Equine Parasite Control

deworming science

*Please note Quest has a lower safety margin than Ivermectin products, meaning that it requires a more exact dose. Therefore it is not recommended in young, debilitated, or older horses.

The Daily Dewormer Option:
Daily fed Strongid in addition to two doses of Ivermectin and Ivermectin/Praziquantel product:

What happened to a rotation schedule, you may be asking?
Research on farm that use a rotation schedule showed that the only effective dewormings are those done with Ivermectin product. Single dose Fenbendazole and Pyrantel products are no longer effective for adult horse dewormings due to resistance. Please note that individual deworming routines may vary for different farms. A farm with a small amount of acreage and large population of horses may require more frequent dewormings.

Recommended Foal Deworming Program
Foals are more susceptible to roundworm (ascarids) infestations than adults who develop a resistance over time. Since worm burdens can be high in foals, they may require monthly dewormings as described below.

recommended deworming schedule
Foals can also be given daily feed dewormer in combination with Ivermectin products, but it is suggested that tehy are weaned first before starting this program. This is to insure that the foal is ingesting the proper dosage of dewormer.

Foals Need Special Consideration – Early experimental work has shown some breakthrough of large strongyles in foals on Strongid pellets. Also known is that all classes of dewormers are not as effective in foals:

• If on contaminated pastures:
Starting at one month of age, use ivermectin at 1.5 times the recommended dosage monthly for the first year. At 6 months of age you should use one of the ivermectin/praziquantel products. At a year of age the horse can be put into the adult deworming schedule.

• If on clean pasture:
Foals are acutely sesitive to parasites especially round worms. Damage can occur prior to the appearance of eggs in the fecal. It is best to deworm at a month of ag with a 1.5 times the recommended dosage of ivermectin and then put into the adult deworming program.

Deworming the Debilitated Horse – Great care must be used in approaching deworming a horse that might be heavily parasitized. Whenever adult or larval stages of most parasites are killed, bleeding and inflammation is created in the wall of the bowel. Also, in the case of round worms or more rarely tapes, there is the potential for a physical obstruction when high numbers of this rather large parasite are present. A fecal flotation for parasite eggs should identify this condition and should have been part of an initial exam.

When this problem is identified or even just suspected, care should be used in the initial dewormings to avoid a rapid kill off of large numbers of parasites. There is no concrete information on what is a safe way to do this and it would probably depend on a number of factors that include condition of the horse, age, type of parasites present, and number of parasites present. The following recommendation should work in most scenarios and is very cautious:

• Remove the horse from contact with other horses and further contact with areas contaminated by parasite larvae.
• Begin with a dose of a good quality fenbendizole paste dewormer like Panacur or Anthelcide or a dose of a pyrantel-based dewormer like Strongid paste.
• If the horse tolerates this well for seven days you can give a whole dose of the dewormer.
• If the horse tolerates this well for seven days give a dose of ivermectin-based dewormer.
• If the horse tolerates this well for the following week give a whole dose of ivermectin-based dewormer.

Deworm monthly with ivermectin or place the horse on Strongid granules until the horse returns to good condition and the horse can be placed in the regular deworming routine at this time. Signs of intolerance would include diarrhea, colic, black stools or blood in the stools, respiratory difficulties or weakness, within the next three days of deworming. Once treated and recovered from the reaction repeat the last step before going on.

Parasite Control: Waging War on Equine
Parasites from AAEP

Internal parasites are silent killers. They can cause extensive internal damage, and you may not even realize your animals are heavily infected. At the very least, parasites can lower resistance, rob the horse of valuable nutrients, and cause gastrointestinal irritation and unthriftiness. At their worst, they can lead to colic,
intestinal ruptures, and death.

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. It’s that important!

There are more than 150 internal parasites that afflict horses, including several major species. Among the most common and troublesome are:

• Large strongyles (bloodworms)
• Small strongyles
• Ascarids
• Pinworms
• Bots
• Tapeworms
• Threadworms
• Lungworms

Any or all of these parasites can be present in the horse at one time, but they may be at different stages in their life cycles. This will influence the deworming program needed to combat them. Also, keep in mind that some species can lay more than 200,000 eggs a day, so parasite loads can escalate quickly.

