Activyl Manufacturer Knocks Effectiveness of Frontline Plus

Comparing spot-on topical flea treatments Activyl and Frontline Plus.

Activyl and Frontline Plus are competing products made by Merck Animal Health and Merial Ltd., respectively.

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A study comparing the efficacy of the spot-on topical flea treatments Activyl and Frontline Plus has left one pet pharmaceutical manufacturer declaring victory and a competitor challenging the research.

Merck Animal Health on Feb. 26 released the results of an in-home study that found Activyl, in the company’s words, “was more effective than Frontline Plus in controlling flea populations on pets.”

Frontline Plus is manufactured by Merial Ltd. of Duluth, Ga.

“Activyl eliminated more than 99 percent of fleas on pets after two monthly applications versus a 54.8 percent reduction achieved by Frontline Plus,” Merck reported. “At the end of the two-month study, nearly five times more pets treated with Activyl were flea free, and Activyl users found significantly fewer fleas in their homes.”

Merial countered that in-home product comparisons are unreliable because of multiple variables.

“These variables include pre-existing flea biomass (eggs, larvae, pupae) in the home, differences in temperature and humidity between different homes, flea development ‘hot spots’ outdoors, and even flea-infested visitor pets,” the company noted in a prepared statement.

“We know from many years of conducting our own flea and tick control research that studies such as this—conducted in pet owners’ homes—are not well suited for making product comparisons,” Merial added.

Merck commissioned Kansas State University parasitologist Michael Dryden, DVM, Ph.D., to conduct the study last summer in Tampa, Fla. Thirty-two dogs and three cats living in 18 homes were treated topically with Activyl (indoxacarb) while 30 dogs and two cats living in 19 homes were treated topically with Frontline Plus (fipronil [s]-methoprene).

Fipronil kills adult fleas and ticks, and (S)-methoprene attacks flea eggs and larvae, according to Merial.

All the animals had what Merck described as natural flea infestations.

“Homes were randomly assigned to treatment,” Merck reported. “All products were applied according to label directions by study investigators on Day 0 and again between days 28 and 30. Flea populations on pets were assessed using visual area counts, and premise flea infestations were assessed using intermittent-light flea traps on days 0, 7, 14, 21, 28–30, 40–45, and 54–60.”

While Summit, N.J.-based Merck went on the offensive, posting the news on the Activyl website, Merial stood by the efficacy of Frontline Plus and pointed out that its formulation “remains the No. 1 veterinarian-recommended product for flea and tick control.”


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