Misunderstood, Misused, & Misdiagnosed Disease #2: Lyme Disease

I hope you enjoyed reading about Misunderstood, Misused, & Misdiagnosed Disease #1: EPM.  In that post I explained how some horse enthusiasts (trainers, owners, etc) have used this disease to explain any number of abnormalities that their horse is exhibiting.  EPM is quite a convenient disease to blame for oddities because it affects horses in so many different ways.

Another disease that I have found that is easy to over-use as a diagnosis is Lyme Disease.  In this post I would like to briefly explain what Lyme disease is, why it is easy to misuse as a diagnosis, and how a veterinarian evaluates a horse to determine if the Lyme Disease is responsible for the clinical abnormalities that the horse exhibits.  I will not get into the complex pathology and treatment options of Lyme Disease in this post.


 

Lyme Disease is one of several nasty diseases that can affect multiple species, including humans, dogs, and horses.  It is caused by spirochete bacteria named Borrelia burgdorferi (Bb).  These spiral-shaped bacteria are transmitted to humans and animals by species of Ixodes ticks.  The deer tick or blacklegged tick (Ixodes scapularis) transmits Lyme Disease to humans and animals on the east coast and north central United States, while the western blacklegged tick (Ixodes pacificus) is responsible for cases on the west coast of the US.

ixodeswcms
The Blacklegged Tick can carry Bb bacteria and typically infects animals and humans on the east coast and upper midwest of the US.  Source:  cdc.gov/lyme/
western_blacklegged_tick
The Western Blacklegged Tick (Ixodes pacificus) can transmit Lyme Disease to animals and humans in the western US.  Source: cdc.gov/ticks/

 

 

 

 

 

 

A tick becomes a host for Bb when it sucks blood from an infected animal or human.  That tick can infect others when it attaches to another being and begins to feed on them.  Ticks salivate excessively during feeding, and the bacteria are present in the saliva.  Usually the tick needs to feed for over 24 hours before the Bb bacteria are transmitted to the host.  The longer the tick feeds, the greater the chance that Bb bacteria will be transmitted to the host.

Once transmitted, the Bb bacteria will be attacked by the body’s immune system.  This attack is what causes the symptoms that are present when an animal has Lyme Disease.  Symptoms/clinical signs are different for humans versus dogs versus horses.  For the purpose of this post, we will only focus on horses.

Now I’d like to focus on what makes Lyme Disease a Misused, Misunderstood, and Misdiagnosed disease.

#1 – Large Variety of Clinical Signs

Below is a graphic listing some of the clinical signs that have been seen in horses with Lyme Disease.

Capture

Important factors to consider:

  • Not every horse infected with Lyme Disease will develop all of these signs.
  • Several of these symptoms are difficult to recognize (low-grade fever, skin sensitivity).

“For some reason humans like to have one explanation for everything, so our minds will want to look for one disease that causes all of these problems.  Lyme Disease is such an easy way to explain all of these issues and it is treatable!  However, things are not usually that simple.”

#2 – Many other (and sometimes more common) diseases show similar clinical signs

Lets look at a few examples.

Case 1:  A performance horse has had chronic weight loss, poor performance, and some behavior changes (lethargy)  over the past 6 months.  Based on the clinical signs listed above it seems like the horse is a shoe-in for Lyme Disease diagnosis.  However, as we gain some more history on the horse we find that it is a nervous horse and many times will not eat his grain.  Based on this information, the vet decides to perform endoscopy and look at the stomach for evidence of ulcers.  In this case it is highly more likely that gastric ulcers are causing the horse to not eat, lose weight, and become more lethargic.

Case 2:  An older horse is a pasture ornament for 90% of the time, but sometimes the owner really feels like taking him camping and riding for 3-4 days over rugged terrain.  The horse always is sore and lame after the first day, but it is a different leg each time.  He seems fine after getting home and spending some time resting though.  Again – Lyme Disease fits right in with a reasonable diagnosis.  But after using some common sense, we can assume that the owner needs to keep her horse in shape and not expect him to be a weekend warrior.

asset_upload_file272_14239
Muscle soreness is a common clinical sign for horses with Lyme Disease, as reported by veterinarians. However, there are many other more common causes for muscle soreness that should be ruled out first before jumping to Lyme Disease. Source: equisearch.com

There are myriads of issues that can have the same symptoms as Lyme Disease, and sometimes more than one problem can be happening at once.  For example, a mare might be in heat (which causes behavior changes and hypersensitivity) and have a injured tendon (causing lameness and swelling).  For some reason humans like to have one explanation for everything, so our minds will want to look for one disease that causes all of these problems.  Lyme Disease is such an easy way to explain all of these issues and it is treatable!  However, things are not usually that simple.

# 3:  Lyme Disease is not easy to definitively diagnose

Like EPM, a diagnosis of Lyme Disease is not simply a test with a positive or negative result.  To reach a diagnosis of Lyme Disease, the vet has to use deductive reasoning and their experience.  For an example I would like to point to a graphic used by veterinarians when trying to make a diagnosis of Lyme Disease in a dog.

Capture
When a dog presents to a vet with lameness and fever, they must use powers of deductive reasoning to determine the diagnosis of Lyme Disease because there are many other disorders that cause lameness and fever.  The same goes when examining horses.  Source:  ACVIM Consensus Statement, Journal of Veterinary Internal Medicine 2006.

When a vet is presented with a horse that is a Lyme Disease suspect (is showing appropriate clinical signs) they must ask themselves several questions:

  1.  Does the horse live or has it been to an area where ticks that carry Bb are present or endemic?
  2. Have ticks been found on the horse?
  3. Have other disorders that cause similar signs be ruled out?

If the answer(s) is(are) yes to those questions, then the next step is to draw a blood sample and send it in for testing.  Usually the test is looking for the presence of antibodies to Bb present in the horse’s blood.  The presence of the antibodies indicate that the horse has been EXPOSED to the Bb bacteria.  It does not tell us if the horse currently is infected and fighting Lyme Disease.  For that answer we have to look at the number and type of antibodies present in the blood.

Large numbers of antibodies in the blood typically indicate an active infection, but these numbers are all relative.  There are no exact cutoff numbers that say “if your horse has X amount of antibodies then they should be treated for Lyme disease”.  The decision on whether to treat or not is best left up to your veterinarian, who has clinical training and experience in determining what horses might benefit from treatment.  For more information on testing and interpreting results, I refer you to this nice summary from Cornell University.


