Subclinical airway inflammation despite high-dose oral corticosteroid therapy in cats with lower airway disease

Reactions to environmental allergens in cats with feline lower airway disease

Objectives

Aeroallergens have been discussed as potential triggers for feline asthma (FA), which can be induced experimentally by allergen sensitization. To date, only few studies have investigated reactions to environmental allergens in cats with naturally occurring feline lower airway disease (FLAD). The aim of the study was to compare results of intradermal testing (IDT) and serum allergen-specific immunoglobulin E-(IgE) testing (SAT) in cats with FLAD, and to investigate possible associations with allergen exposure.

Material and methods

Eight cats with eosinophilic airway inflammation (EI), ten cats with mixed inflammation (MI), six with neutrophilic inflammation (NI), and 24 healthy cats (HC) were included. Cats diagnosed with FLAD were assigned to the different inflammatory groups based on bronchoalveolar lavage fluid (BLAF) cytology. SAT was performed in all cats; IDT was only carried out in cats with FLAD. Information about the cats' environment and potential allergen exposure was obtained using an owner questionnaire.

Results

In comparison to 83% of HC with positive reactions on SAT only 52% of cats with FLAD had positive responses (p = 0.051). Significantly more positive reactions per cat were detected on IDT than on SAT (p = 0.001). No significant difference was found for positive reactions per cat on SAT when compared between HC, NI, EI, and MI (p = 0.377). Only "slight" agreement was found for most allergens when reactions obtained in both tests in cats with FLAD were compared, except for "moderate" agreement for English plantain (k = 0.504) and Alternaria alternata (k = 0.488). Overall, no clear association between the cats' environment and allergen reactions were detected.

Conclusions and clinical importance

Interpretation of allergy test results in cats with FLAD should be done in the context of clinical signs and individual factors.

Correlation of clinical and radiographic variables in cats with lower airway disease

BACKGROUND

Feline lower airway disease (FLAD) is frequently associated with radiographic abnormalities.

OBJECTIVES

To evaluate whether radiographic changes in cats with naturally occurring FLAD improve with treatment and if radiographic changes correlate with clinical signs.

ANIMALS

Twenty-four client-owned cats newly diagnosed with FLAD, based on medical history, typical clinical signs, radiographic findings, and examination of bronchoalveolar lavage fluid, were included in the prospective study.

METHODS

At 2 examination time points (days 0 and 60), an owner questionnaire, clinical examination, and thoracic radiography were carried out. Information from the questionnaire and clinical examination were evaluated on the basis of a 12-point clinical score. Radiographs were assessed using a 10-point radiographic score. Individual treatment was given to all cats over the study period, based on severity of the disease and compliance of the cat. Clinical and radiographic scores were compared statistically for both examination time points and evaluated for correlation.

RESULTS

All cats showed radiographic abnormalities at initial presentation. In addition to significant improvement in clinical variables, the total radiographic score improved significantly (P = .01) during the study period, with significant improvement in the severity of bronchial (P = .01) and interstitial lung pattern (P = .04). Improvement of the clinical and radiographic score was not correlated.

CONCLUSION AND CLINICAL IMPORTANCE

In addition to clinical signs, repeated radiographic examination can be used as a diagnostic tool to evaluate treatment response in cats with FLAD.

Breathe easy: inhalational therapy for feline inflammatory airway disease

PRACTICAL RELEVANCE

Feline inflammatory airway diseases, including (but not limited to) asthma, chronic bronchitis and bronchiectasis, are common and incurable disorders. These diseases require lifelong therapy and may result in substantial morbidity and, in some cases, mortality. Goals of therapy include reduction or resolution of clinical signs and the underlying pathologic processes driving those clinical signs. Inhalational therapy has the advantage of topical delivery of drugs to target tissues at higher doses with fewer systemic effects than oral medications. There are multiple options for delivery devices, and proper selection and training on the use of these devices - including acclimation of the cat to the device - can maximize therapeutic efficacy.

AIM

As inhalational therapy is uncommonly used by many veterinarians and owners, this review article provides a foundation on the selection and use of devices and inhalant medications for specific feline inflammatory airway diseases. Cats present a unique challenge with respect to the use of inhalers, and easy-to-follow steps on acclimating them to the devices are provided. The review also discusses the mechanics of inhalational therapy and helps clarify why certain medications, such as albuterol (salbutamol), fluticasone or budesonide, are chosen for certain diseases. The ultimate aim is that the practitioner should feel more comfortable managing common airway diseases in cats.

