Feline asthma is a common inflammatory disease of the lower airway affecting approximately 1-5% of the cat population and is believed to be triggered by aeroallergens1,2. The median age of presentation is at 4-5 years of age although, it is thought many of the cats presenting at this time will already have a long-term history of the disease, so the actual age of onset could well be significantly younger2.
Clinical signs are variable and are sometimes categorised as acute, where episodic severe respiratory distress on expiration is seen, or as chronic, where more persistent wheezing and coughing of various degrees of severity may be observed1. However, approximately 10-15% of cases will present with a history of vomiting or paroxysmal hacking and coughing. This may result in a diagnostic work-up for gastrointestinal conditions such as hairballs, rather than one for respiratory issues2. Some cats with a history suggestive of asthma may be asymptomatic at the time of presentation. In these patients gentle tracheal palpation will often easily elicit a cough2. The subtly of clinical signs in some cats with chronic disease means the condition can remain undiagnosed for a significant period of time. This delay allows progression of pathological changes within the lung tissue2.
Even with a thorough diagnostic respiratory investigation, discriminating feline asthma from other lower airway disorders (including chronic bronchitis and parasitic, infectious, cardiac or neoplastic conditions) is difficult which is, at least in part, why there are relatively few clinical trials into therapeutics for the disease1-3. Diagnosis is usually through a combination of history, clinical signs, thoracic radiography, exclusion of respiratory parasites, bronchoalveolar lavage cytology and response to trial therapy with bronchodilators and glucocorticoids1. Once a diagnosis has been made, allergy testing can then be used to identify allergens to which the cat is showing a hypersensitivity response2. These are then interpreted alongside the history to establish their clinical relevance. Intra-dermal skin testing and allergen-specific IgE determination by ELISA were both found to specific in a study by Lee-Fowler et al. (2009), with the conclusion being drawn that either test could be used to guide the selection of allergens in allergen-specific immunotherapy (ASIT)4.
Treatments which are typically used include oral, parenteral and/or inhaled steroids and bronchodilators. Lung function may still decline over time as these therapies are palliative in nature and do not ameliorate chronic airway remodelling2. While effective in many cats some cases will be minimally or unresponsive to the drugs, furthermore, the long-term use of steroids is contraindicated for various common feline conditions (diabetes for example) and are not always well tolerated2. Therefore, it is advantageous to consider other treatment modalities as part of the solution for this lifelong condition. When allergen identification has occurred it opens up two additional possibilities; allergen avoidance through environmental changes and allergen-specific immunotherapy (ASIT) which has been shown to be a successful treatment option for some cats5,6.
- Reinero, R. (2011). Advances in the understanding of pathogenesis, and diagnostics and therapeutics for feline allergic asthma. The Veterinary Journal 190: 28–33
- Trzil, J.E. & Reinero, C.R. (2014). Update on feline asthma. Vet Clin North Am Small Anim Pract 44(1):91-105
- Moriello, K.A., Stepien, R.L., Henik, R.A. & Wenholz, L.J. (2007). Pilot study: prevalence of positive aeroallergen reactions in 10 cats with small-airway disease without concurrent skin disease. Veterinary Dermatology 18(2):94-100.
- Lee-Fowler, T.M., Cohn, L.A., DeClue, A.E., Spinka, C.M., Ellebracht, R.D. & Reinero, C.R. (2009). Comparison of intradermal skin testing (IDST) and serum allergen-specific IgE determination in an experimental model of feline asthma. Vet Immunol Immunopathol 132(1):46-52
- Halliwell, R. (1997). Efficacy of hyposensitization in feline allergic diseases based upon result of in vitro testing for allergen-specific immunoglobulin E. Journal of the American Animal Hospital Association 33: 282-288.
- Prost, C. (2008). Treatment of allergic feline asthma with allergen avoidance and specific immunotherapy: Experience with 20 cats. Revue française d’allergologie et d’immunologie clinique 48(5):409-413
Jo Gourlay is the Senior Veterinary Technical Manager for Avacta Animal Health.
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