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Common rabbit respiratory diseases - Coggle Diagram
Common rabbit respiratory diseases
Observation
obligate nasal breather
normal respiration rate in a calm rabbit is 30-60bpm
many will be tachypnoeic due to stress
should be minimal abdominal effort and no respiratory noises should be heard from a distance
very dyspneic animals may benefit from oxygen supplementation prior to examination
open mouth breathing or cyanosis is always a poor prognostic indicated, patients need to be treated with extreme care and handling minimised until stable.
Upper respiratory tract disease
clinical signs
nasal discharge
not always noticed by owners, if rabbit grooming away, but matted fur on the medial forelimbs and paws usually indicates that discharge has been present
unilateral often a foreign body e.g. some hay
snuffling
sneezing
anorexic
markedly dyspneic if URT obstructed
Initial examination
Check both nares for patency
clear glass slide recently wetted with alcohol may be placed beneath nares and observe fogging.
Examine head for symmetry
Palpate the margins of the nasal cavity and sinuses
Full oral examination indicated as dental disease is often associated with URT problems
Ocular discharge
may be observed associated with
conjunctivitis
and
dacryocystitis
neurological signs (head tilt, circling) may be observed if infection has ascended via the Eustachian tube to affect the middle and inner ear
note that pressure over the lacrimal sac over the medial canthus of the eye may result in discharge from the nasolacrimal punctum
in these cases the nasolacrimal ducts should be flushed to ensure patency
Fluorescein dye may be instilled into eyes in dacryocystitis (dye should be visible at both nares if patent)
Lower respiratory tract disease
Clinical signs
Dyspnoea
wheezing
coughing (not common)
Lethargic
Reduced appetite
associated weight loss
often subclinical/subtle until fairly advanced
exercise intolerance hard to assess, but activity levels may be reduced
moderate to severe bilateral hock pododermatitis
rabbits that have been sitting still for longer periods of time, question rabbit activity levels
Auscultation
lung sounds
crackles
usually inspiratory and occur as a result of re-opening the airways that have closed during expiration
wheezes
may be inspiratory or expiratory, but usually higher pitched sounds that occur due to passage of air through narrow bronchi
wait until calm, as these sounds may be referred to the thorax
patchy loss of sounds may indicate lung consolidation or an underlying mass
rule out cardiovascular abnormalities which may be present with similar clinical signs
Diagnosis
Radiography
multiple skull + thoracic views to confirm extent of the disease
skull
lateral
dorsoventral
left and right oblique
rostrocaudal
assess
nasal cavity
sinuses
dental arcades
tympanic bullae
changes may be subtle
any asymmetry, increased opacity or areas of bone lysis may indicate underlying disease
thoracic
lateral
dorsoventral
challenging due to small size of thoracic cavity
may see increased bronchial, interstitial, alveolar or mixed pattern to indicate pneumonia
ideal
1) forelimbs extended cranially
2) rabbit intubated
3) film taken on inspiration
radiographic changes may not be present early in disease process
increased radiopacity of cranial lung lobe, displacement of heart caudally and elevation of trachea may indicate cranial thoracic mass e.g thymoma
evaluate and measure heart for potential cardiac disease
in collapsed dyspneic patients in which GA is risky, conscious radiographs may be preferred and then repeat when patient is stabilised.
Mild sedation with midazolam and butorphanol
reduce stress
allow positioning to obtain more diagnostic films
Ultrasound
limited use for respiratory disease
may be helpful for suspected thoracic mass (USS guided aspirates)
computed tomography
imaging modality of choice for detection and full evaluation of rhinitis, sinusitis, dental disease, otitis media + pulmonary disease
sedation/short GA
more expensive than radiography
magnetic resonance imaging
more useful for soft tissue imaging (e.g. further evaluation of thoracic mass)
more expensive, longer GA
Endoscopy
Rhinoscopy for URT disease
good for rabbits >2kg
1.9mm rigid endoscope sheath recommended
biopsy and histopathology of nasal mucosa can be obtained
care not to damage nasal turbinates, which will bleed profusely
can flush nasal cavity (care to avoid aspiration)
retrograde flexible endoscopy
evaluate the caudal nasopharynx, especially in cases with a suspected foreign body
Tracheoscopy
rigid or flexible
to evaluate LRT
haematology and biochemistry
Haematological abnormalities may be revealed in cases with respiratory disease, though parameters are often within normal limits.
