Introduction

• Pneumonia is inflammation of the lung parenchyma.
• Respiratory disease is a major cause of both morbidity and mortality in pet rabbits. It is often presented in advance stages of respiratory compromise.
• Pasteurellosis Pasteurellosis historically quoted as the primary respiratory disease of rabbits.
• As more pet rabbits make the transition from the garden hutch to the heated home so changes in temperature, ventilation, humidity and environmental pollutants may alter the epidemiology of respiratory diseases.
• Infectious bronchitis and pneumonia have been well documented since the 1920s.
• Cause:
  • May be a secondary or concurrent condition, with underlying disease or immunodeficiency predisposing animals to pneumonia.
  • Several bacterial and viral pathogens can cause pneumonia.
  • Non-infectious bronchitis and pneumonia may become more important in the home environment and may be caused by:
    • Allergies.
    • Respiratory insults (smoke, aerosols).
• Signs: lethargy and malaise, fever, anorexia and weight loss, dyspnea and tachypnea, oculonasal discharge, pale to congested mucous membranes, sneezing and coughing.
• Treatment: correction of underlying factors including poor nutrition and poor environment, antimicrobials and surgical resection if indicated.
• Diagnosis: based upon history, clinical signs (thoracic auscultation), hematology, radiography, advanced imaging (computed tomography), endoscopy, ultrasonography, and lung wash or lung biopsy.
• Prognosis: depends on disease and severity but often guarded given the advanced presentation of most cases.

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Presentating signs

• Presentation depends upon:
  • Nature of the pneumonia, infectious or non-infectious.
  • Virulence of organism.
  • Age and immunocompetence of the rabbit.
• In most cases rabbits present with one or more of the following:
  • Lethargy, malaise and/or unkempt appearance.
  • Fever.
  • Anorexia Anorexia and weight loss.
  • Dyspnea Dyspnea and tachypnea.
  • Oculonasal discharge Nose: nasal discharge - overview.
  • Pale to congested mucous membranes or cyanosis.
  • Sneezing and coughing.
• It is important to realize that many rabbits will mask obvious symptoms of pneumonia until the disease is very advanced.
• Any rabbit showing even mild lower respiratory tract signs should be considered seriously ill until proven otherwise.
• Pasteurellosis Pasteurellosis may cause a myriad of presentations of which respiratory signs may be only one manifestation.

Acute presentation

• Rabbits with acute or peracute pneumonia may simply present as sudden deaths.
• Signs, if noticed, may include:
  • Severe dyspnea Dyspnea with increased respiratory noise.
  • Lateral or ventral recumbency.
  • Open mouth breathing with extended neck.
  • Cyanotic mucous membranes.
  • Hemoptesis (coughing blood).
  • Anorexia Anorexia.
  • Fever or shock hypothermia Hypothermia.

Incidence

• Incidence of pneumonia increases with the following:
  • Age.
  • Underlying concurrent disease.
  • Stress.
  • Overcrowding.
  • Poor husbandry.
  • Immunodeficient animals. 

Geographic incidence

• The incidence and prevalence of disease is increased where temperature fluctuations occur as is more likely in temperate regions. Rabbits exposed to excessively high temperatures in tropical environments may also suffer respiratory embarrassment.
• Temperature variation will be more significant for hutch-housed rabbits than house rabbits. However, house rabbits may be kept too warm in centrally heated homes.
• Distribution of pathogens:
  • Most bacterial pathogens appear to have a worldwide distribution.
  • Herpesvirus Herpes virus has been reported in Europe and Canada.
  • Coronavirus (pleural effusion disease): worldwide distribution unknown, incidence low, first reported in Scandinavia, appears restricted to labs.
  • Chlamydia: appears to be an experimentally induced infection (human model for Chlamydial pneumonia) but natural infection appears uncommon, although it has been isolated from the lungs of pet rabbits with pneumonia.
  • Mycoplasma spp.
• Housing and environment may affect disease:
  • Outside hutch and run provide better ventilation but greater temperature fluctuations.
  • House rabbits have a more stable environment, but it may be too warm and too dry.

