Efficacy of a single dose of a novel topical combination product containing eprinomectin to prevent heartworm infection in cats.

Cats may be infected by heartworm, Dirofilaria immitis, through mosquito bites. They can develop severe heartworm disease when infective D. immitis larvae migrate and develop into adults in the pulmonary vasculature or other tissues. As there is no curative treatment for feline heartworm infection, the monthly administration of preventative treatment is recommended in endemic areas. Three controlled, blinded laboratory studies were conducted to evaluate the preventative efficacy of BROADLINE(®), a novel combination of fipronil, (S)-methoprene, eprinomectin, and praziquantel against D. immitis in cats. In each study, 28 cats were inoculated with approximately 100 (studies 1 and 2) or 40 (study 3) infective third stage D. immitis larvae by subcutaneous injection, thirty days prior to treatment. The larvae were from recent field isolates from naturally infected dogs from three distinct geographic areas (two in the USA and one in Europe). In each study, the cats were allocated randomly to two study groups of 14 cats each. The control group remained untreated. On Day 0, each cat in the treated group received one topical application of the novel topical formulation, delivering the minimum intended dose of 0.5mg of eprinomectin per kilogram of body weight. At 6 months after infection, all cats were humanely euthanized and examined for adult D. immitis. Across all three studies, 28 (68%) of the 41 untreated cats harbored one or more heartworms, while 100% of the 42 treated cats remained free of heartworm infection, demonstrating the 100% preventive efficacy of BROADLINE(®) against D. immitis in cats. The treatment was well tolerated and no health abnormality was observed in any treated cat.