 

To summarize:  Diseases that have many vague and intermittent symptoms are easy to jump to as a diagnosis for any ailment your horse may face.  This is especially true when there is no diagnostic test that is clear cut, and when treatment may or may not improve the clinical signs of the disease.  Too often these type of maladies are misused by horse enthusiasts to explain all of the problems that they see in their horse, mostly because the disease is misunderstood.  It would be best for the horse if we can keep an open mind and scientifically search for a correct diagnosis, instead of conveniently jumping to diseases like EPM and Lyme Disease.

 

 

 

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Horse with fever and diarrhea – could it be PHF?

It is late summer/early fall here in the United States.  The weather can quite variable – one minute its hot and sunny, and the next day it cold and blustery.  During this time of the year veterinarians in certain portions of the country will also start seeing an uptick in cases of horses with fever and/or diarrhea.  I think this would be an excellent time to discuss how your veterinarian might approach the diagnosis and treatment of your horse if it develops these symptoms.  I also think it is pertinent to explain why your vet might lean towards one diagnosis over another, depending on the season.  So, lets go through a typical case that I see during this time of year….

Later summer to early autumn is the classic time to see cases of Potomac Horse Fever in the United States.
Later summer to early autumn is the classic time to see cases of Potomac Horse Fever in the United States. Source: absorbine.com

(phone rings)

Horse Owner:  Hey Doc, I noticed that my mare did not finish her grain this morning and now she won’t even look at her food tonight.  She also is acting dumpy.

Me:  I’m sorry to hear that.  Have you seen her pass any feces?

Horse Owner:  Not yet.  She’s not really acting colicky though.  She just stands in her stall with her head in the corner.  Now that I’m watching her, I can see it looks like she is breathing fast and her nostrils are flaring.

Me:  Oh, well that sounds like a fever.  Can you take her temperature?

Horse Owner:  I don’t have a thermometer and I really don’t feel comfortable doing that.  Can you just come see her?

Me:  OK.  Just keep her in the stall, pull her food away, and keep water available.


(Later, at the barn)

Horse Owner:  I’m really worried about her Doc.  What do you think is going on?

Me:  Well she definitely is fighting something.  Her temperature is 105.0°, which is pretty high.  Anything over 101.5° is what I would consider a fever.  Her lung and heart sounds are normal, but their rate is increased.  Her gut sounds are very active, which means that colic is less likely.  I’m a bit concerned about her gum color though – its kind of pale with a dark purplish line just above the teeth.  It’s what we call a “toxic gum line”.

A "toxic" gum line in a horse refers to the darker pink to purple color above the teeth in contrast to the light pink above that. Source: ckequinehosiptal.com
A “toxic” gum line in a horse refers to the darker pink to purple color above the teeth in contrast to the light pink above that.
Source: ckequinehosiptal.com

Horse Owner:  Toxic gum line?!!  Do you think she ate some poison???!!

Me:  No, no, nothing like that.  The term “toxic” refers to endotoxins, which are toxins that normally are present in certain bacteria.  When the membrane that surrounds the bacteria is disrupted, then these toxins are released into the circulatory system.  The toxins can cause a lot of the clinical signs that your horse is exhibiting – fever, gum color abnormalities, and an elevated heart rate.

Horse Owner:  Do you think she has a bacterial infection?

Me:  I am not sure at this point.  Endotoxemia can be caused by bacteria that normally live inside the horse’s GI tract and release small amounts of endotoxins as they die naturally.  In a normal situation the GI tract has a nice barrier that prevents the endotoxins from getting into the bloodstream.  However,  if the GI tract gets inflamed or loses blood supply, then the endotoxins can get into the bloodstream.  They basically cause a massive inflammatory reaction because the body is trying to get rid of them.  So we can see these symptoms if anything causes the intestinal lining to become inflamed or lose blood supply.

Horse Owner:  So how do we treat this problem?

Me:  First we start by administering anti-inflammatory medication.  This will help decrease her fever and make her feel better.  It also is to prevent laminitis/founder – which is also a side effect of endotoxemia.  Second, I would like to take a blood sample and run a complete blood count and serum biochemistry panel.  This will give me an idea of the severity of the inflammation as well as tell me how her vital organs are functioning.


(The next day I call the owner.)

Me:  How is your horse doing today?

Horse Owner:  She still is pretty dumpy today and now I think she has diarrhea.  Its in her tail and on the stall walls.  Her temperature is normal though!

Me:  I had a feeling this would happen.  The results from the blood work came back showing very low white blood cell counts, which most likely means that her body is fighting an infection and the blood cells have moved out of circulation and to the area of infection.  Her protein and red blood cell counts are up, which means that she probably is also a bit dehydrated.  The good news is her kidneys and liver are functioning.

Horse Owner:  OK.  What kind of infection?

Me:  Based on the time of year (late summer/fall) and her clinical signs (fever followed by diarrhea), we most likely are dealing with Potomac Horse Fever.  According to our records it looks like we didn’t vaccinate for that this year.

Horse Owner:  Yeah, I know.  I was tight on money at that time so I skipped that vaccine.  Plus, I thought you said that the vaccine wasn’t going to protect her from it.

Me:  It’s true that the vaccine is not 100% effective, but horses that are vaccinated and then infected tend to have a less severe form of this disease, at least according to many equine vets out there (myself included).  So we do recommend that vaccine so that if a horse is infected they have a better chance of coming through the disease more quickly and with less side effects.

Horse Owner:  How did she get Potomac Horse Fever (PHF)?  None of my other horses are sick and she hasn’t traveled anywhere.

Me:  Potomac Horse Fever is a disease that is transmitted by the horse ingesting insects or bat feces that are infected with a bacteria called Neorikettsia risticii.  The life cycle is kind of complicated, but basically the bacteria live inside of a parasite (cercariae) that infects fresh-water snails.  When the weather is warm the parasite leaves the snail and gets eaten by the larvae of aquatic insects (May Fly, Caddis Fly, Dragonfly).  Inside the insect larvae, the parasite enters a different part of it’s life cycle and becomes a metacercariae, which is still housing the bacteria (N. risticii) inside of itself.

Potomac Horse Fever Life Cycle Source: threeoaksequine.com
Potomac Horse Fever Life Cycle
Source: threeoaksequine.com

If a horse accidentally ingests a metacercariae, the parasite will pass through the stomach untouched because it is acid resistant.  The parasite carries the bacteria all the way to the intestines of the horse.  The bacteria then infect the cells that line the intestines and cause massive damage to the intestines.  This is what causes the horse to have diarrhea.  Also, a large portion of the white blood cells leave the blood circulation and to attack the bacteria – which is why their counts are low.

Horse Owner:  So the horses get the bacteria from insects in the environment, not other horses?

Me:  Technically, a horse could get the bacteria from another horse if he ate large amounts of the infected horse’s feces, but that is highly unlikely.

Horse Owner:  What about humans or other animals?

