Update, Diagnosis, & Treatment of Feline Asthma

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Figure 1 Bronchoalveolar lavage fluid cytology from a cat. Note the predominance of eosinophils, which is characteristic of feline asthma. Figure courtesy of Carol Reinero, DVM, PhD, DACVIM, University of Missouri

Asthma is a common cause of feline lower airway disease that results in coughing and/or intermittent respiratory distress in most patients. Feline asthma is a Type-1 hypersensitivity reaction to specific aeroallergens.1 The combination of asthma’s hallmark clinical features (ie, eosinophilic airway inflammation, bronchoconstriction, excessive mucus production, airway edema) results in an expiratory respiratory pattern, characterized by prolonged expiratory time and an abdominal push during exhalation. Long-term, these patients can develop irreversible airway remodeling secondary to chronic airway inflammation.

Feline asthma most commonly affects young to middle-aged cats. Clinical presentation varies with some cats having only one clinical sign—a chronic cough or dyspnea (ie, status asthmaticus)2—whereas others may have both a chronic cough and intermittent exacerbations causing expiratory distress.3

Absence of a cough does not rule out asthma because some cats may have respiratory distress as the only presenting complaint. Definitive diagnosis requires imaging and airway sampling combined with ruling out other causes of airway eosinophilia (eg, pulmonary parasites, heartworm-associated respiratory disease). Treatment is aimed at controlling airway inflammation and preventing and/or reducing respiratory distress episodes with bronchodilator therapy. 

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Diagnosis

Definitive diagnosis of feline asthma can be challenging because the disease’s clinical features may overlap with chronic bronchitis, heartworm-associated respiratory disease, or other pulmonary conditions. Diagnosis is achieved with a combination of consistent clinical signs (ie, cough and/or respiratory distress), physical examination, thoracic radiography, and eosinophilic inflammation on airway cytology. (See Figure 1.)

  • Physical examination may be normal or reveal increased bronchovesicular sounds, tachypnea, and/or expiratory wheezes.
  • Classic thoracic radiographic findings in patients with feline asthma include a diffuse bronchial or bronchointerstitial pattern, hyperinflation, and/or collapse of the right middle lung lobe caused by mucus plug obstruction.3,4 (See Figure 2.) Up to 23% of asthmatic cats have normal thoracic radiographs.5
  • Eosinophilic airway inflammation is characteristic of asthma, but veterinarians should keep in mind that other disease conditions can result in similar clinical scenarios and eosinophil recruitment. All cats suspected of having feline asthma should have a heartworm antigen and antibody test and fecal evaluation for other parasitic diseases. 

Figure 2 Thoracic radiograph of a cat with asthma showing a diffuse bronchial pattern and collapse of the right middle lung lobe. Figure courtesy of Oklahoma State University Center for Veterinary Health Sciences

Management

Management of feline asthma can be separated into acute and chronic treatment strategies.

Acute

Acute management is aimed at stabilizing the patient in respiratory distress. Stabilization of the status asthmaticus patient includes minimizing stress (eg, sedation), providing supplemental oxygen, and bronchodilator therapy (eg, inhaled albuterol via metered dose inhaler, nebulization, injectable terbutaline). (See Figure 3.) Identifying an expiratory respiratory pattern can guide the veterinarian to any bronchoconstriction, resulting in early intervention with bronchodilator therapy. The author prefers injectable terbutaline for acute management because relying on appropriate delivery of an inhaled medication in a dyspneic patient can be challenging. Glucocorticoids are important in asthma management to reduce airway inflammation and can be used in an acute setting, but veterinarians should remember that the anti-inflammatory effects take 48 to 72 hours to be fully efficacious. As such, if an asthma diagnosis is highly suspected in a cat with acute respiratory distress, steroids should be initiated as quickly as possible.

Figure 3 Medication administration via a metered dose inhaler using a feline-specific spacer chamber (AeroKat Feline Aerosol Chamber, Trudell Medical International, Ontario, Canada; aerokat.com). Figure courtesy of Laura A. Nafe, DVM, MS, DACVIM (SAIM), and AeroKat

Chronic

Chronic management of feline asthma is aimed at reducing airway inflammation and preventing and/or reducing bronchoconstriction, if applicable.

Reducing inflammation is best achieved by minimizing exposure to aeroallergens and environmental irritants (eg, dust, aerosols) combined with an oral glucocorticoid (eg, prednisolone). Many patients can be transitioned to inhaled steroid therapy (eg, fluticasone) to minimize systemic side effects long-term.6

Bronchodilator therapy is not recommended unless bronchoconstriction is a component of the clinical scenario, manifested as respiratory distress. Some feline asthma patients exhibit only signs of cough and have no respiratory distress, and bronchodilator therapy is neither needed nor recommended in these cases. Though bronchodilator therapy is fairly safe, it is another oral medication for clients to administer daily that can adversely affect the cardiovascular system in at-risk patients. 

