Veterinary Respiratory Diseases Quiz

Lower Respiratory Disease 1 & 2

• Presentation covers lower respiratory disease in dogs and cats
• Lecturer is Amber Harris, DVM, DACVIM(SAIM), Assistant Professor, LAMS 5333
• Date of presentation is January 22, 2025

Outline

• Brief introduction to coughing (respiratory view)
• Cough triggers
• Cough characteristics
• Diagnostic tests (overview)
• Common causes of lower respiratory disease in dogs and cats
• Infectious causes
• Viral
• Bacterial
• Fungal
• Inflammatory causes
• Feline asthma
• Canine chronic bronchitis
• Eosinophilic bronchopneumopathy

Coughing

• A brief overview of coughing within a respiratory context

Triggers

• Owner smoking
• Perfume/cologne
• Air fresheners
• Household cleaners
• Dusty cat litter
• House construction
• Stress/exercise
• Cervical pressure
• Pollution
• Mold, pollen, etc.
• Environmental exposure
• Boarded/groomed/daycare/dog park
• Travel history
• Sick housemates
• Indoor/outdoor status (cats)
• Heartworm prevention
• "Fluffy eats other dogs' poop."
• Filaroides, Eucoleus???
• "Rocco travels to Tucson with us every winter."
• Coccidiomycosis???
• "Mittens loves to bring us dead birds."
• Aleurostrongylus???

Non-productive Cough

• Usually loud, harsh, dry, +/- paroxysmal
• May be described as a "goose-honk"
• Often paroxysmal ("coughing fits")
• Often inducible by cervical palpation
• Commonly associated with upper airway disease, tracheal or bronchial collapse, or infectious tracheobronchitis (kennel cough)

Productive Cough

• Expectoration of sputum
• Fluid/mucus/debris from lower airways
• Commonly associated with lower airway or parenchymal diseases (e.g., pneumonia) or inflammatory conditions (e.g., bronchitis/asthma) or edema
• Typically softer in volume ("huff")
• Less likely to be paroxysmal
• May be difficult to appreciate due to sputum swallowing
• Owner may perceive it as vomiting, while terminal retches are not usually considered productive

"Huffing" Cough

• A description of a specific type of cough sound

Coughing in Cats

• Less common than in dogs
• Most common cause, if present, is lower airway disease (asthma)
• Tracheal disease is less common, while pleural space disease is rare
• Owners often mistake the cough for a sneeze

Diagnostics Overview

• Common "first-tier" tests:
• Complete Blood Count (CBC)
• Thoracic radiographs (+/- cervical)
• Fecal exam (including float, sedimentation, Baermann tests)
• Heartworm testing
• Cytology
• Fine needle aspirate (FNA)
• Skin lesions/masses, lymph nodes
• Nasal discharge

2nd & 3rd Tier Testing

• Chemistry panel
• Urinalysis
• Fungal antigen titers
• Infectious testing (e.g., Respiratory PCR, titers)
• Cardiac testing (e.g., electrocardiogram, NT-pro-BNP)
• Advanced imaging (e.g., fluoroscopy, ultrasound, CT)
• Bronchoscopy
• Respiratory sampling
  • Airway (TTW, ETW, BAL)
  • Parenchyma (lung aspirate)

Transtracheal/Endotracheal Wash

• Diffuse disease (e.g., bronchitis, asthma)
• Theory involves pushing sterile fluid into the airway and aspirating out bronchial fluid
• Patient must be awake or sedated lightly
• Sterile saline used
• Saline aspirated; animal must cough
• A direct method if disease affects the entire airway and in the case where the animal needs to be restrained
• Different from Bronchoalveolar lavage (BAL)

Bronchoalveolar Lavage (BAL)

• Localized or diffuse disease
• Sampling for deeper lung regions
• Sterile intubation and anesthesia are required
• Catheter insertion into lower airway
• Standard method involves bronchoscopy guidance
• Blind method omits bronchoscopy
• Smaller aliquot volume is required
• May require coupage

Wash Fluid Diagnostics

• Cytology (cellular infiltrate?, bacteria, fungi)
• Infectious testing (bacterial cultures, aerobic and anaerobic, Respiratory PCR (mycoplasma), Mycoplasma, +/- full panel)
• Reference ranges provided for neutrophils, eosinophils, monocytes, macrophages, and lymphocytes