Bacterial disease
Pasteurellosis
gram -ve bacterium commensal in resp. tract
Predisposing factors
any potential stressor
chronically poor standards of hygiene
inadequate ventilation
elevated environmental ammonia levels
corticosteroid treatment
transmission
direct contact with nasal secretions, aerosols or fomites
vertical
inoculation
wounds
oral
conjunctival
vaginal
Clinical signs
URT + LRT disease
associated middle/inner ear disease
abscesses
neurological signs (abscesses affecting brain)
reproductive problems in breeding rabbits e.g. mastitis and metritis
On post-mortem examination, rhinitis with turbi- nate atrophy, sinusitis, otitis, well demarcated red–grey foci in the lungs consistent with broncho- pneumonia, pulmonary abscesses and pericarditis may be observed
pasteurellosis may be a
zoonotic
risk to humans and young, old or immuno- suppressed individuals in particular should be warned of this. Susceptible individuals may suffer from skin infections, pneumonia, arthritis, menin- gitis and septicaemia.
Bordetella bronchiseptica
gram -ve, 2nd most common URT disease isolate, commensal of URT.
predisposes to development of pasteurellosis
causes disease in guinea pigs
Diagnosis for URT infections
Deep nasal swab for culture
moisten swab with sterile saline and insert 2-3cm into ventral meatus
sedation often required
sampling stimulates intense bout of sneezing
false -ve common
superficial samples/sample of nasal discharge usually contaminated by environmental bacteria
endoscopically obtained biopsy samples of nasal mucosa more accurate representation on pathogens present
culture nasolacrimal duct flush
false -ve common
Diagnosis for LRT infections
Tracheal wash or bronchoalveolar lavage
Definitive diagnosis of pasteurellosis or other respiratory infections ideally requires isolation of the pathogen and demonstration of associated patho- logy (on biopsy specimens or post-mortem examin- ation). In practice this may be difficult to prove in a live animal, so diagnosis is usually based on culture of the bacteria in association with typical respiratory signs.
Treatment
Emergency (severe dyspnoea, open mouth breathing or cyanosis)
quiet, dark environment
reduce stress
minimise handling for at least initial 30 min unless absolutely necessary
Mild sedation with midazolam may be necessary
oxygen supplementation
Oxygen for longer-term therapy should be humidified and <40%
antibiotic therapy for a minimum of 14 days
Antibiotic choice ideally off culture and sensitivity or in house gram stains
bactericidal drugs preferable for severe disease e.g. pneumonia
Mild cases appear to respond well to
potentiated sulphonamides
not effective if well-established purulent infection
fluoroquinolones
avoid unless c+s indicates
Enrofloxacin
effective in most cases, but may not eliminate the disease
s/c injections (esp if repeated) cause tissue necrosis/sterile abscesses
note effect on growth plates
oral product available
Marbofloxacin
alternative, some studies shown to be more effective
Most strains of Pasteurella also appear sensitive to ciprofloxacin, parenteral peni- cillin, tetracycline, gentamicin and chloramphen- icol. However, the effect on gut flora of some of these antibiotics (such as gentamicin) should be considered, as systemic use may not be appro- priate.
In cases of pasteurellosis, infection and clinical signs are often only suppressed, with disease recurring at any time of stress. Chronic or severe infections may need treatment for up to 3 months
Nebulisation
commonly used as a method of topical treatment alongside systemic antibiotics for both upper and lower respiratory tract disease.
A nebulizer should be chosen that is cap- able of producing particles <0.5 μm.