Morbidity

• Incidence of infection varies:
  • With breed, greater in Flemish Giant Flemish Giant than in New Zealand White New Zealand White.
  • With season, greater in spring and autumn.
  • With temperature, greater with temperature fluctuations and excessively high temperatures.
• Bordetella bronchiseptica Bordetella bronchiseptica may be co-pathogen or predisposing factor to Pasteurella spp Pasteurella multocida.
• Bordetella spp appears to be more common in neonatal/juvenile rabbits while Pasteurella spp is more common in adults.
• Up to 60% of rabbits may carry subclinical Pasteurella spp and of that infected population:
  • 40% may develop clinical signs of respiratory disease.
  • 10% may spontaneously recover.
  • 5% may develop pneumonia.
  • 5% may develop bacteremia.
• Pasteurella-free status is possible only in SPE laboratory populations.
• The numbers of rabbits experiencing clinical pneumonia is quite low but subclinical disease, often as an extension of upper respiratory disease, is very common.

Mortality

• Mortality can be high particularly when the disease is:
  • Caused by a virulent strain of Pasteurella Pasteurella multocida, Staphylococcus Staphylococcus spp Staphylococcus aureus or Pseudomonas Pseudomonads spp.
  • Acute or peracute in nature.
  • Complicated by bacteremia, septicemia, pericarditis, peritonitis, poor environment.

Cost considerations

• Costs will depend on the level of investigation and the duration of therapy.
• Standard investigation, ie consultation, hematology Hematology, anesthesia Anesthesia: overview, radiographs, endoscopy Endoscopy: overview, lung wash cytology or lung biopsy for histopathology and microbiology, prolonged antibiotic therapy.
• Thoracotomy Thorax: thoracotomy and abscess removal will necessitate extensive surgery and critical care nursing.

Special risks

• Blood can be collected from the conscious animal, but radiographs, lung wash or biopsy require sedation Sedation or general anesthesia Anesthesia: overview.
• Respiratory disease does add a significant risk to anesthesia, which must be weighed against the benefits of making a diagnosis. However, short anesthetic restraint greatly facilitates the collection of diagnostic samples and reduces stress of sample collection, thereby ultimately providing a definitive diagnosis and prognosis.