Respiratory PCR

• Oropharyngeal/nasal/conjunctival swab collection
• Influenza- deep nasal examination
• Distemper- conjunctival examination
• Airway wash
• Immunofluorescent assays (IFA) for organism identification
• Panels by IDEXX, Antech, Athens lab (comprehensive assays)

Fungal Specific Diagnostics

• Cytology and histology (visualizing and classifying fungi)
• Blastomyces dermatitidis (large, broad-based budding yeast)
• Histoplasma capsulatum (small, narrow-based budding yeast with halo)
• Coccidioides immitis/posadasii (double-walled structure)
• May be difficult/costly to perform
• Mira Vista urine antigen EIA (detects galactomannan antigen in urine)
• Used to monitor response to treatment or relapse
• Coccidioides monitoring via MiraVista canine IgG antibody EIA

Disease Processes (Infectious)

• Canine infectious respiratory disease complex (CIRDC) (often referred to as "kennel cough")
• Pneumonia (bacterial, community-acquired, pulmonary mycoses)

CIRDC Pathogens

• Most commonly viral origin
• Parainfluenza, Adenovirus type-2, Herpesvirus-1, Distemper, Respiratory corona virus, and Pneumovirus
• Influenza virus
• "Kennel Cough" is not synonymous with Bordetella infection

CIRDC Co-infections

• Multiple viruses, virus + bacteria
• Common bacteria:
  • Bordetella bronchiseptica, Mycoplasma spp., Streptococcus equi ss. zooepidemicus
• Co-infections increase disease severity
• Virus (X) impairs cilia
• Bacteria (Y) colonizes & overgrows

Viruses

• Enveloped, ssRNA virus (e.g., Parainfluenza)
• Non-enveloped, dsDNA virus (e.g., Adenovirus type-2)
• Replicate in upper and lower airways

Bordetella bronchiseptica

• Aerobic, Gram-cocccobacillus
• Highly contagious (Dogs <-> cats; dogs → people)
• Replicates on ciliated epithelium
• Virulence factors/toxins: paralyzes cilia, impairs phagocytosis. Invades intracellularly to avoid detection

Mycoplasma spp.

• Fastidious bacteria, lacks cell wall
• Very difficult to culture/isolate
• Colonizes ciliated and non-ciliated epithelium
• Lower respiratory tract involvement
• Purulent bronchitis

Canine Influenza Virus

• H3N8, circulated in the Northeast US
• H3N2, reportable in some areas
• Mimics kennel cough, often causes mild illness
• Signs: non-productive/productive cough, nasal/ocular discharge, serous/mucopurulent, fever, lethargy, anorexia

CIRDC Pathogenesis

• Source of infection: respiratory secretions & environmental contamination
• Transmission: close/direct contact, aerosolization, +/- fomites
• Highly contagious
• High morbidity, low mortality
• Incubation period
  • ~7 days post-infection
• Pathogen shedding
  • Most < 2 weeks
  • Exceptions: weeks to months (Bordetella, Mycoplasma, Distemper, Herpes)
  • Starts as early as 24 hours before clinical signs
  • Can continue after recovery
• Graphical representations of pathogen shedding and clinical illness timeline

CIRDC Diagnosis

• Signalment & history (age, immunocompromised, exposure, vaccination)
• Clinical signs (Harsh, dry, often non-productive cough; typically inducible, Paroxysmal, usually otherwise healthy)
• Canine respiratory PCR

CIRDC Management

• Most cases are mild, uncomplicated, and self-limiting
• Resolve within 7 days
• Manage as outpatient if possible
• Isolation and supportive care (K-9 influenza)

Think Before Antibiotics

• 2019 CIRDC surveillance program (1602 sick dogs)
• Antibiotic use increased by 25% over 5 years
• No increase in infection rate or poorer outcomes with antibiotic use
• Asymptomatic dogs arriving at US shelter (503 dogs)
• 30% Mycoplasma, 19.5% Bordetella

Treatment Considerations & Indications

• Persistent cough (> 7 days)
• Complicated/progressive disease
• Juveniles (< 6-8 weeks old)
• Quality of life negatively impacted by continuous cough

