The Practical Guide to Equine Parasites and Dewormers

There are at least three ways you can deworm your horse: oral broad-spectrum deworming, rotation, and daily deworming. ORAL BROAD-SPECTRUM DEWORMING Paste wormers have become quite popular among horseowners who maintain a regular schedule of oral administration with a premeasured syringe containing a broad-spectrum dewormer. Each syringe has a full dose in either a paste or a gel compound ROTATION If your veterinarian recommends rotating dewormers for your horse, one of the things he or she may be trying to prevent is "resistance". Resistance in a parasite population develops because there are a few worms that may survive treatment with a product. These survivors breed and their offspring inherit the ability to survive that same type of dewormer. By rotating between chemical classes, it is hypothesized that the first group of survivors may be killed before they breed more worms that are resistant to the dewormers. If you choose this method, be sure to rotate between different chemical classes, or you may risk losing any benefits of rotating. Resistant parasites are resistant to whole classes of drugs, not just subclasses and/or brand names. For example, if you're rotating between an ivermectin product and moxidectin, you are not rotating between two different chemical classes, since both are classified as macrocyclic lactones. Research has shown that parasites, specifically small strongyles, can develop strains resistant to dewormers. In fact, resistance has been shown to occur with most of the benzimidazoles and also to pyrantel pamoate. The drugs simply lose their effectiveness when this happens. That's why your veterinarian may recommend rotation between an ivermectin product, such as ROTECTIN® 1, and a pyrantel pamoate product, such as ROTECTIN® 2. These products are in two distinctly different chemical classes. As an added bonus, ivermectin contains a boticide and has maintained its status as a resistance-free dewormer. Currently there are no dewormers sold in the United States labeled for tapeworm control. However, some clinical trials have demonstrated varying effectiveness using pyrantel pamoate dewormers. Consult your veterinarian for help with tapeworm treatment and control. Whatever the reason for deworming, you must pay careful attention to the season and the parasites that are active during that time. In colder climates, bot season is at its peak in early fall and late winter. However, depending on the geographical region, bots can be a year-round problem. At a minimum, make sure the products in your rotation schedule include a boticide during this time of year. DAILY DEWORMING STRONGID® C and STRONGID® C 2x, which contain pyrantel tartrate, are daily dewormers administered in the feed. Many horse owners use the daily method of deworming because it delivers constant chemical killing of parasites. Parasite larvae are killed before they have a chance to reproduce, which decreases pasture contamination. Ivermectin and moxidectin can also kill immature parasite larval stages before they reproduce. In situations where horses can interact with each other at feeding time, keep a close eye on their daily intake to make sure they are getting their full dose. Pyrantel tartrate doesn't have any effect on bots. TUBING In the not-so-old days, veterinarians relied on the practice of "tubing" to get the dewormers into the horse's system. The technique, which involves inserting a tube through the horse's nostrils and into the horse's stomach, is now considered to be outdated.1 "The tubing technique is rarely used anymore," said Karen E. N. Hayes, D.V.M. "There are other methods now available that for most horses are safer and just as effective, if not more so." Research has shown that tubing is no more effective than oral dosing - and it's certainly not worth the risk.2 1 Medical report: cost-effective deworming. Equus, 1998; 243: 15. 2 A guide to effective deworming, John Lyons' Perfect Horse, September 1996; 11.