be evaluated based on size, motility and bowel wall thickness. Internal abscesses, such as those associated with pigeon fever or Strangles, may also be visualized with ultrasound. In many cases involving eye trauma, examination of the eye may not be possible due to swelling of the eyelids or severe cloudiness of the cornea. Ultrasound allows the veterinarian to evaluate deeper structures and assess the amount of damage within the eye. The iris, lens, optic disc and retina are all readily visible with ultrasound. This allows immediate treatment to begin without waiting for the swelling to subside so that a complete ophthalmic exam can be performed. As you can see, virtually every part of the horse's body can be evaluated to some extent with ultrasound. Ultrasound is a relatively inexpensive and non- invasive means to gather a lot of information regarding disease processes in your horse. So, the next time your horse presents himself as a "diagnostic challenge" ask your veterinarian if ultrasound might shed a little light on the problem...
- The Great Vaccination Debate
By Laramie Winfield, DVM, DACVIM, cVA, CVMMP Annual vaccinations are a large part of our preventative health strategy here at Steinbeck Peninsula Equine Clinics. As your veterinarians, we are happy to be one of your main sources of information concerning your horse’s health and vaccines. However, we also realize that many owners would like additional opinions and sources of information. While there are many excellent sources of information available to you on the internet, there are also many sources of information that are misleading, incorrect, and full of misguided advice. The American Association of Equine Practitioners (AAEP) provides a compendium of sound information and Guidelines for Equine Vaccination. Should you vaccinate your horse or not? An article from Horse & Rider titled "Vaccine Wars: The Great Debate" does an excellent job of answering many of the common questions we hear about vaccination and if it is necessary for your horse. We do recognize that some horses are very sensitive to vaccination and alternative vaccine forms and schedules may be best for those horses. Each horse and situation may benefit from a different protocol and we are happy to develop an individual plan for you and your horse. Rabies is a fatal disease that can be transmitted to humans. Given the severity and significance of rabies infection it is included in the core vaccines recommended for horses. The UC Davis School of Veterinary Medicine offers more information in the article "Do Horses Need Annual Rabies Vaccination?" West Nile is a mosquito born viral disease transmitted to horses causing neurologic signs, fever, and in 30% of horses is fatal. Given that available vaccines are highly effective at preventing disease and safe to administer we strongly support the administration of vaccines to protect against West Nile Virus. The California state government monitors new cases an offers a website with updates and more information on West Nile virus.
- AAEP Vaccination Guidelines
The AAEP Vaccination Guidelines are intended to be a reference for veterinarians who utilize vaccines in their respective practices. They are neither regulations nor directives and should not be interpreted as such. It is the responsibility of attending veterinarians, through an appropriate veterinarian-client-patient relationship, to utilize relevant information coupled with product availability to determine optimal health care programs for their patients. Based on the professional judgment of those involved with the development of these guidelines, the recommendations for vaccine administration in this document may differ from the manufacturer’s recommendation. However, it is incumbent on each individual practitioner to reach a decision on vaccine usage based on the circumstances of each unique situation and his or her professional experience. Information provided in these guidelines addresses only those products licensed by the United States Department of Agriculture (USDA) for use in horses (including draft and pony breeds). There are limited data regarding the use of vaccines in other equidae (i.e. asses, donkeys, mules, miniature horses, and zebra); vaccination of these animals is at the discretion of the attending veterinarian
- Silicosis: A Tragic Irreversible Lung Condition in Horses
