Currently, there are numerous reports of equine herpesvirus myeloencephalopathy (EHM) affecting horses and farms in Colorado and several other Western states. This outbreak appears related to initial cases at a Cutting horse show in Ogden Utah, which was held from April 29th –May 8th. Horses at that event may have been exposed to this virus and subsequently spread the infection to other horses. While the true extent of this disease outbreak is uncertain, there is clearly a very significant elevated risk of EHM cases at this time. At this time control of the outbreak is critically dependent on biosecurity.
We want to address four Frequently Asked Questions in this document:

mitigate the risk at their home facility. Even if these horses are returning home from events at

which no disease was reported, and even if these horses appear healthy, precautions are

needed at this time as these horses could bring it home and spread it at their home farm – this

is the classic way this disease spreads:

facility. Isolation requires housing them away from other horses, using different

equipment to feed, clean and work with them that is used with any other horses, and

rigorous hygiene procedures for horse handlers (hand hygiene, wearing separate

clothes when contacting the horses, etc.). Please discuss this with your veterinarian.

isolated at home, but even if they don't develop fevers this should be at least 14 -21

days.

typically the first and most common sign of infection – horses with elevated

temperatures (101.5 F or greater) should be swabbed by your vet to find out whether

they are shedding EHV-1.

other horses on the premises increases significantly. Those affected farms should

work closely with their veterinarian to manage that situation, if it develops.

on its website, in the member section, that can be used for a more detailed response.

been in contact with them, start isolation procedures to stop further exposure. It is very

important to not mix horses from different groups to accomplish this. Try and isolate the

suspect horse without moving other horses from one group to another – segregation of horse

groups is the key, because this will help you reduce spread if an outbreak starts.

check once daily). If fevers are detected, then test for EHV-1.

disease on the farm is questionable. The treatment is expensive, the drug (Valtrex™ -

valacyclovir) may have limited availability, and prophylactic therapy against EHM will only

work while drug is being administered. Therefore it is more likely to be effective if

administered when fever is first detected (see below).

Stringent quarantine and biosecurity procedures must be implemented immediately.

of anti-viral drugs is not known to be of value at this stage. Use of anti-inflammatory drugs is

recommended: flunixin meglumine (0.5 to 1 mg/kg, IV, q 24 hours).

exposure, anti-viral drugs may decrease the chance of developing EHM.

development of EHM is Valacyclovir (Valtrex™), given orally. The use of oral acyclovir is

unlikely to be of any value, as it is not absorbed from the GI tract.

mg/kg q 8 hr for two days, then 20 mg/kg q 12 hr for 1-2 weeks. Maintain on higher dose rate

if the horse is still febrile. This is an expensive drug, and daily treatment costs can typically

be $20-300 per day. Generic forms of Valacyclovir may be available, and may be marginally

cheaper.

at this time, in that circumstance the use of intravenous Ganciclovir is preferable as it may

have greater potency against the disease. The dose of Ganciclovir is 2.5 mg/kg q 8 hr IV for

one day then 2.5 mg/kg q 12 hr IV for one week.

4. Is there any value to using booster vaccination against EHV-­1 at this time? 
Unfortunately, there is no evidence at this time that current EHV-1 vaccines can prevent EHM.

cases reduce viremia. These products may therefore have some theoretical value against

EHM (by reducing viremia), and certainly against spread of the virus.

• The more potent EHV-1 vaccines include: Rhinomune®, or Calvenza™ EHV, Boehringer

Animal Health.

should quickly increase immunity, and perhaps reduce spread of EHV-1 if it is present.

immunity to EHV-1 may play a role in the development of EHM. While this is unproven, it

remains a possibility. The use of vaccination is therefore a risk-based decision.

         Poisonous snake bites occur in our practice area due to Copperhead Snakes (pictured to the left) and occasionally Timber Rattlesnakes.  Most bites occur when snakes are most active in the spring and summer.  Horses are normally bitten on the nose, head, neck and legs.

 Signs of a snake bite are:

v  Rapid local swelling

v  Pain

v  Redness

v  Fang marks may be seen

Bites of the head or face can be risky due to swelling causing airway obstruction.  Horses are obligate nasal breathers, meaning that they must breathe through their nostrils, they cannot breathe through their mouth.  If their nose swells to the point that their airway is blocked, they require a tracheotomy, or an incision into their trachea to allow them to breathe.

