Lapis ISSN 2398-2969

Pneumonia

Contributor(s): Narelle Walter, Susan Brown, Stephen Hernandez-Divers, Maud Lafortune, Vetstream Ltd

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 has been well documented since the 1920s.
  • 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, hematology, radiography, 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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Presentation

  • 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 and weight loss.
    • Dyspnea and tachypnea.
    • Oculonasal discharge.
    • 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 may cause a myriad of presentations of which respiratory signs may be only one manifestation.

Acute

  • 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

  • The authors are unaware of any studies that have determined the incidence of respiratory disease in pet rabbits.
  • Incidence of pneumonia increases with the following:
    • Age.
    • Underlying concurrent disease.
    • Stress.
    • Overcrowding.
    • Poor husbandry.
    • Immunodeficient animals. 

Geographic

  • 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 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 rare.
  • 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 Pasteurellaspp   Pasteurella multocida  .
  •  Bordetellaspp appears to be more common in neonatal/juvenile rabbits while Pasteurellaspp is more common in adults.
  • Up to 60% of rabbits may carry subclinical Pasteurellaspp 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

Cost

  • Costs will depend on the level of investigation and the duration of therapy.
  • Standard investigation, ie consultation, hematology, anesthesia, radiographs, endoscopy, lung wash cytology or lung biopsy for histopathology and microbiology, prolonged antibiotic therapy.
  • 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.

Cause

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Diagnosis

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Treatment

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Prevention

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Prognosis

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Further Reading

Publications

Refereed papers
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Other sources of information

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