By Matt Durham, DVM, DACVSMR Published in Bay Area Equestrian Network February 2007 In the scenic foothills of the Central Coast of California, there lurks a quiet problem that can lead to severe disease in our horses. Commonly known as ‘chalk rock’, this dusty rock form can cause an irreversible lung condition known as silicosis. Silicosis is a well known occupational disease in humans, typically caused by inhaling rock dust created in mining, masonry work, sandblasting, and many other industries where rock is crushed into an easily-inhaled dust. In horses, the disease was first diagnosed in the late 1970s in the Monterey-Carmel area. Before this time, area veterinarians had noted signs of respiratory disease, but had been unsure of its cause. For years, silicosis in horses was believed to be isolated to this small region. But as awareness of the disease increased, cases started to be diagnosed in other parts of the state. What Causes Silicosis? Briefly, silicosis is caused by inhaling silica dust small enough to travel all the way into the smallest airways and air sacs in the lung. Some sources incompletely describe silicosis as a lung disease caused by inhaling quartz dust. As will be discussed in the section titled Silicates, other crystal forms of silica can also cause silicosis. Once the dust particles become lodged in the lung, the body mounts a strong immune reaction. While bacteria or pollen can be broken down and removed from the lung, silicates can not. This causes an ongoing process which can lead to scarring of the lung, and, in people, certain auto-immune disorders. History In humans, silicosis is a fairly well understood but frustrating disease. As an occupational disease, silicosis may have been recognized by ancient Egyptians, and was described well by Agricola in 1556.Even now, there is no cure. Occupational safety measures have dramatically decreased the incidence of the disease, but cases still occur. The most notorious occupational incident occurred in the early 1930s when at least 700 workers died from silicosis. Workers came from all around to tunnel through a mountain in Gauley Bridge West Virginia, eager for any type of work during the Great Depression. The tunnel was to be used to carry water for a new hydroelectric plant. Although it was well understood at the time that silicosis was a risk if dry-drilling was used, the contractors chose this method over the much safer, but slower, wet-drilling technique. Silicates Silicates are crystalline forms of the element silica. By far the most widespread crystal of silicate is quartz, which is present in most rock types. The form which causes silicosis in horses is cristobalite. Cristobalite causes a more severe reaction in the lung than quartz does. This crystal is present in abundance in the Monterey/Carmel Valley areas. Geologists refer to this particular deposit of rock as the Monterey Formation. Although this rock type is common in this region, it is present from Point Reyes to San Onofre in the coastal ranges, with outcroppings in the San Joaquin valley, and as far south as Baja California. The Monterey Formation developed in shallow seabeds during the Miocene epoch (between 5 and 20 million years ago) from deposits of microorganisms known as diatoms. Diatoms have a non-crystalline form of silica in their structure which, over millions of years, becomes compressed into crystalline forms. Initially, the crystal formed is cristobalite, but with more time, quartz can be formed. Many of the soils of the Monterey Formation have high levels of cristobalite. These soils are often referred to as ‘chalk rock’ locally, as they tend to be dusty and light. (True chalk is actually limestone, which contains no silica.) Geologists refer to some of the various subsets of the Monterey Formation as porcelanite, chert, siliceous mudstone, and siliceous shale. For the rest of this article, the term siliceous soils will be used. Cristobalite can also be formed through volcanic activity. The Sonoma volcanic soils are a likely source of the cristobalite responsible for silicosis in horses from this region. Exposure Areas with siliceous soils are typically in foothill areas. Often, cases are seen not long after recent construction has disrupted the soil, creating a dusty environment. The horses inhale the dust over days to months or even years. Depending on a variety of factors, affected horses may show no signs or could develop severe respiratory compromise. Rate of exposure and individual immune response probably play the biggest roles in terms of severity of signs. Clinical Signs Affected horses will sometimes develop a cough, an elevated respiratory rate (normal resting rate for a horse is typically around 8-16 breaths per minute), flared nostrils at rest, and/or exercise intolerance. It is very important to remember that these signs are typical of respiratory compromise in general, so are not specific for silicosis. Diagnostics Lung x-rays are the simplest test to perform to diagnose silicosis. Abnormal x-rays exhibit classical signs for silicosis in advanced cases. Early or mild cases may have subtle, non-specific