Controlling Internal Equine Parasites

by: Sarah Gee

Internal parasites, more commonly known as worms, are silent killers. They can cause major damage to your horse’s internal organs, and you may be totally unaware of their presence. At the very least, parasites can lower resistance, rob a horse of nutrients, and cause gastrointestinal discomfort. At their very worst, they can lead to colic, intestinal ruptures, and death.

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 (roundworms)

• Pinworms

• Bots

• Tapeworms

• Threadworms

• Lungworms

All or any of these parasites can be present in a horse at one time. Also, keep in mind that some species can lay more than 200,000 eggs a day, so parasite loads can escalate quickly.

Contrary to popular belief, not all horses with dangerous levels of parasites show symptoms. Many appear to be perfectly healthy. However, in some horses, especially young horses, parasites can take a visible toll. Signs of infestation might include:

• Dull, rough haircoat

• Lethargy

• Weight loss

• Coughing and/or nasal discharge

• Tail rubbing and hair loss

• Resistance to the bit due to mouth lesions

• Colic

• Summer sores

• Depression

• Loss of appetite

• Unthriftiness or loss of condition

• Diarrhea

Good management procedures and the use of daily deworming agents are essential in relieving your horse of most parasites. Since parasites are primarily transferred through manure, good management is key. In terms of management priorities, establishing a parasite control program is probably second only to supplying your horse with clean, plentiful water and high quality feed.

To eliminate parasites before they attack your horse, implement these suggestions from the American Association of Equine Practitioners:

• Pick up and dispose of manure droppings in the pasture 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 to graze them, thereby interrupting the life cycles of 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 haircoat to prevent ingestion.

• Rotate deworming agents, not just brand names, to prevent chemical resistance.

• Consult your veterinarian to set up an effective and regular deworming schedule.

There are three primary ways of administering dewormers – oral paste syringe, nasogastric tube (tubing), and as a feed additive. All three methods are effective. The trick is that the deworming product must be given in the proper dose. Deworming pastes and feed additives have become very popular because of their convenience and ease of administration. They are a good choice as long as the horse ingests the entire dose. Problems arise because some horses don’t like the way they taste and spit them out or refuse to eat them. 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. The best way to set up a deworming schedule is to consult your veterinarian.

References

Waging War On Equine Parasites at www.dclahdvm.com/articles/parasite_control.html