Canine CIRDC (Kennel Cough): NAVLE Study Guide

CIRDC comes up on the NAVLE in a few different flavors: the classic post-kennel coughing dog that needs no treatment, the pneumonia complication that does, and the CIV outbreak question that tests whether you know your H3N8 from your H3N2. The pathogen list is long, but the exam almost always anchors on Bordetella and CIV. Know those two cold and the rest falls into place.

The Pathogens: What Each One Actually Does

CIRDC is a syndrome, not a single infection. Multiple pathogens cooperate – viral agents damage the mucociliary apparatus and the epithelial barrier, then Bordetella and Mycoplasma colonize the compromised mucosa. This is why simple cases escalate to pneumonia when the dog’s immune defenses are already stretched by shelter stress, crowding, and suboptimal nutrition.

Clinical Signs: What Looks Like What

The signature of uncomplicated CIRDC is that harsh, honking, dry cough – the kind that sounds like the dog has something stuck in its throat. Tracheal palpation reproduces it. The dog is typically bright, eating normally, and afebrile. That last point is the key examiner tell: no fever, no lethargy, no anorexia. The dog looks fine, it just coughs.

When you see fever above 39.5°C, lethargy, anorexia, or a cough that transitions from dry to productive with mucopurulent discharge, that is bacterial pneumonia until proven otherwise. The physical exam finding that shifts the picture: crackles or increased bronchial sounds on auscultation, not just referred upper airway noise.

CIV vs. Classic Kennel Cough: The Distinction That Gets Tested

The NAVLE loves to put these two next to each other. The setup is almost always a group of dogs in a boarding or shelter setting with respiratory illness spreading rapidly. The question is whether you’re dealing with Bordetella or CIV.

The clinical features that push toward CIV over Bordetella: fever is more consistent and higher, pneumonia develops in 20–25% of H3N2 cases, illness lasts 2–3 weeks rather than resolving in one. The PCR respiratory panel (nasopharyngeal swab) is how you confirm it. H3N8 and H3N2 are antigenically distinct – the monovalent H3N8 vaccine does not protect against H3N2. The bivalent CIV vaccine covers both.

Diagnosis

Most uncomplicated cases are diagnosed clinically. Post-kennel exposure plus the classic cough presentation is enough to start symptomatic management. You do not need a PCR panel on every coughing dog from daycare.

When diagnostics are warranted: PCR respiratory panel from a nasopharyngeal swab for pathogen identification (outbreak investigation, severe disease, immunocompromised dog, atypical presentation). Thoracic radiographs when you suspect pneumonia – look for a cranioventral alveolar pattern, which is the classic distribution for aspiration and bacterial pneumonia in dogs. BAL with culture and sensitivity when you have radiographic pneumonia that isn’t responding to empiric therapy.

Treatment

Uncomplicated CIRDC is managed supportively: rest, isolation from other dogs, and cough suppressants if the cough is severe enough to disrupt sleep or cause distress. Butorphanol (0.05–0.1 mg/kg PO q6–8h) or hydrocodone are the standard choices. No antibiotics.

When pneumonia is confirmed or strongly suspected: doxycycline 5 mg/kg PO q12h is first-line. It covers Bordetella (which produces a BOR-1 β-lactamase that makes amoxicillin and amoxicillin-clavulanate unreliable) and Mycoplasma (which has no cell wall and is intrinsically resistant to β-lactams). Duration is typically 10–14 days, or at least 1 week past clinical resolution. Never suppress a productive cough with mucopurulent discharge – that suppresses the airway clearance mechanism the dog needs.

Vaccination

The Bordetella vaccine question comes down to route and timing. The intranasal modified-live vaccine stimulates local mucosal IgA at the respiratory epithelium – immunity kicks in within 3–5 days. The parenteral (IM/SQ) killed vaccine relies on systemic antibody and takes 2–3 weeks for protection after the primary series. In a shelter intake or outbreak situation, intranasal is the right call every time.

CPiV and CAV-2 are covered in the DA2PP core vaccine – every dog getting their core series gets these. For high-risk dogs (frequent boarding, dog shows, hunt tests, agility): add the bivalent CIV vaccine (H3N8 + H3N2). Initial series is two doses 2–4 weeks apart, then annual boosters.

Isolation Protocols

Standard CIRDC (Bordetella, CPiV, CAV-2): isolate for 2 weeks from onset of clinical signs. CIV H3N8: 7 days minimum isolation. CIV H3N2: 21 days from onset because viral shedding can persist for up to 24 days. Dogs exposed to confirmed H3N2 cases but not yet symptomatic: isolate for 4 weeks. The extended shedding window of H3N2 is why it’s harder to contain and why the exam tests it specifically.