Abstract

During the summer months of 1975/1976, an outbreak of Pseudomonas pseudomallei occurred in dolphins, pilot whales and harbor seals. A total of 25 dolphins, 4 pilot whales and 5 harbor seals died from this disease. This report is composed of the background investigations, the necropsy reports and the development of an oral vaccine. The report also includes the public relation aspect in a multi-lingual society.

Notes

Pseudomonas pseudomallei exists in the soil and enters the zoo environment via fertilizers. Playgrounds in Hong Kong yield cultures of Pseudomonas to which Hong Kong children are resistant but to which European children likely are susceptible. Eighty-five to 90 percent of Australian race-track horses carry P. pseudomallei. Positive titers for this disease have been found in the people of Hong Kong.

P. pseudomallei enters the aquatic park in fertilizer, on farmers' boots and in fish fed to the animals. To minimize the numbers of bacteria entering, disinfectant baths should be set up and zookeepers must not sell infected feces as fertilizer. Also, when cutting fish at feeding time, the knife should periodically be sterilized.

This disease is very species specific. It can kill Tursiops in three hours, though it is but a secondary invader. Harbour seals often die within a month after onset of clinical signs. Sea lions are quite resistant to the organism.

When acute death occurs, few lesions are seen. With subacute death, gastritis may be evident. Abscesses can be seen in the liver and lung of the harbour seal. Since the seal is a bit resistant to the disease, these abscesses have time to form.

Treatment with Tobramycin at 16 mg/kg tid for as long as 3-4 weeks is indicated. Pseudomonas can change its sensitivity and resistance factor within three weeks, however.

A vaccine which doesn't kill dolphins can be made. The polysaccharides of Pseudomonas are not antigenic but if the cell wall is cleaved, the RNA and DNA are exposed and they have much antigenicity.

Note

When vaccinating for Erysipelas, a killed vaccine should be used.