Aquatic insects as seen above can carry the parasite that carries the bacteria that causes PHF.   Source: anokaequineblog.wordpress.com
Aquatic insects as seen above can carry the parasite that carries the bacteria that causes PHF.
Source: anokaequineblog.wordpress.com

Me:  Humans do not seem to get this disease.  There is some thought that bats may carry the disease, but it hasn’t been seen in other animals.

Horse Owner:  I thought horses had to be near water to get Potomac Horse Fever.  Is that not true?

Me:  Unfortunately that is not true.  Any place where there is enough fresh water for insect larvae to live will do.  This includes areas under stall mats, water tanks, etc.

Horse Owner:  So now what should we do?

Me:  Luckily there is an antibiotic that is highly effective for treating PHF – oxytetracycline.  Additionally I recommend some IV fluids to help with hydration, especially since she was already dehydrated last night.  We will keep her on the anti-inflammatory medication to control her fever and prevent laminitis.  Also, it would be a good idea to ice her feet to prevent laminitis.  Most horses make it through the fever and diarrhea just fine (with appropriate treatment).  The part that can be deadly is usually the laminitis.

Horse Owner:  Well I guess I can load her up and take her to stay with you guys at the hospital until she can come home.  Is there anything I can do to prevent my other horses from getting PHF?

Me:  Number one – vaccinate your horses before the warm weather gets here.  The best time is springtime, however in some areas of our country they recommend a booster in the fall.  Number two – practice insect control measures.  Limit places where standing water accumulates and keep the environment as clean and dry as possible.  You should also turn off lights at night to discourage bugs from hanging around the barn and/or sheds.

(End conversation)


I hope you all found this change of pace in my blog refreshing!  Again, please let me know if there are any topics of interest that you would like me to discuss.  Thank you!!

The art and science of a lameness exam

Athletic trainers, orthopedic surgeons, and all the various other professionals involved in human sports medicine have it easy.  Waaaay easy.  When a person has pain when they are doing an activity (running, jumping, etc), they can go into the doctor or trainer and “Here’s where it hurts” and “It hurts whenever I do X activity”.  The doctor can get essential information from the patient in less than 10 minutes simply by asking the right questions and getting detailed, honest answers.

Screen Shot 2015-05-12 at 8.51.37 AMNow lets talk about the difference a veterinarian faces when performing a lameness exam on a horse.  The horse can not tell us which leg hurts, where on the leg it hurts, what activity makes it worse, how long it has been happening, etc, etc, etc.  A veterinarian relies on the owner or horse trainer to gather some of this information, but often the information is vague or conflicting depending on whom you are talking with.  Many times I get some variation of the following history:

“My horse has been ‘off’ for a couple of months now.  It feels like it is in the hind leg but my trainer said she is short striding in the front.  I gave the horse some ‘bute’ but I ran out so I stopped a couple of weeks ago.  My farrier put on shoes last week.”

This type of history is very vague and really does not tell the vet much except this is a chronic mild to moderate lameness.  Now it is up to the vet to figure out what is really going on and how to fix it.

Which leg or legs are lame?

This is the first question the vet attempts to answer when performing a lameness exam.  Sometimes it is very obvious, other times it can hard to tell.  In order to determine which leg or legs are lame, the vet will watch the horse perform different gaits, starting with a basic walk.  If not obvious at a walk the vet will move on to a trot in a straight line.  If it is still not obvious the vet may lunge the horse in different directions and on different surfaces.  Basically the idea is to visualize the lameness or gait abnormality that the owner or rider has noticed.

The vet will watch the horse move at different gaits on different surfaces to help determine which leg is lame. Source: thehorse.com
The vet will watch the horse move at different gaits on different surfaces to help determine which leg is lame.
Source: thehorse.com

Several things can come up that make finding the lame limb difficult or impossible:

1.  The horse is not lame the day of the examination.  This situation happens very often and is a major frustration for owners.  You can have a horse that has been consistently lame for three months but the day the vet examines it the horse will suddenly be sound.  An important piece of advice is to exercise your horse before the vet appointment and make sure his is actually still lame!

2.  Multiple legs are lame.  It is extremely hard to make an accurate diagnosis when a horse has multiple limbs that are making his gait abnormal.  One leg may be compensating for another or the legs may have two completely different issues.

Where in the limb or body is the lameness coming from?

Once the vet determines which limb is lame, the next step is to find where in that limb the lameness is coming from.  Again, sometimes this can be quite obvious.  For instance, if the right front leg is lame and the fetlock is swollen, hot, and painful your vet probably will be confident that the lameness is coming from the fetlock region.  If it is not obvious, your vet can perform certain tests to help localize the lameness.

Your vet may perform a flexion test in order to determine where in the limb the lameness is coming from. Source: vetmed.vt.edu
Your vet may perform a flexion test in order to determine where in the limb the lameness is coming from.
Source: vetmed.vt.edu

One simple test is called a “flexion test”.  Your vet will hold certain joints in flexion for various periods of time and then watch the horse trot.  If flexing a joint makes the lameness worse, it is highly likely that the lameness is coming from that joint.  Another way to help localize a lameness is to test the hoof for sensitivity to pressure.  A hoof tester is a device that puts pressure on certain regions of the foot.  A reaction or pulling  the foot away from the examiner tells the vet that the horse is sore at that particular location in the foot.

If after performing flexion tests, palpating the limb, and manipulating the limb, the location of the lameness is still not obvious your vet make begin “blocking” the limb/joints.  “Blocking” refers to numbing portions of the limb and watching the horse trot. If the lameness disappears after a nerve “block”, then the vet can be confident that the problem area is within the portion of the leg that was numb.  This test does not always pinpoint the exact location of the lameness, and sometimes the results can be questionable – for instance, the lameness might improve by only 50%.  If this is the case your vet may repeat the block on a different day or use a combination of tests to localize the lameness within the leg.

What pathology or abnormality is causing the lameness?

In some cases your horse may need an MRI for accurate diagnosis of the cause of his lameness. Source: purdue.edu
In some cases your horse may need an MRI for accurate diagnosis of the cause of his lameness.
Source: purdue.edu

After your vet is confident that they have pinpointed the lame leg and localized the lameness to a region of the leg, they can begin to look for an abnormality in that region that is responsible for the lameness.  The most common way to detect the abnormality is by using diagnostic imaging (x-rays, ultrasound, MRI, etc).  Depending on the case and the experience of the vet, they will usually start with either x-rays or ultrasound to image the leg.  X-rays are used to visualize bones and joints, whereas ultrasound is better for looking at tendons and ligaments.  Sometimes a defect or abnormality may be very small and impossible to see with x-rays or an ultrasound.  At that point your vet may refer your horse for an MRI or a nuclear scan.  Diagnostic imaging often is the most costly part of the lameness exam.

