BEVA Shares Education
The United Kingdom is famous for its rich history and deeply rooted traditions, but that doesn't mean its veterinarians are bound to ancient methods of equine medicine. Quite the contrary, the British Equine Veterinary Association (BEVA) hosts one of the world's most in-depth, cutting-edge continuing education meetings every year--the BEVA Congress. The 43rd annual Congress, held Sept. 15-18, 2004, in Birmingham, United Kingdom, boasted a program packed full of information on colic, orthopedics, how-to procedures, reproduction, cardiology, foal care, and much more. Following are brief reports of several presentations from the Congress; for more information on these and other presentations, see the British Equine Veterinary Association section under Convention Reports at www.TheHorse.com.
Contact Lenses for Horses
While they aren't used to improve vision in horses, soft contact lenses can be used to protect the eye and facilitate healing in horses with non-infected ulcerations. Robert Lowe, BVSc, MRCVS, CertVOphthal, of Downland Veterinary Group in Hampshire, United Kingdom, discussed the use of contacts for horses.
"I use them often, on any case with superficial ulceration and no infection," Lowe said. "I think they're quite underused. They're used a lot in dogs and cats, but horses as well as humans are better species for them because the eyelids are tighter and hold the lens in better. There's less chance of them rubbing them out."
Reasons to avoid contacts for a particular horse include reduced tear production, infection, deep corneal ulceration where there's a risk of rupture during lens placement, and abnormal corneal curvature (including raised corneal masses), he said.
Lenses for horses come in two sizes--34 mm diameter with 18 base curvature, and 32 mm diameter with 17 base curvature (for comparison's sake, lenses for humans are about 14 mm in diameter with 8.60 base curvature). Lowe recommends using the larger size for horses and the smaller one for ponies and foals. The lenses cost about 45 pounds each (about $76 U.S.).
The procedure for inserting a lens is relatively simple, and it is done by a veterinarian with the horse sometimes under sedation. The only real complication, Lowe said, is lens loss or tearing. Torn lenses must be replaced, and occasionally infection necessitates removal of the lens and treatment of the infection.
Lenses are removed after the ulceration heals fully (they heal at 0.6 mm/day, noted Lowe), again by a veterinarian.
"In summary, lenses are an excellent treatment for sterile, superficial, stubborn ulcers," he concluded.
Postoperative Colic Survival
Can a practitioner predict a horse's chances of survival after colic surgery? Not with absolute certainty, but several factors can help that prediction, said Anthony Blikslager, DVM, PhD, Dipl. ACVS, associate professor of equine surgery at North Carolina State University's (NCSU) College of Veterinary Medicine.
"Recent studies at NCSU suggest that of horses presenting for evaluation of colic that go to surgery, approximately 25% are lost at surgery based on the severity of the lesion, including gastrointestinal rupture, and devitalized bowel beyond accessible regions via a midline laparotomy," he said. "Of the horses that are recovered, approximately 80% will ultimately be discharged, after which a further 10-15% will be lost because of long-term complications."
So what post-operative factors might a practitioner evaluate to predict which cases might make it and which might not? First, consider the following three problems Blikslager discussed that are associated with post-operative mortality: Shock, ileus (intestinal obstruction), and intra-abdominal adhesions.
He noted that several shock parameters "strongly associated with mortality" include the following:
- Heart rate more than 60 beats per minute in the first 24 hours post-surgery (normal range is 36-48 beats per minute; this increases the odds of death, or the odds ratio, OR, nine times);
- Packed cell volume (PCV) greater than 42% in the first 24 hours (the normal range is 31-47%; OR=3.3);
- Total plasma protein (TPP) less than 5.5 g/dL in the first 24 hours (normal range is 6-7.5 g/dl; OR=4.3);
- Prolonged capillary refill time (longer than two seconds); and
- Abnormal mucous membrane color.
For the next problem, postoperative ileus, the risk of mortality in horses with this problem is more than eight-fold. "Interestingly, use of drugs aimed at modifying motility and hand-walking during hospitalization substantially lowered the risk of mortality (decreasing the OR to 0.6 and 0.7, respectively), probably because of reduced severity of post-operative ileus," he said.
Blikslager noted that although adhesions tend to affect horses after discharge from the hospital, some factors during surgery and in the immediate post-operative period can identify horses at risk for adhesions. These include recurrent colic, which might indicate that a horse is developing adhesions (OR=8.5), and repeat laparotomy, which causes additional surgical trauma or might be done to correct adhesions (OR=8.3).
Armed with these parameters, practitioners can give owners a more accurate prognosis for recovery in surgical colic cases. For more information, see www.TheHorse.com/ViewArticle.aspx?id=5353.
