PPID - Equine Cushings Disorder

Equine Cushings Disease (ECD) is also referred to as Pituitary Pars Intermedia Dysfunction (PPID) because it is caused by an enlarged pituitary gland or a tumor within the pituitary gland known as an adenoma.  The pituitary gland is a hormone producing organ located at the base of the skull.  It is controlled by the hypothalamus, a part of the brain that controls many parts of the nervous system related to movement, hormones, food and water intake, and the sleep/wake cycle.

     The pituitary is made up of three sections, anterior, posterior, and intermediate.  In Equine Cushings Disease, the intermediate section becomes enlarged and and over produces ACTH (adrenocorticotropic hormone).  This hormone causes the body to increase its production of glucocorticoids (normally produced steroids).  This increases the level of cortisol in the blood, which in turn causes the clinical signs of Equine Cushings Disease.

This is different from the cause of Canine Cushings Disease, hence we now prefer to diagnose this as PPID.

Clinical Signs

     Horses with PPID are often prone to laminitis, and may have elevated blood insulin and/or glucose levels because cortisol decreases the body's normal response to insulin, which causes it to produce more insulin in an effort to decrease high glucose levels.  The elevated glucose levels mimic the effects seen when glucose sensitive horses develop laminitis on fresh spring grass.

     PPID horses often present with a long, curly coat that doesn't shed normally as the season changes, called hirsutism.  They may lose their topline as their back muscles weaken.  A "hay bellied" appearance may be seen as they deposit fat around their abdomen, tail head, and neck.  They may appear to have a cresty neck without much muscling or body condition in normal locations.  They may be lethargic, sweat easily, and often drink more water and urinate more frequently than unaffected horses.

Testing

     The preferred test to diagnose PPID is Resting Adrenal Corticotropic Hormone (ACTH) level. Plasma ACTH is increased in the presence of pituitary hyperactivity and hypersecretion. This may be caused by PPID but is also known to occur in most normal horses and ponies in the autumn. Although this has been considered a reason to avoid testing for PPID in the autumn, this potential problem may be overcome by applying properly derived and calculated seasonally adjusted reference ranges. Testing in the autumn may actually allow the greatest differentiation between PPID cases from normal horses and there is no reason at all to avoid testing for PPID in the autumn. ACTH may also be affected by pain and stress (e.g. from laminitis) although this does not appear to have a large effect in most horses unless pain is marked.

What about Testing Blood Glucose/Insulin Levels?

     Many PPID horses are insulin resistant and will have elevated insulin and/or blood glucose levels, however this is not recommended as the only method of testing for PPID because it is not specific.  There are many diseases that can cause elevated insulin/glucose levels.  It is most accurate to test the function of the pituitary via ACTH levels, because the disease is caused by a malfunctioning pituitary.

Treatment

     Diet is an important factor in treating PPID horses.  Starches and simple sugars should be decreased, and lush grass and sweet grains should be avoided.  This is especially helpful in preventing the development of laminitis in these horses.  Hay with low levels of non structural carbohydrates (sugar) should be fed, and can be soaked for 30 minutes prior to feeding to decrease sugar levels even more.

     Medical treatment when needed is most commonly Pergolide (Prascend).  An PPID horse needs to be treated with pergolide if it has elevated levels of fat and glucose in its blood, has developed laminitis, showing signs of muscle wasting, lethargy, depositing fat in abnormal places, is having fertility problems, or any of the many other symptoms of PPID.  Pergolide can also help PPID horses shed and grow their coat normally.  Pergolide is a dopamine receptor agonist and acts on receptors within the nervous system. ACTH levels should be used to monitor treatment effectiveness at 6 to 12 month intervals.

Fecal Egg Counts and Parasite Management Plans

What is a Fecal Egg Count (FEC)?

FEC is a quantitative assessment of internal parasite eggs shed by your horse in its manure.  A measured volume of manure is mixed with a flotation solution and evaluated on a specially calibrated microscope slide.  This allows us to calculate the number of parasite eggs per gram of manure.

The current recommendation is to deworm based off fecal egg counts rather than an every other month rotation.  FEC’s are useful to determine:

• Which dewormers are effective on a particular farm
• Which horses are high vs low shedders by nature (creating a customized parasite management program for your horse)
• The interval between dewormers that is required (decreasing unnecessary chemicals in our horses when they don’t need it)
•  If parasite resistance is developing on a farm (monitoring trends to see if resistance is developing or going away)

Why Do Some Horses Shed More Eggs Than Others?

Horses on the same pasture or management plan may be found to consistently have very different amounts of internal parasite eggs in the manure.  Approximately 20% of horses will carry 80% of the parasites on most farms!

