Efficacy of imidacloprid 10%/moxidectin 1% spot-on formulation (Advocate®) in the prevention and treatment of feline aelurostrongylosis

Abstract

Background: In three randomized, controlled laboratory efficacy studies, the efficacy in the prevention of patent infections of a topical combination of imidacloprid 10%/moxidectin 1% (Advocate ® spot-on formulation for cats, Bayer Animal Health GmbH) against larval stages and immature adults of Aelurostrongylus abstrusus, as well as the treatment efficacy of a single or three monthly treatments against adult A. abstrusus, were evaluated. Methods: Cats were experimentally inoculated with 300-800 third-stage larvae (L3). Each group comprised 8 animals and the treatment dose was 10 mg/kg bodyweight (bw) imidacloprid and 1 mg/kg bw moxidectin in each study. Prevention of the establishment of patent infections was evaluated by two treatments at a monthly interval at three different time points before and after challenge infection. Curative efficacy was tested by one or three treatments after the onset of patency. Worm counts at necropsy were used for efficacy calculations. Results: In Study 1, the control group had a geometric mean (GM) of 28.8 adult nematodes and the single treatment group had a GM of 3.4 (efficacy 88.3%). In Study 2, the control group had a GM of 14.3, the prevention group had a GM of 0 (efficacy 100%), while the treatment group had a GM of 0.1 (efficacy 99.4%). In Study 3, the GM worm burden in the control group was 32.6 compared to 0 in all three prevention groups (efficacy 100% for all of those groups). Conclusions: The monthly administration of Advocate ® reliably eliminated early larval stages and thereby prevented lung damage from and patent infections with A. abstrusus in cats. Regarding treatment, a single application of Advocate ® reduced the worm burden, but it did not sufficiently clear the infection. In contrast, three monthly treatments were safe and highly efficacious against A. abstrusus.

Efficacy of Bravecto® Plus spot-on solution for cats (280 mg/ml fluralaner and 14 mg/ml moxidectin) for the prevention of aelurostrongylosis in experimentally infected cats

“…Thus, lung pathology appeared to be a suitable additional parameter to assess the preventive efficacy, and the observed data fit with a previous study, which reported marked differences in the gross lung appearance between control cats and those preventively treated against aelurostrongylosis [33]. This latter study showed the efficacy of two treatments of an imidacloprid 10%/moxidectin 1% spot-on formulation (Advocate ® ; Bayer Animal Health [part of ELANCO Animal Health]) at the minimum recommended dose of 10 mg/kg BW imidacloprid and 1 mg/kg BW moxidectin applied at a 4-week interval in preventing cat aelurostrongylosis [33]. The first treatment was performed either 4, 10 or 20 days before and the second 24, 14 or 4 days after experimental infection, respectively.…”

“…A known issue of the experimental A. abstrusus infection model (inoculation of digested snail solution) is vomiting after inoculation [ 1 , 33 , 40 ]. Here, 23 cats vomited despite the administration of metoclopramide.…”

“…Nevertheless, a minor impact on the lung pathology score cannot be excluded. However, the study groups were evenly affected by the “cat flu,” while lung appearance during necropsy showed clear differences: In the control group, the lungs showed severe to very severe pathological findings typical of aelurostrongylosis such as emphysema, subpleural opaque or yellowish nodules and areas of hyperaemia [ 1 , 33 , 40 ]. In all treated groups such findings were either absent or only mild to moderate.…”

“…The first treatment was performed either 4, 10 or 20 days before and the second 24, 14 or 4 days after experimental infection, respectively. As a single administration of moxidectin is reported to be effective at least in terms of suppressing larval excretion and resolving clinical signs in a patent infection [ 2 , 6 , 45 ], the protective effect of the first treatment in the mentioned study [ 33 ] applied prior to the challenge infection cannot be properly assessed. Therefore, it remains unclear whether and to what extent the treatment prior to infection had a preventive effect against subsequent challenge infection.…”

“…In this regard, an experimental study provided encouraging results, as eprinomectin was able to prevent clinical aelurostrongylosis and larval shedding when applied as early as 4 days post infection [ 32 ] and led to the license of a spot-on formulation containing eprinomectin against fourth- (L4) and fifth- (L5) stage larvae of A. abstrusus . Likewise, a product containing moxidectin is licensed against third-stage larvae (L3) and L4 if applied at monthly intervals, since it has been demonstrated that two moxidectin treatments 4 weeks apart at different time points before and after experimental infection reliably eliminate larval stages of A. abstrusus and hence can prevent lung damage and a patent infection [ 33 ]. Indeed, the long-lasting property of moxidectin makes this molecule a promising candidate for the prevention of aelurostrongylosis even after a single treatment several weeks prior to infection.…”