Comprehensive Guide to Feline Asthma: Pathogenesis, Diagnosis & Therapy

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Respiratory System is divided into conducting, translational, and exchange systems. Any deviation in the functioning leads to respiratory system disorders, which then become the cause of morbidity and mortality in animals across species. Asthma is one such pathology of the respiratory system occurring in felines.

What is Asthma?

Asthma is a chronic respiratory disease that affects the airways in the lungs, causing breathing difficulty by narrowing the tubular structures and inflammation of the mucosal lining. It is characterized by recurrent bronchoconstriction, cough, or dyspnea (difficulty in breathing). In Felines, Asthma is also known as Feline Allergic Bronchitis.

Pathogenesis is not well-establisehd in felines, but it is belived that its triggered by aeroallergens.
Clinically the condition is associated with cough, episodic expiratory respiratory distress. But the immuno-pathonesis is something which is used to understand the asthamic reaction.

Immunopathogenesis –

When an allergen is inhaled, dendritic cells absorb it and use it to process antigens that are taken from the lumen of the airway. In mucosal inductive sites below the epithelial surface, these allergens are processed and delivered along with major histocompatibility complex class II (MHC II) to naïve Th0 (T-helper) cells. The subsequent polarization to Th2-mediated immunity in susceptible individuals with the right co-stimulatory factors causes the synthesis of cytokines that coordinate the production of immunoglobulin (Ig)E and the allergic-inflammatory response. IgE is firmly bound by basophil and mast cell high affinity receptors. Re-exposure to the allergen causes bound IgE to cross-link, which causes degranulation and intensifies the inflammatory cascade.

Look for these signs –

Cats suffering from asthma may exhibit symptoms such as difficulty breathing, wheezing, rapid breathing, coughing or hacking, open-mouthed breathing, or vomiting. These signs can vary in severity, in case of acute respiratory distress to chronic, low-grade coughing, elevated respiratory rate, or increased respiratory effort. During an asthma attack, many cats assume a characteristic hunching posture their bodies close to the ground and extending their necks forward.

Diagnosistics Tools –

• Physical and Clinical Examination – focusing mainly on the respiratory system.

• Exhaled Breath Condenstate (EBC) Analysis for identification of oxidant-anti oxidant imbalance. The result is dependent on the ratio between H₂O₂ and Eosinophil in the Bronchoalveolar Fluid (BALF). Increased Ratio is an indicative of a positive allergy in cat.
• BALF Cytology is the gold-standard for asthma in felines.
• Species-specific enzyme-linked immunosorbent assay (ELISA) which is linked with allergen-specific IgE.
• Thoracic Radiographs and Bronchoscopy
• Intra-dermal skin test

Differential Diagnosis (DDx) – is quite difficult in felines due to very similar signs especially between chronic bronchitits and asthma because both are lower respiratory tract diseases. Every disease have that differencial sign, which gives it away and in case of Asthma it is intermittent expiratory respiratory distress. Lungworm and Heart associated respiratory disease (HARD) have eosiniphilic inflammatory reaction which is similar to the asthma. Trichobezors also be considered when diagnosing feline asthma.

Treatment – Pin-pointing the exact diagnosis leads to a correct treatment plan, which ultimately causes recovery.

Glucocorticoid therapy (Prednisolone) is recommended only for cats showing clinical signs at least twice a week. Administration of Glucocoticoids by inhalation (nebulization) have great theraputic index.

Bronchodilators can be used to allevate respiratory distress and to relieve bronchospasm. LABA (long-acting beta agonists), SABA (short-acting beta agonists), Methylxanthines andanticholinergics are bronchodilators used in cats. In cats with lower airway illness, the injectable SABA terbutaline (0.01 mg/kg) caused a partial reversibility of airway blockage.

The immunomodulator feG-COOH (a salivary tripeptide involved in neuroendocrine immunology) a single dose @ 1 mg/kg was administered orally had significant reductions in airway eosinophilia.

Listen to the sounds that your feline counterpart is making carefully.

The Geek Veterinarian