Respiratory Disease in Rabbits
John Chitty BVetMed CertZooMed MRCVS
Anton Vets, Anton Mill Road, Andover, Hants SP10 2NJ UK
[email protected]
Unfortunately, the rabbit’s respiratory anatomy predisposes to disease:
 Narrow nostrils. These are very sensitive with many vibrissae
 Narrow nasal airways with large amounts of secretions, both mucous and
serous. These are produced by glands along the septum and the lateral nasal
gland that occupies the wall between the nasal cavity and maxillary sinus.
 The purpose of the mucus is to protect respiratory membranes, prevent water
loss and to enhance the sense of smell by trapping molecules where they can
contact chemoreceptors.
 Serous discharges moisten air
 Conchal and maxillary sinuses are present though there is no frontal sinus.
 The narrow oropharynx and large tongue base result in difficulty in mouth
breathing.
 The larynx is narrow and the trachea has complete cartilaginous rings.
 The lung anatomy is similar to that in other mammals. The thoracic cavity is
small with an anteriorly placed thymus gland
 Respiratory movements stem mainly from the diaphragm.
History
When investigating any clinical problem it is vital to take a good clinical history. The
following are particularly relevant when investigating respiratory problems:
 Signalment. Age, gender, breed, etc
 When purchased?
 Have any other rabbits been introduced recently? Where were they obtained
from?
 Onset of symptoms. Have symptoms changed since onset?
 Previous episodes and previous disease history
 Other affected rabbits?
 Vaccine status
 Husbandry: inside/ outside? Bedding? Feeding? This is very relevant as
bedding and substrates can play a major role in respiratory disease. Hay or
straw may be dusty and irritate respiratory membranes and allergy is possible.
Similarly they are also sources of nasal foreign bodies. Wood-based substrates
may contain aromatic chemicals that may irritate membranes or may produce
irritant chemicals when contacting urine. It is also important to find out how
often bedding is changed, when it was last done and whether a new type is
being used. When dealing with respiratory disease in rabbits (either upper or
lower respiratory tract disease I will usually recommend a change to paper
bedding)
 Ability to exercise. Fat rabbits may suffer further chest compression.
Restriction to a hutch may keep them in contact with the factors mentioned
above than is ideal.
Examination
A full clinical examination is essential. This should start BEFORE the rabbit is
handled, ideally while a history is being taken:
1. Observation. Either watch the rabbit in its carrier or let it hop around the
consulting room, taking care that it can neither escape nor harm itself! The
following should be observed:
a. Attitude
b. Head position
c. Respiration rate (30-60/ minute normally) cf nasal twitches (2120/min).
d. Respiratory effort and noise
e. Presence of discharge from nose/ eyes
2. Examination. Consider the ease of handling dyspnoeic rabbit. It may be
worth cleaning blocked nostrils first so the rabbit can breathe easier.
a. Body condition
b. Full clinical examination
i. Oral examination, including membrane colour and examination
of teeth
ii. Aural examination
iii. Assessment and collection of nasal/ ocular discharges. Always
remember to check the front legs for evidence of the famous
“carpal handkerchief”!
iv. Ocular examination
v. Auscultation of chest
vi. Abdominal palpation
c. Assessment for anaesthesia. This is important as, firstly, the
examination may be a pre-anaesthetic check and, secondly, many of
the diagnostic tests required may need to be performed under general
anaesthesia
3. Preparation for Anaesthesia
a. Preliminary therapy. In many cases, if anaesthesia can be delayed it
may be ideal to give supportive care in the form of antibiosis, antiinflammatories, and fluids prior to anaesthesia.
b. Cleaning/ flushing of nostrils enable easier breathing.
c. Support feeding and fluids
d. Conscious capnography appears to give a reasonable assessment of
lung perfusion (and hence efficiency)
4. Further tests
a. Haematology/ biochemistry? These may show underlying renal or
hepatic disease. Haematology may indicate inflammation/ infection
although changes are often in white cell morphology rather than
counts.
b. Serology. Antibodies to the following may be measured. It is important
to remember that this indicates exposure rather than actual disease
(although paired quantitative titres may be helpful).
i. Encephalitozoon cuniculi. This is not a respiratory pathogen.
