Pneumonia in rabbits
Esther van Praag, Ph.D.
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Rabbits are sensitive to respiratory diseases. The most common have a bacterial or fungal origin, but they may also be secondary to viral diseases such as myxomatosis or rabbit. They can affect the upper respiratory tract (nasal cavity), or the lower respiratory tract (bronchia, lungs).
Numerous bacteria or microorganisms can infect rabbit lungs :
• Escherichia coli,
• Pseudomonas aeruginosa, Pseudomonas sp.,
• Staphylococcus aureus, Staphylococcus sp.,
• Streptococcus sp.,
• Francisella tularensis (tularémie)
• Yersinia pseudotuberculosis (pseudotuberculose),
• Vibrio fulnificus,
• Moraxella bovis,
• Bacillus sp.
A variety of infectious bacteria has also been observed in rabbits, such as Bordetella bronchiseptica and Pasteurella multocida; Pasteurella multocida and Escherichia coli; Escherichia coli and Bordetella bronchiseptica; Pasteurella multocida and Pseudomonas aeruginosa.
This diversity of bacteria makes that the frequently used designation of “pasteurellosis” is outdated and not reflecting the current knowledge.
Pneumonia is difficult to diagnose in rabbits. Clinical signs may be absent or limited to sneezing or a deep coughing that sounds similar to the barking of a dog. In other cases, the rabbit has a light nasal secretion, a lack of energy (lethargy) and a decreased appetite.
At an advanced stage, a rabbit can start to suffer from respiratory disease, with mouth breathing and fever.
Bacteria infecting the respiratory tract of the rabbit can spread to other parts of the body or organ and cause conjunctivitis, middle ear infection with torticollis, pleuritis (inflammation of the tissues surrounding the lungs), pericarditis (inflammation of the tissues surrounding the heart), pyometra, or testicular abscess.
If the infectious bacteria infiltrate the bloodstream, septicemia develops, which is usually fatal in the rabbit, even with an aggressive antibiotics treatment.
The autopsy of a rabbit deceased by pneumonia shows a reddish or grayish cranio-ventral congestion of the tissue of the lungs, which is typical of pneumonia in rabbits as well as the presence or absence of emphysema.
The following points should be checked when a respiratory infection is suspected::
1. Complete examin of the rabbit. Control of respiratory rhythm (30 to 60/min). A higher rhythm is normal, a lower rhythm is abnormal. Detect respiratory distress, or mouth breathing.
2. Carefully examine the presence of mucus in the nostrils. This is not always easy, as rabbits wash themselves meticulously and regularly. Sometimes the presence of wet and tangled fur on the front legs is observed, a possible sign of the presence of nasal mucus.
3. Complete blood examination (CBC) to discover hematological changes, such as increased neutrophil count (neutrophilia) or decreased white blood cell count (leukopenia). This examination allows also to check the function of the vital organs.
4. Chest X-ray, which detects the presence of bacterial infection (increased opacity), bronchitis, mass (abscess or neoplasia) or edema (abnormal accumulation of fluids around the lungs and of the heart).
5. Examine the head and facial bones to note irregularities such as the presence of a swelling, abscess. Check the presence of conjunctivitis or dacryocystitis (lacrimal gland infections) in the eyes.
6. If necessary, take a nasal and / or tracheal sample to make a bacterial culture. Ideally proceed on both sides when a sample is taken in the nostril, as an infection can be unilateral. Nasal sampling can be done using a swap with a calcium alginate tip mounted on a flexible wire, embedded at a depth of 1 and 4 cm into the nostrils or the nasopharyngeal region. An alternative method is a nasal aspiration.
7. Examine the ears for possible infections. An X-ray of the head may reveal an increased opacity of the middle and inner ear. Ear infections often accompany respiratory infections, as bacteria can migrate to the inner ear through the Eustachian tube.
Treatment of pneumonia is difficult. It must be long (at least 4 to 12 weeks) and aggressive and essentially aims to increase the quality of life of the rabbit. If pneumonia is mild, oral administration of enrofloxacin or ciprofloxacin, accompanied by nasal drops of gentamicin, may help in the recovery of the rabbit.
Trimethoprim sulfadiazine is a bactericidal antibiotic often used in the treatment of disorders of the gastrointestinal and urinary system. It is effective against many bacterial infections that affect rabbits, such as Pasteurella sp., Clostridia sp., Staphylococcus sp., Bordetella sp., etc. It can be used for a long period of time, at reduced dosis. This antibiotic does, however, have poor result in rabbits and often the disease relapses in an aggravated form after discontinuation of the treatment. This may be due to the fact that the half-life of trimethoprim in rabbits is only 40 minutes.
Azythromycin, a modified erythromycin which does not cause side effects in rabbits, is very effective in the treatment of Bordetella sp. (as well as enrofloxacin). The dosage of azythromycin used in rabbits (50mg/kg PO QD (SID)) is much higher than that used in other small animals, such as dogs or cats (5-8 mg/kg). The treatment usually lasts between 7 and 10 days, after which an evaluation is made and a possible prolongation of the treatment is envisaged.
Cephalosporins are broad-spectrum antibiotics used to treat bone, genitourinary, soft tissue and respiratory tract infections (associated with Pasteurella sp.). There are several generations of cephalosporins, and each is targeted against specific groups of bacteria. Although these antibiotics are mostly safe for the rabbit (injected only), they are potentially nephrotoxic.
Treatment against Pseudomonas sp., one of the most difficult bacterial infections to treat, must be aggressive. A sensitivity test must be performed as this bacterium is resistant to many antibiotics. Treatments include a combination of antibiotics, such as:
• Enrofloxacine + gentamycin nasal drops,
• Enrofloxacine + nébulisation with amikacin (if located in the upper respiratory airways enrofloxacine + doxycycline),
• Céphalosporine/tobramycine (both injected only).
Azythromycine does not help in case of a Pseudomonas sp. infection.
Further antibiotics, safe for use in rabbits that have shown good results in the treatment of respiratory tract disease, include:
For more information, see: Antibiotics *safe* for use in rabbits
Aside a longer systemic antibiotic therapy, additional therapy comprises:
· Nasolacrimal flushes;
· Nebulization with a saline solution, mucolytics and antibiotics help bring the medication deep in the bronchia and lungs in cases of rhinitis, sinusitis or pneumonia;
· Fluid therapy and assisted force-feeding, when the rabbit refuses to drink and eat.
If the respiratory disease is accompanied by conjunctivitis and/or dacryocystitis, local antibiotic therapy (e.g. enrofloxacin, gentamycin) must accompany the treatment protocol
Un grand merci au Dr. Estella Böhmer (Chirurgische u. Gynäkologische Kleintierklinik, Ludwig-Maximilians-Universität München, Germany), à Michel Gruaz (Suisse), à Kim Chilson (USA) et à Tal Saarony (USA) pour la permission d’utiliser leurs photos. Un grand merci à Debbie Hanson. Sans son aide, temps et expertise, ces vidéos au sujet de la nébulisation d’un lapin n’auraient pas pu être réalisées. Un grand merci aussi à Rachel Ihlenfeldt et son lapin Bunbun pour la démonstration des différentes techniques.
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