University of Kentucky College of Agriculture, Food & Environment


Gluck Center > Equine Disease Quarterly > July 2014


Material published in the Quarterly is not subject to copyright. Permission is therefore granted to reproduce articles, although acknowledgment of the source and author is requested.
Logo for Lloyds


A good friend at Texas A&M once told me that no matter how much we accomplish in our careers, it is the accomplishments of those we teach that defines us. I couldn’t agree more with his wisdom. How lucky I have been to be mentored by so many great people that taught me my craft and instilled a love for the horse in my being.

We have a calling as representatives from all areas of the equine community to display our professions in such a wonderful way that the best and brightest want to be involved. The only way this is ever going to be possible is by inviting them into our world. The uninitiated need to spend time with the established. They need to be made to feel welcome and to taste the unique rewards that come from participating in the world of horses.

Young people need to be taught how to think, not what to think. But we need to do more than just teach; we need to display our careers in such a light that it inspires. Young people with high potential need to be challenged to recognize a need that they can fill. If we don’t define that path in a manner with a mission, they will move on to other things that offer more challenges and rewards.

The next generation of horse people is out there. Some of them don’t even know it yet. They are waiting on someone like you or me to recognize their potential and talent and embrace them. It takes time getting to know these horsemen and women of the future in order to inspire them.

We are at a crossroads in the horse world today. Many activists and journalists are focusing on anything bad they can find to report and debate. These negativities are trickling down to a generation of Americans who have no experience working with any facet of equine society. We have to be the voice for our great profession and we have to do it one bright mind at a time, as a team of people who love what we do and are ready to teach others, that it is wonderful.

Each year our veterinary clinic takes two interns and dozens of externs. We bring these people into our lives and, more often than not, we are as rewarded as they are. They bring fresh minds and excitement to our world. They kindle our enthusiasm and remind us of ourselves when we were younger and unfolding life’s adventures.

Make a commitment today. Make it a goal to actively look for some bright young person and teach him or her how fun and wonderful it is to do whatever it is that makes them a part of the horse industry. You never know, it just might make you love what you do even more.

Dr. Bo Brock, (806) 872-3183

Brock Veterinary Clinic
Lamesa, Texas


First Quarter 2014

The International Collating Center, Newmarket, United Kingdom (UK), and other sources reported the following disease outbreaks.

South Africa reported the seasonal occurrence of African horse sickness. Outbreaks were confirmed on properties in several districts in the protection and surveillance zones of the Western Cape Province.

Strangles outbreaks were report by Denmark, France, Germany, Ireland, Switzerland, United Arab Emirates (UAE), the UK, and the USA. Two outbreaks involving eight horses were confirmed in Denmark. France recorded 12 outbreaks. A limited number of cases were diagnosed on two premises in Germany. Ireland reported 19 cases on premises in two provinces, and Switzerland reported two cases. The UAE reported a carryover of the disease from late 2013, with an overall estimate of 77 cases on nine premises. Dual strangles and equine herpesvirus-4 infection was diagnosed in the UK. Strangles was reported to be endemic in the USA.

Limited cases of equine influenza were recorded in Ireland, the UK, and the USA.

Respiratory disease caused by EHV-1 was confirmed in France (six outbreaks) and the UK. France, Germany, Japan, Switzerland, the UK, and the USA all recorded outbreaks of EHV-1 abortion. Sporadic cases were confirmed in France and the UK; multiple cases were recorded in Germany (eight premises), Japan (16 premises), Switzerland (one premises), and the USA (two premises).

EHV-1 related neurologic disease was reported by France (sporadic), Germany (sporadic), Japan (sporadic), New Zealand, and the USA. New Zealand recorded the first outbreak of the disease in the country that encompassed 15 cases on one farm of which seven were euthanized or died. The USA confirmed a significant number of outbreaks in eight states. Whereas many outbreaks involved one to two cases, those in Illinois and Utah were more significant, with a high clinical-attack rate and case-fatality rate.

EHV-4 related disease was reported by France (10 outbreaks of respiratory disease), Germany (single case of abortion), and the UK (isolated cases of dual infection with strangles on two premises).

Evidence of equine arteritis virus infection was reported from Germany (three carrier stallions), Switzerland (one case), and the USA (serologic evidence of infection in breeding stock in eight states).