What can an owner do prepare for a lameness exam?

If a horse owner has never had the experience of dealing with lameness issues, there are several things that I think they should know before having a lameness exam done on their horse.

– Do not give your horse any pain medication (bute, Banamine, etc) at least 48 hours before a lameness exam.  The vet wants to see your horse when it is as lame as possible.  This make localizing the lameness much easier.

– Bring your tack with you and be prepared to ride.  Sometimes a gait abnormality is only visible under saddle.  The vet needs to see the lameness in order to make a diagnosis, so you will need to recreate the situation in which the lameness occurs.

A nerve block numbs portions of the limb.  If the lameness improves by 80% or more, it is likely the cause of the lameness is in that region.  If the lameness only improves slightly then different nerve blocks may need to be attempted. Source: research.vet.penn.edu
A nerve block numbs portions of the limb. If the lameness improves by 80% or more, it is likely the cause of the lameness is in that region. If the lameness only improves slightly then different nerve blocks may need to be attempted.
Source: research.vet.penn.edu

– The examination may take several hours, maybe even days.  The more difficult it is to determine where the lameness is coming from, the longer the exam will take.  If blocking the leg doesn’t show >80% improvement then it may need to be blocked a different way (for example a joint blocked instead of a region of the leg) to narrow down the source of the pain.  The numbing effect of a block can last hours and the vet needs to be sure that the first block has completely worn off before trying a second one in the same region.

– Lameness examinations can be expensive.  A subtle lameness with a hard-to-visualize abnormality can be very difficult and time-consuming to correctly diagnose.  An owner needs to be prepared that in order to get definitive answers, they may be spending thousands of dollars.  On the other hand, an obvious lameness that is easy to diagnose (example: hoof abscess) will not be so costly.

To summarize….

In order for a veterinarian to be proficient in lameness diagnostics, they must be experienced in the observation of gaits, recognition of subtle abnormalities, interpretation of test results and diagnostic imaging.  The lameness exam is an exercise of both the art and science of veterinary medicine.

Equine Herpesvirus 1 – What you need to know when facing current outbreaks

Outbreaks of diseases are scary.  The disease can be a brand new virus, a bacterial “superbug”, a virus that has mutated, a parasite that has spread to a new geographic location – you get the idea.  The recipe for a contagious disease outbreak calls for two basic things:

Ok, we aren't talking about an outbreak of zombies, but horse disease outbreaks are scary too! Source:  inkace.com
Ok, we aren’t talking about an outbreak of zombies, but horse disease outbreaks are scary too!
Source: inkace.com

1) a susceptible population of living things (humans, animals, plants, etc) that do not have immunity to the pathogen

2) a pathogen (virus, bacteria, etc) that is easily transmitted between individuals it infects

The disease does not have to be deadly, its main goal is just to replicate in its host.  For instance, the flu virus is not often deadly but it transmitted very easily between individuals.  This ability allows the virus to find a new host before it is destroyed by the original host’s immune system.  The ease of transmission causes a lot of individuals to become sick in a short amount of time.  Additionally, if the pathogen can replicate in its host, and that individual becomes contagious before they realize they are sick, the disease has an extra advantage.

So how does all of this figure into the current outbreaks of Equine Herpesvirus-1 (EHV-1)?  Well, first I am going to discuss a little bit of background information on this virus (which is not a new virus, by the way).  Then I will delve into how it has evolved to cause current outbreaks of disease.  Finally, I will go over ways horse owners can prevent and prepare for an outbreak of EHV-1.

What is EHV-1?

Source: Gluck Center at University of Kentucky
An electron photomicrograph of EHV-1          Source: Gluck Center at University of Kentucky

EHV-1 stands for Equine Herpesvirus Type 1.  There are several types of Equine Herpesviruses but the main ones that cause serious health problems  in horses are Types 1, 3, and 4.  In this post I am only going to discuss EHV-Type 1.  EHV-1 can cause 4 different manifestations or clinical presentations:

1.  Neurologic – aka Equine Herpesvirus Myeloencephalopathy (EHM).  This form affects the nervous system (brain and spinal cord).

Just to be clear – EHM is a form of EHV-1 – not a separate disease.

2.  Respiratory – Affects the respiratory system (lungs, sinuses, trachea, nasal passages, etc.)

3.  Abortive – Affects the reproductive tract of a pregnant mare causing fetal death and subsequent abortion

4.  Neonatal – Newborn foal is born apparently normal but then becomes severely ill 1-2 days after birth.  Despite the best supportive care these foals often die from severe respiratory disease and it’s complications.

How does EHV-1 affect the horse?

The virus can affect 3 different types of body systems: neurologic, reproductive, and respiratory.  Once a horse is infected with the virus, the virus travels to the lymph nodes and infects certain types of white blood cells.  The infected cells are released out into circulatory system, where they travel in the blood to different sites in the body.  They can travel to the lungs, uterus, or spinal cord.

One key point here is that it is unknown why the virus attacks certain areas of the body.  There is research currently being performed that is attempting to figure out why an outbreak of neurologic disease will affect one group of horses, but another group may only show up with respiratory disease.  One recent finding is that there seems to be some genetic varieties of the virus that tend to cause the neurologic form more often, but not all cases of EHM are caused by these mutant varieties.

How is EHV-1 transmitted or spread?

EHV-1 has several of what I like to call “superpowers”.  The way it is transmitted is one of its superpowers.  Most of the time the virus is transmitted by horse-to-horse contact.  We all know how curious horses like to smell everything and everyone, especially new horses.  In fact, most horses introduce themselves by intensely smelling one other’s nose – it’s like they are smelling each others breath!  EHV-1 (cleverly) is easily transmitted through nasal secretions from one horse to another.

Horses naturally communicate with one another by touching noses and smelling.  EHV-1 has adapted so that it is transferred to a new horse when this happens.   Source: thehorse.com
Horses naturally communicate with one another by touching noses and smelling. EHV-1 has adapted so that it is transferred to a new horse when this happens.
Source: thehorse.com

However, EHV-1 has also evolved to be able to survive on the surfaces of objects that are contaminated by an infected horse (tack, human clothing, stalls, fences, etc).  And that’s not all – the virus can live (in the ideal conditions) up to 21 days on an object!  Furthermore, foals can be infected in utero and other horses can be infected by contact with an infected placenta or fluids from the mare.

So I can just keep my horse away from sick horses and he will be fine, right?

Wrong :(.  Another superpower of EHV-1 is that it can infect a horse and the horse can become contagious to others even before it shows physical symptoms of being ill.  By the time you see that the horse is sick he could have already infected all of his pasture mates.