However, affected rabbits may be run-down and more
susceptible to respiratory disease. Similarly, sick rabbits may
show recrudescence of encephalitozoonosis
ii. Pasteurella multocida. See later.
c. Radiography. Of thorax and head. Lateral and dorso-ventral views of
each are recommended
d. Ultrasonography. This may be of use when radiography indicates a
mass in the thorax or cardiomegaly.
e. Bacteriology. Although Pasteurella multocida is frequently isolated as
a cause of respiratory disease, it (like many of the other bacteria
implicated) may be found as a commensal in both upper and lower
respiratory tract. When there are few actual pathogens likely to be
detected, bacteriology may be deemed not to be of great importance
especially when bacterial resistance is relatively uncommon amongst
those organisms that are usually found. However, bacteriological
investigation should be carried out when:
i. Logical antibiotic therapy is not successful and underlying
causes are controlled.
ii. In outbreaks of respiratory disease in colonies or groups.
Deep nasal swabbing techniques should be employed using micro
swabs. This may avoid some bacterial contamination from the skin or
nares. This may be done under anaesthesia or in the conscious rabbit
after a drop of local anaesthetic solution (without adrenaline) has been
introduced via the nostril..
Bacteriology of lung wash samples may be performed in cases of
lower respiratory disease.
f. Cytology. I have found this of little use in cases of upper respiratory
tract disease. However, cytology of lung wash samples does give
valuable information.
g. Endoscopy of the nasal cavity is useful in determining the extent of
damage to the turbinates (useful for determining prognosis) and may
enable detection of nasal foreign bodies
h. CT/MRI. These advanced imaging techniques may be extremely
valuable. However, cost and availability will limit their use.
Diseases
Non-respiratory disease
Some diseases may produce signs that mimic respiratory disease:
1. Those that produce discharges blocking nostrils/ airways; eg. dacryocystitis,
dental abscesses
2. Those that occlude nostrils; eg treponemiasis, tumours, abscesses
3. Those that compress the thorax; eg tumours, bloat
4. Cardiac disease
5. Heat stroke
Underlying Factors
Many of the infections seen in this system occur as the result of various underlying
factors or diseases
 Husbandry
o Irritants (see above)
o Allergens
o Foreign Bodies
 Dental disease
 Anatomical abnormalities
 Previous respiratory infection
 Stress
Myxomatosis
This viral infection will certainly produce respiratory signs due to swelling of the
nares. In intensive systems a pneumonic form may be seen.
In cases where there is nasal and/ or ocular discharge myxomatosis should be
considered. There will usually be concurrent swelling of the ears and genitalia or the
disease will become progressively worse in spite of therapy.
Pasteurellosis
Primary disease or secondary?
Various factors determine this:
1. Virulence factors of the organism, Pasteurella multocida. These include
adhesins, resistance to phagocytes, endo- and exo-toxin production, iron
regulation and production of filaments (pili) to assist binding to membranes.
2. Host resistance
There are various subtypes of this organism. These are categorised according to their
Capsule Type (A-F) and capsular antigen. Type A is generally more adhesive to
respiratory membranes but Type D appears more pathogenic.
Type A appears the most common isolate (12:A in snuffles; 3:A, 3:D in pneumonia)
However, all types may be found in normal rabbits!
Consequences of infection with Pasteurella multocida may therefore range from
elimination of the organism with no disease, induction of a carrier state, or disease
(localised to generalised; acute to chronic).
Once the respiratory system has been colonised, organisms may disseminate to other
sites in the body. A frequent route is via the Eustachian tubes to the middle ear. It is
therefore essential to radiograph the tympanic bullae in cases of upper respiratory
infection.
