Management Strategies to Decrease Parasite Exposure

(Based on a Northern Climate)

Spring will come, eventually, and that means manure clean-up in the paddocks, sheds, and pastures that the horses have used all winter.  The following strategies can help decrease the parasite burden and exposure through out the year.

  • Make your manure pile outside of the horses paddock or pasture.
  • Feed horses away from potentially contaminated areas, or use feeders to avoid feeding on the ground.
  • Manure should be picked from paddocks, lean- tos or any areas where horses are eating regularly (ideally every 2-3 days a week)

Pasture management is very important.  Ideally horses should be rotated to a new pasture manure happenswhen they have eaten the grass down to 4 inches high.  The tall clumps should be mowed down to this height.  Keeping the pastures mowed allows manure to properly desiccate.  Horses should be allowed back out to graze when the grass has grown up to 8 inches high.  This may mean the horses are in a designated dry lot until the pasture has grown back.

During very hot dry weather, pastures can be mowed and then harrowed to disperse manure and facilitate desiccation of parasites.    Horses should be kept off the harrowed pasture for 7 days to ensure all parasites are dead.

Do not spread manure on the pasture while horses are using the pasture.  If you are going to spread manure it should be done during the very hot dry season, after the pasture has been mowed.  It should then be harrowed so that it can desiccate properly.  The horses should be kept off that pasture for 7 days.

Horses should be grouped together by the type of shedder into separate paddocks/pastures if possible.  This decreases contamination levels overall and each group (example yearlings) can be dewormed similarly.  Do you know what type of shedder your horse is?

The use of routine fecal testing allows veterinarians to decide which horses to deworm, how often, and which class of dewormer is appropriate.  Additionally, they can help identify anthelmintic resistance on individual farms.

It is important that the fecal sample is collected and handled properly for accurate results.

Sample Collection

It is ideal to collect the fecal sample from the horse immediately after the horse has defecated.  The sample should be placed in a Ziplock bag with minimal air inside, labeled with the date, horse’s name, and promptly placed in a refrigerator or cooler with an ice pack.  The sample should remain refrigerated until delivered to the clinic (within 36 hours from sample collection).

McMasterThe fecal sample is evaluated under the microscope and the species of parasite eggs are noted as well as the overall count.  A McMaster’s fecal egg count* is performed and the sample is also checked for the presence of sand.

Horses are categorized into 3 groups depending on the number of strongyle eggs per gram as determined by the fecal egg count using the McMasters technique:

<200 eggs per gram               low shedder

200-500 eggs per gram         moderate shedder

>500 eggs per gram               high shedder

It is not necessary to completely remove all internal parasites each time you deworm your horse.  Moderate and high shedders should have a Fecal test repeated 2 weeks after deworming.  In addition, assessing risk factors including age, horse density, movement on/off the property, manure management, and pasture rotation can help decrease parasite exposure and minimize future infections.

Young horses(<5years) and older horses(>15 years) along with any horses diagnosed or displaying signs of Cushings Disease should be monitored more closely as they are  often the high shedders.

Uncontrolled parasitic infections can cause problems, especially in foals, yearlings, older, or debilitated horses.  Internal parasites can cause poor hair coat, ill thrift, pneumonia (secondary to the presence of migrating larvae through the lungs), colic, and diarrhea.

*NOTE-only strongyle type eggs are counted in the FEC.  Ascarid, strongyloides, or tapeworm eggs are clinically relevant and therefore considered when determining the deworming program but not included in the Fecal Egg Count.

For a schedule for deworming based on the level of shedder that your horse it. 2015 Deworming Schedule.


Types of Parasites

Large Strongyles

strongyleEffects: Fever, loss of appetite, weight loss, progressive weakness, anemia, recurring colic, diarrhea, hepatitis, blood clots and organ damage from the larval migration. Young horses are particularly susceptible to strongyles.

Source: From manure; Eggs survive winter on pasture.

Small Stronglyes

Effects: Fever, loss of appetite, weight loss, progressive weakness, anemia, recurring colic and diarrhea. Young horses are particularly susceptible to strongyles.

Source: From manure; Eggs survive winter on pasture.

Ascarids (Roundworms)

Effects: Primary Damage: impaction, colic and possible rupture of the small intestine. Lung migration can produce respiratory disease; common cause of slow growth & unthriftiness in young horses.

Source: From eggs in manure that survive winter on pasture.


Effects: Cause unthriftiness and irritation of the stomach.

