Severe respiratory signs in two cats following the inhalation of a footwear proofing aerosol

Sir,

Two sibling, 3-year-old neutered female Bengal cats presented with tachypnoea. The owner reported audible wheezing heard in one of the cats. Neither cat had a history of any coughing, sneezing, dyspnoea or nasal discharges prior to this event. The cats were kept indoors with only occasional restricted access to the outdoors. The owner revealed that the cats would have had access to a room shortly after an aerosol footwear proofer had been sprayed, with the clinical signs being seen 12 h after exposure.

Clinical examination revealed both cats to be bright but anxious. Tachypnoea was evident in both cats. Thoracic auscultation of cat 1 revealed an expiratory wheeze heard in the cranial regions of both hemithoraces. Cat 2 was considered to have accentuated bronchovesicular sounds heard equally in all lung fields. Both cats displayed a regular tachycardia with no abnormal heart sounds heard. The cats received oxygen supplementation via an oxygen chamber before further investigation.

Complete blood cell counts, serum biochemistry profiles and routine urinalysis were all carried out with no abnormalities being detected.

Standing two dimensional thoracic ultrasound revealed no pleural effusions and that the left atrial size in both cats was normal.

The right lateral radiograph of cat 1 (Fig 1) revealed a pneumomediastium seen in conjunction with an interstitial lung pattern. Radiographs of cat 2 were unremarkable. Arterial blood gas analysis was not available and neither cat would tolerate measurement of blood oxygen saturation.

Fig 1.

Right lateral thoracic radiograph of cat 1. A pneumomediastium is present.

At this stage a tentative diagnosis of toxic pneumonitis was considered likely.

Both cats were medicated with salbutamol (Ventolin; Evohaler 100 μg per metered dose q 4 h) and amoxicillin/clavulanate (Synulox; Pfizer) on day 1. A single injection of dexamethasone (Dexadreson; Intervet Schering–Plough 0.1 mg/kg) was given on day 2, followed by prednisolone (Prednicare; Animal Care, 1 mg/kg q 12 h reducing to 0.25 mg/kg every other day). The respiratory rate of both cats remained elevated (>40 bpm) until day 3 despite the above medication. The owner declined further investigation including bronchoscopy with cytology and follow-up radiography. By day 5 the clinical signs had resolved and both cats were discharged from the hospital. The cats were re-examined on day 10 and thereafter at routine vaccination examinations. Neither cat has suffered relapse of these clinical signs to date (>690 days).

Footwear proofers are waterproofing sprays which are used to protect outdoor footwear. Severe respiratory signs following exposure to waterproofing sprays have been reported in the human literature. ^1,2 Toxic pneumonitis caused by inhalation of a waterproofing agent has been reported in two dogs. ³ A literature search reveals no reports of exposure in cats.

In general, most waterproofing sprays contain a mixture of solvents, a propellant and a repellent. In this case the footwear proofer (Caterpillar footwear proofer aerosol) contained a potentially toxic mix of a fluoro copolymer, isoparaffinic hydrocarbons (C₁₀–C₁₂) and butane.

Exposure of mice to a fluororesion repellent has been reported to lead to severe respiratory illness. ⁴ To the author's knowledge exposure to fluorocarbons has not been reported in cats. However, exposure to hydrocarbons including petroleum distillates, white spirit and kerosene is known to be toxic in cats. ⁵ Clinical signs are reported to include tachycardia, ataxia, tremor, weakness, excitability, agitation, convulsion, tachypnoea and pyrexia. Respiratory signs develop after either inhalation or are noted after aspiration pneumonia following ingestion of the hydrocarbon compound. In this case it is not possible to determine whether a single component or a mixture of components from the aerosol caused the clinical signs in these cats.

Clinical signs in two dogs after exposure to a hydrocarbon waterproofing spray ³ included tachypnoea, lethargy, vomiting and anorexia. In this case both cats displayed tachypnoea and lethargy but neither developed vomiting nor anorexia. In contrast to this case, the dogs developed abnormalities in their haematology and biochemical profiles. These included neutrophilia and increased alkaline phosphatase and alanine aminotransferase activity.

Due to the expiratory wheeze that was noted in cat 1, it was considered that bronchoconstriction may have been contributing to the dyspnoea. This is consistent with reports of human toxic inhalation where bronchoconstriction is a known pathologic effect. ⁶ A bronchodilating agent, salbutamol (Ventolin; Evohaler) was delivered via a spacing chamber (Feline Aerosol Chamber; Aerokat). This method of administration was well tolerated by both cats. In this case there was no subjective improvement in either cat (respiratory rate or attitude) with this treatment. Corticosteroids were administered as there had been no clinical improvement with the bronchodilators. Glucocorticoids have been used in humans with hydrocarbon pneumonitis. ¹ Failure to administer glucocorticoids has been reported to result in a human patient developing pulmonary fibrosis. ¹

Antimicrobial therapy (Synulox; Pfizer) was initiated as a precaution due to a possible increased susceptibility to bacterial infection secondary to airway inflammation.

Although there is no direct proof, it is suspicious that exposure to footwear proofer is a potential toxin to cats upon inhalation.