Colic in Geriatrics
Older horses are at higher risk for certain types of colic, said Blikslager in another presentation. "According to recent studies, colic is the single most common disease requiring medical attention in geriatric horses," he stated. Two types of colic common to the older horse are impaction colic from poor dentition and the strangulating lipoma, or a fatty tumor on a stalk that "strangles" some part of the intestine, hampering its function.
"The reason for the predisposition of aged horses to lipomas probably relates to the number of years required to form a lipoma with a sufficient length of stalk to strangulate intestine," he explained. Metabolic changes due to age might also play a role.
Older geldings, he said, have a 2.3-fold increase in the risk of this tumor than mares or stallions, and ponies have a 3.7-fold increase in risk. Why? "They have a greater propensity to lay down body fat," Blikslager explained. "The short-term survival rate (for horses having this tumor) is 48-79%, and the long-term survival rate is 38-50%. However, it's been shown that there is no decrease in survival rate with an increase in age (of the patient)."
Blikslager also discussed a study on colic survival in which 697 colic cases from 1990-93 were followed. He and colleagues found that horses older than 20 years were significantly less likely to survive in the short term (odds ratio=5.5, or these horses are 5.5 times less likely to survive), and these horses also had a much higher rate of strangulating lipomas affecting the small intestine (OR=11.8). However, he said, "The survival of aged horses within each lesion type was not significantly different (from younger horses). The prognosis is based on the lesion, not on age (of the horse).
"However, veterinarians should also consider the quality and length of life that may be expected following colic surgery," he went on. "When considering the fact that full recovery from colic surgery requires up to six months, owners should very carefully consider the repercussions of the recovery phase in very old horses. Horses nearing the age of 30 may lack the muscular strength to have a good anesthetic recovery, and may lack the energy reserves to make a rapid recovery in the post-operative period.
"Colic is a major problem in geriatrics," he concluded. "Pay close attention to their dentition and feed, and keep in mind that while they are still good surgical candidates, that they are at higher risk for strangulating lipomas."
For more information, see www.TheHorse.com/ViewArticle.aspx?id=5354.
Cauda Equina Syndrome
In the roll call of neurological diseases from which horses can suffer, there is one many horse owners don't yet know about--cauda equina syndrome. Caused by myriad infectious, inflammatory, and/or traumatic factors, the syndrome includes many hind-end neurological clinical signs stemming from damage to the cauda equina, the tapered end of the spinal cord along with the extensions of spinal nerve roots extending alongside and past it. Scott Pirie, BVM&S, PhD, CertEP, CertEM, MRCVS, described cauda equina syndrome in depth at the Congress.
"The cauda equina is so called due to its gross resemblance to a horse's tail," he began. "The most common clinical signs of cauda equina syndrome include tail paralysis/weakness, anal hypotonia/atonia (poor or no muscle tone), rectal and bladder paralysis/weakness, and relaxation and protrusion of the penis. Other signs include lack or absence of skin sensation (hypalgesia or analgesia) of the tail, anus, and skin of the perineum; and muscle atrophy of the coccygeal muscles (which control tail movement). Occasionally, hindlimb weakness, ataxia, and muscle atrophy have been associated with damage at the more cranial (forward) aspect of the cauda equina region. Less common signs are pelvic limb/rump muscle weakness and atrophy. Subtle signs might be reproductive dysfunction such as urospermia (urine ejaculated in semen), impotence, and urine pooling in mares.
"The signs observed depend on the site of the damage," Pirie explained. "There is usually no major gait abnormality if there is minimal involvement of the lumbosacral nerve roots."
Cauda equina causes--Trauma to the sacral/coccygeal area is the most common cause of the syndrome and can result from falls, reversing under obstructions (such as backing under a closed top stall door), and tail pulling such as occurs when using the tail to help pick up a down horse. "The deficits are usually immediate, but beware of delayed signs, which can be caused by unstable fractures, hematomas (bruises), or abscesses," Pirie noted. Some causes of the syndrome can also damage neurons elsewhere, thus causing more clinical signs.
Several other problems can also cause clinical signs of cauda equine syndrome. For more information on these, see www.TheHorse.com/ViewArticle.aspx?id=5356.
Treatment--"Treat the underlying cause where appropriate--i.e., medications for EPM, fixation for fractures, etc.," Pirie recommended. Non-specific treatments include non-steroidal anti-inflammatory medication, and supportive nursing care that includes bladder drainage/lavage, prophylactic antibiotics to decrease cystitis (bladder infection), topical skin treatment to prevent urine scald, manual fecal removal, and fecal softeners. "Prognosis is largely dependent on the initial cause of the syndrome," he concluded.