Source: Yellow eggs of bot fly laid on hair => licked by horse => hatch in mouth => create oral ulcers and larvae that attach to stomach lining.


Effects: Excessive tail rubbing, digestive disturbances, retarded growth, loss of condition and irritability. Young horses are more susceptible.

Source: Eggs in manure and found on places where the horse rubs it’s tail; eggs die quickly on pasture.


Effects: Colic, marked digestive disturbances, unthriftiness.

Source: Eggs in manure; pasture mites as intermediate hosts.

Intestinal Threadworms

Effects: Erode small intestine lining. Produce weight loss, anemia, diarrhea, & lack of appetite.

Source: Passed to foal via mare’s milk; possible contributing factor “foal heat” diarrhea.

Stomach Worms

Effects: Digestive disorders, summer sores, inflammation of stomach wall, & skin ulcers.

Source: Eggs in Manure with fly maggots as the intermediate host that deposits the larvae on the horse.




We have had many questions on what product is best to use in the protection against EHV-1.

Anoka Equine is recommending Chlorhexidine (also known as Nolvasan). We do not stock this for re-sale but it can be purchased at most farm supply stores. The dilution is 1 ounce of Chlorhexidine/Nolvasan per 1 gallon of water. This can be used in a spray bottle, as a dip, or in a foot bath. Our veterinarians as well as many local farriers are using this as precaution between visits. As a side note, many of the farm supply stores also sell plastic gloves and over-shoes.

We also suggest washing your hands very well and changing clothing and shoes between visits to help prevent the spread of this virus. If we all do our part and keep our horses at home this virus will run its course more quickly. It is much better to lose a month of riding rather then lose the whole summer.

Link to biosecurity toolkit 19 pages long but good resource: Biosecurity Tool Kit for Equine Events” from the State of CA

Biosecurity risk calculator link:

Biosecurity recommendations from the AAEP:

It Has Been a Long, Long Winter

By: Tracy Turner, DVM, MS, DiplACVS

Winter will be over (sometime).  This means that you’re going to want to get back in the saddle and out on the trail, cross country course, sorting pen, or any number of venues.  Winter (especially this one) keeps many horse owners from riding as much as they would like because they don’t have access to indoor facilities or the temperatures are simply not conducive to outdoor riding. This means that as spring comes with warmer temperatures, horses are going to be ridden a lot more than they are used to after such a long break. When you’re getting ready to ride after so much time off, it’s important to keep in mind that just because your horse takes off running in the pasture doesn’t mean he’s ready for hard riding. These horses are going to need some conditioning as well.

Conditioning Pic 1Conditioning your horse involves more than a 10-minute lunge.  It’s not uncommon for people to bring the horse out of his stall, throw the saddle on and get to riding.  This is hard on a horse in more ways than one and is similar to you going to the gym and running a mile on the treadmill after not running all winter.  It’s hard on you and you’re going to get tired very quickly.  The same is true for your horse.

There have been numerous studies done on equine conditioning.  Most have found that conditioning is very important to prevent injury to your horse after a long winter.  They suggest that when you bring your horse up to the barn after a long layover, you should begin with easy and slow work that will help them to regain their muscle and bone strength. Research also suggests you give your horse ample time to warm-up.  Start with the slow paces and then incorporate small bursts of speed worked into your riding routine.  These bursts will help the horse’s muscles get prepared for exertion and allow them to reach their peak oxygen consumption levels sooner.  You also want to warm your horse up at various levels of speed.

In general for the unfit horse, one needs to ride at least three days a week and keep your horse in a large pasture with company the other days. Start with 30-minute rides and gradually, over a four-week period, work up to 90 minutes per ride. For the first few rides, walk and trot for 15 minutes, alternating as many time you’d like. Over time you can add canter work. A good four-week goal is 90-minute rides with 20 minutes at a walk, 50 minutes at a trot, and 20 minutes at a canter, again, broken up and ridden in any order you’d like. Where you ride is also important. Train for where you want to ride. If you are training for trail work, ride on the trails.

As your horse’s fitness increases, you will notice that the work will become less laborious for the horse and the pulse recovery after fast work will drop into the 60s in five minutes or less. You can check the pulse with a stethoscope or your fingers with a bit of practice. Even if you don’t use pulse rate as an indicator, you’ll notice your horse’s fitness increasing in other ways, your horse will not become “winded” as easily, the horse’s body will become more muscular and the gaits will be “forward” and the horse will be eager to work for longer periods of time.