A limited number of cases of EHV-2 and EHV-5 infection were reported by the USA.

Canada and the USA recorded outbreaks of equine infectious anemia. Twenty-one cases were diagnosed in Canada: three in Alberta (one premises) and 18 in Saskatchewan (five premises). The disease was confirmed in six horses on two shared premises in Tennessee in the USA.

Piroplasmosis was reported by France (endemic), Spain (endemic), UAE (endemic in non-Thoroughbreds), and the USA. The USA diagnosed Theileria equi infection in three Quarter Horse racehorses and one Spanish purebred.

Germany confirmed contagious equine metritis in 20 non-Thoroughbred horses (14 stallions and six mares).

Abortions due to leptospiral infection were confirmed in the USA (10 cases).

Eight cases of nocardioform placentitis and abortion associated with Amycolatopsis spp. infection were confirmed in Kentucky, USA.

Abortions due to Salmonella Abortusequi were reported by Japan. The disease was confirmed in four non-Thoroughbred mares on one premises.

Germany, Ireland, Switzerland, and the USA recorded limited numbers of cases of salmonellosis, with Group B salmonellae implicated in USA cases.

Cases of proliferative enteropathy due to Lawsonia intracellularis infection were reported in several states in the USA. Clostridial enteritis was only recorded in the USA. Several cases of C. difficile toxin types A and B and six cases of C. perfringens type A were diagnosed in young foals.

France and Germany reported a very limited number of outbreaks of rotaviral diarrhea, one in France and two in Germany, the latter involving a total of six foals.

Rhodococcal disease was recorded in the USA, where it is endemic.

Isolated cases of Lyme disease (Switzerland), tetanus (Switzerland), and rabies (USA) were reported during the period under review.


Reducing Risk from Tick-Borne Diseases

According to the Centers for Disease Control and Prevention, the numbers of human cases of Lyme disease and other tick-borne diseases (TBD) reported each year in the United States (US) have been increasing steadily, currently totaling tens of thousands annually. The US Animal and Plant Health Inspection Service has identified Lyme disease and anaplasmosis as the most common tick-borne diseases for horses in the US. In some regions, 50% of horses may show antibodies to the Lyme disease pathogen, but only about 10% show clinical symptoms. Over 70% of the ticks reported to feed on horses also feed on humans, transmitting the same pathogens causing TBD.

Ticks can also be an irritant to people and animals. In severe infestations, ticks can cause anemia in small and young animals, and in some instances, a single tick bite can cause paralysis.

The US Environmental Protection Agency (EPA) and US Department of Agriculture (USDA) have developed a smart, sensible, and sustainable approach to reduce the transmission of tick-borne diseases through tick management practices. The recommendations below help people protect themselves and their horses from TBD.

In addition to providing information for protection, an effective tick integrated pest management plan includes a tick surveillance program. Currently, the Centers for Disease Control and Prevention collects reported TBD data in humans. Discussions are under way in the federal and private sectors on appropriate methods to collect tick surveillance data including tick identification and species distribution in the US. This type of collected information could be very useful in identifying areas posing the highest risk to horses and their riders from TBD in the future.

Tick Management Practices


Centers for Disease Control and Prevention, Division of Vector-Borne Diseases.  Tick-borne disease data in humans. Page last updated: June 17, 2014.

Centers for Disease Control and Prevention.  Tick resources. Page last updated: May 5, 2014.

Stafford III, Kirby C. 2004. Tick Management Handbook. Connecticut Agricultural Experiment Station. New Haven, CT. .

US Department of Agriculture, Animal and Plant Health Inspection Service, Veterinary Services.  Horse Disease Information. Last modified: May 30, 2014.

US Environmental Protection Agency, Office of Pesticide Programs, PestWise. Last updated on May 27, 2014.