Multiple Limb Lameness
"Horses with lameness in more than one limb are a diagnostic challenge, especially if both a forelimb and a hindlimb are involved," said Sue Dyson, MA, VetMB, PhD, DEO, FRCVS, of the Center for Equine Studies at the Animal Health Trust, during her presentation on the topic. "The first key to successful diagnosis is determination of which are the lame limbs.
"This is particularly difficult if the horse moves with a short, shuffling gait rather than overt lameness," she added. "Very careful evaluation of the horse under various circumstances, straight lines, circles on soft and hard surfaces, and if necessary ridden, and assessment of response to flexion tests, are crucial. The investigator should first evaluate the overall way the horse moves, focusing first on the forelimbs and then on the hindlimbs. Watch the horse carefully as it turns to change direction; discomfort while turning may reflect foot pain."
She noted that practitioners should pay close attention to the rider's hands when a horse is worked under saddle, as some riders can induce a head nod in a sound horse, making him appear lame. "You need a skilled rider to help you assess response to nerve blocks," she said.
"I strongly advocate targeted rather than systematic blocking based upon the clinical signs, type of horse, and prevalence of different sources of pain in a horse used for that discipline," Dyson concluded. With tough cases, scintigraphy can be helpful for confirming positive findings or targeting further investigation, she added.
She also offered several more tips for practitioners on assessing lameness. For more information, see www.TheHorse.com/ViewArticle.aspx?id=5355.
Several lameness cases were presented with video and any pertinent exam findings to a panel of experts during an informal session chaired by Dyson and Mike Ross, DVM, Dipl. ACVS, of the University of Pennsylvania's New Bolton Center. The panelists included Andy Parks, MA, VetMB, MRCVS, of the University of Georgia; Fabio Torre, DVM, Dipl. ECVS, of the Clinica Equina Bagnarola in Italy; and Andy Bathe, MA, VetMB, DEO, Dipl. ECVS, MRCVS, of Rossdale and Partners in England. The audience participated enthusiastically with questions.
The cases presented included the bizarre, such as an elite jumper with a sudden-onset "hitch" in one hind leg that looked like a lateral stringhalt-type motion (later treated with a lateral digital extensor tenectomy). There was also the confusing, such as an amateur show jumper that was sound to all diagnostics, neurological examination, and in hand, but stumbled and hopped oddly with a rider. Dyson commented that some horses with weird (i.e., undiagnosable) hind end lamenesses or gait problems might have tension issues that respond fully to light sedation.
Another example was a young rider's competition horse referred because he suddenly refused to turn left under saddle. No lameness had been noticed in this horse beforehand. During an extensive workup, this horse was found to be quite tender on hard surfaces, particularly on the left front. After palmar digital blocks of both front limbs (deadening the back of the foot), he was much more comfortable and his left turn problem completely disappeared. He was found to have collateral ligament desmitis of the coffin joint in both front feet.
"We see many horses much like this, where the owners aren't aware of any lameness at all, and behavior dominates the issue," commented Dyson. "I think it's a great example of how foot pain can manifest itself as something completely different."
"Management of severe skeletal pain in the horse can be a challenging task in practice, and it is complicated by the fact that many drugs used for this purpose are controlled substances," said Jessica Kidd, BA, DVM, CertES (Orth), DipECVS, MRCVS, of the University of Cambridge. She described several options for controlling severe skeletal pain, including systemic opioids, epidurals, transdermal narcotics, and slings.
The indications for using these powerful pain management methods, she said, include the following:
- Septic arthritis or osteomyelitis;
- Following orthopedic surgery;
- Some tendon injuries, including tendon lacerations;
- Myopathy (a painful condition of muscles either following exercise or anesthesia muscle disease); and
- Neuropathy (a painful condition of peripheral nerves usually seen as a complication of anesthesia nerve disease).
Of the pain management options discussed, Kidd said systemic opioids are not generally used "as there is a very narrow margin between achieving analgesia and the development of side effects such as excitement and the potential to slow intestinal transit time (increasing the risk of colic)." However, intramuscular detomidine is effective (detomidine is an alpha-2 agonist marketed under the trade name Domosedan) and easy to use, she said. It does have mild side effects, including sedation and sweating, which are not usually problematic, but she noted that owners should be warned so they know what to expect.
"Epidurals are the next step," Kidd went on. "These effects are limited largely to the perineal region and the hindlimb and are less useful for forelimb pain." She then explained epidural technique and dosages, and noted that a commercially available epidural catheter can be used if repeat epidurals need to be given.