EVIDENCE BASE

In compiling their review, the authors searched the veterinary literature for articles in English that discuss inhalational therapy in cats, and which focus primarily on inhaled glucocorticoids and bronchodilators. While most literature on inhalational therapy in cats is based on experimental feline asthma models, there are some studies demonstrating successful treatment in cats with naturally occurring inflammatory airway disease.

[Evaluierung der Langzeittherapie bei Katzen mit felinem Asthma und chronischer Bronchitis]

GEGENSTAND UND ZIEL

Felines Asthma (FA) und chronische Bronchitis (CB) sind häufige entzündliche Erkrankungen der Atemwege der Katze. Obwohl beide Krankheitsbilder durch eine Infiltration mit unterschiedlichen Entzündungszelltypen gekennzeichnet sind, sind die therapeutischen Maßnahmen oft ähnlich. Über mögliche Unterschiede im therapeutischen Management dieser beiden Atemwegserkrankungen ist wenig bekannt. Ziel der Studie war es daher, bei Katzen mit FA und CB die Erst- und Langzeitbehandlung, Therapieerfolg, Nebenwirkungen und Besitzerzufriedenheit zu vergleichen.

MATERIAL UND METHODEN

35 Katzen mit FA und 11 Katzen mit CB wurden in die retrospektive Querschnittstudie eingeschlossen. Einschlusskriterien waren kompatible klinische und radiologische Befunde sowie der zytologische Nachweis einer eosinophilen Entzündung (FA) oder einer sterilen neutrophilen Entzündung (CB) in der bronchoalveolären Lavage-Flüssigkeit (BALF). Katzen mit CB wurden ausgeschlossen, wenn Hinweise auf pathologische Bakterien vorlagen. Besitzer wurden gebeten einen standardisierten Fragebogen zum therapeutischen Management und Ansprechen auf die Behandlung auszufüllen.

ERGEBNISSE

Im Gruppenvergleich wurden keine statistisch signifikanten Unterschiede der Therapie festgestellt. Die meisten Katzen wurden anfänglich mit Kortikosteroiden mittels einer oralen (FA 63%/CB 64%, p=1), inhalativen (FA 34%/CB 55%, p=0,296) oder injizierbaren Applikationsform (FA 20%/CB 0%, p=0,171) behandelt. Zusätzlich wurden in einigen Fällen orale Bronchodilatatoren (FA 43%/CB 45%, p=1) und Antibiotika (FA 20%/CB 27%, p=0,682) verabreicht. In der Langzeittherapie erhielten 43% der Katzen mit FA und 36% der Katzen mit CB inhalative Kortikosteroide (p=1), orale Kortikosteroide (FA 17%/CB 36%, p=0,220) und orale Bronchodilatatoren (FA 6%/CB 27%, p=0,084) sowie phasenweise Antibiotika (FA 6%/CB 18%, p=0,238). Behandlungsbedingte Nebenwirkungen (Polyurie/Polydipsie, Pilzinfektion im Gesicht und Diabetes mellitus) wurden bei 4 Katzen mit FA und 2 Katzen mit CB registriert. Die Mehrheit der Besitzer gab an, mit dem Ansprechen auf die Behandlung äußerst oder sehr zufrieden zu sein (FA 57%/CB 64%, p=1).

SCHLUSSFOLGERUNG

Signifikante Unterschiede hinsichtlich des Managements und des Therapieansprechens konnten bei beiden Erkrankungen laut Besitzerbefragung nicht festgestellt werden.

KLINISCHE RELEVANZ

Laut Besitzerumfrage können chronische Bronchialerkrankungen der Katze wie Asthma und chronische Bronchitis können mit einer ähnlichen Behandlungsstrategie erfolgreich therapiert werden.

Evaluation of barometric whole-body plethysmography for therapy monitoring in cats with feline lower airway disease

OBJECTIVES

Feline lower airway disease (FLAD) is a common respiratory condition in cats. Traditionally, response to therapy is monitored only by evaluation of clinical signs and radiographic examination of the lungs. Barometric whole-body plethysmography (BWBP) is considered a non-invasive, well-tolerated form of measuring airway reactivity in cats. The aim of the study was to assess pulmonary function testing by BWBP for non-invasive evaluation of response to therapy in cats with FLAD and to investigate whether BWBP parameters correlate with clinical severity.

MATERIAL AND METHODS

The prospective study included 25 client-owned cats, diagnosed with FLAD on the basis of their medical history, clinical signs, radiographic findings, and bronchoalveolar lavage fluid (BALF) examination. At three time points (day 0, 14, and 60), a standardised owner questionnaire, a clinical examination and BWBP measurements were carried out. Results of the questionnaire and the clinical examination were evaluated using a clinical 12-point score. Individual therapy was administered to all patients after diagnosis, based on the severity of disease and compliance of the cat.