Pathogenesis

Diagnosis

Treatment

Prevention

Outcomes

Further Reading

Publications

Refereed papers

• Recent references from PubMed and VetMedResource.
• Jekl V (2021) Respiratory disorders in rabbits. Vet Clin Exot Anim 24 (2), 459-482 PubMed.
• Sharma R, Kapoor D & Kumar R (2017) A rare case of verminous pneumonia in domestic rabbit. J Parasit Dis 41 (3), 716-717 PubMed.
• Sutherland M, Higbie C T, Crossland N A et al (2017) Aberrant migration of Cuterebra larvae in 2 domestic rabbits (Oryctolagus cuniculus). J Exot Pet Med 26 (1), 57-62 PubMed.
• Roels S, Wattiau P, Fretin D et al (2007) Isolation of Morganella morganii from a domestic rabbit with bronchopneumonia. Vet Rec 161 (15), 530-531 PubMed.
• Deeb B J & DiGiacomo R F (2000) Respiratory diseases of rabbits. Vet Clin North Am Exot Anim Pract 3 (2), 465-480 PubMed.
• Langan G P, Lohmiller J J, Swing S P et al (2000) Diseases of rodents and rabbits. Vet Clin North Am Small Anim Pract 30 (6), 1309-1335 PubMed.
• Hyde D M, Downey G P, Tablin F et al (1997) Age-dependent neutrophil and blood flow responsiveness in acute pulmonary inflammation in rabbits. Am J Physiol 272 (3 Pt 1), 471-478 PubMed.
• Mazars E, Guyot K, Durand I et al (1997) Isoenzyme diversity in Pneumocystis carinii from rats, mice and rabbits. J Infect Dis 175 (3), 655-660 PubMed.
• Ramírez-Romero R, Brogden K A & Cutlip R C (1997) Influence of immunization on the pulmonary inflammatory response of rabbits induced by Pasteurella haemolytica A1 lipopolysaccharide. J Comp Pathol 117 (2), 137-145 PubMed.
• Richardson M, Fletch A, Delaney K et al (1997) Increased expression of vascular cell adhesion molecule-1 by aortic endothelium of rabbits with Pasteurella multocida pneumonia. Lab Anim Sci 47 (1), 27-35 PubMed.
• Moazed T C, Kuo C, Patton D L et al (1996) Experimental rabbit models of Chlamydia pneumoniae infection. Am J Physiol 48 (2), 667-676 PubMed.
• Vernau K M, Grahn B H, Clarke-Scott H A et al (1995) Thymoma in a geriatric rabbit with hypercalcaemia and periodic exophthalmos. JAVMA 206 (6), 820-822 PubMed.
• DiGiacomo R F, Deeb B J, Brodie S J et al (1993) Toxin production by Pasteurella multocida isolated from rabbits with atrophic rhinitis. Am J Vet Res 54 (8), 1280-1286 PubMed.
• DeLong D, Manning P J, Gunther R et al (1992) Colonization of rabbits by Pasteurella multocida - serum IgG responses following intranasal challenge with serologically distinct isolates. Lab Anim Sci 42 (1), 13-18 PubMed.
• Dugal F, Bélanger M & Jacques M (1992) Enhanced adherence of Pasteurella multocida to porcine tracheal rings preinfected with Bordetella bronchiseptica. Can J Vet Res 56 (3), 260-264 PubMed.
• Onderka D K, Papp-Vid G & Perry A W (1992) Fatal herpesvirus infection in commercial rabbits. Can Vet J 33 (8), 539-543 PubMed.
• Zimmerman T E, Deeb B J & DiGiacomo R F (1992) Polypeptides associated with Pasteurella multocida infection in rabbits. Am J Vet Res 53 (7), 1108-1112 PubMed.
• Broome R L & Brooks D L (1991) Efficacy of enrofloxacin in the treatment of respiratory pasteurellosis in rabbits. Lab Anim Sci 41 (6), 572-576 PubMed.
• Chrisp C E & Foged N T (1991) Induction of pneumonia in rabbits by use of a purified protein toxin from Pasteurella multocida. Am J Vet Res 52 (1), 56-61 PubMed.
• Choi-Kim K, Maheswaran S K, Felice L J et al (1991) Relationship between the iron regulated outer membrane proteins and the outer membrane proteins of in vivo grown Pasteurella multocida. Vet Microbiol 28 (1), 75-92 PubMed.
• Gunther R, Manning P J, Bouma J E et al (1991) Partial characterization of plasmids from rabbit isolates of Pasteurella multocida. Lab Anim Sci 41 (5), 423-426 PubMed.
• Lu Y S, Lai W C, Pakes S P et al (1991) A monoclonal antibody against a Pasteurella multocida outer membrane protein protects rabbits and mice against pasteurellosis. Infect Immunol 59 (1), 172-180 PubMed.
• Zaoutis T E, Reinhard G R, Cioffe C J et al (1991) Screening rabbit colonies for antibodies to Pasteurella multocida by an ELISA. Lab Anim Sci 41 (5), 419-422 PubMed.
• Deeb B J, DiGiacomo R F, Bernard B L et al (1990) Pasteurella multocida and Bordetella bronchiseptica infections in rabbits. J Clin Microbiol 28 (1), 70-75 PubMed.
• DiGiacomo R F, Taylor F G R, Allen V et al (1990) Naturally acquired Pasteurella multocida infection in rabbits - immunological aspects. Lab Anim Sci 40 (3), 289-292 VetMedResource.
