Murray County Veterinary Services 

Deworming recommendations

There are two methods used for deworming horses. The first method is to administer paste dewormers on a given schedule.  However, it MUST be emphasized that resistance to dewormers can develop - the answer is NOT regular rotation of the dewormer.  The best way to reduce the development of resistance in equine parasites is to only deworm horses who actually need it.   Certain horses tend to be easier for intestinal worms to infect, shedding more eggs into the pasture than other horses.  All of your horses should have their manure checked regulary by a veterinarian, and only those horses with high fecal egg counts should be dewormed.  A more detailed outline is below.

The second method of deworming is to keep the horse on a daily dewormer and paste deworm twice a year.  Resistance can also develop with this protocol.  Also, the horse may not eat all of the daily dewormer every day.

In addition to regular screening and deworming, there are many things you can do in your horse's environment to reduce (but unfortunately not eliminate) the worm burden.  Click here for suggestions (takes you to the HorseQuest site).   

We recommend that a fecal exam be performed any time there is diarrhea or weight loss, as it is possible for worms to develop resistance to dewormers that are used incorrectly.

1.  Paste Deworming Protocol:

a) Deworm all horses twice yearly, usually after the last frost and again in the spring, with an ivermectin or moxidectin product to kill large stongyles and bots. At least one of these dewormers should contain praziquantal to kill tapeworms (not always found on fecal examination).

b) Fecal egg counts can be done on all horses in the spring PRIOR to giving any dewormers to help identify horses who are heavily infected and may require continual deworming. It is estimated that only 20% of horses will be "heavy shedders" and need to continue on a regular deworming program every 8-12 weeks throughout the spring, summer & fall. These horses should also have an additional fecal egg count 2 weeks after deworming to determine if the parasites are being effectively killed by the dewormer selected.

c) It is estimated that 80% of horses will fall into the not infected or "low shedder" category. In general, these horses do not require deworming beyond twice yearly. Through the spring, summer, and fall these horses should have fecal egg counts checked every 8-12 weeks to see if additional deworming is needed.

d) Horses under 18 months of age should be routinely dewormed every 8 weeks due to risk of roundworm infection.

e) To submit a sample, bring one manure ball per horse in an individually labeled plastic bag or container, also labeled with your name and date.  The sample can be refrigerated for up to 24 hours, but not frozen.  You should get this sample prior to giving any dewormers - a minimum of 8 weeks after any ivermectin product or 12 weeks after moxidectin.

(above outline courtesy www.vtnhvet.com)

**Remember to read the active ingredient of any dewormer. For example, fenbendazole is the active ingredient in Panacur and Safeguard.

2. Daily Deworming Protocol

Deworm December and June with Ivermectin/praziquantel combination(Equimax) and keep horse on a daily dewormer, pyrantel pamoate (Strongid 2 x). If you choose this protocol, we recommend enrolling in the Preventicare Program offered by Pfizer. 

Note* Before starting the continuous deworming program, deworm with Equimax, Quest or a Panacur Power Pac.

TIPS ON USING WEBSITES FOR INFORMATION:  There are several reputable websites with additional information - always consider the source of the information.  Equine journals and magazines, university cooperative extension agencies, and veterinary colleges are all great sources of reliable, tested, and current information.  There are also several great veterinary clinic websites available.  The following is an article on deworming, found on 'The Horse' website.  Some of the articles on this website require a subscription.  http://www.thehorse.com/ViewArticle.aspx?ID=15854