NAVLE Rabbits

Rabbit Pasteurellosis Study Guide

📅 March 28, 2026 ⏱ 25 min read

Overview and Clinical Importance

Pasteurellosis is one of the most significant bacterial diseases affecting domestic rabbits, caused by Pasteurella multocida. This multisystemic disease is highly prevalent, with 30-90% of apparently healthy rabbits being asymptomatic carriers. Understanding pasteurellosis is critical for the NAVLE as it represents a common clinical challenge in rabbit medicine and has important zoonotic implications for veterinarians and pet owners.

Clinical Form	Clinical Signs	Key Features
Upper Respiratory Disease (Snuffles)	Serous to mucopurulent nasal discharge Sneezing, snorting Matted fur on forepaws Nasal stridor	Most common manifestation. Rabbits wipe nasal discharge with forepaws creating characteristic matted fur. May progress to sinusitis and pneumonia.
Conjunctivitis and Dacryocystitis	Mucopurulent ocular discharge Conjunctival hyperemia Epiphora with facial scalding Nasolacrimal duct obstruction	Second most common manifestation. Chronic epiphora leads to stenosis of nasolacrimal ducts. May occur independently or with rhinitis.
Pneumonia	Dyspnea, tachypnea Moist rales on auscultation Anorexia, depression May die acutely without signs	Can be acute or chronic. Chronic pneumonia often asymptomatic in caged rabbits with minimal respiratory demands. Radiographs show cranioventral consolidation and abscesses.
Otitis Media and Interna	Head tilt (torticollis) Rolling, circling Nystagmus Ataxia, loss of balance	Infection spreads from nasopharynx via eustachian tube. Tympanic bullae filled with inspissated pus. Occurs in approximately 15% of rabbits with otitis media when vestibular apparatus involved.
Subcutaneous Abscesses	Firm subcutaneous swellings Thick, creamy, caseous exudate May have draining tracts Most common on head and shoulders	Result from contaminated wounds, bite injuries, or hematogenous spread. Rabbit abscesses are thick-walled and do not drain well. Surgical excision en bloc is preferred over drainage.
Genital Infections	Females: Serous to mucopurulent vaginal discharge, metritis, pyometra, infertility, abortion Males: Orchitis, epididymitis, decreased fertility, enlarged firm testicles	Transmitted venereally. Infected does may transmit to offspring during birth. May present as reproductive failure in breeding operations.
Septicemia	Peracute death without premonitory signs Depression, anorexia Fever, hypothermia	Secondary to pneumonia or rhinitis. Post-mortem findings: serosal and endocardial hemorrhages. Type D strains more commonly cause septicemia.

Etiology

Organism Characteristics

Pasteurella multocida is a Gram-negative, non-motile, non-spore-forming coccobacillus belonging to the Pasteurellaceae family. The organism is pleomorphic and facultatively anaerobic with fermentative metabolism.

Capsular Types and Virulence

P. multocida strains are classified into five capsular serogroups (A, B, D, E, F) and 16 somatic serotypes. In rabbits:

Capsular Type A (12:A and 3:A): Most common in rabbits and humans, typically associated with upper respiratory disease (snuffles). Type 12:A causes rhinitis while 3:A more commonly causes lower respiratory disease.

Capsular Type D (3:D): Less common but more virulent, frequently associated with septicemia and higher mortality.

Capsular Type F: Occasionally isolated from rabbits, but significance is still under investigation.

NAVLE TipRemember the 'A' capsular types for rabbits: Type A is the most common cause of pasteurellosis in rabbits AND the most common type transmitted to humans from rabbits. If you see a NAVLE question about rabbit pasteurellosis with zoonotic transmission, think Type A first.

