Fecal Egg Counts and Deworming

As spring begins to show its face in beautiful flowers and new grasses, the parasite life cycle is renewed.  Warmer weather encourages larval maturation from fecal contamination in pastures. As these larvae mature they make the progression up the blade of grass and await consumption by a new host.  As your horse grazes on the fresh spring grass, transmission occurs. This is a very simple representation of a parasite life cycle. 

Fecal egg counts (FEC) have been a hot topic for many years now, and they remain the best way to monitor and treat for parasite infestation in our equine partners.  Performing a FEC gives us an understanding of what your horse is shedding at that time, and is a likely representation of what they are dealing with internally.  Understanding this, we selectively prescribe dewormer for that particular horse and their individual issues.  Two or three weeks later, we recheck FEC to be sure that the dewormer did what we needed it to do! 

In Colorado, it is not uncommon for a horse to show no signs of parasites in an FEC. Our unique environment of generally dry and freezing conditions helps to reduce the transmission of parasites in general, and many horses lack substantial grazing opportunities. But they certainly still do occur. 

Since responsible deworming of your horse is a bit more involved than it used to be, each case and circumstance can be unique.  If you have questions about your particular horse, the environmental conditions, or their potential for exposure, you should have a discussion with your veterinarian. 

Rotational Deworming… What’s the Right Choice?

QUESTION: 

Can you please discuss “appropriate” rotational deworming?

Due to the influx of deworming questions, we will tackle them in 2- 3 parts over the next few months.

 

ANSWER:   

Standing in the feed store, there are dozens of packages of dewormers, and the age old question of, “which one do I use now?” goes through every horse owners mind.  The answer to this question is not always a simple one.  To appropriately deworm your horse through the year, a rotational deworming program is essential. 

            Here in Colorado, we usually recommend quarterly rotational deworming.  Some herds may require more frequent or less frequent deworming, depending on fecal egg counts. (To be discussed here at a later date). 

Rotational deworming is exactly what it sounds like, rotating through different chemical classes of drugs throughout a year’s timeframe.  Though the name brand might be different, the active ingredient is the important part to rotate.  The idea behind rotating the chemical classes is to reduce the chance of a parasite developing resistance to a type of drug (much like antibiotic resistance).

            To begin rotational deworming this fall on an adult horse our recommendation is using an avermectin product.  There are dozens of avermectin products on each shelf, with various name brands (to name a few – Equell, Equimectrin, Ivercare, Rotectin, Zimectrin, and Horse Health Ivermectin and Quest Gel).  Avermectins have a very broad base of activity, but there are a few types of worms that are not killed.

            In the winter quarter, we usually recommend, for an adult horse a benzimidazole product.  When you’re at the counter, the easy way to remember is that you are looking for an active ingredient that ends with “azole.”  A few name brands in this class are Safe-Guard, Panacur, and Anthelcide EQ. 

            In the spring quarter (usually about the time you see us for spring shots), we rotate back to an avermectin product, but usually include praziquantel.  The praziquantel is effective against tapeworms.  The name brands in this class are Equimax, Zimectrin Gold, and Quest Plus.

            To come full circle and cover a full year, in the summer MVS likes to use a pyrantel salt based dewormer.  Some name brands in that class are Strongid Paste, Rotectin P, Pyrantel Pamoate paste and Liqui- Care P.

As another alternative to quarterly deworming, there is the option of daily deworming (feeding a small amount of dewormer every day).  Using one of these products, you still need to “rotate” and 2 times a year give a paste dewormer.  Our recommendations for these horses on daily dewormers are to use an avermectin once a year, and then a benzimidazole about 6 months later. 

            With appropriate rotation of deworming products, your horse should maintain a minimal parasite load. 

            Look for the next post regarding Fecal Egg Counts to round out your deworming knowledge.

 

 

In Summary:

MVS Rotational Deworming Recommendations (Quarterly Deworming Schedule):

 

–         Fall:  Avermectin (Ivermectin or Moxidectin)

–         Winter:  Benzimidazoles (Fenbendazole or Oxibendazole)

–         Sping: Praziquantel w/ Avermectin

–         Summer:  Pyrantel Pamoate