Efficacy of a moxidectin/imidacloprid spot-on formulation (Advocate^®) for the treatment of Troglostrongylus brevior in naturally infected cats in a field study in Greece

Background: Troglostrongylus brevior is a lungworm of wild felids that recently has been recognized as agent of severe respiratory disease in domestic cats in Mediterranean and Balkan countries. Nevertheless, the information on treatment options for feline troglostrongylosis is still poor. The aim of this pilot field trial was to evaluate the efficacy of the spot-on formulation containing 1% w/v moxidectin and 10% w/v imidacloprid (Advocate^® spot-on solution for cats, Bayer Animal Health GmbH) in the treatment of T. brevior infection in naturally infected cats in Greece.

Methods: The trial was a negative control, multicentre, clinical efficacy study conducted according to the standards of Good Scientific Practice (GSP). Sixteen cats in two study sites, naturally infected with T. brevior, were allocated to an untreated control group (G1, n = 8) or a treatment group (G2, n = 8), according to a randomization list. Animals assigned to G2 were treated with Advocate^® for cats on days 0 and 28 at the recommended dose rate and animals assigned to G1 received a rescue treatment with the same product on days 56 and 84. Efficacy was assessed on days 28 and 56 in G2 and on days 84 and 112 in G1 by faecal larval counts. The primary efficacy criterion was the absence of T. brevior first-stage larvae (L1) following treatment. Other efficacy parameters were the quantitative comparison of L1 presence before (baseline) and after one or two treatments in both groups.

Results: All G2 cats were negative for T. brevior L1 at the first post-treatment evaluation (100% efficacy) while G1 cats were persistently shedding L1. The difference of the mean number of L1 per gram between G2 and G1 was statistically significant (P < 0.001). All G1 cats were negative (100% efficacy) for T. brevior L1 at the first post-rescue-treatment evaluation. Therefore, treatment efficacy at study completion was 100% in both groups in terms of stopping the L1 shedding in the faeces of the animals. No adverse effects were observed during the study.

Conclusions: These results indicate that Advocate^® spot-on solution for cats represents an option for treating cats naturally infected with T. brevior.