A third superpower of EHV-1 is it’s ability to become latent (dormant).  A horse can be a “carrier” of this virus (a reservoir) and not show any outward abnormalities.  At some point, though, the virus can be reactivated in the carrier horse – who can now spread the disease to others.  Things like stress or a different illness can cause EHV-1 to be reactivated.  It is no wonder that  weaning, training at the racetrack, and traveling for shows are common times where we see outbreaks of EHV-1.

What about vaccines?

Vaccination is an excellent way to prevent spread of EHV-1 and has worked wonders for the breeding industry in preventing abortion outbreaks.  It also seems to protect against respiratory disease.  However, there is no current vaccination that is able to completely prevent the neurologic form of the disease.  This is a hot area of research and scientists are working on ways to improve the current vaccines or possibly manufacturing new vaccines to protect against EHM.

Source:  The Gluck Center at the University of Kentucky
Source: The Gluck Center at the University of Kentucky

EHV-1 has been around for a long time.  Why the big concern about it now?

The concern over the recent outbreaks has to do with the fact that EHM (caused by EHV-1) is an emerging disease.  The neurologic form of EHV-1 (EHM) used to be quite rare.  However, in the early 2000’s we started to see outbreaks of horses affected with EHM in various spots across the US and the world.  The virus has seemed to change in its severity and/or behavior in affected animals.  Furthermore, since vaccinations do not protect against this form of the virus, there is no way to systematically control it.  And remember how easily it is spread (its superpowers)?  The fact that the virus can spread to hundreds of horses without seeing a single horse look sick makes it a big cause for concern.

What are the clinical signs of EHV-1 and EHM?

Screen Shot 2015-04-24 at 10.59.00 AM

The signs listed in the tables above are seen with lots of diseases – not just EHV-1 or EHM!  One important characteristic is that your horse needs to have made contact with new horses or their bodily fluids, and that the onset of the neurologic signs is very fast.  Usually the signs show up and progress for 24-48 hours and then stop progression.  After that 48 hour period, the worst appears to be over and how bad each individual horse is affected will determine their prognosis.  If the horse goes down and can’t get back up then the prognosis is grave.  If the horse is only minimally affected then the odds are good that they will gradually recover.

What about treatment?

There is currently no specific treatment for EHV-1 and EHM.  Because they are viruses, antibiotics will not fight them.  However, sometimes horses are given antibiotics to prevent opportunistic bacterial infections because the horse’s immune system is working overtime on fighting the virus.

There is no specific treatment for EHV-1 and EHM, so we rely on supportive treatments (like IV fluids) assist the horse in it's recovery.
There is no specific treatment for EHV-1 and EHM, so we rely on supportive treatments (like IV fluids) assist the horse in its recovery.

The treatments your horse will receive are all supportive – meaning they are just supporting his basic bodily functions until his immune system takes care of the virus and healing takes place.  Examples of supportive treatments are IV fluids and anti-inflammatory drugs.

How can I prevent my horse from getting EHV-1 or EHM?

Even though the vaccine does not specifically protect against the neurologic form of EHV-1 (EHM), it is still a good idea to vaccinate your horse for EHV-1.  The vaccination does protect against the respiratory form and the abortive form of EHV-1, so your horse will be protected against those manifestations of this disease.  The vaccine does also seem to decrease viral shedding, so if your horse does become infected with the neurologic form you can help prevent shedding and infecting other horses with the virus.

Another was to prevent EHV-1 and EHM is to practice good biosecurity around the farm.  This means that any incoming horses are isolated from your herd for a period of at least 21 days.  That means that nothing that the isolated horse touches is allowed to touch anything that your herd horses may touch (tack, buckets, stalls, fences, etc).  Wash your hands between caring for your new horse and the rest of the herd.  Take the temperature of the new horse twice daily to make sure he does not spike a fever.  Isolating new horses protects against many diseases, including all the forms of Equine Herpesvirus and Strangles.

Horses that travel to shows or clinics should also be isolated from your herd when returning.  It is a good idea to take the temperature of your horse twice daily for 14 days before returning him to the herd.  If he develops a fever, call your vet.

There is a ton of information on the internet regarding what happens if your horse is at a show when there is an outbreak and various scenarios of the like.  Sources that are reputable include AAEP and APHIS.USDA.gov.  Another thing you can do is call your vet and see if they know about any current outbreaks in the area.  And it is never a bad idea to contact the shows and places you are traveling to see if they know of any outbreaks or precautions you should take to protect your horse.

Equine Corneal Ulcers – The Case of the Squinty, Watery Eye

Imagine that you are going out to feed your horses for the evening and you notice that one of them is holding her eye shut.  It looks pretty swollen and there is a bunch of watery discharge coming from the corner of the eye.  You put her in the cross ties and try to pry her eye open to have look at the eyeball, but those darn eyelids are so strong!  Finally you result to just standing there are staring at her, waiting for her to open the eye.  When she finally does, you notice the eye looks cloudy.  Time to call the vet……

Swollen, teary eyes that have a blue or cloudy tinge should be examined by your vet ASAP. Source: oceanstateequine.com
Swollen, teary eyes that have a blue or cloudy tinge should be examined by your vet ASAP.
Source: oceanstateequine.com

What could be going on with this eye?

The cornea is the clear tissue that covers the surface of the eye.  This is a diagram of a cross-section of the eye. Source:  thehorse.com
The cornea is the clear tissue that covers the surface of the eye. This is a diagram of a cross-section of the eye.
Source: thehorse.com

When a vet is presented with a horse that has a squinty and watery eye, we can assume that the eye is causing pain to the horse.  A cloudy eye usually indicates that there is “corneal edema”.  The cornea is the tissue on the surface of the eye that is normally clear/transparent.  When the cornea is damaged or irritated is becomes swollen, which creates a blue/cloudy tinge to the surface of the eye.  Corneal edema is not specific for any one disease or injury – it just means that the cornea is injured/irritated.  So the only information we have right now is that the eye is painful and the cornea is swollen.

What happens next?

Your vet will examine the eye.  This may take some sedation, depending on how the horse is behaving.  In some cases the vet may even “block” the eye, meaning they may use local anesthesia to numb the surface of the eye and eyelids as well as prevent the eyelids from squeezing shut.  You would be surprised how crazy strong those eyelids are – I am not kidding.

When doing an eye exam it is best to have the horse in a DARK quiet area.  It may seem counterintuitive, but it is much easier to examine the eye using an ophthalmoscope in the dark than in bright daylight.  Your vet will look through the ophthalmoscope to see the surface of the eye and possibly the back portion of the eye.