What to Treat With

• Persistent cough (> 7 days):
  • Step 1: Anti-inflammatory +/- antitussive
  • Step 2: Doxycycline (5 mg/kg PO q12h for 7-14 days) or Minocycline (5-10 mg/kg q12h)
• Severe/complicated/progressive: Doxycycline, Minocycline
• Pneumonia (additional options, including appropriate antibiotic)
• Juveniles (< 6-8 weeks): Clavamox (15-20 mg/kg PO q12h for 7 d), Doxycycline (caution with pregnant/nursing bitches)

Prevention

• DHPP vaccination (Distemper, infectious hepatitis, adenovirus type-1, parainfluenza)
• +/- influenza vaccination (at-risk individuals)
• Reduce disease (incidence, severity, shedding)
• Accidental injection of Bordetella bronchiseptica vaccine
• Can cause serious, severe injection site reaction
• Septic hepatitis
• Death

Cough Suppresion Points

• What are you treating? (e.g., collapsing trachea vs pneumonia?)
• Who are you treating? (patient vs client)
• Cough is protective mechanism!
• Contraindicated if productive cough or infectious disease

Infectious Pneumonias

• What impaired host defenses? (Congenital defect? Ciliary dyskinesia? Immune compromise: latrogenic, comorbidity? Prolonged recumbency? Sedation/anesthesia? Critical illness? Disease-induced: Bronchitis/asthma, Viral infection, Laryngeal paralysis, Regurgitation)
• Route of infection (Aspiration? Community acquired? Hematogenous? Cat > Dog? Traumatic/penetrating injury/open wound)
• Organisms isolated in bacterial pneumonia can include E. coli, Klebsiella, Streptococcus, and Staphylococcus

Community Acquired Pneumonia

• Bordetella bronchiseptica (most common CAP in dogs)
• Important in dogs < 1 year (pups&adults)
• Age of CAP ~5 months

Aspiration Pneumonia

• Most common pneumonia cause in adult dogs
• Healthy stomach/upper GI poorly colonized by bacteria
• Initial problem: airway irritation & caustic injury ("pneumonitis")
• Factors increasing gastric bacteria: antacid use, oral disease, intestinal ileus, enteral feeding
• History of vomiting/recent anesthesia/common co-morbidities (regurgitation, megaesophagus, laryngeal paralysis, myasthenia gravis).
• Common isolated organisms (E. coli, Enterococcus, Mycoplasma, Pasteurella, Pseudomonas, and Proteus)
• Aerobes >> Anaerobes
• Clinical findings (lethargy, reduced appetite, exercise intolerance, tachypnea/dyspnea, fever, cough, productive/huffing, +/- nasal discharge, +/- crackles)

Diagnosis of Pneumonia

• CBC
• Inflammatory leukogram
• Thoracic radiographs (3-views)
• Pulse oximetry/blood gas analysis
• Airway wash
• Culture & sensitivity (identifying causative agents for specific treatment)

Aspiration Pneumonia Location

• Right middle lung lobe is frequently involved
• Right cranial lobe/caudal subsegment of left cranial lobe
• X-ray examples for identifying affected regions.

Empirical Treatment of Bacterial Pneumonia

• Uncomplicated (mild) disease
• Narrow spectrum, single therapy (e.g., Amoxicillin/Amoxicillin clavulanate, Cephalexin, Trimethoprim sulfamethoxazole [TMS], Doxycycline [Bordetella, Mycoplasma], Azithromycin [cats] for ~7-14 days)
• Complicated/severe disease
  • Broad-spectrum, combination therapy (e.g., Amoxicillin/Clavulanate/Ampicillin Sulbactam, Clindamycin, plus [2nd/3rd gen cephalosporin, Fluoroquinolone, Metronidazole, Amikacin for potentially severe/drug-resistant cases) for ~2-4 weeks
• Empiric antibiotic selection & Multi-drug resistance (resistance to 3 or more drug classes in ~25% of cases; risk increases with recent antibiotic use)
• Culture & sensitivity is important
• Overall survival rate for pneumonia ~85% (Community acquired pneumonia = 96%, Aspiration pneumonia = 83%)
• Radiographic location correlation with prognosis (more lobes involved = poorer prognosis)