She noted that "Transdermal narcotics are useful when the pain is not limited to the hindlimbs, as the effects are systemic." These deliver continuous pain relief, and probably the most well-known is fentanyl (used at up to three patches per horse). She warned that the potential for human abuse of these patches is high, and that they should be accounted for at all times, including disposal.
In the non-medication area of severe skeletal pain control, Kidd discussed slings that bring relief from some limb and foot pain by allowing the horse to take his weight off of the painful limb(s). However, care must be taken to manage pressure from the harness to avoid too much compression of the thorax and abdomen. Intolerance of the sling by the patient can be a problem.
For more information, see www.TheHorse.com/ViewArticle.aspx?ID=1866.
Maximizing the Benefits of Influenza Vaccination
"Beware the vaccination paradox!" began J. Richard Newton, BVSc, MSc, PhD, DLSHTM, DipECVPH, FRCVS, of the Animal Health Trust in Suffolk, United Kingdom, during his presentation on influenza vaccination. He described the vaccination paradox as follows:
- A disease is highly prevalent.
- People vaccinate against it.
- The disease incidence is notably reduced.
- People stop vaccinating because it doesn't appear to be a common threat.
- The number of susceptible individuals increases.
- The disease reappears!
Most outbreaks occur in non-vaccinated animals, he said, although vaccine "breakdown" does occur periodically, mostly in young Thoroughbreds (usually because of their frequent exposure to other horses, but also possibly through travel and exercise stress). This breakdown in vaccination protection (i.e. appearance of infection and clinical signs in properly vaccinated animals) happens when the virus that causes the disease mutates, thereby becoming less susceptible to the immune response produced by vaccines containing older strains of virus. In other words, the viruses in the vaccine and those that a horse encounters in the field are sufficiently different that the vaccine is no longer effective in conferring complete protection.
"This confirms the need for a potent vaccine with epidemiologically relevant strains," Newton said. He added that researchers need to better understand "the real-life factors" that affect an animal's ability to respond to vaccination and therefore facilitate the best use of current vaccines.
He discussed several studies on flu vaccine effectiveness; based on these studies, Newton made several recommendations for influenza vaccination as follows:
- Use a potent vaccine with epidemiologically relevant virus strains (i.e., the viruses in the vaccine should be closely related to those strains circulating in different parts of the world at the present time).
- Give the first vaccination to foals at six months of age or older.
- Vaccinate before high-risk periods (sales, races, start of training, etc.).
- Extend the primary course interval in primed horses (the time between the first two doses of the year in previously vaccinated horses). He noted that the British Jockey Club recommendations allows up to 92 days between primary course doses.
- Decrease booster intervals to around six months in young horses.
- Decrease intervals between primary and other courses to about three to four months.
For more information, see www.TheHorse.com/ViewArticle.aspx?id=5357.
Valvular Heart Disease and Performance
Results of a four-year prospective study designed to determine the influence of training and heart size on atrioventricular (AV) valvular regurgitation (backflow of blood from the lower to the upper heart chambers) in Thoroughbred racehorses, and to determine any association between AV valve regurgitation and performance in Thoroughbreds, were presented by Lesley Young, BVSc, PhD, DVA, Dip ECVA, DVC, MRCVS, of the Animal Health Trust (AHT) in Newmarket, England.
She said the causes of poor performance in racehorses include:
- Unreasonable owner expectations;
- Lack of genetic ability;
- Lack of enthusiasm;
- Orthopedic problems (most common);
- Respiratory disease (close second); and
- Cardiovascular dysfunction (consider after above causes).
"How important is cardiac disease to racehorse performance?" she asked the audience. "It's believed to be the primary cause of, or a significant contributor to, poor or loss of performance in less than 6% of horses referred for performance investigation on the treadmill to AHT."
While that might seem like an insignificant number of affected horses, equine veterinarians know that many racehorses have cardiac abnormalities, although in the majority of cases these abnormalities do not affect the horse's performance.
Via cardiac auscultation (listening to the heart), confirmed by color flow Doppler electrocardiography (CFM) of the study horses, which ran in flat or National Hunt races, the researchers found murmurs of mitral valve regurgitation of various grades (backflow of blood through the mitral valve) in 7% of flat racehorses and 21% of fit chasers. They also found murmurs of tricuspid valve regurgitation in 12% of flat racehorses and 46% of chasers, while murmurs of aortic valve regurgitation are less common and were not present in this group of flat racehorses and in only 5% of the National Hunt group. In race-fit steeplechasers, significant (grade of murmur 2.5/6 or greater) mitral valve murmurs were associated with lower Timeform racing ratings, and moderate to severe mitral regurgitation imaged by Doppler echocardiography also resulted in lower win-to-run ratios.