All horses are exposed to parasites throughout their life.  They develop varying levels of intestinal immunity which allows them to hold adult intestinal parasites in check.  

The immune systems of young horses (<3yrs) and aged horses are less able to adapt to and hold intestinal parasites at low levels.

What is a High, Medium, or Low Shedder?

Adult healthy horses consistently carry similar worm burdens through the year, which allows us to customize parasite management plans based on the level of intestinal parasite eggs that they are shedding.

High Shedding horses will need more frequent strategic deworming, compared to Medium or Low shedders.

This allows us to decrease unnecessary use of dewormers by using them strategically in the horses with less natural immunity to intestinal parasites

Henderson Equine Clinic recommends a Fecal Egg Count be performed every Spring (April/May) and Fall (October/November) to assess your horse’s parasite burden/shedding status and to allow us to create a customized Parasite Management Program.  

Follow up Fecal Egg Counts may need to be performed at specific times throughout the year depending on your parasite management program.

What else can we do to control Parasites on farm?

In our area, the highest risk for parasite eggs on pasture is May/June through October.

Techniques for Pasture Management:

• Don't overstock your pastures (over grazed pastures increase ingestion of parasite eggs)
• Regularly dispose of manure and don't spread onto pastures currently being grazed
• Drag/harrow paddocks to break up manure piles and leave open for 2-3 weeks
• Use feeders for hay or grain rather than feeding off the ground
• Keep foals and weanlings separate from yearlings to help prevent ascarid infections

Why do we care about changing the way we deworm?

     Across the country, all types of horse farms have reported resistance to certain dewormer classes.  The most commonly reported resistance is to fenbendazole and ivermectin products.  There are very few new deworming drugs being developed (and none for horses).  Our goal is to use the options we have intelligently to minimize the further development of parasite resistance. Many serious conditions have been almost eliminated by modern deworming programs and we would like to keep it that way.  New deworming and Fecal Egg Count recommendations are aimed at achieving this by focusing on individual horses.

Henderson Equine Clinic's Deworming Recommendations

Collect and submit a fecal sample on each horse (or a grouped sample on horses kept in large groups) in the spring (March/April) and fall.

• For each horse to be tested a fecal sample is submitted BEFORE to deworming. 

• To collect a fecal sample:

1.  Collect 2 fecal balls of manure ideally passed within 1-2 hours but definitely less than 24 hours
2.  Place the manure in a plastic ziplock bag, removing all air possible
3.  Store the sample in a refrigerator until it can be picked up or delivered to the clinic.

You will receive a custom Parasite Management Plan for each horse (or group). 

• Most low shedding horses will have Fecal Egg Counts and be treated biannually (early spring and fall)
• Moderate and high shedding horses will need additional deworming and strategic Fecal Egg Count Assessments during times of highest parasite risk.
• Foals and Senior horses will require different strategic deworming programs than mature horses.

Once per year a Fecal Egg Count Reduction should be performed on atleast one horse on your farm.

• Submit a fecal sample just prior to deworming and ten days to two weeks after deworming depending on dewormer used.
• Comparing the Fecal Egg Count results from just prior to deworming to those two weeks after deworming provides a quantitative measure of resistance.  These results will help determine if this deworming product is effective on your property and for your horse(s), and therefore whether it should or should not be used again in the future.

Equine Parasite Control Part 1: Common Internal Parasites

Equine internal parasite management is a confusing and seemingly ever changing subject.  Daily dewormers? PowerPaks? Rotate dewormers? Don't rotate dewormers? Fecal flotations? High, Medium, Low shedding programs? 

Parasitologists are constantly updating their parasite control recommendations based on new research to try to control parasite resistance to dewormers while continuing the excellent control of internal parasites that we have become accustomed to. 

Let's start from the beginning. Part 1 of this discussion will be.....

What are the common internal parasites we are attempting to control in our horses?

Small Strongyles (Cyathostomes) - Have become an important group of intestinal parasites in horses.  Larvae burrow into the lining of the intestine and remain dormant or "encysted" for several months before completing their life cycle.  During this time the larvae are resistant to most dewormers.

Small strongyle larvae can cause severe damage to the lining of the intestine, especially when large numbers of larvae emerge from the encysted stage all at once.  Colic and diarrhea are common in heavily infected horses.  These parasites also cause weight loss, slowed growth in young horses, poor coat condition and lethargy, or lack of energy.  While lighter infections are not obvious, it is common for a horse's general health and performance to improve after treatment for these parasites.

