Parasite Control in Horses
Effective parasite control is a critical part of responsible horse care. Horses are susceptible to a variety of internal and external parasites, and without an effective prevention plan, these pests can cause serious health issues before symptoms even appear. A consistent parasite control program not only protects your horse’s health but can also save money on feed costs and veterinary bills.
Common Internal Parasites in Alberta Horses
Horses can become infected with parasites when they are exposed to contaminated environments and ingest parasite eggs or larvae. For example, transmission commonly occurs when horses graze in a pasture that was infected by the parasite-infected manure of another horse.
Horses can be affected by several types of internal parasites, often at the same time. The most common in Alberta include:
- Large strongyles
- Small strongyles
- Ascarids (roundworms)
- Pinworms
- Tapeworms
Depending on the parasite, infestations may damage tissues and vital organs, cause obstructions and ulcerations within the digestive tract, and cause irritation as eggs are laid.
Signs of Parasite Infection
Parasite infections are not always obvious. Some horses (particularly young ones) may show obvious signs of heavy worm loads, while others can appear healthy despite dangerous parasite levels. The best way to assess infestation is through regular fecal egg counts performed by your veterinarian.
The Alberta Veterinary Medical Association (ABVMA) cautions horse caregivers that the following symptoms may indicate a parasite infection:
- Dull coat
- Lethargy (low energy) or decreased performance
- Weight loss or poor body condition
- Slowed growth in young horses
- Pot belly (especially in young horses)
- Colic or other digestive issues
- Diarrhea
- Visible worms in feces
It is important to consult with a veterinarian if any of these symptoms are observed.
Building a Parasite Control Plan
The most effective preventive strategy involves collaboration with your veterinarian and combines deworming (reactive) with good management practices (proactive prevention). This approach reduces the viability of parasites already in the horse and lowers the risk of re-infestation.
Deworming
Many safe, effective, and convenient deworming products are available today. Consult your veterinarian to select a product and establish a program tailored to your horse’s individual needs and risk factors. While a minimum deworming schedule of two treatments per year is common, many situations require more frequent deworming.
Key tips from the ABVMA:
- Use dewormers only when necessary, based on your veterinarian’s recommendations.
- Follow the medication directions carefully.
- Always give the full, correct dose as directed.
- Deworm all horses on the property at the same time.
- Ask your veterinarian which products are best at different times of the year.
Parasite Management Practices
Chemical dewormers are only one part of an inclusive parasite control plan. Good management practices are essential as parasites are most frequently transferred though manure.
- Pasture Management: Keep the number of horses per acre to a minimum to prevent overgrazing and reduce pasture contamination with parasite eggs and larvae.
- Manure Disposal: Pick up and dispose of manure regularly (at least twice a week, even in dirt or sand yards). Do not spread manure on fields to be grazed by horses; compost it in a pile away from the pasture.
- Pasture Maintenance: Mow and harrow pastures periodically to break up manure piles and expose parasite larvae to the elements.
- Rotational Grazing: Consider rotating pastures by allowing sheep or cattle to graze them, thereby disrupting the parasite life cycles.
- Separation: Keep foals and weanlings separate from yearlings and older horses to minimize the foal’s exposure to roundworms and other parasites.
- Quarantine: Isolate new horses and perform fecal examinations between introducing to the rest of the herd.
- Feeding Practices: Use a clean feeder for hay and grain rather than feeding on the ground.
External Parasites
In addition to internal parasites, horses can be affected by external parasites such as lice, ticks, and fleas, usually through direct contact with an infected horse. If you notice symptoms such as itching, hair loss, or other skin issues, consult your veterinarian for diagnosis and treatment.