lung x-ray findings. Lung x-ray of a horse, showing severe lung fibrosis from silicosis (normal lung is nearly black on x-rays) Samples of fluid and cells from the lungs can be obtained in two ways: a transtracheal wash, or a bronchoalveolar lavage (BAL). Affected horses may exhibit pink crystals within a type of white blood cell called a macrophage. The crystals are silicate crystals, and the macrophages are the cells that attempt to destroy or remove the particles. At Steinbeck Country Equine Clinic, we typically choose the BAL technique for this diagnosis. Ultrasound is occasionally useful in imaging silicosis cases, particularly with advanced cases. Most silicosis changes are deep within the lung, and the ultrasound beam does not penetrate through the air present within the lung, so less advanced cases do not show up well. Treatment In horses, as in humans, there is no cure for silicosis. Treatment involves removing the horse from the silicate dust as well as from other types of dusty or moldy environments. In mild to moderate cases, short courses of steroids and bronchodilators can get a horse through a flare-up. Affected horses may not be able to regulate their temperature, so it is important during hot weather to provide shade, or other means to create a cool environment. Silicate Associated Osteoporosis In horses living on siliceous soils, certain bone deformities and fractures can develop. Horses with silicate associated osteoporosis can develop signs years after moving away from an area with siliceous soils. This disease typically occurs in horses with a longer-term exposure to silicate dust. The bones develop osteoporosis which, as in people, can predispose to fractures. Horses typically develop bowed shoulders, a swayed back, and often a stiff neck secondary to osteoporosis and secondary arthritis in the cervical spine, although early cases have no obvious outward signs. Horse with silicate associated osteoporosis, showing swayed back and bowing of the shoulder blades. Footing material is siliceous shale. [Image courtesy Dr. Coral Armstrong] Body soreness and exercise intolerance are common in horses with silicate associated osteoporosis, and some horses may develop neurologic signs. Fractures are most common in the spine, ribs, pelvis and shoulder blades. Affected horses may or may not have respiratory signs, but will typically have some degree of respiratory involvement. Diagnosis of silicate associated osteoporosis is simple in advanced cases, where outward signs alone are diagnostic. In mildly affected horses, diagnosis is challenging, because vague lameness or stiffness may be the only signs (as can be seen in countless other disease processes). In these cases, nuclear scintigraphy (bone scan) is very sensitive at detecting the disease. Ultrasound of the shoulder blades and x-ray images of the neck can help define the disease as signs progress, but will often be normal in early cases. Treatment for silicate associated osteoporosis with typical anti-inflammatories such as phenylbutazone is often minimally effective. Sometimes steroids will improve the comfort level, but not always. Intravenous Legend® can help with the arthritis pain in the neck that commonly develops, but does not help with bone pain. Tildren® may help decrease bone pain and possibly stop the progression of osteoporosis. Tildren® is in the same family of drugs as Actonel®, Fosamax®, and Boniva®, which are used to treat osteoporosis in people. Recently, zoledronate (Zometa® or Reclast®) has been used experimentally at UC Davis, with promising results. Prevention of Silicosis Prevention of silicosis requires limiting the amount of inhaled silicate dust. Areas of new construction should be avoided. Dry lot situations should be altered as much as is possible. The ideal solution is to plant grass over the area and irrigate throughout the summer months, but this is often very impractical. Incorporating organic material into the soil can help to retain moisture and minimize dustiness. Wood chips or composted manure are fairly effective and inexpensive methods. Topsoil brought in from an unaffected area may also be effective. Future Directions in Silicosis Study Control of the excessive immune response is the primary direction of research in the human field. In horses, the primary areas of study involve silicate associated osteoporosis. We are currently working in conjunction with researchers at UC Davis on studies to determine the exact nature of the bone disease. Currently, Dr. Murray is studying two blood tests, which appear to be promising in detecting the disease process. With earlier detection and monitoring of bone density, we hope to be able to prevent the catastrophic fractures and other bone-related pain.