RESULTS

The total clinical score significantly improved over the entire study period (p<0.001). Significant improvement was detected for the frequency of coughing (p = 0.009), respiratory distress (p = 0.001), lung auscultation findings (p = 0.002), and general condition and appetite (p = 0.045). The BWBP parameter Penh, an indicator of bronchoconstriction, improved significantly under initial therapy between day 0 and 14 (p = 0.009). A significant correlation between Penh and the severity of auscultation findings was seen on day 0 (r = 0.40; p = 0.013).

CONCLUSION

The study supports the role of Penh as a non-invasive parameter for monitoring initial treatment response in cats with FLAD. Further studies are needed to address whether other BWBP parameters might be suitable for non-invasive therapy monitoring of FLAD. Clinical evaluation is always essential in cats with FLAD to evaluate treatment response.

[Inhalation therapy in dogs and cats with chronic lower airway disease - a literature review]

Chronic respiratory diseases are prevalent medical conditions in dogs and cats requiring lifelong treatment. Mainstay of therapy for chronic inflammatory respiratory diseases are glucocorticoids. Concurrent treatment with bronchodilators may be necessary to control clinical signs sufficiently. Due to the successful use in people as well as subsequent reduction of adverse effects of long-term glucocorticoid therapy, inhalative therapy has become increasingly important in veterinary medicine as well. Primarily spacers or valved holding chambers, in combination with metered dose inhalers, are used in dogs and cats. The technical properties of these devices, as well as their use and maintenance will be described in the following article. Furthermore, the existing literature regarding efficacy of inhalative medications for therapy of chronic inflammatory airway diseases in dogs and cats will be summarized.

Immunopathogenesis of the feline atopic syndrome

BACKGROUND

Feline diseases of possible allergic origin with similar clinical phenotypes can have a varied underlying pathogenesis. Clinical phenotype, precise aetiology and underlying immunopathogenesis all need to be considered if advances in this neglected area of dermatology are to be made.

OBJECTIVES

To document the status of research into the immunopathogenesis of the diseases that fall within the spectrum of the feline atopic syndrome (FAS ), to summarize the conclusions, identify the limitations and recommend future research directions.

METHODS AND MATERIALS

A search of the literature was undertaken. The strengths and validity of the data and the contributions to our current understanding of the immunopathogenesis were analysed. Skin diseases of presumed allergic aetiology and asthma were assessed separately, as was the role of antibodies, cells and cytokines in each.

RESULTS

The research varied in its quality and its impact often was limited by a failure to employ strict criteria in case selection. This reflected the difficulties of skin reaction patterns associated with a number of inciting causes. Research into feline asthma was handicapped by the difficulties of investigating clinical material, and much of the useful information was derived from experimental models.

CONCLUSIONS AND CLINICAL IMPORTANCE

The evidence reviewed was supportive of a role for immunoglobulin (Ig)E in the pathogenesis of both feline atopic skin syndrome (FASS) and asthma, albeit not strongly so. The inflammation noted in both FASS and asthma is accompanied by eosinophils and lymphocytes, and these findings, together with the cytokine expression, are suggestive in some (not all) cats of T-helper type 2 immune dysregulation.

Feline Asthma: Diagnostic and Treatment Update

Asthma is an important allergic lower-airway disease in cats affecting approximately 1% to 5% of the pet cat population. New diagnostics are being developed to help better differentiate asthma from other lower-airway diseases and improve monitoring. In addition, new treatments are being developed to help in refractory cases or in those cases in which traditional therapeutics are contraindicated. This article discusses potential pitfalls in the diagnosis of asthma. In addition, current literature investigating new diagnostic tests and therapies for feline asthma is reviewed.

Feline asthma and heartworm disease: Clinical features, diagnostics and therapeutics

PRACTICAL RELEVANCE

For feline practitioners, the cat with a cough or respiratory distress and thoracic radiographs with a bronchial or bronchointerstitial pattern suggests lower airway disease. Two important differentials, allergic asthma and heartworm disease (HWD), have many overlapping clinicopathologic features, but also clear and important differences in terms of cause and disease progression, treatment and prognosis. Notably, asthma is readily treatable and HWD is preventable.