Candace Brassard, (703) 305-6598

Denise Greenway, (703) 308-8263
US Environmental Protection Agency
Washington, DC
Dr. Angela James, (970) 494-7278
US Department of Agriculture
Fort Collins, Colorado


The Thoroughbred Racehorse Foot

Foot problems can commonly cause horses to be scratched from a race, lose training days, overload other structures and have shortened careers. Functionally adapted for speed and efficient use of energy, the Thoroughbred foot is light and lacks the mass for protection commonly seen in heavier boned breeds. The relatively thin walls and sole of the Thoroughbred foot make it more susceptible to trauma, injury and hoof capsule distortion. Hoof capsule distortion refers to misshapen/imbalanced hooves such as flares, cracks, under-run, and collapsed and sheared heels. Distortions affect function and have been correlated with musculoskeletal injuries and lameness. Foot shape and balance are paramount to maintaining soundness and optimal performance. Maintenance and development of a healthy functional foot are necessary for well-being and longevity of racehorses, requiring a proactive approach including balanced shoeing and support.

The heel region is designed to impact the ground first and dissipate vibrations. This is usually the first part of the foot to display distortion since it is made up of soft, elastic structures. The toe is stiffer and designed to cut into the ground for traction. Hoof capsule distortions occur slowly over time and result from long-term abnormal weight bearing. The most common imbalance encountered is feet shod with too much toe length and inadequate heel length. The center of the shoe’s weight bearing surface should line up with the center of the coffin joint which is aligned at the widest part of the sole. Balanced shoeing around the coffin joint helps to distribute force more appropriately over the hoof.

The foot has the ability to handle large impact forces without structurally collapsing. Most hoof capsule deformities (under-run, collapsed heels) develop slowly and result from long periods of constant low level loading. Racehorses spend 22 or more hours a day standing in a straw bedded stall, and most distortions likely occur while the foot is semi-static. During this period the foot is mostly dependent on its architecture for support.

Horses standing with little arch or sole support slowly fatigue the integrity of the capsule. The arch of the sole slowly flattens, the heel becomes under-run and folded inward, and the heel bulbs can become sheared. The insidious nature of hoof capsule distortions slowly compromise the foot, rendering it more susceptible to acute injury. Providing support to the arch is very important, especially when the horse is standing for long periods. When exercising, the track surface packs into the sole and provides support. When in the stall, the hoof has little arch support and relies on the perimeter hoof capsule for support.

Using temporary arch supports bandaged onto the feet when stalled is often very helpful. These can be taken out when exercising. Other options include stabilizer plates and heartbars which are welded into the shoe. These provide support and protection while exercising, but do add weight to the foot and may affect the horse’s gait. Various options are available for treating the distorted foot. Detecting a compromised hoof capsule, ensuring it is shod in a balanced manner and implementing one of the methods of support can help maintain or develop a functional sound foot.

Dr. Scott E. Morrison, (859) 233-0371
Rood and Riddle Equine Hospital
Lexington, Kentucky


Equine Lyme Disease

Lyme disease in North America is caused by the bacteria Borrelia burgdorferi sensu stricto. Borrelia burgdorferi survives in a small rodent and Ixodes spp. tick cycle. Horses and many other mammals may become infected during tick feeding. Generally, 24 to 48 hours of attachment are required to transfer B. burgdorferi from the tick to the mammalian host. Female adult Ixodes spp. ticks are believed to be primarily responsible for transmitting B. burgdorferi to horses, while in humans the smaller and harder to see nymphs are responsible for more infections. Several strains of B. burgdorferi exist and prior infection may not provide cross-protective immunity against other strains. Ixodes ticks may simultaneously harbor other pathogens, e.g., Anaplasma phagocytophilia, causing co-infections in many horses.

B. burgdorferi infection in horses is common in several areas of North America. Horses in the mid-Atlantic and northeastern states have a high seroprevalence for B. burgdorferi, as do horses in areas of Minnesota, Wisconsin, and extending into southern Canada. Infected horses also are reported in regions of California and sporadically throughout other areas of North America. Both human and equine B. burgdorferi infections are expanding geographically.

A wide variety of clinical signs have been attributed to B. burgdorferi infection in horses, but cause and effect have been difficult to document in most cases. Clinical signs most often attributed to equine Lyme disease include stiffness and lameness (generally in multiple limbs), muscle tenderness, increased sensitivity to touch and sensation (hyperesthesia), lethargy, and behavioral changes. Muscle wasting, pain upon palpation of the topline and occasionally ataxia may occur. Infection of the nervous system (neuroborreliosis), uveitis, dermal inflammation mimicking lymphoma, and synovitis are documented; all occur with a characteristic lymphohistiocytic inflammatory response.