• Glávits R & Magyar T (1990) The pathology of experimental respiratory infection with Pasteurella multocida and Bordetella bronchiseptica in rabbits. Acta Vet Hung 38 (3), 211-215 PubMed.
• Kurisu K, Kyo S, Shiomoto Y et al (1990) Cilia-associated respiratory bacillus infection in rabbits. Lab Anim Sci 40 (4), 413-415 PubMed.
• Okerman L, Devriese L A, Gevaert D et al (1990) In vivo activity of orally administered antibiotics and chemotherapeutics against acute septicaemic pasteurellosis in rabbits. Lab Anim 24 (4), 341-344 PubMed.
• DiGiacomo R F, Deeb B J, Giddens W E Jret al (1989) Atrophic rhinitis in New Zealand White rabbits infected with Pasteurella multocida. Am J Vet Res 50 (90), 1460-1465 PubMed.
• Foged N T, Nielsen J P & Jorsal S E (1989) Protection against progressive atrophic rhinitis by vaccination with Pasteurella toxin purified by monoclonal antibodies. Vet Rec 125 (1), 7-11 PubMed.
• Shell L G & Saunders G (1989) Arteriosclerosis in a rabbit. JAVMA 194 (5), 679-680 PubMed.
• Spreadbury C L, Krausz T, Pervez S et al (1989) Invasive aspergillosis: clinical and pathological features of a new animal model. J Med Vet Mycol 27 (1), 5-15 PubMed.
• Al-Lebban Z S, Corbeil L B, Coles E H (1988) Rabbit pasteurellosis - induced disease and vaccination. Am J Vet Res 49 (3), 312-316 PubMed.
• Ikeda J S & Hirsh D C (1988) Antigenically related iron-regulated outer membrane proteins produced by different somatic serotypes of Pasteurella multocida. Infect Immun​ 56 (9), 2499-2502 PubMed.
• Duclos P, Caillet J & Javelot P (1986) Aerobic bacterial flora of the nasal cavity of farmed rabbits. Ann Rech Vet 17 (2), 185-190 VetMedResource.
• Nakagawa M, Nakayama K, Saito M et al (1986) Bacteriological and serological studies on Pasteurella multocida infection in rabbits. Jikken Dobutsu 35 (4), 463-469 PubMed.
• Zeligs B J, Zeligs J D & Bellanti J A (1986) Functional and ultrastructural changes in alveolar macrophages from rabbits colonized with Bordetella bronchiseptica. Infect Immun 53 (3), 702-706 PubMed.
• Matsui T, Taguchi-Ochi S, Takano M et al (1985) Pulmonary aspergillosis in apparently healthy young rabbits. Vet Pathol 22 (3), 200-205 PubMed.
• Anderson L C, Rush H G & Glorioso J C (1984) Strain differences in the susceptibility and resistance of Pasteurella multocida to phagocytosis and killing by rabbit polymorphonuclear neutrophils. Am J Vet Res 45 (6), 1193-1198 PubMed.
• Percy D H, Prescott J F & Bhasin J L (1984) Characterization of Pasteurella multocida isolated from rabbits in Canada. Can J Comp Med 48 (2), 162-165 PubMed.
• Corbeil L B, Strayer D S, Skaletsky E et al (1983) Immunity to pasteurellosis in compromised rabbits. Am J Vet Res 44 (5), 845-50 PubMed.
• DiGiacomo R F, Garlinghouse L E Jr. & Van Hoosier G L Jr. (1983) Natural history of infection with Pasteurella multocida in rabbits. JAVMA 183 (11), 1172-1175 PubMed.
• Glorioso J C, Jones G W, Rush H G et al (1982) Adhesion of type A Pasteurella multocida to rabbit pharyngeal cells and its possible role in rabbit respiratory tract infections. Infect Immun 35 (3), 1103-1109 PubMed.
• Lu Y S, Pakes S P, Rehg J E et al (1982) Pathogenicity of serotype 12 - A Pasteurella multocida in hydrocortisone treated and non-treated rabbits. Lab Anim Sci 32 (3), 258-262 PubMed.
• Mushin R & Schoenbaum M (1980) A strain of Pasteurella multocida associated with infections in rabbit colonies. Lab Animal 14 (4), 353-356 PubMed.
• Patton N M, Holmes H T, Caveny D D et al (1980) Experimental inducement of snuffles in rabbits. J Appl Rabbit Res 3, 8-12.
• Okerman L, Spanoghe L & De Bruycker R M (1979) Experimental infections of mice with Pasteurella multocida strains isolated from rabbits. J Comp Pathol 89 (1), 51-55 PubMed.
• Lu Y S, Ringler D H & Park J S (1978) Characterization of Pasteurella multocida isolates from the nares of healthy rabbits and rabbits with pneumonia. Lab Anim Sci 28 (6), 691-697 PubMed.
• Stephen G W & Cooper L V (1977) The role of analgesics in respiratory depression: a rabbit model. Anaesthesia 32 (4), 324-327 PubMed.
• Watson W T, Goldsboro J A, Williams F P et al (1975) Experimental respiratory infection with Pasteurella multocida and Bordetella bronchiseptica in rabbits. Lab Anim Sci 25 (4), 459-464 PubMed.
• Deeb B J & Kenny G E (1967) Characterization of Mycoplasma pulmonis variants isolated from rabbits - 1. identification and properties of isolates. J Bacteriol 93 (4), 1416-1424 PubMed.
• Hagen K W Jr. (1958) Enzootic pasteurellosis in domestic rabbits - 1. pathology and bacteriology. JAVMA 133, 77-80 VetMedResource.

