Equine Preventative Medicine

Equine Health Maintenance

Equine Preventative MedicineAshley R. Berthelot, DVM1Equine Preventative Medicine Health maintenance, early detection of problems, good diagnostics, and high quality treatment translates to long-term savings for the owner. In addition, the overall well-being of the horse improves and the longevity of life and career can be increased.

Equine preventative medicine is a combination of health maintenance, early detection of problems, good diagnostics, and high quality treatment which trans- lates to long-term savings for the owner. In addition, the overall well-being of the animal improves and the longevity of life and career can be increased.

2Parasite ControlEstablishing an effective parasite control program is probably second only to supplying the horse with clean, plentiful water and high quality feed.There multiple components of preventative equine medicine, one of which is parasite control. This does not exclude or decrease the importance of vaccinations, routine dental care and proper hoof trimming. In terms of management priorities, establishing an effective parasite control program is probably second only to supplying the horse with clean, plentiful water and high quality feed.3Parasite ControlInternal Parasites:

Silent thieves and killersCause extensive damageEffect the horse from a dull haircoat and unthriftiness to colic and deathCan decrease resistance to infectionCan rob a horse of valuable nutrientsInternal parasites are silent thieves and killers. They can cause extensive internal damage without realizing that your horse is heavily infected. The effects of internal parasites range from a dull haircoat and unthriftiness to colic and death. Internal parasites lower the horses resistance to infection, rob the horse of valuable nutrients and in some cases, cause permanent damage to the internal organs. 4Types of Internal ParasitesLarge strongylesSmall strongylesRoundwormsTapewormsLungwormsPinwormsThreadwormsBots

There are more than 150 species of equine internal parasites. The most common and the ones that create the most problems are listed here, with the first 4 being the most important. 5

The lifecycle of most internal parasites involves eggs or larvae which are deposited onto the ground in the manure of an infected horse. These eggs or larvae are then ingested while the horse is grazing and the larvae mature into adults inside the digestive tract. In some species of parasites the larvae migrate out of the intestine and into other tissues before returning and maturing into egg-laying adults.

6The Big Four

Large Strongyles:

Penetrate lining of the bowel and migrate along the blood vessels that supply intestine

Cause unthriftiness, weight loss, poor growth in young horses, anemia, and colic

Infection with large strongyles can cause unthriftiness, weight loss, poor growth in young horses, anemia 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. Fortunately, large strongyles can be effectively controlled by most available dewormers.

7The Big Four

SmallStrongyles : (cyathastomes)

Burrow into lining of intestine and become encystedCause severe damage to the lining of intestineCan cause colic and diarrhea with heavy infectionsWeight loss, slowed growth, poor coat, and lack of energySmall strongyles have become a group of major importance. Unlike the large strongyles, small strongyle larvae do not penetrate the intestinal wall or migrate through the tissues. Instead, they burrow into the lining of the intestine and remain dormant, or encysted for several months before completing their lifecycle. 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 lack of energy. The early and late larval stages and the adult parasites are susceptible to several dewormers.

8The Big FourRoundworms (Ascarids):

Several inches longMost often a young horse problemIn large numbers they can cause impactionsMigrate through the internal organs to the lungs, coughed up, swallowed back into the digestive tract to complete lifecycle.Can cause coughing, poor body condition and growth, pot belly, rough haircoat and colic.

Roundworms, or ascarids, are 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 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. 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 that have a large worm burden when dewormed for the first time.

9The Big Four

Tapeworms:

Can cause mild to severe colic

Lifecycle involves a tiny mite as a host that horses ingest in the grass, grain or hay.Tapeworms werent considered to be a significant problem in horses. We now know that tapeworms can cause colic, ranging from mild cramping to severity requiring surgical treatment. 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.Until recently, no equine dewormer was approved for use against tapeworms. Praziquantel has been demonstrated to be highly effective against tapeworms, and is often combined with other deworming medications such as ivermectin, one example of this combination is Equimax.

