- About Us
- Valley Vet
- Cascade East
- Printable Client Forms
Equine Internal Parasite Management & Deworming Guide
Internal parasites are still a major health concern in horses. Preventable illness and death due to these "worms" is still being seen by our veterinarians. Also, in recent years the concern has become parasites that escape traditional deworming methods?encysted small strongyles and tapeworms.
At the same time, concern has arisen with potential development of resistance to traditional dewormers in large animal species, including horses. In some cases, horses are being "over-dewormed."
For these reasons, newer recommendations focus on "targeted deworming," based on fecal egg counts of parasites in individual horses. We now know that with different equine immune systems, parasite susceptibility varies from horse to horse. Twenty percent of horses in a herd account for 80% of the parasites shed onto the ground. The goal is to identify equine "shedders" (often young horses or those with stressed immune systems) through fecal testing. Testing also allows you to determine how effective your deworming medication is on your horses' parasites, and how often treatment is needed. In the long run, this can save you time and money and helps slow down the onset of resistance to deworming medications.
Since fecal testing will NOT identify encysted small strongyle larvae and is limited in detecting tapeworms, these parasites should be targeted 1-2 times annually.
Fecal testing identifies strongyle, roundworms, pinworms, and other parasite eggs. We use the most current laboratory procedures in detecting these parasites (sugar-centrifugation/flotation).
If you choose not to have fecal testing done, we recommend deworming your horse every 3-4 months with a moxidectin or ivermectin product, taking into account the guidelines in (#1) above. Keep in mind that a fecal egg count test is less expensive than the cost of two deworming treatments! (Fecal: $26.75, additional horses $20.25 each when submitted at the same time). A common scenario is that testing reveals that less deworming treatments are necessary for your horse, and that saves time and money.
Specific risk category groups:
1. Young horses
Horses less than 5 years of age have higher parasite rates. Yearlings and weanlings are most susceptible. All foals should receive their first deworming by 2 months of age and may be dewormed with an ivermectin or pyrantel product.
2. Pregnant mares
Most commercially available dewormers are labeled safe to use in pregnant mares. We recommend the spring deworming treatment be given 4-6 weeks prior to foaling, as this will help to protect the foal.
3. Newly acquired horses
They can have a big impact on parasite levels in your pasture and herd. Prevent problems by quarantining until fecal egg testing and deworming can be completed.
Other parasite management recommendations:
1. Pasture management (also contact Kittitas Co Conservation District)
Manure should be collected and/or dispersed frequently. Grazing more than 1 horse per 2 acres results in higher parasite levels.
Interesting Fact: moxidectin, the ingredient in Quest Deworming, is non-toxic to "fecal fauna", such as dung beetles, which are beneficial to pastures. Other dewormers can have a negative effect on these beneficial organisms.
2. Separate pastures
Graze yearlings and weanlings on separate pastures from older horses.
3. Understanding dosing
Under dosing deworming medications is a frequent problem that allows resistance to develop more rapidly. If in doubt of your horse's weight, ask us for estimation, or use a weight tape.