Your vet also will most likely stain the eye at this point.  A particular stain, fluorescein, is used to detect defects in the corneal tissue.  In the normal cornea the stain will not attach to the eye because of the surface of the cornea is covered by cells that don’t allow the stain to penetrate them.  If the cornea is damaged or ulcerated the underlying cells of the cornea (stromal cells) will be exposed and they will take up the stain.  The vet can now see where the cornea is ulcerated or damaged.

Fluorescein eye stain can show the location and size of a corneal ulcer. Source: ckequinehospital.com
Fluorescein eye stain can show the location and size of a corneal ulcer.
Source: ckequinehospital.com

If no stain taken up by the eye, the vet will then have to look for other possible reasons to explain why the cornea is swollen.  For the purpose of this article, however, let’s say that your horse had an area of stain uptake of about 2mm diameter.  Your vet now can be confident that a corneal ulcer is responsible for the clinical signs your horse is exhibiting.

How is a corneal ulcer treated?

Like many things in medicine, the answer is “It depends.”  In this case it depends on how deep the ulcer is, how long it has been going on, and how the ulcer responds to initial treatment.  In most cases of a simple ulcer that is caught early in its progression, treatment consists of topical antibiotic ointment, anti-inflammatory medication, and topical atropine.  In other, more complicated cases your vet may want to use additional medications like topical anti-fungals and serum.  In any case, do not use over-the-counter eye medication on your horse!  Do not use Neosporin in the eye!  The eye is VERY sensitive and needs ointment specifically designed to be applied to the eye.

Most of the time the topical medications are applied several times a day to the affected eye.  The constant manipulation of the eye can lead to a very cranky horse.  Sometimes owners will have such a difficult time with their horse that the medication never properly gets in the eye and the eye doesn’t heal.  In these cases there is a special medication delivery system that can be placed around the eye so that the medication can be applied without having to manhandle the horses eye.  The subpalpebral lavage system is definitely something to ask your vet about if you are having difficulty getting eye medications into your horse.

A subpalpebral lavage system allows medication to be administered through a syringe, where it travels down a tube and is deposited under the upper eyelid.   Source: veterinare-ophtalm-lengelle.be
A subpalpebral lavage system allows medication to be administered through a syringe, where it travels down a tube and is deposited under the upper eyelid.
Source: veterinare-ophtalm-lengelle.be

Finally, your horse will need to be kept out of daylight if she is receiving atropine topically to the affected eye.  Atropine forces the pupil to dilate, which is beneficial is terms of preventing pain and permanent damage to the eye.  However, the eye will not be able to adjust to light (by constricting the pupil), so your horse will need to either be in a dark stall or have a patch placed over the affected eye.  Once the atropine is out of the system, the horse can return to her normal turnout schedule.

How long does it take to heal?

Ulcers not treated properly can become infected with bacteria and/or fungi.  Infected ulcers take months to heal and can have major complications. Source: northfloridaequine.com
Ulcers not treated properly can become infected with bacteria and/or fungi. Infected ulcers take months to heal and can have major complications.
Source: northfloridaequine.com

A normal, uncomplicated ulcer should heal within a week or two.  Larger and deeper ulcers take longer to heal than small ones.  Ulcers that become infected with bacteria or fungi can take months to heal.  There are also “indolent” ulcers, which are ulcer that just seem very resistant to healing despite all therapies.  These are fairly rare.  The most important thing to remember is that early recognition and treatment can save you weeks of treatment and loads of money in the long run.  The “wait and see” approach is never a good idea when it comes to the equine eye.  There are several cases each year of clients who end up spending a lot of money treating an infected ulcer for months because they wasted three days treating the horse with an over-the-counter medication.

Any prevention tips?

There is no possible way to 100% prevent the equine eye from getting injured – sorry.  But, keeping a vigilant eye out for areas that look like a good place to scratch or poke an eye can help.  Nail heads, chipped wood, or any piece of wire hanging around is an easy place for a horse to injure his eye.  Also, horses can get ulcers even if they have on a fly mask, so make sure to take off the mask every day and look at the horse :).

Foaling basics by the numbers

Equine reproduction and neonatal care are my favorite parts about veterinary medicine.  I absolutely love breeding and foaling season, despite the busy schedule and unpredictable hours.  A foal’s first whinny and the mare’s returning nicker are the some of the greatest sounds in the world, and there is nothing like watching a foal stand and try to figure out how to nurse for the first time!

Foaling is an amazing process!  The first look and nickers between the mare and foal are wonderful to observe.
Foaling is an amazing process! The first look and nickers between the mare and foal are wonderful to observe.

For the horse owners that have not had a mare and foal before, it can be quite intimidating to read about all of the aspects of foaling and caring for the new arrival.  Just like humans, each equine pregnancy is different and each foal is different.  What looks like no big deal to the average horse person may mean something different to a veterinarian. Furthermore, as you read this article, you will notice that foaling is a fast process where a lot can go drastically wrong in a short period of time.  Thus, one piece of very important advice is to develop a good relationship with your equine veterinarian before your mare is due.  Make sure they (or one of their colleagues) are available to answer your questions 24/7.  Ask them if they have a way to receive pictures on their phone.  Place their phone number up in the barn in big easy-to-read numbers.  This is to ensure you that when the big day comes you are prepared and can easily reach a trusted medical professional if needed.

Because foaling and neonatal care seems to revolve around some very important numbers, I would like to go over the basics of foaling by emphasizing these numbers and explaining what they mean.

320 days

This is the shortest gestation length for a mare.  Any less than 320 days from ovulation and the foal is considered premature.  The average length of gestation is 330-345 days, however some mares will go over 390 days.  We commonly get calls from worried owners because their mare is overdue by weeks, and they are concerned that the foal will be too big for her to deliver.  Many owners wonder if we can just induce the mare to deliver.  It is strongly discouraged in almost every case to induce a mare to foal.  First of all, the longer the gestation length, the smaller the foal tends to be when born – so the chance that the foal will be too big is very small.  Second, we need to remember that sometimes “nature knows best” and that it is the foal that tells the mare when it is ready to be born.  Hormones produced by the foal basically tell the mare that the foal is mature enough to be born and cause the onset of parturition (labor).  When inducing a mare, you run a high risk of having a dysmature foal, dystocia (difficult birth), poor quality colostrum, and a host of related issues.  It is better to let nature take its course and keep the “bun in the oven” longer.

4 to 6 weeks

It is ideal to vaccinate your mare approximately 4 to 6 weeks before her due date.  This ensures that she has the highest level of immunity to those diseases when she foals.  The colostrum (first milk) that she produces will have high levels of antibodies, which will pass to the foal when it nurses.  If the foal ingests the proper amount of colostrum from a vaccinated mare, then it will be protected from those diseases until about 4 to 6 months of age.

