Effectiveness of Moxidectin vs. Fenbendazole

Newsdate: Fri, 19 Aug 2011 - 01:44 pm
Location: MADISON, New Jersey

 For horse owners and veterinarians, selecting a dewormer that is safe and effective is essential  to the health of the horse. Pfizer Animal Health in conjunction with Maxwell H. Gluck Equine Research Center and the University of Kentucky performed an important study to better understand the inflammatory responses first noted in a 2006 European study comparing two anthelmintic treatments against encysted small strongyles1. 

Along with the findings came statistically significant evidence showing QUEST® (moxidectin) to be more effective against parasite egg shedding than PANACUR® PowerPac  (fenbendazole) without inflammation2.

Cyathostomes, more commonly known as small strongyles, are the principle parasite in horses. If a horse becomes infected with small strongyles, it can lead to a potentially fatal clinical condition known as larval cyathostomiasis2. This is thought to be caused by a sudden mass emergence of small strongyle larvae from encysted stages in the large intestine2,[i].

Cyathostomiasis can be prevented through a deworming program that effectively controls small strongyle infections. Use of the long-lasting dewormers QUEST® (moxidectin) gel or QUEST® PLUS (moxidectin/praziquantel) effectively helps protect against a broad range of parasites including small strongyles and encysted small strongyles.                

“Encysted small strongyles are extremely dangerous to a horse’s health, which makes using the most effective, longest lasting dewormer crucial,” said Tom Lenz, DVM, MS, Diplomate ACT and Senior Director, Equine Veterinary Services for Pfizer Animal Health. “In the Gluck study, QUEST provided 100% fecal egg reduction through an entire 28-day study period in just a single dose. Other dewormers, such as fenbendazole, require 5 doses. Be sure to consult a veterinarian before making any changes to your deworming program.”

The Gluck study included three treatment groups of ponies infected naturally with small strongyles and other parasites. The groups included a control, a group of ponies given 5 daily doses of fenbendazole (20mg/kg/day) and a group given a single dose of moxidectin (400 µg/kg) 2. By day 7, through day 28, all ponies treated with moxidectin tested negative for parasite eggs, meaning a 100% fecal egg reduction2. Ponies treated with moxidectin also showed no significant proinflammatory cytokine gene expression prior to day 142.

The lack of significant proinflammatory cytokine gene expression was consistent with the findings in the original 2006 study that revealed no severe inflammatory intestinal lesions associated with encysted strongyle death in moxidectin treated horses1.

The ponies treated with fenbendazole showed only an average 65% fecal egg reduction by day 72, and this sub-optimal efficacy was short-lived.  By day 14, strongyle fecal egg shedding was statistically identical to pre-treatment levels.  In other words, after the five dose PANACUR PowerPac was administered, ponies were shedding eggs at a rate no different than before treatment. 

Additionally concerning was the finding that fenbendazole treated horses with encysted small strongyle infections experienced an inflammatory response detectable in the peripheral circulation.  This finding was consistent with the 2006 study that found severe intestinal tissue damage at the site of dying encysted small strongyle larvae in fenbendazole treated horses1.

QUEST® (moxidectin) gel or QUEST® PLUS (moxidectin/praziquantel) are long-lasting, effective dewormers that help protect against a broad range of parasites including large and small strongyles, roundworms, pinworms, hairworms, stomach worms, bots, and most importantly encysted small strongyles.

QUEST PLUS also offers treatment and control of tapeworms (A.perfoliatum). QUEST and QUEST PLUS are a smart choice to help save money and get up to 84 days of protection from strongyle egg reinfection and 14 days without inflammation in just one dose.

QUEST and QUEST PLUS are proven safe for use in numerous breeds of horses and ponies. They are also approved for use in breeding mares and stallions, and foals six months of age and older. For more information on QUEST and QUEST PLUS, visit www.Questhorse.com.

Important Safety Information

Extreme caution should be used when administering QUEST and QUEST PLUS to foals, young and miniature horses, as over dosage may result in serious adverse reactions. Do not use in sick, debilitated or underweight animals. These products should not be used in other animal species, as severe adverse reactions, including fatalities in dogs, may result. For more information on QUEST or QUEST PLUS visit www.QUESThorse.com.

About Pfizer Animal Health

Pfizer Animal Health, a business unit of Pfizer Inc, is a world leader in the discovery, development and manufacture of innovative animal health vaccines, medicines, and diagnostic products.  Pfizer Animal Health invests more in research and development than any other animal health company.  We work to assure a safe, sustainable global food supply from healthy beef and dairy cattle, swine, poultry and fish while helping dogs, cats and horses live healthier longer lives.  We strive to be the animal health company that provides full healthcare solutions to veterinarians, livestock producers, and pet owners.  To learn more, visit www.us.animalhealth.pfizer.com.

All brands are the property of their respective owners. ©2011 Pfizer Inc. All rights reserved


1 Steinbach, et al, Strongyle infection: Consequences of Larvicidal Treatment of Horses with Fenbendazole and Moxidectin.  Vet Parasitology 139 (2006) 115-131.

2 Betancourt,A., E. Lyons, and D. Horohov. The Effect of Anthelmintics on Proinflammatory Cytokine Responses in Treated Horses. 2010 Conference of Research Workers in Animal Diseases. December 5-7 2010.

3 Small Strongyle (cyathostomes or Small Redworms) Life Cycle Illustration. Pfizer Animal   Health, 2010.

About the Author

Flossie Sellers

As an animal lover since childhood, Flossie was delighted when Mark, the CEO and developer of EquiMed asked her to join his team of contributors.

She enrolled in My Horse University at Michigan State and completed a number of courses in everything related to horse health, nutrition, diseases and conditions, medications, hoof and dental care, barn safety, and first aid.

Staying  up-to-date on the latest developments in horse care and equine health is now a habit, and she enjoys sharing a wealth of information with horse owners everywhere..