Respiratory disease (Proceedings)
Rabbits with respiratory disease may present with a variety of clinical signs. These may be as subtle as a mild to moderate amount of discharge matted on the medial aspect of the forepaws. This is a result of the rabbit's fastidious grooming behavior of cleaning its face with its forepaws.
Respiratory disease can be caused by bacterial and viral organisms, nasal foreign bodies, neoplasia and heart disease. The most common bacterial etiology is Pasteurella multocida (Harcourt-Brown, 2002). However, other organisms such as Staphylococcus aureus, Enterobacter sp., and Pseudomonas aeruginosa are not uncommon pathogens cultured from rabbits' respiratory tracts. Bordetella bronchiseptica has been reported as a common inhabitant of the rabbit respiratory tract that doesn't usually cause clinical disease (Deeb, 1997). This author has seen rabbits with significant upper and lower respiratory tract disease whose deep nasal and tracheal wash cultures produced a pure growth of Bordetella bronchiseptica. Explanations for this could include the possibility that the rabbits were immune compromised by some other condition, the Bordetella was dominating the culture and other organisms were not able to proliferate, or that Bordetella truly is a primary pathogen of rabbits.Bacterial infections of the upper respiratory tract are usually characterized by a mucopurulent discharge from one or both nasal passageways. Since the modern-day rabbit owner is usually very vigilant, rabbits may present to the veterinarian at the earliest signs of disease such as an increase in sneezing. At such an early stage of infection the discharge may not be evident on the nose or even on the forepaws. However, close examination of the nasal passageways with an otoscope cone often reveals the discharge. Culture of the discharge alone is often not fruitful in diagnosing the causative agent. A deep nasal culture provides the best specimen. Micro-tipped culturettes are very useful for this purpose. The culturette should be inserted at least 2cm into the nasal cavity. Holding the rabbit in such a manner that it is on its back and slightly tranced, or by using light sedation are two ways to make this feat possible. An otoscope also may be used to explore the rostral aspect of the nasal passageways if the practitioner suspects that an upper respiratory tract infection is being caused by a nasal foreign body. It is not uncommon for a rabbit to get hay or hair up its nose. Until the foreign body is found and removed, treatment will be futile. Rabbits with nasal foreign bodies often present with very copious mucopurulent discharge, especially from the offending side. They also tend to paw at the side of their nose and sneeze forcefully. If a foreign body is not recognized on the initial cursory exam with an otoscope and the rabbit has a persistent, intractable URTI exploration of the nasal passageways with a rigid endoscope is indicated and often very useful.
Bacteria also can be responsible for abscesses in the rabbit's chest. These can be very large in size and compromise the lung capacity significantly. Clinical signs may be only tachypnea and a mild to moderate decrease in activity level. If heart sounds are not audible on one or both sides of the chest upon auscultation, a chest abscess or neoplastic mass should be considered as differentials.
Therapeutic agents for the treatment of respiratory infections in rabbits must be considered carefully. Severe dysbiosis and life threatening enteritis can occur if the wrong antibiotic is chosen. Safe antibiotic choices include the fluoroquinolones, enrofloxacin and ciprofloxacin at 5-10mg/kg PO, SQ BID, chloramphenicol at 50mg/kg PO TID, tribrissen at 30mg/kg PO BID, azithromycin at 50mg/kg PO QD X 10-14 days (Plumb, 2002) and parenterally administered penicillin at 42,000-84,000IU/kg SQ, IM q 24h (Carpenter, 2001).
A very useful adjunct to systemic antibiotic therapy is the use of nebulization. Antibiotics, a mucolytic agent, a broncodilator and saline can be combined for this therapy. The following recipe has been very useful: 5ml of saline, 0.25cc of 20% acetylcysteine, 0.5cc of amminophylline (25mg/ml), and 1ml of amikacin. The rabbit is nebulized with a mask over its nose. This treatment can be repeated every 4-12 hrs. Even the most distressed rabbits seem to tolerate this treatment quite well.