What has Bordetella bronchiseptica infection got to do with cats?
Bordetella bronchiseptica is a bacterium which is now known to be a primary respiratory pathogen in cats. Bordetella bronchiseptica should be considered in all instances of feline upper respiratory tract disease (URTD) as a secondary or potential primary pathogen.
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Does B. bronchiseptica cause disease in other species?
B. bronchiseptica causes respiratory disease in several species including dogs where it causes tracheobronchitis (kennel cough), and pigs where it contributes towards atrophic rhinitis.
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Can Bordetella bronchiseptica cause URTD in cats by itself?
Yes. Studies have shown that B. bronchiseptica can cause clinical signs of upper respiratory tract disease (URTD) in experimental cats known to be free of all other known respiratory pathogens. In the field it is highly likely that B. bronchiseptica also causes URTD in combination with other respiratory pathogens eg FHV, FCV.
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What clinical signs are associated with B. bronchiseptica infection?
B. bronchiseptica associated URTD is a complex disease. There is a considerable overlap between the clinical signs seen with other agents that can cause URTD including FCV and FHV. In studies in cats in which B. bronchiseptica is known to be the only causative agent, clinical signs have included:
- fever
- sneezing
- nasal discharge
- submandibular lymphadenopathy
- coughing and
- rales
In most cats the disease is usually mild and signs normally disappear after about ten days. However, in some cats, particularly younger animals, it can develop into bronchopneumonia and be life threatening.
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How quickly do infected cats show clinical signs?
Research in SPF cats indicates that cats can demonstrate visible signs of infection within five days of exposure. On average, the duration of clinical signs will last 10 days. However, in clinical cases, particularly in young kittens, the disease may progress to more life-threatening bronchopneumonia. Some cats may become carriers and have been shown to shed bacteria for at least 19 weeks.
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Can the clinical signs of B. bronchiseptica infection resemble those of other feline respiratory pathogens?
Yes. The clinical signs are very similar and in some cases concurrent infection can occur.
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How is feline B.bronchiseptica infection diagnosed?
B. bronchiseptica infection is best diagnosed from oro-pharyngeal swabs, or from swabs of nasal discharge of affected animals. Samples should be taken using sterile cotton wool swabs placed into charcoal transport medium before plating on to a selective medium such as Bordet-Gengou. However, chronic carrier cats often shed relatively few organisms and may require repeated oropharyngeal culturing.
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What is the likelihood of cats being exposed to B. bronciseptica?
Serological surveys indicate that exposure in the feline population is quite common, with approximately one cat out of four being exposed to the bacterium. However, the risk of exposure is considerably greater for cats that frequently come into contact with other cats. As many as eight out of every ten cats are at risk of exposure if they come from multi-cat households, catteries or rescue shelters. Cats that are boarded in catteries or exhibited are similarly more at risk.
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How common is B.bronchiseptica as compared to other feline respiratory pathogens?
The relative contribution made by FHV, FCV and B.bronchiseptica towards feline URTD is unknown. In a UK survey of 740 convenience-sampled cats B.bronchiseptica was isolated in 11% of all cats sampled as compared to 26% for FCV and 5% for FHV. However, since many chronic carriers of B.bronchiseptica and FHV are missed by such sampling it is likely that these figures underestimate the incidence of these two pathogens.
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What factors predispose towards disease?
B. bronchiseptica is widespread in the feline population but is probably usually carried asymptomatically. A variety of host and environmental factors, particularly involving stressful conditions, may result in opportunistic disease. Hence, disease is most frequently associated with cats kept in breeding catteries or research facilities but may also occur in household cats taken to cat exhibitions, boarded in catteries or living in multi-cat households. During the stressful act of parturition, queens may pass B. bronchiseptica to their offspring, kittens obtained from breeding catteries and rescue shelters are therefore particularly at risk.
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Can individual cats act as carriers?
Long-term asymptomatic carriage of B. bronchiseptica commonly occurs in cats. Shedding of bacteria is associated with a variety of factors including stress such as that caused by weaning, visiting catteries, travelling to cat exhibitions, overcrowding in catteries or poor hygiene. It may also be related to phase variation in virulence determinants as seen in dogs and pigs. The importance of carrier cats has been confirmed in experimental studies where recovered cats have been shown to shed the organism for at least 19 weeks. In addition, the organism has been recovered post partum from clinically healthy queens kept under barrier conditions suggesting that the stress of birth can induce shedding .
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Can the bacterium spread from dogs to cats and vice versa?
Yes. Epidemiological evidence shows that the isolation of B. bronchiseptica from cats is frequently associated with the presence of dogs with recent respiratory tract disease in the same household. B. bronchiseptica infection in cats has been reported following reports of kennel cough in dogs within the same households. Furthermore, in one such case the isolates from the two species were shown, by molecular techniques, to be identical.
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Is the disease seasonal?
In general, no. The risk may, however, increase during holidays or vacation periods due to an increase in boarding and exposure to other cats. Shelters and catteries may see more severe problems in the winter because of decreased ventilation due to concerns of heat conservation.
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Are there any breed or sex predispositions for B.bronchiseptica?
There are no clearly demonstrated breed or sex predispositions. Some studies indicate that pedigree cats are more susceptible but this is possibly explained on the basis that these breeds are more likely to have originated in breeding catteries or be exhibited on a regular basis.
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What is the recommended treatment for B. bronchiseptica infection in cats?
B. bronchiseptica infection can be treated with tetracycline (10mg/kg PO q8h), doxycycline (10mg/kg PO q24h) or amoxicillin/ clavulonic acid (12.5mg/kg PO q12h). Resistance to trimethoprim and ampicillin is widespread. The latter is worth noting since ampicillin is commonly used to treat URTD in cats. There have also been reports of the emergence of tetracycline-resistant plasmids in B. bronchiseptica isolated from cats.
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How can the disease be prevented?
At present preventative methods are limited to avoidance of stress and hygiene in catteries. Removal of chronically-infected cats from affected catteries may also be considered. An intranasal vaccine is available in some countries and may be considered for use in preventing URTD outbreaks in catteries or to help prevent respiratory disease in cats which come into contact with other cats and dogs, are boarded at catteries or exhibited.
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