Test	Method and Interpretation	Limitations
Bacterial Culture	Deep nasal swab or samples from affected sites plated on blood agar. P. multocida: Gray, translucent, non-hemolytic colonies. Grows on blood agar but NOT MacConkey agar. Best growth at 34-35°C. Gram-negative coccobacilli with bipolar staining.	False negatives common. Organism may be deep in sinuses. Survives less than 24h in transport media. Many healthy carriers test positive. Must correlate with clinical signs.
PCR (Polymerase Chain Reaction)	More sensitive than culture. Can detect P. multocida DNA from nasal swabs even when culture negative. Can identify capsular type (A, B, D, E, F) and virulence genes.	Detects DNA, not necessarily viable organisms. Cannot distinguish between colonization and active infection. May detect DNA after antibiotic treatment.
Serology (ELISA)	Detects antibodies to P. multocida. Rising titers indicate recent exposure or active infection. Various antigens used (whole cell lysate, NanH sialidase, outer membrane proteins).	Presence of antibodies does not confirm active disease. Cannot distinguish between carriers and clinically ill rabbits. Best used in combination with other tests.
Hematology	Neutrophilia or shift in neutrophil:lymphocyte ratio (normal approximately 2:3) suggests bacterial infection. Leukocytosis with left shift in acute cases.	Nonspecific. Many infected rabbits have normal CBC. Cannot differentiate from other bacterial infections.

Epidemiology

Transmission

Direct contact is the primary mode of transmission. Rabbits become colonized soon after birth, typically from infected dams during nursing. Transmission also occurs through aerosol spread, venereal contact, and contaminated fomites.

Prevalence: Studies show 30-90% of clinically normal rabbits harbor P. multocida in their nasal passages, making asymptomatic carrier status extremely common.

Predisposing Factors

Clinical disease typically manifests when the balance between host immunity and bacterial virulence is disrupted:

Environmental stressors: Poor ventilation, high humidity, high ammonia levels from soiled bedding, overcrowding, temperature extremes.

Immunosuppression: Concurrent disease, malnutrition, pregnancy, weaning stress, transport stress, immunosuppressive medications.

Anatomical factors: Rabbits have poor mucociliary clearance and drainage in the upper respiratory tract, predisposing them to respiratory infections.

High-YieldOn the NAVLE, if you see a scenario describing a rabbit with recent stress (transport, new environment, weaning) developing respiratory signs, strongly consider pasteurellosis even if the rabbit was previously healthy. The stress trigger is key.

Antibiotic	Dosage	Duration	Notes
Enrofloxacin (First-line)	5-20 mg/kg PO, SC, IM q12-24h OR 200 mg/L in drinking water	Minimum 14-30 days; chronic cases may require 4-6 weeks or longer	Most effective. Safe in rabbits. Penetrates well into tissues.
Trimethoprim-Sulfonamide	15-30 mg/kg PO q12h	14-30 days minimum	Alternative to enrofloxacin. Lower cost.
Azithromycin	15-30 mg/kg PO q24h for 3 days, then q48-72h	Several weeks	Good tissue penetration. Long half-life allows extended dosing intervals.
Penicillin G Procaine	40,000-60,000 U/kg IM q24h	14-21 days	CAUTION: Risk of fatal clostridial enterotoxemia. Use with care.
Tilmicosin	25 mg/kg SC once	Single dose or repeat weekly	Macrolide antibiotic. Effective for respiratory pasteurellosis.
Doxycycline	5-10 mg/kg PO q12h	14-30 days	Alternative option. Good penetration.

Pathogenesis

P. multocida possesses numerous virulence factors that enable colonization, invasion, and immune evasion:

Capsular polysaccharides: Inhibit phagocytosis and confer resistance to complement-mediated killing.

Lipopolysaccharides (LPS): Provide resistance to serum bactericidal activity and stimulate inflammatory responses.

Fimbriae and adhesins: Facilitate attachment to respiratory epithelium (fim4, fimA, tadD, pfhA).

Iron acquisition systems: Essential for survival in the host (hgbB, exbB, fur, tbpA).

Sialidases (neuraminidases): NanH and NanB enzymes degrade host glycoconjugates, facilitating colonization and tissue invasion.

