Permethrin spot-on intoxication of cats: Literature review and survey of veterinary practitioners in Australia

Survey aimsA questionnaire was sent to veterinarians in Australia to determine the approximate number of cats presenting for permethrin spot-on (PSO) intoxication over a 2-year period.FindingsOf the 269 questionnaires returned, 255 were eligible for analysis. A total of 207 respondents (81%) reported cases of PSO intoxication in cats over the previous 2 years. In total, 750 individual cases were reported, with 166 deaths. While all deaths were generally attributable to intoxication, 39 cats were euthanased because owners were unable to pay the anticipated treatment costs. Brands of PSO implicated included Exelpet Flea (and Tick) Liquidator (Mars Australia) (146 respondents), Bayer Advantix (48), Purina Totalcare Flea Eliminator Line-On (19), Troy Ease-On (six) and Duogard Line-On (Virbac) (four); 67 respondents were not able to identify a specific product. Permethrin spot-on formulations were most commonly obtained from supermarkets (146 respondents), followed by pet stores (43), veterinary practices (16), and a range of other sources including produce stores and friends. The majority of intoxication cases reported involved PSOs labelled for use in dogs with specific label instructions such as ‘toxic to cats’. Owners applied these PSO products to their cats accidentally or intentionally. In some cases, exposure was through secondary contact, such as when a PSO product was applied to a dog with which a cat had direct or indirect contact.RecommendationsIn the authors' view, because of the likelihood of inappropriate use and toxicity in the non-labelled species, over-the-counter products intended for use in either dogs or cats must have a high margin of safety in all species. Furthermore, PSOs should only be available at points of sale where veterinary advice can be provided and appropriate warnings given. As an interim measure, modified labelling with more explicit warnings may reduce morbidity and mortality.