Anti-toxin isn’t normally administered in equine snake bites. Treating the symptoms of the bite with anti-inflammatories and hydrotherapy (cold or warm hosing) are the initial treatment steps. Anti-biotics are very important to prevent a secondary bacterial infection of the damaged tissue.  It is impossible to tell initially how much tissue injury will occur with a snake bite.  The amount and strength of the venom injected in the snake bite determines the amount of tissue damage that will occur.  Skin, tendons and muscles that are affected by the venom can die and need to be debrided or surgically removed.  The degree of long term damage that results depends on the location of the snake bite and the strength of the venom injected.  Most snake bites recover fully, especially if identified and treated as early as possible. 

With the winter weather we've been experiencing lately, the care of our equine friends becomes more difficult.  Impaction colic, an accumulation of dehydrated fecal material in the large colon, is a common type of colic in the cold weather. This type of colic is caused by not drinking enough water and inactivity.  To encourage your horse to drink enough water, provide lukewarm water.  A heated water bucket, adding hot water to warm up available drinking water or even dumping and re-filling water can increased the temperature of the water offered to your horse.  Adding table salt to your horse's grain, a teaspoon twice a day, can also increase their water consumption.

Here are some more recommendations to prevent colic from the American Association of Equine Pracititoners:

10 Tips for Preventing Colic

1. Establish a daily routine – include feeding and exercise schedules – and stick to it.
   
2. Feed a high quality diet comprised primarily of roughage.
   
3. Avoid feeding excessive grain and energy-dense supplements. (At least half the horse’s energy should be supplied through hay or forage.  A better guide is that twice as much energy should be supplied from a roughage source than from concentrates.)
   
4. Divide daily concentrate rations into two or more smaller feedings rather than one large one to avoid overloading the horse’s digestive tract.  Hay is best fed free-choice.
   
5. Set up a regular parasite control program with the help of your equine practitioner.
   
6. Provide exercise and/or turnout on a daily basis.  Change the intensity and duration of an exercise regimen gradually.
   
7. Provide fresh, clean water at all times.  (The only exception is when the horse is excessively hot, and then it should be given small sips of luke-warm water until it has recovered.)
   
8. Avoid putting feed on the ground, especially in sandy soils.
   
9. Check hay, bedding, pasture, and environment for potentially toxic substances, such as blister beetles, noxious weeds, and other ingestible foreign matter.
   
10. Reduce stress.  Horses experiencing changes in environment or workloads are at high risk of intestinal dysfunction.  Pay special attention to horses when transporting them or changing their surroundings, such as at shows.
    

For more information about colic prevention and treatment, ask your equine veterinarian for the “Colic” brochure, provided by the American Association of Equine Practitioners in partnership with Educational Partner Bayer Animal Health.  Additional colic information is available by visiting the AAEP’s horse health web site, www.myHorseMatters.com.

What you see: After eating, food material and saliva are coming from your horses nostrils.  He/she is anxious and uncomfortable. This is shown by coughing, head shaking, stretching out the neck, chewing, pacing.

What it is: An obstruction of the esophagus, usually with feed material.  This is different than a human choking which is an obstruction of the trachea.  A horse with choke can still breathe. So while this is a an urgent situation, the airway is not blocked and the horse can still breathe.. There is no urgent, life-saving need to resolve the choke.

Causes: Eating too quickly, trying to swallow a large piece of feed - carrot, apple, corn cob, not enough chewing due to poor teeth, eating while sedated, malformation of the esophagus.

What to do: Remove all feed and water, do not allow the horse to graze. Encourage him to stand quietly with his head down. Call the clinic.  Sedation may be recommend until a veterinarian can examine the horse.  Monitor the amount of discharge coming from the horse's nostrils. If the discharge stops, he may have cleared the choke on his own.

Treatment: Most chokes are mild and may clear with time.  Sedation can relieve the esophageal spasm that accompanies choke and allow food to pass from the esophagus to the stomach.  If extra treatment is required, a veterinarian can pass a stomach tube into the esophagus and lavage the feed material with water.

After-care: The esophagus is often irritated and inflamed after a severe choke.  Anti-inflammatories are often used to decrease the pain and resulting inflammation. Witholding food for 24 hours will help the esophagus heal and prevent re-choking. Pneumonia due to food being inhaled into the lungs can occur after a prolonged choke. Monitor for any signs of nasal discharge and monitor the temperature. A temperature greater than 101.5 can indicate a problem. Call the clinic if this occurs.

