Parasite Control Recommendations

Parasite control needs to be tailored to your horse’s specific needs, taking into consideration age, immune status/individual susceptibility, time of year, and management practices.  The following are basic recommendations that can be further tailored to suit your horse’s specific needs.

MATURE HORSES (>3 years old)

  • Small strongyles (cyathostomins) are the main parasite of mature horses, and these parasites are developing resistance to commonly used dewormers.

  • Horses vary in their susceptibility to small strongyles, and can be classified as Low, Medium, or High shedders based on fecal egg counts (FECs). 

  • Low shedders require 1-2 treatments/year, with Medium and High Shedders requiring 3-4 treatments/year.  The dewormer used depends on what remains effective in your herd—please ask us about performing fecal egg count reduction tests (FECRTs) to determine what is effective for your horse! We recommend using Eqvalan in early spring, and QuestPlus in the fall as the foundation program for all mature horses.  This will provide appropriate control of small strongyles, as well as large strongyles, tapeworms, bots, and pinworms and helps ensure that the parasites remain susceptible to the available dewormers.

  • It is no longer necessary, or recommended, to deworm every horse in a herd every 2-3 months, as this practice promotes the development of drug resistant cyathostomes.  It is also recommended to not treat during the winter months, as the eggs that are shed during this time will be prevented by climactic conditions from developing into infective larvae. 

     Strategic deworming is the best practice for minimising parasitism and slowing the development of drug resistant parasites.


  • Ascarids (roundworms) are the major parasite in foals, and can cause serious damage.  Fortunately, as they age they acquire immunity to ascarids.  Begin treating at 60 days of age with a benzimidazole (Panacur, SafeGuard) and alternate every one-two months with pyrantel (Strongid) until the foal is weaned. 

JUVENILES (Yearlings, 2 and 3 year olds)

  • Young horses are more susceptible to both ascarid and strongyle parasites than mature horses and should be treated as High shedders.  FECs help determine whether the ascarids or strongyles are the primary burden, and dewormer choice can be made accordingly. 


  • New arrivals to your herd should be dewormed with a larvicidal dewormer (ivermectin, moxidectin, or Panacur PowerPak), and quarantined for 96 hours (after the last dose if a PowerPak is used).  The manure passed in that time should be disposed of, and not spread on pastures.  Note:  The 96 hours pertains only to parasites—new arrivals should be kept separate from the herd for at least two weeks to minimise the risk of introducing bacterial or viral diseases.


Submitting Samples for FECs:

Collect 1-2 fresh fecal balls.

 Place in a sealable plastic bag. 

Squeeze all the air out and seal bag. 

Label with your horse’s name. 

Submit for analysis within 12 hours.  Keep sample from freezing!

We perform FECs in house.

Ask us about our discount for group samples!

The date and type of the last dewormer administered is required for interpretation of results.



  • Twice weekly removal of manure from your horse’s paddock is very effective at reducing parasitism.  Timely harrowing and cross grazing of pastures with other species also helps reduce a pasture’s infectivity.

  • We are not advocates of anecdotal methods such as diatomaceous earth, chewing tobacco, pine needles, apple cider vinegar, etc.  These are ineffective at best, and at worst can cause significant damage to the GI tract.  The approved dewormers administered at the correct dose and times are safe. 


Weight (kg) = [(heart girth)2 x (body length)] /11,990 where heart girth is measured in cm.  Body length is measured from the point of the shoulder to the point of the buttock. Heart girth is taken around the barrel, behind the elbow, and beyond the highest part of the withers. 

Example Protocols for a mature horse that has been classified by FECs as a Low, Medium, or High Shedder.

                     APRIL               JUNE                   AUGUST                OCTOBER

LOW             IVER                                                                                 MX-P 

MED             IVER              BZD** or PYR                                                                     MX-P 

HIGH            IVER              BZD** or PYR              BZD or PYR or IVER               MX-P 

IVER=Ivermectin. MX-P=Moxidectin-Praziquantel. BZD=Benzimidazole. PYR=Pyrantel **If there is no resistance to these classes.

These are only guidelines—some horses may require an off season treatment (they are horses after all!) if they are showing signs of intestinal parasitism.