Principles of Conditioning

Conditioning Pic 2The success of a conditioning program relies on the horse’s adaptive response to the stress of exercise. If the horse performs the same amount of exercise every day, a certain level of fitness is attained as the horse adapts to the workload. However, without a further increase in training load (an increase in training duration, intensity, or both), there will be no further increase in fitness. To achieve a conditioning or training effect, the horse must be subjected to gradual increases in workload. Each new level of training is maintained until the body has adapted to the added stress, after which a further increase in training load can be applied. Alternating periods of increased workload with a period of adaptation is known as progressive loading.

The idea behind progressive loading is to prescribe exercise that will gradually stress the horse sufficiently, such that the horse will be able to tolerate the same exercise the next time with less stress. For aerobic conditioning (endurance), progressive loading is accomplished through gradual increases in either the duration or intensity (speed) of the exercise on a weekly basis. For anaerobic conditioning (speed), progressive loading is accomplished by a weekly increase in the exercise intensity (speed) or in the number of repetitions of high-intensity activity.

For any equine discipline, performance is most effectively improved by training the specific muscles and systems involved in that discipline. In other words, training exercise must be focused on the specific demands of the particular event the horse is training for. The physiologic and psychological demands of competitive events such as the 3-day event, show jumping, dressage, endurance rides and racing over distances of 400 m to 3200 m are extremely different. Therefore, training should be specific to the event, thus training the appropriate structures and physiologic systems. This principle of conditioning is known as specificity.

Training of horses should be specific to the athletic event involved whenever possible. This principle need not be followed rigidly, since there are circumstances when alternative types of exercise are appropriate for certain horses. For example, working the horse over hilly terrain has the advantage of increasing heart rate (workload) without increasing speed, thereby sparing the bones, tendons and ligaments from excessive stress.

One of the most important principles of conditioning is that of individual differences. Horses vary in their individual response to conditioning. Some horses will respond more quickly than others and will tolerate faster increases in training load. The magnitude of the overall training response will also vary among horses. Genetic factors play a major role in this variation in training response, but another consideration is the state of fitness at the beginning of a training program. A horse which has been inactive for a long time (12 months or more) will require a longer period of training to reach a certain level of fitness compared to a horse which has had a six or eight-week layoff after a season of training and competition. Age is also important. Younger horses are capable of greater adaptations in response to training. By comparison, recent studies have confirmed that older horses (age 20+ years) have a reduced capacity for exercise. Ultimately, training programs must be individualized in order to attain maximum benefit while minimizing the risk of injury.


What is EHV-1

  • Contagious equine virus that can cause four clinical presentations: neurological disease, respiratory disease, neonatal death, and abortion.

Clinical Signs

  • Fever commonly precedes other clinical signs
  • Respiratory Disease
    • Fever, coughing, nasal discharge
    • Abortion
      • Usually occurs in late pregnancy (8+ months, but as early as 4 months) with no warning signs
      • Neurologic Disease – also known as Equine Herpesvirus Myeloencephalopathy (EHM)
        • Hind-end weakness and incoordination
        • Leaning against wall or fence to maintain balance
        • Urine dripping or inability to urinate
        • Down and unable to stand


  • Highly variable, incubation period may be as short as 24 hours, but is typically 4-6 days
  • When neurologic disease occurs, it is typically 8-12 days after fever begins

How is the virus spread?

  • The most common way to spread EHV-1 is by direct horse-to-horse contact
  • EHV-1 can also spread indirectly through contact with physical objects contaminated with virus
    • Tack, grooming equipment, feed and water buckets, people’s hands or clothing


  • Supportive care, anti-inflammatory drugs
  • Antiviral medications for horses with the neurologic form
  • Sling support for horses with severe weakness and in-coordination
  • Antibiotics may be given if your veterinarian is concerned about secondary bacterial infection
  • Isolate affected horses to prevent spread of infection


  • Vaccines are available to control the respiratory and abortion manifestations of EHV-1
  • Current vaccines do not reliably prevent development of the neurological form
  • Your veterinarian may recommend vaccination to help reduce spread of the virus
    • Calvenza
    • Pneumabort

Does EHV-1 affect other animals?

  • EHV-1 does not affect humans, dogs, cats, sheep, goats, cattle, pigs, or birds
  • Alpacas and llamas are susceptible to EHV-1

More information on EVH-1 and control measures that you can take are posted on the University of California Davis’s website.

Check out our blog post on ways that you can prevent the spread of EHV-1 by disinfecting your barn.

Please feel free to call the clinic at 763-441-3797 with any questions.