10Signs of ParasitesDull, rough haircoat

Decreased energy

Unthriftiness, loss of condition

Slow growth in young horses

Colic

Pot-bellied appearance

Diarrhea

Contrary to popular belief, horses can have potentially dangerous numbers of internal parasites while still appearing to be relatively healthy. But in some individuals, especially young horses, parasites can take a visible toll. 11DewormersBroad spectrum

Safe

No dewormers are 100% effective

Not necessary to kill every worm to improve health, minimize risk of disease, reduce pasture contamination, and improve feed efficiencyThere are several different dewormers currently available. Most are broad-spectrum, meaning that they are effective against several different types of parasites. It is generally best to use a broad-spectrum dewormer as the basis of your deworming program. If a specific problem is identified, such as tapeworms or encysted small strongyles, a more specific dewormer can be used.No deworming product is 100 percent effective. However, it is not necessary for a product to kill every worm in order to improve the horses health, minimize the risk of serious disease, improve feed efficiency and reduce pasture contamination with parasite eggs and larvae.

12Most Common DewormersIvermectin (aka Eqvalan) is effective against:

Large StrongylesSmall Strongyles, or cyathstomes, adult onlyPinworms, adult and L4Ascarids, adultHairwormsLarge-mouth Stomach WormsBots Lungworms Intestinal Threadworms Summer Sores caused by Habonema and Draschia spp.

Ivermectin was introduced in 1983 and is actually an antibiotic that is a fermentation product of a microorganism. Ivermectin acts to disrupt a neuro-muscular transmitting chemical called GABA. In parasites, GABA is found throughout the body. Disruption of GABA causes the parasite to become immobile and causes death. In horses, GABA is limited to the central nervous system, brain and spinal cord and is therefore protected from the effects of ivermectin by the blood brain barrier.

13Most Common DewormersIvermectin is not effective against:

Encysted early third-stage cyathostome larvae

Late third-stage cyathostome larvae Lumenal larvae and adult cyathostomes

Tapeworms

The encysted larval stage of small strongyles or cyathostomes are not affected by ivermectin. Some parasites, such as tapeworms, do not contain GABA. Therefore, ivermectin has no effect on these parasites either.

14Most Common DewormersFenbendazole (aka Panacur, Safeguard)Large strongyles Small strongyles or cyathostomesEncysted third stage cyathostome larvaePinworms Ascarids

Research indicates that fenbendazole's primary mode of action is through absorption by the worm. This interferes with the parasite's energy metabolism and affects its intracellular structures and functions.Fenbendazole kills adult worms and many of their developmental stages - including some immature and pre-adult juvenile stages, making it a highly-effective anthelmintic.When ascarids are a problem in foals, weanlings and yearling, fenbendazole can be dosed at 2 times the normal dose to ensure an almost 100% efficacy.For control of encysted cyathostome larvae, the double dose daily for 5 days is used. Studies have revealed that up to 75% of encysted small strongyles are actually in stage 3. Using a larvicidal treatment with fenbendazole can provide a 98% reduction of encysted larvae, and as great as a 96% reduction in larval stage 3 and stage 4 larvae.

15Most Common DewormersPyrantal Pamoate (aka Strongid)Large strongylesPinwormsLarge roundwormsSmall strongyles

Pyrantal pamoate is effective against large stronglyes, pinworms, large roundworms and certain stages of small strongyles.16Deworming Program3 Basic Types of Deworming Programs:

1.Continuous2.Interval3.Strategic

No deworming program suits all situations

The ideal program depends on the type, number and ages of the horses, pasture management and location

There are three basic types of deworming programs:Continuousfeeding a daily dewormer year-round or throughout the grazing seasonIntervaldeworming at regular intervals depending upon the product and the management systemStrategicdeworming only at certain times of the year or when fecal egg counts riseCombination programs can also be used. For example, continuous deworming can be supplemented with strategic deworming for bots.There is no single deworming program that suits all horses and all situations. The ideal program for your horse depends on the type, number and ages of the horses on your farm, pasture management and your geographic location.

17Continuous DewormingSmall quantity of dewormer daily

Effectively prevents new infections picked up during grazing

May not resolve existing infections

Does not kill bots

Need bi-annual supplemental deworming Daily dewormers can be worthwhile in grazing horses. With these products, a small quantity of dewormer is fed to the horse each day. They effectively prevent new infections by larvae picked up during grazing. But they may not resolve existing infections and they do not kill bots, so they should not be relied upon as the sole method of parasite control.

18Interval DewormingSystematic, seasonal deworming program

Deworm horses six times a year (every 60 days)

Rotating different compounds based on seasonal parasite prevalence

Rotating among the three main chemical classes of compounds available (ivermectin, fenbendazole and pyrantel pamoate)

Combat the parasites that are prevalent in that season.

