Combined Use of Frontline Tri-Act and NexGard Spectra

Researchers in Italy recently examined safety and efficacy associated with combined use of 2 new antiparasitic products (Frontline Tri-Act and NexGard Spectra, both manufactured by Merial, now part of Boehringer Ingelheim) in client-owned dogs. The authors aimed to determine an effective prophylactic regimen against ectoparasites, endoparasites, and vector-borne diseases in endemic regions. Intestinal nematode infection is common in Italy, and canine leishmaniasis and dirofilariasis have overlapping distributions.

Study Design

Apparently healthy, client-owned dogs in endemic regions of southern Italy underwent initial screening for internal and external parasites and vector-borne diseases.

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Assessment included:

• physical examination

• fecal examination
• CBC
• Modified Knott’s test for D immitis
• Rapid ELISA for Leishmania, Anaplasma, Borrelia, Ehrlichia, and D immitis

Frontline Tri-Act (fipronil/permethrin) and NexGard Spectra (afoxolaner/milbemycin oxime) were then administered every 28 days for 6 months, and diagnostic tests were repeated throughout the study to re-evaluate parasite burdens.

Results

Thirty-seven dogs with a mean age of 3.6 years and weight range of 3.4 to 32 kg completed the study. All dogs either lived in single-pet households or in 1 of 3 kennels consisting of multiple hunting dogs.

No adverse events were observed from concurrent administration of Frontline Tri-Act and NexGard Spectra, and all biological parameters, including weight, body condition, and hematological parameters, remained within physiological limits throughout the study.

At the beginning of the study, 19% and 84% of pet and hunting dogs, respectively, were infected with gastrointestinal nematodes, mostly consisting of Trichuris vulpis and Ancylostomatidae. Fourteen days after the first administration of Frontline Tri-Act and NexGard Spectra, 40% of hunting dogs continued to shed eggs. All pet dogs remained nematode-free from Day 14 until the end of the study, while several hunting dogs continued to shed hookworm eggs for the study’s duration.

Nineteen percent of pet dogs and 84% of hunting dogs were infested with fleas at the beginning of the study, while 98% of all dogs were flea-negative 1 day after Frontline Tri-Act and NexGard Spectra administration. Four weeks later, 28% of hunting dogs again had flea burdens, but the authors noted most fleas were dead or moribund.

Ticks were initially observed on 6% and 12% of pet and hunting dogs, respectively, but dogs were all tick-free from Day 14 until the end of the study. While 6 hunting dogs were serologically positive for Leishmania at the beginning and end of the study, all other dogs tested negative for Leishmania, Anaplasma, Borrelia, Ehrlichia, and D immitis.

Final Thoughts

The study’s authors deemed that combined use of Frontline Tri-Act and NexGard Spectra for 6 months was safe and effective against endo- and ecoparasite infections in client-owned dogs. Although all dogs appeared clinically healthy, many were infected with intestinal parasites on initial examination. Also, hookworm infections were particularly persistent in kennel-housed dogs, which may necessitate milbemycin oxime dosing every 2 weeks for initial control, according to the authors.

Dr. Stilwell received her DVM from Auburn University, followed by a MS in fisheries and aquatic sciences and a PhD in veterinary medical sciences from the University of Florida. She provides freelance medical writing and aquatic veterinary consulting services through her business, Seastar Communications and Consulting.