Other sources of information

• Lennox A & Mancinelli E (2021) Respiratory Disease. In: Ferrets, Rabbits and Rodents. Clinical Medicine and Surgery. 4th edn. Eds: Quesenberry K E, Orcutt C J, Mans C & Carpenter J W. Elsevier, USA. pp 188-200.
• Delaney M A, Treuting P M & Rothenburger J L (2018) Lagomorpha. In: Pathology of Wildlife and Zoo Animals. Eds: Terio K A, McAloose D & St. Leger J. Academic Press, UK. pp 481-497.
• Varga M (2014) Cardiorespiratory Disease. In: Textbook of Rabbit Medicine. Elsevier, UK. 390-404.
• Hedley J (2014) Respiratory Disease. In: BSAVA Manual of Rabbit Medicine. Eds: Meredith A & Lord B. BSAVA, UK. pp 160-167.
• Johnson D (2011) Pneumonia in Small Mammals. In: Proc Association of Avian Veterinarians Conference.
• Kelleher S (2008) Rabbit Respiratory Disease. In: Proc Western Veterinary Conference.
• Murray M J (2006) Rabbits it's not always Pasteurella. In: Proc North American Veterinary Conference.
• Hoefer H (2001) Rabbit Respiratory Disease. In: Proc Atlantic Coast Veterinary Converence.
• DiGiacomo R F & Mare C J (1994) Viral Diseases. In: Biology of the Laboratory Rabbit. Eds: Manning P, Ringler D H & Newcomer C E. Academic Press, USA. pp 171-204.
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• Rimler R B & Rhoades K R (1989) Pasteurella Multocida. In: Pasteurella and Pasteurellosis. Eds: C Adlam & J M Rutter. Academic, UK. pp 37-73.
• Flatt R E (1974) Bacterial Diseases. In: Biology of the Laboratory Rabbit. Eds: S H Weisbroth, R E Flatt & A K Kraus. Academic Press, USA. pp 193-236.