- Long Toes in the Hind Feet and Pain in the Gluteal Region: An Observational Study of 77 Horses
By Richard A.Mansmann, Sarah James, Anthony T.Blikslager, Kurtvom Orde Published in the Journal of Equine Veterinary Science (Purchase access to read the complete article) Abstract This study deals with the relationship between long toes in the hind feet and pain in the gluteal region in horses, and the remedial value of trimming/shoeing that moves the breakover point back at the toe. 77 client-owned horses were studied, 67 shod riding horses retrospectively and 10 barefoot broodmares prospectively. The 10 mares were evaluated twice, and 24 of the 67 riding horses were re-evaluated at the next shoeing, for a total of 111 observations. Each horse underwent gluteal palpation and lateral radiographs of both hind feet. Toe length was quantified as breakover distance (BD), the horizontal distance between the tip of the third phalanx and the dorsalmost point at which the wall/shoe was in contact with the ground. The BD was then shortened with trimming +/− shoeing to a length of ≤15mm (shod horses) or ≤20 mm (barefoot horses). The 24 riding horses were re-evaluated 4-6 weeks later and the 10 broodmares 1 week after trimming. The results showed that of the 67 riding horses, 75% were positive for gluteal pain at initial evaluation. The mean BD for the positive and negative horses was 24.2 ± 1.3 mm and 18.8 ± 2.0 mm, respectively (p = 0.04). At the next shoeing, the mean BD was 10.9 ± 2.3 mm and gluteal pain was improved in all 24 horses; 20 horses (83%) were negative and 4 horses (17%) were now only mildly positive. The 10 broodmares were all positive for gluteal pain initially. The mean BD before and after trimming was 23.7 ± 1.2 mm and 10.9 ± 1.1 mm, respectively. One week later, gluteal pain was improved in all 10 mares; 8 mares (80%) were negative, and the other 2 mares (20%) were only mildly positive. The conclusion is that excessive toe length in the hind feet may be accompanied by pain in the gluteal region and, in our experience, may be associated with gait or performance problems. Shortening the toe can alleviate this pain within days or weeks. Aiming for a BD of between 0 and 20 mm probably is appropriate for the average-size horse.
- Pemphigus Vulgaris in a Welsh Pony Stallion: Case Report and Demonstration of Antidesmoglein Autoant
By Verena K. Affolter, Dominic Dawson, Keita Iyori, Koji Nishifuji, Thierry Olivry, Catherine A. Outerbridge, Anna C. Renier, Yu Hsuan Wang, Stephen D. White, and Laramie D. Winfield Published in the Equine Veterinary Journal (Purchase access to read the complete article) Abstract Hypothesis/Objectives: To describe the clinical, histological and immunological findings of an equine case of pemphigus vulgaris, including the demonstration of antidesmoglein (anti-Dsg) autoantibodies. Case Report: The diagnosis of pemphigus vulgaris was confirmed in a 9-year-old Welsh pony stallion with both direct and indirect immunofluorescence and immunoprecipitation studies, the latter identifying circulating anti-Dsg3 IgG. Treatment with immunosuppressive medications was initiated. Lesions were seen in the perineal area, sheath, mane, tail, eyelids, coronary bands and mucosa of the mouth and oesophagus. Initial corticosteroid treatment improved the clinical signs, but the onset of laminitis necessitated a reduction in dosage, which was associated with a recurrence of lesions and development of oral ulcers. A corneal ulcer developed after 60 days of treatment. Despite treatment with azathioprine, gold salts and dapsone, the disease progressed and the pony was euthanized. Postmortem examination showed additional lesions of the cardia of the stomach. Conclusions and Clinical Importance: Pemphigus vulgaris is rarely diagnosed in equids. We describe a case that was substantiated by the demonstration of anti-Dsg3 IgG. Response to treatment was poor, with the best response to high doses of prednisolone. Equine pemphigus vulgaris is likely to carry a poor prognosis and if there is no response to treatment, humane euthanasia is warranted.