So, if you culture Pasteurella multocida from a rabbit (deep nasal swabs should
always be used)?
1. Healthy rabbit. Of no consequence unless being brought into a disease-free
colony
2. Diseased rabbit. This may be a significant factor in respiratory disease, but in
the older pet rabbit underlying disease processes (see above) should not be
forgotten.
Serology: useful in screening rabbits before entering a colony. Also useful in
determining pathogenicity of organisms in a colony disease outbreak. However, of
little value in older pet rabbits as most will have encountered the organism at some
stage in their lives and will have antibodies to it; little clinically relevant information
will be derived.
Other Bacteria
Recent studies have shown that, in the pet situation, Pasteurella multocida may no
longer be the most frequent isolate in disease. Other bacteria including
Staphylococcus spp and Bordetella bronchiseptica are also found.
The fact that these are also found commonly as commensals illustrates the importance
of underlying factors in the development of respiratory disease and that the bacteria
often merely represent secondary invaders.
Pseudomonas spp have also been isolated from cases of upper respiratory disease.
This is not a normal commensal nor a primary pathogen. Nonetheless it is an
important finding as it shows contamination from the environment and can be very
difficult to treat.
Other therapies may also be needed in the treatment or management of respiratory
disease:
1. Nebulisation. This can range in complexity from simply placing the rabbit in
a steamy room, using bowls of steaming water (Olbas Oil may be useful in
these situations, but care should be taken not to overdose or make too
concentrated) to use of a commercial nebuliser to deliver antimicrobial drugs.
This may have beneficial effects due to:
a. Expectorant effect. Improves clearance of discharge.
2.
3.
4.
5.
6.
7.
b. Hydration of mucous membranes. Improves local immunity and
increases resistance to bacterial invasion. Both (a) and (b) make the
patient “feel better”.
c. Direct delivery of drug to diseased areas although there is debate
whether drugs will penetrate consolidated areas of the lungs or pusfilled cavities in the nose.
In the author’s clinic F10SC (Health & Hygiene Pty) is used at a dilution of
1:250. This is nebulised for thirty minutes twice a day and many rabbits with
mild signs have been managed using nebulisation alone.
Nasal Flush. Physically introducing drugs into the nasal cavity. Again effects
may be due to
a. Physically removing discharges/ foreign bodies/ etc
b. Instillation of drug into diseased areas, eg sinuses (if maxillary or
frontal sinusitis are identified as problems, needles may be drilled into
the sinus and the region irrigated/ flushed with dilute F10)
Again, the author uses F10SC. A dilution of 1:250 is used with 0.5ml being
introduced into each nostril.
Non-steroidal Anti-Inflammatory Drugs (NSAIDs). Pain and inflammation
are often features of respiratory disease and/or many of the conditions that
may underly respiratory disease.
Mucolytic drugs may aid clearance of discharges.
Supportive Care
a. Gut motility agents. If gut stasis is a feature of the overall condition
b. Supportive feeding, especially if the rabbit is thin and/or anorexic.
Care must be taken when force-feeding dyspnoeic rabbits.
c. Rehydration. Oral or systemic depending on severity. The dehydrated
rabbit will have dry mucous membranes enabling easier bacterial
invasion.
d. Cleaning of discharges especially round the nares.
Oxygen Therapy. In cases of acute respiratory disease supplemental oxygen
may be useful.
Immunostimulants. I have used Propolis and the herbal form of Echinacea in
some chronic cases with some apparent benefit.
Further reading
Harcourt-Brown, F 2002 Textbook of Rabbit Medicine. Butterworth-Heinemann,
Oxford, UK
Oglesbee, BL 2006 The 5-minute Veterinary Consult; Ferret and Rabbit. Blackwell,
Ames Iowa US
Krautwald-Junghanns, M-E; Pees, M; Reese, S; Tully, T 2011. Diagnostic Imaging of
Exotic Pets. Schlutersche, Hannover, Germany