The early and late larval stages (before and after they burrow into the lining of the intestine) and the adult parasites are susceptible to several dewormers.  But currently there are only two types of dewormers that are effective against the encysted larval stage.

Large Strongyles - As larvae they penetrate the lining of the bowel and migrate along the blood vessels that supply the intestines.  Even small numbers of these larvae can cause extensive damage.  Infection with large strongyles can cause unthriftiness, weight loss, poor growth in young horses, anemia (low number of red blood cells) and colic.  In most cases, colic caused by these parasites is relatively mild, but severe infections can result in loss of blood supply to a portion of the intestine, leading to severe and potentially fatal colic.  These intestinal parasites have been controlled for the most part by our routine deworming protocols.

Roundworms (Ascarids) - Greatest concern for horses under 6mo of age.  Healthy older horses have immunity but may still shed eggs (mostly eliminated by modern deworming programs).  Adults cluster in the small intestine causing impaction, often with colic, can result in rupture and death

Most often a problem in young horses (especially foals, weanlings, and yearlings).  Adult roundworms are several inches long and almost the width of a pencil; in large numbers they can cause blockage (or impaction) of the intestine.  In addition, roundworm larvae migrate through the internal organs until they reach the lungs.  They are then coughed up and swallowed back into the digestive tract to complete their lifecycle.  Large infections can lead to damage to the liver or lungs due to migration of these larval forms.  

Roundworm infection in young horses can cause coughing, poor body condition and growth, rough coat, pot belly, and colic. Colic is most likely in older foals (over 3months of age) that are heavily parasitized with roundworms when dewormed for the first time.

Tapeworms - Found in virtually all grazing animals.  Contribute to colic by causing inflammation, ulceration and bowel obstruction.  The tapeworm lifecycle involves a tiny mite as an intermediate host, and horses are at risk of developing tapeworm infection when they eat this mite in grass, hay or grain.   Praziquantel has been demonstrated to be highly effective against tapeworms.  

Pinworms - Lay eggs on the skin around the horse's anus.  The irritation they cause makes the horse repeatedly rub its tail. The eggs can sometimes be found by placing a piece of scotch tape on the skin around the horse's anus and then viewing under a microscope.

Bots - Not usually a cause of major health problems, although they can damage the lining of the stomach where they attach.  They may also cause small areas of ulceration in the mouth where the larvae burrow into the tissue for a time after the eggs are taken into the mouth.  

Stay tuned for Part 2 of Equine Parasite Control; Fecal Egg Counts and Control Programs

Learn to Recognize your Horse’s Dental Problems

Cold weather increases a horse's caloric requirements and this need for increased feed may exacerbate weight loss or other chronic problems in horses with dental problems. 

Horses with dental problems may show obvious signs, such as pain or irritation, or they may show no noticeable signs at all.  This is because some horses simply adapt to their discomfort.  For this reason, periodic dental examinations are essential to your horse’s health. 

      It is important to catch dental problems early.  If a horse starts behaving abnormally, dental problems should be considered as a potential cause.  Waiting too long may increase the difficulty of remedying certain conditions or may even make remedy impossible.  Look for the following indicators of dental problems from the American Association of Equine Practitioners (AAEP) to know when to seek veterinary attention for your horse:

1. Loss of feed from mouth while eating, difficulty with chewing, or excessive salivation.
2. Loss of body condition.
3. Large or undigested feed particles (long stems or whole grain) in manure.
4. Head tilting or tossing, bit chewing, tongue lolling, fighting the bit, or resisting bridling.
5. Poor performance, such as lugging on the bridle, failing to turn or stop, even bucking.
6. Foul odor from mouth or nostrils, or traces of blood from the mouth.
7. Nasal discharge or swelling of the face, jaw or mouth tissues.

Oral exams should be an essential part of an annual physical examination by a veterinarian.  Every dental exam provides the opportunity to perform routine preventative dental maintenance. Mature horses should get a thorough dental exam at least once a year, and horses 2 –5 years old should be examined twice yearly.

Early and regular examination of your horse's mouth will decrease the chances of broken teeth, requiring extractions. or pain and oral ulcers.  

Additional information is available on the AAEP’s website www.aaep.org/horseowner.

Sections reprinted with permission from the American Association of Equine Practitioners. 

RAO/COPD/Heaves

Good infographic about Heaves (Recurrent Airway Obstruction or Chronic Obstructive Pulmonary Disease - depending on your veterinarians diagnosis and preferred terminology)

This time of year we start to see an increase in respiratory cases due to horses spending more time in closed barns or being fed from round bales where they may bury their faces into areas of the bale with high levels of allergens.

Controlling this condition is easiest when identified quickly and changes in management used as well as medical therapy.