6 to 48 hours

Colostrum forms a waxy plug at the end of the teats 6 to 48 hours before foaling in 95% of mares. Source: extension.org
Colostrum forms a waxy plug at the end of the teats 6 to 48 hours before foaling in 95% of mares.
Source: extension.org

Approximately 95% of mares will develop “waxing” on their teats about 6 to 48 hours before the beginning of labor.  The waxy buildup is just colostrum that is starting to leak from the teats as the body prepares for foaling.  The mammary glad will develop and the udder begin to fill with colostrum several days before parturition.  Other signs that the mare may foal soon include relaxation of the vulva and relaxing of the ligaments on either side of the tailhead.

30 minutes

This is the maximum amount of time that a normal foaling should take after the mare’s “water breaks”.  Stage II of labor is the active delivery of the foal and begins once the chorioallantois (bag) ruptures and ends with foal being expelled from the birth canal.  During this stage the mare actively pushes and usually lays down to deliver the foal.  If progress is not being made, then it generally means something is wrong.  Because this stage of labor is so fast, it means that the foal will die very quickly if it is not expelled in the appropriate amount of time.  Improper position and/or presentation of the foal is the typical reason for a difficult birth in the horse.  The normal position and presentation is with both front feet coming out first, followed by the head and the rest of the body and hind limbs.  Any deviation from this positioning can cause a difficult delivery, which may need veterinary assistance.  Since equine labor is a fast and vigorous process, for delivery of a healthy foal by a healthy mare, it is important to have access to a vet nearby.  If you live far from your vet and your mare has a history of difficult deliveries or has any other health problems, it may be a good idea to see if you can have your mare foal at your veterinarian’s office.  Equine vets typically offer this service and may even have wi-fi cameras set up so you can watch the foaling from your home.

anterior_dorsosacral_deliverymerkvetmanual
Normal position and presentation during delivery. Any deviation from this form can cause difficulties for the mare and foal. Source: merckvetmanual.com

3 hours

The placenta or fetal membranes should be passed within 3 hours of delivering the foal. Source: horsejournals.com
The placenta or fetal membranes should be passed within 3 hours of delivering the foal.
Source: horsejournals.com

This is the maximum amount of time that it should take for the mare to deliver the placenta or fetal membranes.  Once 3 hours have passed, the mare is considered to have “retained fetal membranes” and begins to be at risk for infection and laminitis.  At that point it is important to call your veterinarian.  DO NOT try to pull the membranes out yourself!!!  You may end up leaving a piece of the membrane in the uterus, which can serve as a source of infection.  Your vet may give your horse oxytocin (to stimulate uterine contractions), manually remove the membranes, and/or flush out the uterus.  Additionally the mare will probably be given antibiotics and anti-inflammatories.

24 hours

This is the period of time that the gut of the foal can absorb antibodies from the mare’s colostrum.  It is imperative, therefore, that the foal nurses as early as possible and ingests an adequate amount of colostrum from the mare.  The only immune system that the foal has is that which he gains by ingesting his mother’s colostrum.  If the foal does not get enough antibodies from the colostrum, they are immunocompromised and extremely susceptible to any infection.  The normal foal should be standing by 1 hour after birth and nursing within 2 hours.  If you do not see this happen, you may need to hand milk the mare and bottle-feed the foal.  Over the first 24 hours of life the foal should ingest 1-2 pints of colostrum.  If the foal will not take the bottle, then you will have to call the veterinarian to come and place a tube down its nose and into the stomach.  The vet can then pour colostrum down the tube.  Again, this only works in the first 24 hours of life!  After that, any antibodies will have to be transferred to the foal in the form of intravenous plasma ($$$).

The foal in this picture hasn't figured out how to nurse yet but he should be nursing normally within 2 hours of birth.
The foal in this picture hasn’t figured out how to nurse yet ( :)) but he should be nursing normally within 2 hours of birth.

Additional numbers that are important to be familiar with are seen below in a graph borrowed from Foalcare.com.

foalingWatchChart

I highly recommend the Foalcare website for more detailed information on foaling and prenatal care for the mare.

Owning a mare and foal is a rewarding experience that can (at times) be stressful.  One way to ease some worries regarding the health of the mare and foal is to have a mare and foal check performed by your veterinarian 12-24 hours after the foal is born.  At that time the vet can:

– Check the placenta to look for any missing pieces or abnormalities indicating possible infections in utero.

– Make sure the mare has not torn her vulva and/or vagina during delivery.

– Look at the mares milk production to determine if it is adequate.

– Examine the foal for any congenital defects such as cleft palate, juvenile cataracts, hernias, and limb deformities.

– Determine if the foal has ingested enough colostrum to have an adequate immune response to pathogens by measuring the level of immunoglobulins in the plasma of the foal (IgG test).

– Make sure the umbilicus is dry and clean.  The umbilicus should be dipped in a chlorhexidine solution after it breaks off from the placenta.

– Give a tetanus vaccination to the foal.

Remember, timing is important and the earlier an abnormality can be recognized, the earlier treatment can begin.  For any issues regarding foaling and neonatal medicine, when it doubt – call the vet!

Good luck to all of you equine breeders out there and have a wonderful foaling season!

Continue reading Foaling basics by the numbers

Founder and Spring Grass

Springtime is amazing.  Finally we can see signs of life again outside!  I have crocuses blooming in my gardens and the tulips and daffodils are starting to emerge.  My hay fields are gradually taking on a shade of green, as is the yard.  Pretty soon the pastures will be full of bright green lush springtime grass.  The kind of grass that horses just devour.  I imagine that a nice spring pasture is similar to them as a buffet spread is to us.  There is just so much food to try, and all of it is so wonderful and before you know it you have gorged yourself and want to vomit.  In the case of horses, they will gorge themselves on the green springtime grass and not necessarily have a bellyache but possibly will end up with a case of laminitis or “founder”.

In order to explain why horses can founder when eating lots of lush pasture in the spring, I need to go over what founder actually is and how it happens.  Then I will explain how scientists currently understand why overeating rich grass can result in a case of founder.  Additionally, I will include some ways that you can prevent your horse from foundering on springtime grass.

What is “Founder”?

“Founder” is an old term used to describe a stage of the disease we know term as “laminitis”.  From now on, I will use the term laminitis in place of founder, just to be more exact with terminology.  Laminitis refers to inflammation of the laminae in the hoof.

