Recommendations for Equine Parasite Control on Southern Vancouver Island
The changing patterns of resistance among target nematodes lend an element of urgency to implementing major changes in parasite
control strategies for horses. The most critical change will be in the attitudes of horse owners and equine veterinarians because the
notion of limiting treatment to certain seasons of the year seems radical, and the prospect of leaving certain animals untreated is
tantamount to heresy. However, the recommendations presented will provide effective control, will decrease selection pressure for the
development of anthelmintic resistance, and may accomplish both at a lower cost, or at least at no increase than current, inefficient
practices. Before next deworming your horses, rethink your parasite control strategy! Quantitative Fecal Egg Count (QFEC) tests will improve
your parasite control, and may even save you money. Research has proven that on any given farm, only 25% of the horses are
causing 85% of the pasture contamination. On the other end of the spectrum, ~25% of the horses have almost no parasite burden.
Using QFEC tests, we can accurately assess each individual horse’s parasite burden and use the correct anthelmintics (dewormers)
at the correct time. No more guesswork and random dewormer rotations. Many, if not most horses will only require deworming
once per year!
The QFEC testing should be started 4 weeks after
the Egg Reappearance Period (ERP). Collect a fresh fecal sample and bring it to us
within 6 hours of collection for most accurate results. The ERP for moxidectin (Quest products) is 12 weeks, so a sample should be
collected 16 weeks after administration. The ERP for ivermectin (Eqvalan products) is 8 weeks, so a sample should be collected 12
weeks after administration. All other products are around 4 weeks for ERP, and so samples should be collected at 8 weeks after
administration. QFEC should be routinely performed in the spring, prior to pasturing horses, mid-summer, and late fall after pasturing
The results of the first QFEC test will determine if worming is necessary and what product to use. Some horses may need to be
dewormed right away. Ideally, a series of 3 QFEC tests will be run based on an individualized timeline. Using the results of the series,
the horses in your herd will be categorized as low, moderate, or high contaminators based on how many parasite eggs they are
shedding. The first year may involve an unusual timeline for deworming, as we work around the various ERP’s. In successive years,
we recommend testing with a QFEC at the beginning of the season (April 1st), and then following the chart below to schedule
dewormings. The October dewormings will always be with a praziquantel product (like Eqvalan Gold) to combat tapeworms and bots.
If horses are closely monitored and subject to good management protection, they may require only one deworming per year.
For the health of horses and the environment, consider QFEC testing as an alternative to calendar deworming. Contaminator Level 1st Annual Deworming Additional Dewormings** Final Annual Deworming
**Additional treatments are best administered suppressively to coincide with the expiration of the ERP of the dewormer used most frequently.
Central Saanich Animal Hospital
1782 Stelly’s X Road
Saanichton, BC V8M 1S8
Burnside Pet Clinic ♦ Hollywood Pet Hospital ♦ Vetcetera Pet Hospital
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