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

Abstract

SURVEY AIMS: A 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.

Findings: Of 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.

Recommendations: In 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.

Fig 1

Survey questionnaire (including list of approved PSO products available in Australia) distributed to veterinary practices via the Centre for Veterinary Education 's (CVE 's) Control and Therapy Series publication, and by repeated e-mails from the CVE and the Australian Small Animal Veterinary Association. The questionnaire was also available on the CVE 's website

Fig 2

PSO products implicated by respondents in feline cases of permethrin intoxication (see text for product names in full)

Fig 3

Sources of PSO products implicated by respondents

Fig 4

Distribution of practices seeing permethrin intoxication cases in Sydney (a) and Melbourne (b) metropolitan areas. Blue signifies postcodes where practices had not seen cases, whereas red signifies postcodes where permethrin intoxication had been reported. Note the large number of unshaded regions for which no data was obtained because of the poor response rate to the survey

Fig 5

Packaging of the most popular PSO product available in Australia. (a) Note that the warning icon on the cardboard box is quite small (arrow). Critically, further warnings do not appear on either the foil packet (b) or the applicator pipette (c)

Fig 6

Labels using humour and dramatic emphasis to highlight the extreme risk of PSO products to cats may be utilised as an adjunct to written warnings when veterinarians dispense products containing permethrin to canine patients. These cartoons were created by the veterinarian and cartoonist Frank Gaschk (Grrinninbear Designs) and a number are available as free downloads from the resources section at www.cve.edu.au