Current serologic tests are sensitive and specific for detecting B. burgdorferi antibodies, but these may not distinguish between prior and current infections. The clinical diagnosis of Lyme disease is difficult and might best be based upon the following parameters: geographic location, known exposure to B. burgdorferi by serologic testing, probability of the clinical signs being due to B. burgdorferi infection based on where the organism can reside (synovial membranes, skin, fascia, meninges, nerves, and sometimes vitreous eye fluid), laboratory testing of tissue or fluid by polymerase chain reaction and/or histopathology, and most importantly ruling out other diseases. Response to treatment and change in antibody levels are of modest benefit in confirming a diagnosis due to the anti-inflammatory properties of tetracyclines and the prolonged antibody response that can occur even after seemingly appropriate antimicrobial therapy.

Tetracyclines are the most frequently used drugs for treatment of equine Lyme disease. In an experimental pony infection model, intravenously administered tetracycline was highly effective in eliminating B. burgdorferi while an intramuscularly administered cephalosporin and orally administered doxycycline were somewhat effective. Because of ease of treatment, doxycycline and minocycline are the two most commonly used drugs for Lyme disease treatment in horses.

Horse owners in high risk areas of Lyme disease, and those who are traveling with horses to these areas should consult their veterinarians about appropriate protective measures.

Dr. Thomas Divers, (607) 253-3226
Dr. Linda Mittel, (607) 253-3633
Cornell University
College of Veterinary Medicine
Ithaca, New York


Reproductive Leptospirosis

Figures 1 and 2Pathogenic leptospires are zoonotic, spirochete bacteria. They have a world-wide distribution, and can infect a wide variety of species. Leptospires are most commonly maintained in the urinary tract of small mammals and are transmitted through contact with the urine. Though exposure to leptospires is generally through small mammals, affected horses can also shed bacteria in their urine and be a source of infection. In horses, abortion is the most economically significant manifestation.

Infection of pregnant mares with pathogenic leptospires can result in abortion, stillbirth, birth of live, non-viable foals and, rarely, viable foals. Live but non-viable foals are often born significantly premature. Foals that survive intrauterine infection are generally weak at birth, but can recover through intensive supportive care. From July 1, 2011 through May 28, 2014, 57 cases were recorded at the University of Kentucky Veterinary Diagnostic Laboratory; 50 abortions (88%), four live but nonviable foals (7%), and three viable foals (5%). The 54 abortions and live but non-viable foal data are represented in Figure 1, in addition to previously reported data.* A foaling season spans July 1 to June 30, i.e., the 2013 foaling season ended June 30, 2013.

Diagnosis of leptospirosis from the fetus and placenta is rarely complicated; however, identification of infected pregnant mares can be difficult. Unlike many other bacterial causes of abortion, mares that abort due to leptospirosis rarely show premonitory signs. Surveillance of mares using serologic testing is often performed in the fall. However, the significance of positive findings can be complicated because many uninfected mares are seropositive for Leptospira spp. A polymerase chain reaction assay on urine can identify animals that are shedding leptospires, and these animals can be managed to reduce the risk of exposure of other horses, humans and animals.

The incidence of reproductive leptospirosis can vary widely by year (see Figure 2). There is anecdotal evidence that this variation is associated with wet weather in the fall. However, it is important that surveillance should not be eased due to weather patterns. Leptospirosis generally occurs sporadically, though farms can occasionally experience multiple cases of reproductive leptospirosis within one foaling season.


Dr. Laura Kennedy, (859) 257-8283
Veterinary Diagnostic Laboratory
University of Kentucky Lexington, Kentucky


Free Subscription

There are 2 ways to receive the Equine Disease Quarterly:


Roberta Dwyer
Alan Loynachan
Peter Timoney

Diane Furry
Tawana Brown
Dennis Duross

Correspondence should be addressed to the editors,
Department of Veterinary Science, Gluck Equine Research Center,
University of Kentucky, Lexington, KY 40546-0099;
Phone (859) 257-4757; FAX (859) 257-8542.


Maxwell H.Gluck Equine Research Center
Department of Veterinary Science, University of Kentucky
Lexington, Kentucky 40546-0099

Main Office (859) 257-4757
Fax (859) 257-8542