CLINICAL SIGNIFICANCE

Feline HWD comprises two clinical syndromes: the comparatively recently described heartworm-associated respiratory disease (HARD) and adult HWD. The former is much more common; very few cats with HARD develop adult HWD. In HARD, following death of immature worms, pulmonary lesions may improve over time ('self-cure'). Lesions of adult HWD also improve over time as long as reinfection does not occur; however, with death of adult heartworms, mortality is high, and the prognosis is guarded. In asthma, morbidity is relatively high, but mortality is low, with an overall good to excellent prognosis.

DISEASE RECOGNITION

Feline asthma is encountered worldwide. In the authors' impression, feline HWD is often under-recognized.

AIMS

The aim of this review is to assist clinicians in differentiating feline asthma from feline HWD; as such, the emphasis is on distinguishing clinical features, as well as on diagnostics, therapy and prognosis. In differentiating these conditions, clinicians can attempt the goal of properly managing these diseases and can best educate owners on prognosis.

EVIDENCE BASE

For both feline asthma and feline HWD, the authors have drawn on the available peer-reviewed literature studies involving experimental models as well as spontaneous disease.

Intravenous adipose-derived mesenchymal stem cell therapy for the treatment of feline asthma: a pilot study

OBJECTIVES

The aim of this study was to evaluate the feasibility and efficacy of serially administered adipose-derived mesenchymal stem cells (MSCs) in an experimental feline asthma model.

METHODS

Allergic asthma was acutely induced with Bermuda grass allergen in six purpose-bred cats. Five intravenous infusions of allogeneic MSCs (n = 4; MSC-treated) or saline (n = 2; placebo-treated) were administered over the first 130 days after asthma induction. Infusions contained 2 × 106, 4 × 106, 4.7 × 106, 1 × 107 and 1 × 107 cryopreserved MSCs/cat. For thoracic imaging additional cats were enrolled as control groups: four untreated, experimentally asthmatic cats (combined with placebo-treated cats), and six healthy, non-asthmatic cats. Outcome measures included airway eosinophilia, pulmonary mechanics, thoracic computed tomography and several immunologic assays.

RESULTS

Cats were assessed for 9 months after treatment. At early points, airway eosinophil percentage was not affected by MSC administration (post-treatment average of days 12, 26, 47, 108 and 133 in MSC-treated cats was 41 ± 15% and in placebo-treated cats it was 34 ± 16%). By month 9, eosinophil percentages in all MSC-treated cats decreased to normal reference intervals (MSC-treated 6%; placebo-treated 20%; normal <17%). Diminished airway hyper-responsiveness was noted in all MSC-treated compared with placebo-treated cats at day 133 (dose of methacholine to double baseline airway resistance: MSC-treated median 22.9 mg/ml [range 6.4-64.0]; individual placebo-treated cats 1.1 and 5.0 mg/ml). Lung attenuation (mean ± SEM MSC-treated -865 ± 12 Hounsfield units [HU]; untreated asthmatics -820 ± 11 HU; P = 0.004) and bronchial wall thickening scores (median [interquartile range] MSC-treated 0 [0-1.5]; untreated asthmatic 11.6 [7.3-27.3]; P = 0.010) were significantly reduced in MSC-treated vs untreated asthmatic cats, consistent with decreased airway remodeling at month 9. No clear immunologic mechanisms by which MSCs act were determined.

CONCLUSIONS AND RELEVANCE

MSCs may have a delayed effect in reducing airway inflammation, airway hyper-responsiveness and remodeling in experimentally induced asthmatic cats. Results warrant additional investigation of MSC therapy for asthma in cats.

Treatment of feline asthma with ciclosporin in a cat with diabetes mellitus and congestive heart failure

A 5-year-old domestic shorthair cat that had been previously diagnosed with diabetes mellitus was presented for episodes of coughing and respiratory distress. Diagnostic testing revealed congestive heart failure secondary to hypertrophic cardiomyopathy and concurrent asthma. All clinical signs and eosinophilic airway inflammation resolved with oral ciclosporin while the cat was concurrently receiving medications for treatment of heart failure (furosemide and enalapril). Ciclosporin should be considered for treatment of feline asthma in patients with concurrent diseases (eg, diabetes mellitus, severe heart disease) that may contraindicate use of oral glucocorticoid therapy.

Functional phenotype and its correlation with therapeutic response and inflammatory type of bronchoalveolar lavage fluid in feline lower airway disease

Background

Currently, functional assessment to monitor therapeutic response in feline lower airway disease (FLAD) has limited application.

Objectives

To evaluate if expiratory indices derived from pseudo‐tidal breathing flow‐volume loop (pTBFVL) representing lower airway obstruction would decrease after clinical improvement and to investigate the correlation between functional phenotype and inflammatory cell type in bronchoalveolar lavage (BAL) fluid.

