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84 Asthma, Feline

Asthma, Feline Client Education
Sheet
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• Cytokines promote allergen-specific immuno-
BASIC INFORMATION
asthma.
globulin E (IgE) production, inflammatory cell ○ Absence of eosinophilia does not rule out
Definition influx (the hallmark cell is the eosinophil), Fecal analysis (Baermann test):
A syndrome triggered by allergen-specific activa- airway hyperreactivity, and lung remodeling. • Perform multiple times on different stool
tion of immune cells culminating in cough, • Airway inflammation and hyperreactivity samples because respiratory parasites are
wheeze, and/or respiratory distress, eosinophilic provoke bronchoconstriction, leading to intermittently shed.
inflammation of airways, bronchoconstriction, cough and respiratory difficulty. Remodeling • +/− Antiparasitic trial (e.g., fenbendazole
and structural pulmonary changes changes (e.g., smooth muscle hypertrophy) 50 mg/kg PO q 24h × 10-14 days) to
can further reduce luminal diameter of small empirically treat for pulmonary parasites
Synonyms airways, contributing to airflow limitation. Heartworm antibody/antigen test (p. 415):
Feline allergic asthma, feline allergic bronchitis, • Reduction in diameter of small airways • Alternative cause of cough and peripheral
feline eosinophilic bronchitis impairs expiration more than inspiration, eosinophilia
leading to the expiratory push observed
Epidemiology during physical examination and air trapping Advanced or Confirmatory Testing
SPECIES, AGE, SEX on thoracic radiographs. • Respiratory wash with cytologic analysis and
Typically young to middle-aged at onset; either culture
sex DIAGNOSIS ○ Collected by blind bronchoalveolar lavage
(BAL) through an endotracheal tube or
GENETICS, BREED PREDISPOSITION Diagnostic Overview by bronchoscopy (pp. 1073 and 1074)
Possible breed predisposition in Siamese cats Asthma is suspected in cats exhibiting cough, ○ Submit a portion of the wash sample for
wheeze, and/or respiratory distress when other culture to exclude secondary bacterial
GEOGRAPHY AND SEASONALITY causes of cardiac or respiratory disease have infection and another for Mycoplasma spp
Seasonality depends on the allergen (e.g., indoor been excluded. Airway eosinophilia in conjunc- polymerase chain reaction (PCR).
allergens, year-round; outdoor allergens may tion with a favorable response to therapy ○ Cytology demonstrates increased per-
be seasonal). supports the diagnosis. centages of eosinophils (>16%) in BAL
fluid with asthma and increased percent-
ASSOCIATED DISORDERS Differential Diagnosis ages of neutrophils (>7%) with chronic
Secondary bacterial infections of the lower Physical examination findings (cough, wheeze, bronchitis.
airways respiratory distress): ■ Reference ranges for BAL fluid cell
• Pleural effusion (any cause; e.g., chylothorax, differentials are controversial.
Clinical Presentation pyothorax, transudate associated with heart ■ Coexistence of eosinophilic and neu-
DISEASE FORMS/SUBTYPES failure) trophilic inflammation suggests chronic
• Acute, life-threatening disease (status • Cardiogenic or noncardiogenic pulmonary asthmatic bronchitis (long-standing
asthmaticus) edema asthma-associated inflammation can
• Chronic persistent signs • Pneumonia (infectious, aspiration, foreign promote concurrent chronic bronchitis
• Waxing and waning signs body) with neutrophilic inflammation) or
○ Note: airway inflammation persists in the • Neoplasia secondary bacterial infection (may also
absence of clinical signs. • Interstitial lung disease see degenerate neutrophils).
• Laryngeal disease (musical noises are loudest • Serum allergen-specific IgE testing may help
HISTORY, CHIEF COMPLAINT over the larynx; characterized by inspiratory determine which aeroallergens contribute to
Cough (which owners may interpret as unsuc- distress) clinical signs or are triggers for status asth-
cessful attempts to vomit a hairball), wheeze, Radiographic findings: maticus, potentially helping guide environ-
tachypnea, respiratory distress • Chronic bronchitis mental management.
• Lung worms • Thoracic CT may provide details of airways
PHYSICAL EXAM FINDINGS • Heartworm-associated respiratory disease and interstitium (including vasculature) that
• Cough, may be inducible with tracheal (HARD) could help differentiate asthma from parasitic
palpation • Toxocara cati larval migration disorders (e.g., HARD, Toxocara cati).
• Expiratory wheezes sometimes audible with • Pulmonary function testing with broncho-
or without a stethoscope Initial Database provocation: limited availability; mainly a
• Respiratory distress, often with a promi- Thoracic radiographs: research tool
nent expiratory component (expiratory • Bronchial or bronchointerstitial pattern • Serum vitamin D concentration may be
push) • Lung hyperinflation (air trapping) determined in refractory cases.
• Tachypnea ○ Expanded lung fields ○ Although unproven in cats, human asth-
• Paradoxic breathing (chest and abdomen ○ Increased radiolucency of lung fields matics with vitamin D deficiency respond
move in opposition) ○ Flattened diaphragm to supplementation with improved sympt-
• Increased bronchovesicular sounds ○ Increased distance between the caudal oms and quality of life.
• Physical exam may be normal between cardiac silhouette and diaphragm on the
episodes. lateral view TREATMENT
• Lung lobe collapse (usually right middle lobe)
Etiology and Pathophysiology • May be unremarkable Treatment Overview
• Sensitization to aeroallergens activates type CBC: In an acute crisis, rapid stabilization of
2 helper T cells (T H 2), leading to production • Eosinophilia: compatible with allergic or respiratory function with oxygen and broncho-
of proinflammatory cytokines. parasitic disease dilators is critical. Chronic therapy consists of

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