The laminae are soft tissues that attach the coffin bone to the hoof.  They hold the coffin bone suspended inside the hoof capsule.   Source: founderwarriors.com
The laminae are soft tissues that attach the coffin bone to the hoof. They hold the coffin bone suspended inside the hoof capsule.
Source: founderwarriors.com
thenaturalhoof.co.uk.hoofpic
The dermal or sensitive laminae interlace with the epidermal laminae to hold the hoof and the coffin bone together. When the laminae become inflamed (laminitis) the attachment weakens. Source: thenaturalhoof.co.uk

The laminae are soft tissue structures located inside the hoof that attach the hoof capsule to the coffin bone or third phalanx.  There are basically two layers of laminae – one that attaches to the hoof (epidermal or insensitive laminae) and one that attaches to the coffin bone (dermal or sensitive laminae).  These two layers are attached to one another and that attachment is what keeps the coffin bone in place within the hoof capsule.

When the laminae inside the hoof become inflamed, the attachment between the two different layers of laminae becomes weak.  Without that attachment to hold the coffin bone suspended in the hoof, the coffin bone can do one of 3 things: 1) rotate, 2) sink downwards, or 3) both rotate and sink.

When the laminar attachment weakens the coffin bone can rotate because of the pull of the DDFT.  The coffin bone may also sink downwards. Source: redlodgevetclinic.com
When the laminar attachment weakens the coffin bone can rotate because of the pull of the DDFT. The coffin bone may also sink downwards.
Source: redlodgevetclinic.com

1) Coffin bone rotation

Normally the coffin bone should be parallel to the hoof wall.  "Rotation" refers to the degrees the coffin bone has rotated from being parallel to the hoof wall. Source:  infovets.com
Normally the coffin bone should be parallel to the hoof wall. “Rotation” refers to the degrees the coffin bone has rotated from being parallel to the hoof wall.
Source: infovets.com

Normally the coffin bone is suspended in the hoof by the laminae so that the top or dorsal aspect of the bone is parallel to the hoof wall.  At the same time, the deep digital flexor tendon (DDFT) is attached to the bottom or ventral aspect of the coffin bone, and puts tension on the coffin bone in the opposite direction.  The balance of these forces keeps the coffin bone in its normal orientation.  If the attachment of the laminae at the dorsal or top part of the hoof weakens, the tension of the DDFT will start pulling the ventral aspect of the coffin bone downwards and backwards (caudally).  This results in rotation of the coffin bone.

2)  Coffin bone sinking

The laminae also help suspend the coffin bone inside the hoof so that it doesn’t touch the bottom of the hoof (sole).  If the laminae all around the hoof (both sides and front or dorsal part) are affected and weaken together, then the coffin bone can begin to sink towards the bottom of the hoof.

3)  Coffin bone rotation and sinking

wocestershirefarrieryservices.co.uk.forces
An imbalance in the forces that hold the coffin bone in its normal position inside the hoof lead to rotation and/or sinking. Source: Wocestershirefarrieryservices.co.uk

Sometimes the attachment of the laminae at the dorsal portion of the hoof weaken first, and the coffin bone begins to rotate.  If the rest of the laminae around the hoof also become affected then the coffin bone can also sink.

How can lush pasture cause laminitis?

The exact mechanism of how ingesting lush pasture can cause laminitis is unknown.  There are many theories and there just isn’t enough room or time to go over all the details of them.  So, since this is supposed to be a blog that simplifies horse health, I will attempt to explain this very complex topic the best way I know how.

As grass grows throughout the seasons its nutritional content changes.  Springtime grass contains very high amounts of easily-digestible carbohydrates, particularly those known as fructans.  Fructans tend to travel through the digestive system quickly and are not absorbed into the bloodstream (like other carbohydrates) in the small intestine.  Instead, they pass through the small intestine and head to the cecum and large colon, where fermentation takes place.  An excess of carbohydrates available for fermentation in the cecum and colon causes fermentation to go into overdrive.  This results in changing the pH of the gut, a leaky GI tract, shifts in GI bacteria populations, spikes in glucose and insulin, and setting off the inflammatory cascade.

Basic pathophysiology of starch overload in the horse and it's effects on the body.  Eating a large amount of lush spring pasture is akin to grain overload in some horses. Source: Nutrena
Basic pathophysiology of starch overload in the horse and it’s effects on the body. Eating a large amount of lush spring pasture is akin to grain overload in some horses.
Source: Nutrena

To further complicate issues, some horses seem to do fine on spring pasture, while others are extremely prone to bouts of laminitis when grazing.  Certain breeds (ponies) and body types (overweight) tend to be more affected by large amounts of lush grass.  It is thought that because those particular horses tend to be resistant to the effects of insulin (glucose uptake into the cells), that the high levels of insulin constantly present in their blood leads them to be prone to developing laminitis when they take in large amounts of fructans.  High insulin levels have been shown to keep individuals in a pro-inflammatory state, which may be why horses with insulin resistance are much more prone to inflammation of the laminae (laminitis).

How can pasture-associated laminitis be prevented?

In the long-term, it is very important to keep your horses’ weight under control.  Horses that are overweight tend to develop insulin resistance, just as overweight humans tend to develop diabetes.  In particular, horses that appear to have a “cresty” neck seem to have a predilection  for insulin resistance.  If you think your horse may be overweight, please call your vet or nutritionist to look at the horse and develop an appropriate diet and exercise regime for him/her.

In the short-term, here are some tips to prevent laminitis in the spring:

– Have a designated “dry lot” without grass where you can keep your horse when you don’t want him to be eating grass.  This way he won’t have to spend all his time in a stall and can still get the exercise he needs.

– Begin with a very limited pasture turnout time, such as 1/2 hour per day, at the beginning of the spring.  The time can gradually be increased by 1/2 hour per week.  If at any point your horse shows signs of laminitis or begins gaining too much weight, decrease the pasture turnout time.

During daylight hours, photosynthesis causes an increase in sugars available in grass.  Also any stress (frost, draught, etc) causing slow growth will cause an increase in grass sugar. Source:  Atlantaequine.ecom
During daylight hours, photosynthesis causes an increase in sugars available in grass. Also any stress (frost, draught, etc) causing slow growth will cause an increase in grass sugar.
Source: Atlantaequine.com

– Turn the horses out to pasture during the time when the level of fructans in the grass is at its lowest – dusk till dawn.

– Place a grazing muzzle on your horse, which will decrease the amount of grass he can ingest over a particular time.  Horses are genius at figuring out how to remove these muzzles, so you may have to try several types until you find one that works for you.

– Avoid turnout after the pasture grass has been stressed – frosty nights, droughts, etc.

– Rotate pastures with other grazing animals, such as sheep or goats, which will keep grass less stressed from over- or under-grazing

I hope these tips help you to prevent any bouts of laminitis this spring!  Thanks for reading!