Abstract
Bordetella bronchiseptica is a well-recognized, respiratory pathogen of many mammalian species and frequently co-infects the nasal cavity and upper airways of many species along with other pathogens to cause respiratory diseases like atrophic rhinitis in pigs, acute infectious tracheobronchitis in dogs and cats, and upper respiratory tract infections in rabbits.1 Though not previously directly associated with clinical signs of disease in seals, B. bronchiseptica has been previously isolated from harbour seals, grey seals, and Caspian seals.1,4,5 A novel clone of B. bronchiseptica was characterized in seals by ribotyping and restriction endonuclease activity.2 Harbour seal pups at the Vancouver Aquarium's Marine Mammal Rescue Centre frequently present with respiratory disease, including lungworm infections. Bacterial bronchopneumonia is prevalent in stranded harbour seals and commonly occurs secondary to infestation with Otostrongylus circumlitus.3 Between October and November 2013, 12 of 14 harbour seal pups undergoing rehabilitation at the Vancouver Aquarium's Marine Mammal Rescue Centre developed a dry, non-productive cough. Some affected animals demonstrated nasal discharge in conjunction with frequent coughing. Nasal swabs were collected from all 14 harbour seals at the rescue centre for aerobic culture when affected seal pups developed a cough. B. bronchiseptica was isolated from nasal swabs of 5 of the 12 affected animals, while no B. bronchiseptica was isolated from the nasal swabs of the other 9 animals. Susceptibility to doxycycline was confirmed. Eleven seal pups exhibiting a cough were treated orally with a 10-day course of 10-mg doxycycline per kg of body weight every 12 hours. All animals responded to initial treatment with the exception of one seal, whose clinical signs fully resolved after two separate 10-day courses of doxycycline. Nasal swabs and cultures were repeated on the 14 seals upon completion of doxycycline and resolution of clinical signs. Thirteen of the 14 swabs yielded no B. bronchiseptica. One swab from a previously treated, asymptomatic seal yielded B. bronchiseptica. Twelve of the 14 seals were released, and 5 of those 12 were equipped with satellite-linked transmitters for tracking, including the animal with a Bordetella-positive follow-up nasal swab. All of the tracked animals appeared to exhibit normal post-release distribution and habitat use. To the authors' knowledge, this is the first reported outbreak and successful management of bordetellosis in a group of phocid seals. Though likely a normal part of the flora of the harbour seal respiratory tract, B. bronchiseptica may, under certain conditions, cause opportunistic respiratory disease in phocid seals. Timely diagnosis, appropriate therapy, and careful management can result in successful resolution of an outbreak.
Acknowledgements
The authors wish to thank Sion Cahoon, Taryn Roberts, Kate Cooper, Chelsea Roberts, and all of the volunteers at the Vancouver Aquarium's Marine Mammal Rescue Centre who helped to collect swabs, process samples, and collect data for this study. We would also like to thank the laboratory technicians at IDEXX Laboratories for processing samples submitted for this study.
* Presenting author
+ Student presenter
Literature Cited
1. Goodnow RA. Biology of Bordetella bronchiseptica. Microbiol Rev. 1980;44:722–738.
2. Register KB, Sacco RE, Foster G. Ribotyping and restriction endonuclease analysis reveal a novel clone of Bordetella bronchiseptica in seals. J Vet Diagn Invest. 2000;12:535–540.
3. Dunn JL, Buck JD, Robeck TR. Bacterial diseases of cetaceans and pinnipeds. In: Dierauf LA, Gulland FMD, eds. CRC Handbook of Marine Mammal Medicine. Boca Raton, FL: CRC Press LLC; 2001:309–335.
4. Baker JR, Ross HM. The role of bacteria in phocine distemper. Sci Total Environ. 1992;115:9–14.
5. Kuiken T, Kennedy S, Barrett T, Van de Bildt MWG, Borgsteede FH, Brew SD, Codd GA, Duck C, Deaville R, Eybatov T, Forsyth MA, Foster G, Jepson PD, Kydyrmanov A, Mitrofanov I, Ward CJ, Wilson S, Osterhaus ADME. The 2000 canine distemper epidemic in Caspian seals (Phoca caspica): pathology and analysis of contributory factors. Vet Pathol. 2006;43:321–338.