By administering a systematic, seasonal deworming program, parasites can be controlled. In a rotational deworming program you should deworm horses six times a year, rotating among the three main chemical (such as ivermectin, fenbendazole and pyrantel pamoate) based on seasonal parasite prevalence.

19Sample IntervalDeworming ScheduleJanuary - Ivermectin/Praziquantel (Equimax)

March - Pyrantel Pamoate (Strongid); fecal egg count preformed 10 days post deworming

May - Ivermectin (Eqvalan)

July - Ivermectin (Eqvalan)

September - Double dose of Fenbendazole granules once a day for 5 straight days;fecal egg count preformed 10 days post deworming

November - Ivermectin (Eqvalan)

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Strategic DewormingDeworming based fecal egg counts

Aka: Test and TreatStrategic deworming is based on only deworming when fecal egg counts rise.21Testing for ParasitesFecal Egg Counts

Microscopic examination of fresh manure for parasite eggs

Results expressed in EPG (eggs per gram) of manure

Fecal egg count of less than 200 epg suggests light parasite load

500-1000 epg is moderate to heavy load

Negative fecal count does not mean parasite freeOne of the most useful tools in a parasite control program is the fecal egg countmicroscopic examination of fresh manure for parasite eggs. This simple test allows the veterinarian to determine which parasites are present and whether the infection is light, moderate or heavy. This information is important in monitoring the effectiveness of the program. Fecal egg count involves collecting two or three fresh manure balls from the horse to be tested and sending the manure sample to a veterinary laboratory. Results are expressed as eggs per gram (epg) of manure. A fecal egg count of less than 200 epg suggests a light parasite load. High fecal egg counts of 5001,000 epg suggest the interval between deworming is too long.A negative fecal examination does not mean the horse is free of internal parasites. Some types of parasites produce eggs only intermittently. Larvae do not produce eggs at all and may be present in large numbers in a horse with a fecal egg count of zero. And tapeworm eggs may be missed with routine fecal egg count techniques. The results are most useful when several horses on a farm are tested on the same day.

22Resistance

Certain compounds combat specific parasites more effectively than others

Repeat exposure can lead to resistance

Correct seasonal compound selection can decrease resistance and increase protection Certain compounds combat specific parasites more effectively than others. But, when parasites are repeatedly exposed to the same compounds, they can develop resistances.

Most research authorities today believe that no matter what compound is used to battle parasites, exclusive use of any one over a period of time can result in resistance.

Ultimately, no one deworming compound is equally effective against all organisms, or all stages of a parasite's life cycle. And any one has the very real potential to create resistance over time.

23Solution for Resistance?No great solution for preventing resistance

One way to try to avoid creating resistance is to:

Test and TreatThere is no great solution for preventing resistance. One way to try to avoid creating resistance is to test and treat.

24MonitoringImportant to perform fecal egg counts every 6 12 months to measure the effectiveness of your program.Whichever deworming program or product you use whether its continuous, interval or strategic, perform fecal egg counts every 612 months to make sure your program is effective. The outlay of time and money will be well spent.

25Complete Management ProgramPrevent overgrazing

Reduce pasture contamination

Remove manure regularly

Mow/harrow pastures periodically to expose parasites to heat/sunlight

Rotate pastures with other livestock

Chemical control using dewormers is just one part of a complete parasite control plan. As parasites are primarily transferred via manure, good management is essential.Keep the number of horses per acre to a minimum to prevent overgrazing and reduce pasture contamination .Pick up and dispose of manure regularly.Mow and harrow pastures periodically to break up manure piles and expose parasite larvae to the elements. Larvae can survive freezing, but they cannot tolerate extreme heat and drying for very long.

26Complete Management ProgramKeep foals and weanlings separate from yearlings and adults

Use a feeder for hay and grain rather than feeding on the ground

Consult your veterinarian to set up appropriate program

Perform fecal egg counts to monitor effectiveness

Consider rotating pastures by allowing sheep or cattle to graze them, thereby interrupting the lifecycles of equine parasites.Use a feeder for hay and grain rather than feeding on the ground.

27Mankind's true moral test, its fundamental test (which lies deeply buried from view), consists of its attitude toward those who are at its mercy, animals.

Milan Kundera, 1929

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