Different parasites harm the horse in different ways. They can damage tissues and vital organs, including the major blood vessels to the intestines, lungs, liver, stomach, and intestines, as they migrate through the horse’s system to complete their life cycles. They can cause obstructions and ulcerations within the horse’s digestive tract, and they can also cause intense irritation as they lay eggs, such as pinworms do.

Contrary to popular belief, many horses that have dangerous parasite levels appear to be perfectly healthy. From the outside they may be fat, sleek and shiny, while on the inside the worms are doing irreparable damage. But in other horses, especially young horses, parasites can take a visible toll. Signs of infestation might
• Dull, rough hair coat
• Weight loss
• Tail rubbing in hair loss
• Colic
• Depression
• Unthriftiness or loss of condition
• Lethargy or decreased stamina
• Coughing and/or nasal discharge
• Resistance to the bit due to mouth lesions
• Summer sores
• Loss of appetite
• Diarrhea

One of the most under-utilized tools in an effective parasite control program is the fecal examination, which merely involves taking two to three fresh fecal balls to your veterinarian for laboratory analysis. This simple process can identify the specific parasites infecting a horse. Rarely are the worms themselves visible in the manure. But by counting the types and numbers of parasite eggs present in the fecal sample, your veterinarian can recommend the right deworming agents to do the job. Fecal eggs per gram counts (EPG) also tell an owner about the degree of parasite infestation on a farm or within a herd. The fecal exam is a cost-effective follow-up to deworming to determine whether the dewormer has worked. It’s good practice to do a fecal EPG count within two weeks after deworming.

There are three primary ways of administering dewormers. They are:
1. Oral paste syringe
2. Nasogastric tube (tubing)
3. Feed additive

All three methods are effective. The key is that the deworming product must be given in the proper dose at the proper time, and that it is fully consumed and retained by the animal. Deworming pastes and feed formulations have come into widespread use because of convenience and ease of administration. They are a good choice as long as the horse ingests the entire dose. (The dose must be calculated based on the horse’s weight.) The problem is that some horses may find them unpalatable and spit them out. Tube deworming, once the method of choice, is still a highly effective means of controlling parasites. The advantage of administering dewormers via a nasogastric tube is that the veterinarian can ensure the proper dose is delivered directly to the horse’s stomach. The disadvantage is that it causes the animal temporary discomfort when it is passed through the nostrils and down the esophagus into the stomach. Because of the skill required to safely insert the tube, only a veterinarian should perform this method of deworming.

The best way to set up a deworming schedule is to consult your veterinarian. Horses at different ages and stages have varying needs concerning parasite control. For example, young foals are especially susceptible to ascarid (roundworm) infestation, and may require deworming at thirty-day intervals until they build some
natural resistance. Older horses turned out on a large acreage might do well on a semiannual schedule. And some owners may prefer to have their horses on a continuous control program whereby the horse is given a daily dose of dewormer through a feed additive. Climatic conditions and season of year can also influence
parasite levels. Your veterinarian may recommend that you concentrate deworming efforts when your horse’s exposure to parasites is at its peak. Other veterinarians may prefer that you deworm at regular intervals, such as every sixty to ninety days. Still others may recommend that you prevent parasitism with a daily dewormer. In any case, the goal is to keep parasite loads to a minimum.

Importantly, chemical control is just one part of a total parasite control plan. Since parasites are primarily transferred through manure, good management is also key.

You should:

• Pick up and dispose of manure droppings on a regular basis (at least twice weekly)

• Mow and harrow pastures regularly to break up manure piles and expose parasite eggs and larvae to the elements

• Rotate pastures by allowing other livestock, such as sheep or cattle, to graze them, thereby interrupting the life cycles of equine parasites

• Group horses by age to reduce exposure to certain parasites and maximize the deworming program geared to that group

• Keep the number of horses per acre to a minimum to prevent overgrazing and reduce the fecal contamination per acre

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

• Remove bot eggs quickly and regularly from the horse’s hair coat to prevent ingestion