Ask the Vet?

What do you recommend for parasite management for my horse?

SES Parasite Management

The management of internal parasites can be a confusing area of horse care. Environmental care is used in conjunction with commercial deworming products to keep the parasite burden within a horse to an acceptable number. However, the use of deworming products should be judicious and appropriate. Only a few drug classes of dewormers or anthelmentics exist, but many brand name products contain the same drugs. Classes of dewormers are typically broad and target more than one internal parasite. The rotation of dewormer classes and the careful timing of use are helpful for reducing parasite resistance. Parasite resistance is the result of the overuse of dewormers and the improper timing and selection of drug class. This results in the proliferation of parasites that are not sensitive to the available dewormers.

Creating a deworming strategy should be a decision between you and your veterinarian but many factors are included in the selection of treatments. At Southern Equine Service, we recommend using fecal analysis to quantify the eggs per gram (EPG) of feces. The EPG of feces is reflective of the internal parasite load and is used in conjunction with the horse's overall health and environmental challenges to determine if deworming is recommended and which drug class is appropriate.

Fecal Analysis:

A McMaster's Fecal Analysis is used at Southern Equine Service to determine the EPG of feces present in a horse at a given time. Not all internal parasites are consistently detected using routine fecal analysis because eggs are only shed at select intervals in parasite life cycles. Strongyles, roundworms (ascarids), and pinworms are routinely detected while tapeworms are only seen on occasion. The EPG of feces is a measurement of the degree of parasite egg shedding within a horse. Horses are categorized as low (< 250 EPG), moderate (250-500 EPG), or high (>500 EPG) shedders. In general, a low shedder has a "negative fecal" and should not be treated with dewormer at that time. A high shedder has "positive fecal" and should be treated with dewormer. Moderate shedders fall within a gray zone where the recommendation to deworm is based upon many factors including the physical condition of the horse and environmental factors. Regardless of these results, horses should receive a dewormer with praziquantel for tapeworms.

Determining the frequency of fecal analysis should be tailored to individual horses or farms. Typically, horses that are consistently low shedders only need to be tested every 4 months. Horses that show signs of parasitism or are high shedders should be tested every other month. Horses may also be tested 10-14 days after being dewormed to determine if the dewormer class used was effective.

Signs of Internal Parasitism:

Looking at a horse is not enough to determine if he/she has a high parasite burden; however, some external signs may be seen. Here is a list of the most common signs in horses:

• Dull, rough haircoat
• weight loss / loss of condition
• tail rubbing and hair loss
• colic
• lack of energy
• coughing and/or nasal discharge
• summer sores
• diarrhea
• pot belly appearance (in young horses)

Environmental Management:

Reducing the exposure to parasites in the environment may help prevent reinfection. There are many tips to managing your horses especially in the pasture setting to minimize parasite ingestion. Some of these tips include:

• feeding horses hay and grain off the ground in feeders
• rotate pastures to allow pastures to rest
• keep low stocking rates to reduce overgrazing
• pick manure from turnout areas twice weekly
• mow/harrow pastures to spread out manure
• avoid spreading manure in pastures currently housing horses

Weather conditions also influence the ability of parasites to survive outside of the horse. In this area of the southeast, high temperatures in the summer kill off many parasites harboring in the pastures. During the summer, deworming is often needed less frequently as the environmental parasite burden is minimized.

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1258 Banks Mill Rd.
Aiken, SC 29803

Tel: 803.644.1544
Fax: 803.644.1599

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