Animals

Nineteen client‐owned cats with FLAD.

Methods

Prospective observational study. Functional assessment with pTBFVL indices (eg, peak to mid‐expiratory flow; PEF/EF50) and conventional barometric whole body plethysmography (BWBP) parameters (eg, enhanced pause) was carried out before receiving treatment. BAL was performed to analyze inflammatory cell types. Signs were assessed by scoring. The cats were treated with glucocorticoids daily and functional testing was repeated.

Results

Loop indices PEF/EF50 and PEF/EF25 were significantly decreased after treatment (P < .001). Conventional BWBP parameters were not significantly different before and after treatment. Cats with PEF/EF50 > 1.51 before treatment had a significantly higher granulocyte (eosinophil plus neutrophil) percentage in BAL fluid (P = .014). Granulocyte percentage in BAL fluid was strongly correlated with PEF/EF25 (P = .001, r_s = 0.74) and moderately correlated with PEF/EF50 (P = .022, r_s = 0.57), whereas eosinophil or neutrophil percentage alone had no significant correlation with functional parameters.

Conclusions and Clinical Importance

Functional parameters including PEF/EF50 and PEF/EF25 can be used for monitoring therapeutic response. The presence of airflow limitation during mid‐ to late expiration is affected by the overall extent of granulocyte infiltration.

Functional assessment of expiratory flow pattern in feline lower airway disease

Feline lower airway disease (FLAD) is a chronic respiratory disease of which there is a lack of information on functional assessment in current veterinary medicine. The purposes of this study were to investigate expiratory pattern and evaluate the diagnostic utility of functional parameters in cats with FLAD. Thirty-three client-owned cats (23 FLAD cats and 10 control cats) were studied. Under quiet tidal breathing, pseudo-tidal breathing flow-volume loop (pTBFVL) was obtained from a barometric whole body plethysmography (BWBP) device. There were significant differences in the shapes of expiratory, but not inspiratory, curves between FLAD and control cats. The incidence of the presence of concave expiratory curve indicating lower airway obstruction was 74% in FLAD cats. To assess the diagnostic utility of pTBFVL indices in cats with FLAD, area under the receiver-operator curve was 0.86 for PEF/EF50 (peak expiratory flow divided by expiratory flow at end expiratory volume plus 50% tidal volume); a cuff-off value of PEF/EF50 >1.51 distinguished normal from FLAD (73.9% sensitivity, 100% specificity). There were no significant differences in traditionally measured BWBP parameters (ie, enhanced pause) between cats with and without FLAD in the present study. In conclusion, underlying change on expiratory flow pattern during natural tidal breathing existed in FLAD cats, and selected pTBFVL indices were useful in discriminating FLAD from normal cats. Tidal breathing pattern depicted by pseudoflow-pseudovolume loops from a BWBP system could be a non-invasive tool for functional assessment in client-owned cats.

Update on feline asthma

This article provides an overview of recent advances in the diagnosis and treatment of feline asthma. The authors discuss the potential pitfalls in the diagnosis of feline asthma. In addition, current literature investigating new therapies for the treatment of feline asthma is reviewed.

Inhaled budesonide therapy in cats with naturally occurring chronic bronchial disease (feline asthma and chronic bronchitis)

OBJECTIVES

To describe the long term use of inhaled budesonide in cats with naturally occurring asthma and chronic bronchitis and to measure its effects.

METHODS

Owners of 43 cats diagnosed with asthma or chronic bronchitis, which had been prescribed 400 µg of inhaled budesonide twice daily, were contacted and information was retrieved by a questionnaire. Nineteen cats still receiving inhaled budesonide after more than 2 months were re-evaluated clinically and underwent barometric whole body plethysmography and adrenocorticotropic hormone-stimulation testing.

RESULTS

In 20 of the cats, therapy had been withdrawn by the owners. Cats (n=23) still receiving inhaled budesonide improved clinically and 19 cats that were reevaluated had significantly lower basal PENH (P=0·048) and higher PCPenh300 (P=0·049) values than before treatment. Corticosteroid-induced side effects were not observed in any cats but hypothalamic-pituitary-adrenal axis suppression was detected in 3 of 15 cases.

CLINICAL SIGNIFICANCE

Treatment with inhaled budesonide was well tolerated, resulting in improvement of clinical signs and barometric whole body plethysmography parameters. Although inhaled budesonide therapy was found to cause suppression of the hypothalamic-pituitary-adrenal axis in some cats, no cats showed clinical signs attributable to corticosteroid side effects.