Out of concern for the S-enantiomer’s proinflammatory effects, racemic albuterol should be avoided in patients requiring chronic management of bronchoconstriction.7 Oral terbutaline or theophylline are preferred for chronic bronchodilatory therapy. Novel therapeutics used as monotherapy for management of experimental asthma management (eg, cyproheptadine, cetirizine, nebulized lidocaine, maropitant) are ineffective.8-10 Immunotherapy and mesenchymal stem cell therapy have shown promise as future novel therapeutics.11,12

Conclusion

Feline asthma is a common cause of cough and intermittent respiratory distress in cats that can be challenging to diagnose and treat. However, prognosis is generally good with the appropriate treatment. Veterinarians should suspect feline asthma in young to middle-aged cats presenting for cough and/or respiratory distress and understand that not all asthmatic cats have both cough and dyspnea. Important differential diagnoses that can be challenging to differentiate clinically and radiographically include chronic bronchitis, heartworm-associated respiratory disease, and pulmonary parasites; this emphasizes the importance of pursuing additional diagnostics (eg, heartworm testing, airway wash) when possible. Treatment is aimed at reducing aeroallergen exposure, reducing airway inflammation, and managing bronchoconstriction in cases that have concurrent expiratory respiratory distress.

1Identify an expiratory respiratory pattern early in dyspneic cats to confirm the presence of bronchoconstriction and to guide treatment with bronchodilators as quickly as possible.

2Be familiar with the novel therapeutics that have been investigated in experimental models of feline asthma and have been shown to be ineffective, as they should not be recommended as monotherapy.

References and author information Show
References
  1. Reinero CR. Advances in the understanding of pathogenesis, and diagnostics and therapeutics for feline allergic asthma. Vet J. 2011;190(1):28-33.
  2. Trzil JE, Reinero CR. Update on feline asthma. Vet Clin North Am Small Anim Pract. 2014;44(1):91-105.
  3. Corcoran BM, Foster DJ, Fuentes VL. Feline asthma syndrome: a retrospective study of the clinical presentation in 29 cats. J Small Anim Pract. 1995;36(11):481-488.
  4. Foster SF, Allan GS, Martin P, Robertson ID, Malik R. Twenty-five cases of feline bronchial disease (1995-2000). J Feline Med Surg. 2004;6(3):181-188.
  5. Adamama-Moraitou KK, Patsikas MN, Koutinas AF. Feline lower airway disease: a retrospective study of 22 naturally occurring cases from Greece. J Feline Med Surg. 2004;6(4):227-233.
  6. Cohn LA, DeClue AE, Cohen RL, Reinero CR. Effects of fluticasone propionate dosage in an experimental model of feline asthma [published online July 31, 2009]. J Feline Med Surg. 2010;12(2):91-96.
  7. Reinero CR, Delgado C, Spinka C, DeClue AE, Dhand R. Enantiomer-specific effects of albuterol on airway inflammation in healthy and asthmatic cats [published online April 2, 2009]. Int Arch Allergy Immunol. 2009;150(1):43-50. doi:10.1159/000210379
  8. Grobman M, Graham A, Outi H, Dodam JR, Reinero CR. Chronic neurokinin-1 receptor antagonism fails to ameliorate clinical signs, airway hyper-responsiveness or airway eosinophilia in an experimental model of feline asthma. J Feline Med Surg. 2016;18(4):273-279.
  9. Nafe LA, Guntur VP, Dodam JR, Lee-Fowler TM, Cohn LA, Reinero CR. Nebulized lidocaine blunts airway hyper-responsiveness in experimental feline asthma [published online February 7, 2013]. J Feline Med Surg. 2013;15(8):712-716. doi:10.1177/1098612X13476705
  10. Schooley EK, McGee Turner JB, Jiji RD, Spinka CM, Reinero CR. Effects of cyproheptadine and cetirizine on eosinophilic airway inflammation in cats with experimentally induced asthma. Am J Vet Res. 2007;68(11):1265-1271.
  11. Reinero CR, Byerly JR, Berghaus RD, et al. Rush immunotherapy in an experimental model of feline allergic asthma [published online December 2, 2005]. Vet Immunol Immunopathol. 2006;110(1-2):141-153. 
  12. Trzil JE, Masseau I, Webb TL, et al. Long-term evaluation of mesenchymal stem cell therapy in a feline model of chronic allergic asthma. Clin Exp Allergy. 2014;44(12):1546-1557.
Author

Laura A. Nafe

DVM, MS, DACVIM (SAIM) Oklahoma State University Center for Veterinary Health Sciences

Laura A. Nafe, DVM, MS, DACVIM (SAIM), is an assistant professor of small animal internal medicine at Oklahoma State University. She earned her DVM from University of Missouri in 2009, followed by completing a rotating internship in small animal medicine and surgery at North Carolina State University and a residency in small animal internal medicine at University of Missouri in 2013. Her clinical and research interests include respiratory, vector-borne, and immune-mediated diseases.

FUN FACT: Laura enjoys wakeboarding, fly fishing, watching and playing sports—she played basketball in college—and spending time with family and friends. She lived in New Zealand for 4 months.

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