In race-fit hurdlers, only aortic valve regurgitation decreased performance. Flat racehorses seemed to be unaffected by valve regurgitation or murmurs, but there were few flat horses with these problems, so the power of the study might have been limited, Young noted.
"Many affected horses are commercially successful racehorses," she commented. "It therefore seems very unlikely that compensated cardiac valve regurgitation has any noticeable effect on performance in horses engaged in less strenuous disciplines, unless secondary left atrial enlargement results in the development of atrial fibrillation (disorganized electrical conduction and pumping of the atria).
She also discussed training effects on the heart, and atrial fibrillation, in more depth. "Horses' hearts are so big, they're an atrial fibrillation accident waiting to happen," Young commented. "Is this just another downside of two millennia of breeding for speed?" For more information, see www.TheHorse.com/ViewArticle.aspx?id=5358.
RESEARCH: Short and Sweet
The Congress also featured Free Communications sessions, which provided a forum for short presentations on research grouped into several topics. Following are selected reports.
Deworming Program Success--Compared to a farm's previous parasite control program of either ivermectin or pyrantel at two- to three-month intervals, a more comprehensive program of specific parasite-targeted seasonal drugs and quarantine/treatment of new arrivals decreased colic and diarrhea. Fecal egg counts were maintained below 120 eggs per gram.
Counting Parasite Eggs--The traditional method of counting eggs in fecal samples, the McMaster technique, was found by one study to be less sensitive for detecting low egg levels than FECPAK kits, which use a larger sample volume.
Supernumerary (extra) Cheek Teeth--Although they don't always cause problems, they can; unilateral nasal discharge (from one nostril only) was the major presenting clinical sign in 11 of 15 cases, with bit evasion behavior (six cases) and oral phase dysphagia (three cases) also seen in this study. Two cases were resolved with repulsion of the tooth and sinus flap surgery, three with oral extraction, six with no or conservative treatment, and four with euthanasia.
Dorsal Displacement of the Soft Palate
Conservative Treatment--The authors of this study noted similar rates of success with conservative treatment (rest, improved fitness, and/or a tongue tie) in National Hunt horses compared with previously described surgical success rates.
Antimicrobial Fabrics--When tolnaftate, an antifungal agent, was incorporated into fabrics (such as blankets and saddle pads) in this study, it significantly inhibited the growth of the fungal agents that cause ringworm in horses, cats, and dogs. Its efficacy was not decreased by washing the fabric in detergent at 40 or 90ºC.
Laminitis and Cushing's Disease--The incidence of pituitary pars intermedia dysfunction (PPID, also called Cushing's disease) in six years' worth of laminitis cases in one practice (those not known to be on medication that would alter the hypothalamic-pituitary-adrenal axis) was 70%. Chronic laminitis was significantly more common in PPID horses.
Laminitis and Nerve Problems--Another study found sensory nerve damage in laminitic horses and noted that treating neuropathic pain with analgesics might be helpful.
Trilostane for Metabolic Syndrome--In 21 horses presented for recurrent or chronic laminitis (and confirmed to not have Cushing's disease), a reduction in clinical signs and in serum cortisol was seen in 67% of horses following long-term trilostane treatment.
Salivary Cortisol in Aged Horses--One study that evaluated salivary cortisol concentrations in aged horses with and without hirsutism (overly long hair coat) and acute colic found that salivary cortisol levels might be more useful for diagnosing stress than Cushing's disease.
Feed Type and Chewing--Chewing is associated with saliva production, which helps buffer stomach acid and decrease ulcers. This study found that small pellets and larger low-bulk-density compound feeds cause more saliva production than pelleted diets, which might maintain normal gastric acidity and keep ulcers at bay.
Mannose Intrauterine Lavage--This study found no significant difference in pregnancy rates of barren mares treated with mannose intrauterine lavage vs. those given parenteral antimicrobials and ecbolics (which stimulate uterine contractions).
Hermaphroditic Ponies--Six intersex Welsh Mountain ponies with male external genitalia and female tubular tracts and ovotestes all had normal male chromosome types (XY). After ruling out several particular gene mutations as the cause, the authors concluded that these ponies might present an opportunity to discover and study a new gene mutation that causes these characteristics.--Christy West
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About the Author
Christy West has a BS in Equine Science from the University of Kentucky, and an MS in Agricultural Journalism from the University of Wisconsin-Madison.