Efficacy of a novel topical combination of fipronil, (S)-methoprene, eprinomectin and praziquantel against larval and adult stages of the cat lungworm, Aelurostrongylus abstrusus

AbstractThe efficacy of a novel topical combination of fipronil 8.3% w/v, (S)-methoprene 10% w/v, eprinomectin 0.4% w/v, and praziquantel 8.3% w/v (BROADLINE®,11Broadline® is a trademark of Merial; all other marks are the property of their respective owners. Merial) against larval and adult Aelurostrongylus abstrusus lungworms in cats was assessed in a controlled laboratory study. The study included 48 purpose-bred, short-haired cats which were each inoculated with 225 infective A. abstrusus larvae. The cats were formed into eight blocks based on pre-treatment bodyweight and were then, within each block, randomly allocated to one of six treatment groups: untreated control; treated once when A. abstrusus were expected to be third-stage larvae (4 days post inoculation [dpi]), fourth-stage larvae (7dpi), immature adults (14dpi) or adult nematodes (32dpi), or treated twice, once when A. abstrusus were expected to be third-stage larval and once again when A. abstrusus were expected to be adult nematodes (4dpi+32dpi). Cats weighing ≥0.8–2.5kg received one 0.3mL applicator and cats weighing >2.5–7.5kg received one 0.9mL applicator. For determination of the efficacy of treatments, lungworm larval counts were established on faecal samples collected from all cats 32, 39, 46, 53 and 60dpi. At each occasion from 46dpi on, cats treated with fipronil, (S)-methoprene, eprinomectin and praziquantel had significantly lower A. abstrusus larval counts than the untreated controls with percentage reductions of 91.6% (cats treated 14dpi; P=0.012), ≥98.9% (cats treated either 4dpi, 7dpi or 32dpi; P<0.001) or >99.9% (cats treated 4dpi+32dpi; P