  De-worming protocol         
Variations in each horse’s immune system and management situation should be reflected in its ndividual de-worming program.  Many horses, especially if kept at an appropriate number of horses per acre, with good pasture maintenance, do not require de-worming every 2 months.  Studies have shown that in most horse populations, 20% of the horses carry 80% of the parasite burden. These horses with high worm loads should be treated more frequently than those with a naturally high resistance to worms. To determine whether de-worming is necessary, fecal flotations should be performed 2 to 3 times a year. This test measures the number of parasite eggs being shed in the manure.

The appropriate time to take a fecal test is determined by the type of de-wormer last administered.  Parasite eggs, which are being measured in the fecal flotation, are not shed for 4 - 6 weeks after de-worming with fenbendazole (Panacur) and pyrantals (Strongid), 8– 10 weeks after using an ivermectin product and 12 –16 weeks after moxidectin (Quest) administration.  Samples should be taken 1 to 2 weeks after the horses are beginning to shed to determine the level of parasites still present. 

 By using the results of fecal flotations in the decision to de-worm, anti-parasite drugs can be used more effectively. This will result in less de-wormers being used, especially for those horses with a naturally high resistance to parasites. Horses that have a low parasite load should still be de-wormed with an ivermectin product at least twice a year – preferably in the fall (September/October). This de-wormer will be timed to kill strongyles they picked up in spring and to kill any bots they ingested.  A second de-worming with ivermectin or moxidectin can be performed, again after a fecal sample is submitted 9-10 weeks after de-worming with ivermectin, in December/January.  Winter is also the best time to de-worm for tapeworms.  The combination products of ivermectin/praziquantel (Equimax or Zimectrin Gold) and moxidectin/praziquantel (Quest Plus) are ideal for the winter de-worming.  As the grass begins to grow in the spring, a fecal sample should be taken. Horses appropriately de-wormed with a high resistance to worms may not need to be de-wormed before being turned out on pasture.  Horses with a high fecal count should be de-wormed for their own health and to ensure they do not contaminate the pasture. Fecal samples can be collected by us during spring and fall vaccines, or can be submitted to the clinic. 

Procaine Penicillin G Administration
   Penicillin is an excellent antibiotic against certain bacterial infections.  Procaine Penicillin G (“PPG”) is a type of penicillin administered intra-muscularly every 12 hours. Procaine is added as a local anesthetic to decrease pain at the injection site.  PPG is an effective drug, however it does have some side effects. The most common side effect is pain and swelling at the injection sites.  However, if this drug enters a blood vessel, a serious reaction can occur due to the procaine.  As blood vessels are present in muscle tissue, vessels can be inadvertently entered during an intra-muscular injection.  Seizures, trembling and possibly death can occur if a large amount of PPG is injected into a blood vessel.  If a procaine reaction does occur confine the horse to a quiet, dark stall.

To minimize the possibility of a reaction follow these steps:

• Ensure the penicillin is well mixed by shaking until there is no white layer left in the bottom of the bottle.
• Draw up the prescribed dose of penicillin.
• Separate the needle from the syringe and place the needle, all the way up to the hub, into the muscle. Sites that can be used are:
    o    The muscle of the neck: at the base of the neck, approximately 4” (the width of a hand)  down from the crest and 4” from the bottom of the neck
    o    The “hamstrings”: either side of the tail in the muscular part of the back of the hind legs.
• Look at the hub of the needle. If blood is in the hub, remove the needle and place it in another
site. If there is no blood in the hub, attach the syringe to the needle.
• Before injecting, draw back on the plunger and observe for blood being drawn in to the syringe. If blood is observed in the syringe, which will be a pink tinge in the penicillin, remove the needle and start over. If no blood is seen, depress the plunger to inject.
• Inject no more than 15 cc at one site. Pull back frequently (after every 5 cc is injected) to check for blood during the injection.
• After 15 cc has been injected in one site, re-direct the needle. Do this by detaching the syringe from the needle. Pull the needle out of the muscle, leaving the tip under the skin.  This is less painful for the horse, as most of the pain of injection is from pushing the needle through the skin. Re-direct the needle into another area of muscle. Again check for blood in the hub of the needle. Attach the syringe and continue injecting, checking frequently for blood.
• Rotate injection sites. Ex. Left side of the neck in the morning then left hamstring in the evening.

Please call with any concerns (540)832-3030.

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Vaccination and Deworming Schedules

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