Superoxide dismutases: SodA and SodC protect against oxidative killing by host phagocytes.

Dermonecrotic toxin (PMT): Some strains produce toxin contributing to atrophic rhinitis and tissue damage.

Clinical Manifestations

Pasteurellosis is a multisystemic disease with variable clinical presentations depending on the site of infection and strain virulence.

Diagnosis

Diagnosis requires a combination of clinical signs, imaging, and laboratory confirmation. No single test is 100% sensitive or specific.

Clinical Diagnosis

Presumptive diagnosis based on signalment (rabbit), characteristic clinical signs (snuffles, conjunctivitis), and history of stress or exposure. However, other pathogens (Bordetella bronchiseptica, Staphylococcus aureus, Pseudomonas spp) can cause similar signs.

Laboratory Diagnostics

Imaging

Radiography: Thoracic radiographs may show cranioventral consolidation, abscesses (round white areas in lungs), or pleural effusion. Skull radiographs can reveal increased opacity in tympanic bullae, nasal passages, or sinuses indicating infection. CT/MRI provides more detailed visualization of affected structures.

NAVLE TipThe NAVLE loves the combination approach. Remember: PCR + serology is more specific than culture alone from nasal swabs. If given a choice between diagnostic tests, select PCR for highest sensitivity in detecting P. multocida.

Treatment

Treatment of pasteurellosis is often challenging. Antibiotics may provide clinical improvement but rarely eliminate the organism. Many treated rabbits become chronic carriers.

Antimicrobial Therapy

CRITICAL: Always base antibiotic selection on culture and sensitivity when possible. Treatment duration is key - premature discontinuation leads to relapse and carrier state. Most cases require 4-6 weeks minimum.

Surgical Management

Abscesses: Complete surgical excision en bloc is preferred. Unlike cats and dogs, rabbit abscesses are thick-walled with caseous exudate that does not drain well. Drainage alone has high recurrence rates. Facial abscesses often associated with dental disease require tooth extraction and aggressive debridement.

Nasolacrimal duct flushing: For chronic dacryocystitis with duct stenosis. Requires anesthesia and gentle cannulation.

Supportive Care

Nebulization with saline or antibiotics, assisted feeding if anorexic, fluids if dehydrated, NSAIDs for pain and inflammation, humidified oxygen if dyspneic, gentle cleaning of nasal discharge and ocular discharge.

High-YieldEnrofloxacin is the GOLD STANDARD for rabbit pasteurellosis on the NAVLE. If you see a question asking for first-line treatment, choose enrofloxacin. Remember: treat for at least 4-6 weeks and warn owners that elimination is rare - most rabbits become carriers even with treatment.

Prevention and Control

Environmental Management

Optimize ventilation to reduce ammonia and humidity
Regular cleaning and disinfection of housing
Reduce stressors: avoid overcrowding, minimize handling stress, maintain stable temperatures
Provide dust-free bedding to minimize respiratory irritation
Ensure proper nutrition for immune function

Vaccination

Commercial inactivated vaccines are available in some countries. Autogenous vaccines can be prepared from farm isolates. Vaccination reduces clinical disease severity but does NOT prevent infection or colonization. Best used as part of integrated control program in breeding operations.

Breeding Considerations

Treat does with enrofloxacin from day 14 of gestation through kindling to reduce transmission to kits. Some rabbitries employ test-and-cull programs, but this is controversial as many healthy rabbits test positive. Closed herd management and isolation of new arrivals helps reduce introduction of virulent strains.

Zoonotic Precautions

Human infections occur via bites, scratches, licks, or aerosol inhalation. Immunocompromised individuals, elderly, and those with pulmonary disease are at highest risk. Veterinary staff should use proper PPE when handling infected rabbits. Educate rabbit owners about proper hygiene and warning signs of infection.

Practice NAVLE Questions

Test your knowledge with 10,000+ exam-style questions, detailed explanations, and timed exams.

Start Your Free Trial →