Fungal Pneumonias

• Blastomyces dermatitidis
• Histoplasma capsulatum
• Coccidioides immitis (Southwest US, esp. Arizona)
• Cryptococcus neoformans
• Feline nasal granuloma
• Clinical findings: not always respiratory-related (typical signs include fever, lethargy, anorexia, weight loss) – Chorioretinitis, uveitis, lameness, bone pain, lymphadenopathy, cutaneous or dermal lesions/nodules are alternative possible findings
• Work-up includes CBC, chemistry, thoracic radiographs (miliary or nodular pattern, solitary mass/granuloma), urine antigen testing, cytology (airway wash, fine needle aspirate, lymph node, skin lesions/nodules, lung),

Pulmonary Mycoses treatment

• Itraconazole (5 - 10 mg/kg q24h PO)
• Fluconazole (5 - 10 mg/kg q12h PO)
• Amphotericin B (liposomal)
• Minimum 3-6 months
• Potential for worsening prior to improvement
• Potential need for intensive supportive care, oxygen

Inflammatory Airway Disease

• Feline asthma & bronchitis
  • Prevalence ~1 - 5%
  • Siamese cats over-represented
  • Eosinophilic inflammation
• Canine chronic bronchitis
  • Exact prevalence unknown
  • Considered "moderately common"
  • Co-morbid diseases often present
  • Neutrophilic inflammation
• Often diagnosed in middle age (median age ~4-8 y)

Pathophysiology

• Likely multi-factorial.
• Prior single respiratory insult, or repeated injury?
• Chronic irritant exposure?
• Culmination of multiple minor insults over time?

Clinical signs of inflammatory airway disease

• Chronic cough (starts as non-productive)
• Tachypnea at rest
• Expiratory dyspnea (prolonged expiration/expiratory push)
• Exercise intolerance
• Problem with cats: Signs may only be intermittent and not seem severe, including acute respiratory distress. (Emergent presentation Cats >> Dogs)
• Airflow limitation, positive intra-thoracic pressure on expiration, and air trapping are implicated in wheezing

Bronchiolar Disease

• Characterized by airway narrowing.
• Possible structural changes (eg. thickened walls) affecting gas exchange
• Classic findings in radiographs include “donuts” and “tram lines”.

Airway Reactivity

• Chronic bronchitis: little to no spontaneous bronchoconstriction (static narrowing)
• Feline asthma: reversible spontaneous bronchoconstriction (dynamic narrowing)

Work-Up for Inflammatory Airway Diseases

• Physical exam, including listening for/presence of wheezes
• CBC
• Evidence of inflammation (eosinophilia?)
• Thoracic radiographs
• Infectious screening (e.g., heartworm, fecal float/sedimentation, fecal Baermann, respiratory PCR)
• Airway wash and cytology

"Classic" Asthma Radiographs

• Broncho-interstitial pattern
• Pulmonary hyperinflation
• Right middle lobe atelectasis ("flattened/caudadly displaced diaphragm")
• Rib fractures?

End-Stage Airway Disease

• Common conditions: Pulmonary fibrosis, Airway remodeling (Bronchomalacia/Bronchiectasis); Pulmonary hypertension, and Cor pulmonale

Treatment Goals

• Resolve clinical signs (resolved cough/resolved inflammation)
• Prevent remodeling (Bronchiectasis, Pulmonary Fibrosis, Pulmonary Hypertension, Cor pulmonale)
• Decisions based on repeated airway washes and cytology

Eosinophilic Bronchopneumopathy

• Typically idiopathic
• Eosinophilic infiltration of pulmonary interstitium and on airway washes
• Over-representative breeds: Rottweiler, Husky, Malamutes.
• Varied radiographic findings (localized... diffuse... multi-focal; Interstitial... alveolar... nodular... mass-like)
• Oral steroids (1.0-2.0 mg/kg/d) are a treatment option
• Often responsive to inhaled therapy if initially unresponsive.

Case Study (5y FS Chow mix)

• Chief complaint: chronic cough
• 4 weeks post-prednisolone treatment
• Bronchial lavage (cytology/cellular differential)
  • Mixed (predominantly eosinophilic, mildly suppurative) inflammation.

Questions to [email protected]

• Specific questions regarding case study.