Abstract
Burkholderia (formally Pseudomonas) pseudomallei, the causative agent of melioidosis, has caused considerable mortalities in
cetaceans at Ocean Park especially in the 1970s and 80s. The bacterium is mainly indigenous to South-East Asia and Northern Australia although it is sporadically
isolated from Europe, Central & South America, Africa, Middle East and India.
Melioidosis affects a wide range of species with a preponderance of infections occurring during the rainy or wet season. In the earlier years
of the park, the clinical syndrome was an acute septicemia resulting in sudden death. In recent years the disease has presented as a more chronic and debilitating
syndrome, characterized by abscess formation in virtually any organ system. Research carried out since the early 1980s at Ocean Park have included epidemiological
studies, serological examinations, specific media for isolation of the bacterium, appropriate and effective therapy and a protein-polysaccharide vaccine3
which has been used at the park since 1987.
Burkholderia pseudomallei is a gram-negative, nonacid fast, non-sporebearing rod which shows characteristic bipolar staining. The
organism has been isolated from aerosol adjacent to the cetacean holding facilities during typhoons and can infect its host via the respiratory route, ingestion
or wounds and abrasions. It may remain quiescent in infected individuals for many years, and factors that reactivate dormancy probably include environmental
variables, stress and immunological status2. BurkhoMeria pseudomallei could be a serious threat to cetaceans in endemic areas and awareness of
this disease is important although it appears that improvements in facilities, husbandry practices and the implementation of a preventative medicine program have
decreased the prevalence of the disease at Ocean Park.
Acknowledgments
The authors wish to thank the staff of Ocean Park Laboratory for their contribution to this work.
References
1. Dance DAB. 1991. Melioidosis: The Tip of the Iceberg? Clinical Microbiology Reviews Vol. 4 No. 1:52-60.
2. Leelarasamee A, S Bovornkitti. 1989. Melioidosis: Review and Update. Reviews of Infectious Diseases Vol. 11 No. 3:413-425.
3. Vedros NA, D Chow, E Liong. 1988. Experimental vaccine against Pseudomonas pseudomallei infections in captive cetaceans.
Disease of Aquatic Organisms Vol. 5:157-161.