Equine Herpes Virus
Nathan Voris, DVM
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Over the last 6 years, an old nemesis of equine health has evolved into a potentially emerging disease with increasing virulence. Equine Herpes Virus (EHV-1), commonly referred to as “rhino” or more specifically the paralytic form of Herpes virus, is showing itself to be a threat equal to West Nile Virus, but more contagious among horses.
Disease surveillance reports indicate there was 1 reported outbreak in Wyoming in 2001 and 1 reported outbreak in Virginia in 2002. Since 2001, 16 states Colorado, Florida, Georgia, Kentucky, Maine, Maryland, Michigan, New Hampshire, New Jersey, New York, Ohio, Oregon, Pennsylvania, Virginia, Wisconsin and Wyoming) have reported outbreaks of EHV-1. In 2006 alone, there were 11 outbreaks in 8 states. Of the 403 known horses exposed during the outbreaks occurring from 2001-2005, there was a 40% fatality rate.
Equine Herpes Virus is primarily transmitted via nasal secretions that are aerosolized into the environment when an infected horse coughs or snorts. The virus can remain in the environment for several weeks once it has been shed by the horse. Indirect contact through sharing of equipment or transmission through human contact between infected and non-infected horses is a major threat for spreading the infection.
The incubation period, or time from infection to the horse exhibiting clinical signs, can range between 24 hours and several (4-6) days. The first clinical sign is usually a fever (normal equine temperature is between 99-101 degrees Fahrenheit). Additional signs include coughing and nasal discharge. Some horses can quickly progress into neurologic signs without showing other signs. Neurologic signs include: incoordination of the hind (and occasionally fore) limbs, urine retention/dribbling, bladder atony, recumbency (or loss of the ability to get up). Abortion in pregnant mares can occur weeks or months following infection.
Protecting your horses from EHV-1 involves vaccination and diligent monitoring of vital signs (especially temperature). Horses at greatest risk are those who attend shows or are commingled with other horses for events or activities. Because EHV-1 can be spread through indirect contact, and can last several weeks in the environment, vaccination of all horses that come in contact with high risk horses is advisable. In other words, if you take horses to show, all horses, even those that never leave the farm, are at risk and should be vaccinated.
Adequate vaccination requires repeat booster shots every 60-90 days due to the relatively short-lived protection immunization affords. The United States Equestrian Team Foundation is requiring documented proof (signed by a veterinarian) of EHV-1 vaccination between 7-90 days prior to entering USET Foundation property for clinics or events. I would expect other organizations and individual shows to follow suit in the near future.
If a horse is suspected of having EHV-1, strict quarantine procedures in accordance to the Equine Infectious Disease Outbreak: AAEP Control Guidelines should be initiated immediately (see www.AAEP.org), and a veterinarian should be contacted to assist with testing, treatment and control.
All I want for Christmas is my Two Front Teeth….
Heather Landrey, DVM
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As we all know, children lose their baby teeth when their adult teeth are ready to erupt. But did you realize that the same process occurs in a horse’s mouth? That’s right; horses have deciduous or baby incisors and premolars which are replaced by permanent or adult incisors and premolars. As the permanent tooth erupts it wears away the root of the deciduous tooth and eventually pushes the remnant of the baby tooth out. This remnant of the baby tooth is often referred to as a “cap”. The molars, wolf teeth and canines do not develop caps because they erupt as permanent teeth with no deciduous teeth to replace.
The incisors are the teeth in the front of the horse’s mouth. There are twelve incisors total; six on top and six on the bottom. The central incisors are the first to be shed, and this process usually occurs at about 2 ½ to 3 years of age. At around 3 ½ to 4 years of age, the caps of the middle incisors are shed. The corner deciduous incisors are lost between 4 ½ and 5 years of age. In each case, the caps of the lower arcade are shed before the corresponding upper arcade.
As previously stated the incisors are the teeth in the front of the mouth, the other teeth are collectively called cheek teeth. There are a total of 24 cheek teeth, 12 in the upper jaw and 12 in the lower jaw. The cheek teeth consist of molars and premolars. From age 2 years to 4 years the deciduous premolars will be replaced with permanent premolars. The first set of premolar caps are shed at 2 ½ years, the second set at 3 years, and the third set at 4 years. Unlike the incisors, the upper and lower premolars are lost close to the same time.
Most deciduous teeth are lost without complication, but occasionally problems can occur. For instance, when a cap becomes loose, food can become impacted between the cap and the permanent tooth causing pain. A second potential complication is when a cap is retained. Retained deciduous caps are those which do not fall out when the permanent tooth replacing it has erupted. The retained cap puts pressure on both the upper and lower permanent teeth and causes discomfort and chewing complications. Another complication arises when a cap becomes fractured. The fractured cap will have sharp edges which might cut the soft tissue of the mouth or put pressure on the gingiva (gums).
Once identified, dental problems associated with caps are easy to resolve. Dental care for the young horse is important for more than just its health and well being. A horse with pain from a tooth may develop some bad behaviors while working as a result of trying to escape pain. If the problem persists, the behavior may become a habit-and we all know young horses in training do not need any additional excuses to learn bad habits. Regular dental examinations, with the first exam prior to starting a horse in training, will insure that the mouth is not a source of discomfort and allow you to focus more on teaching the horse good habits.
Colic….a real pain in the gut!
Nathan Voris, DVM
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Without a doubt, colic is the number one reason horse owners (and their veterinarians) lose sleep at night. While most horses are very resilient when it comes to showing pain due to injury, horses are very sensitive when it comes to abdominal pain. There is nothing that will wake you faster than seeing a horse in abdominal distress.
The term “colic” simply refers to anything that causes abdominal discomfort. Clinical signs may include loss of appetite, depression, stretching, repeatedly posturing as to urinate or defecate without urinating or defecating, curling the upper lip, pawing the ground, looking at their flank, laying down, rolling, getting cast in their stall and even throwing themselves to the ground.
Risk factors that are known to increase the incidence of colic include:
- Inadequate parasite control-Nothing has reduced the incidence of colic more than the development of oral paste de-wormers.
- Chronic water deficiency-Lack of water causes the digested feed material to become dry and hard, complicating passage through the intestines. Horses that are group watered are less likely to colic.
- High concentrate diet-For every 5.5 pounds of grain fed per day, the risk of colic is doubled over horses that are not fed grain. At least 60% of a horses diet should be grass or hay.
- Sudden diet change-Horses are 5-10 times more likely to colic within 2 weeks of a sudden change in hay. Changes should be made gradually over a period of 7-10 days.
- Transport-Stress associated with transport increases the incidence of colic, especially if grain is fed immediately prior to transport.
- History of previous colic-Horses that have suffered colic in the past are 4 times more likely to suffer a repeat episode.
Research suggests that the normal incidence of colic is 4-10 cases per 100 horses per year. In other words, if you have 10 horses, every year you should expect 1 or less colic episodes or, your horse has a 4-10% chance of colic each year. If your horses are experiencing a higher-than-average annual colic rate, there may be some modifications in daily routine that can help reduce colic on your farm.
Of course, if your horse is suffering from colic, you should call your veterinarian as soon as possible. Some episodes of colic that begin as uncomplicated cases can become serious if not evaluated and properly treated. Fortunately, most causes of colic are uncomplicated and respond quickly to medical treatment. However, a small percentage of cases will require surgery, and the earlier that decision is made, the more successful the outcome.