A wide range of drugs may be nebulized, including antibiotics, muco- lytics, bronchodilators + F10 disinfectant
antibiotics should be chosen that can penetrate the lipid barrier within the respira- tory system to reach an adequate concentration at the airway surface.
Fluoroquinolones
Tetracycline
azithromycin
metronidazole
saline alone may be useful to rehydrate the natural mucociliary escalator and remove bacteria from lungs
2 or 3 times daily for a period of 15 minutes is sufficient for most drugs.
Viral disease
Myxomatosis
Common signs include swell- ing around the eyes and genitals but upper respira- tory signs may also be seen.
euthanasia should be con- sidered owing to the poor prognosis
annual vaccine and good flea control recommended
Rabbit haemorrhagic disease
calicivirus
Rabbits <2 months of age appear resistant to the disease but may become long-term carriers
Older animals are normally found dead. There are often no ante-mortem signs but sometimes dyspnoea and haemorrhagic dis- charges from the nares and anus may be observed.
Diagnosis via post mortem
Haemorrhages in the lungs, liver and other visceral organs may be seen
euthanasia is advised
Herpesvirus
rare, but should be considered in group situations
Rabbits presented with dyspnoea, conjunctivitis, periocular swelling, anorexia, weakness, ulcerative dermatitis and abortion.
Neoplasia
Carcinoma and adenocarcinoma of the turbinates should be considered where bone destruction with or without proliferation is visible radiographically
LRT
only 1ry neoplasia reported is
pulmonary carcinoma
lymphosarcoma may affect the lungs and the mediastinal lymph nodes
mainly seen in young rabbits and can also involve other visceral organs including the liver, spleen and kidneys.
Lungs are one of the most common sites of metastases
usually 2ry to uterine adenocarcinoma in entire female rabbits
poor prognosis
Once clinical signs of dyspnoea are noted, euthanasia is advised as tx unsuccessful
consider thoracic radiographs if rabbit presents for lameness (as reports of hypertrophic osteopathy with some neoplasia)
Thymoma
gradual onset of dyspnoea and exercise intolerance as thymoma slowly increases in size and restricts size in the thoracic cavity
may present in acute respiratory distress with tachypnoea, dyspnoea and open-mouth breathing
bilateral exophthalmos, and head, neck and forelimb oedema may be seen as a result of impaired venous return to the heart
Both eyes can usually be retropulsed normally and without pain, but exophthalmos may be induced by ventroflexion
Thoracic radiographs most useful diagnostic aid
A rounded soft tissue opacity is gener- ally visible cranial to the heart. The trachea is often displaced dorsally and the lungs displaced caudally. Pleural effusion may be present
Bone marrow cytology may be useful if meta- static disease is suspected
surgical extraction
Intensive postoperative care, including a thoracotomy tube and excellent analge- sia, is require
Radiotherapy may be useful if the neoplasm appears invasive or as follow-up treatment after surgery. But, the proximity of the thymus to the heart and lungs will limit the radiation dose, and will predispose to side effects such as fibrosis and pneumonitis.
Respiratory irritation
smoke
cigarette smoke causes severe lung changes e.g. congestion, thrombosis and haemorrhage within lungs, emphysema and alveolar destruction
dust
household chemicals
wood shaving vapours
elevated ammonia levels from inadequate cleaning
Allergic rhinitis and bronchitis
Owners should be advised to place the rabbit in a well ventilated room or ideally outside if not too hot or cold. If severe dyspnoea is still present by the time of presentation, rabbits may be given supplementary oxygen and the administration of bronchodilators espe- cially by nebulization may be useful. Antihistamines have been used but their efficacy is uncertain.
Foreign bodies
sneezing, snuffling, unilateral nasal discharge
Forceps may be used to grasp the foreign body under endoscopic guidance and gently remove it. GA required. Antibiotic cover and NSAIDs will generally need to be provided owing to the resulting soft tissue trauma.
Aspiration pneumonia is possible but uncommon.
