Prepare for Spring Deworming with Superior Results from QUEST Gel Head-to-Head Study

Protect your horses from parasites this spring with an effective dewormer. A recent study shows QUEST (moxidectin) Gel was 99.9% effective at reducing small strongyles on a herd of embryo transfer recipient mares compared with Panacur PowerPac (fenbendazole), which was only 41.9% effective 14 days post-treatment.1

“The only two active ingredients labeled to kill the dormant stage of small strongyle worms are moxidectin and fenbendazole. This study provided an apples-to-apples comparison to find the most-effective protection against this equine parasite in the adult horse,” explained one of the study’s authors, Nathan Voris, DVM, senior veterinarian, Equine Technical Services, Zoetis. “While we anticipated a certain amount of resistance to the fenbendazole product, the results far surpassed our initial expectations.”

The study, published in the Oct. 15 issue of the Journal of the American Veterinary Medical Association (JAVMA), investigated horses from various geographies in the United States. Study results were based on suppression of fecal egg counts (FEC) to help understand the biological impact of anthelmintic treatment choice on parasite egg shedding and pasture contamination created by the herd.

Mares were split into treatment groups according to the parasiticide treatment they received:

  • Group 1 received a single dose of QUEST Gel.
  • Group 2 received a regimen of five double doses of Panacur PowerPac.

Researchers recorded observations from each group at 14, 45 and 90 days post-treatment, noting statistically significant differences in fecal egg count (FEC) levels between groups at each observation.

“In just 45 days, the difference in the parasite loads the horses were carrying and shedding onto pastures was astounding,” Voris said. “The mares treated with Panacur PowerPac were shedding at a 10-times-higher rate than the mares treated with QUEST Gel.”

Contrary to popular belief, the physical appearance of horses does not accurately determine which horses have high or low parasite levels. Therefore, horse owners should collaborate with their veterinarian and obtain FEC tests for each horse to best determine the most effective parasiticide treatment or dewormer, Voris suggested.

“The mare in this study with the highest fecal egg count, more than 4,200 eggs per gram, was actually one of the fattest, healthiest-looking horses on the farm,” Voris said. “Physical appearance is not an accurate depiction of worm count. These horses, like many others, travel a lot and can be constant parasite carriers, bringing parasites back to the farm.”

The appropriate dose and/or product for reducing parasite loads is critical, particularly in horses that shed high numbers of eggs. Choosing an effective product helps minimize pasture contamination, reduces exposure to infective parasites and inhibits the risk of parasitic infection as well as complications resulting from the infection.

“Successful parasite control relies heavily on using dewormers that are effective for their intended use,” Voris continued. “From this study, we were able to conclude there was a high level of fenbendazole resistance within this herd. Given the diverse geographic origins of the study mares, these results confirm previous findings that fenbendazole resistance is widespread, and moxidectin remains an effective treatment option.”

To view a technical bulletin outlining the study results, click here. To learn more about QUEST Gel and QUEST PLUS (moxidectin/praziquantel) Gel, visit

IMPORTANT SAFETY INFORMATION: Do not use QUEST Gel or QUEST PLUS Gel in foals less than 6 months of age or in sick, debilitated and underweight horses. Do not use in other animal species, as severe adverse reactions, including fatalities in dogs, may result.

Zoetis (zō-EH-tis) is the leading animal health company, dedicated to supporting its customers and their businesses. Building on more than 60 years of experience in animal health, Zoetis discovers, develops, manufactures and markets veterinary vaccines and medicines, complemented by diagnostic products and genetic tests and supported by a range of services. In 2013, the company generated annual revenues of $4.6 billion. With approximately 9,800 employees worldwide at the beginning of 2014, Zoetis has a local presence in approximately 70 countries, including 27 manufacturing facilities in 10 countries. Its products serve veterinarians, livestock producers and people who raise and care for farm and companion animals in 120 countries. For more information, visit






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