NEW BACTERIA DEPLETING FISH POPULATION IN CHESAPEAKE BAY

A new species of bacteria is the cause of a disease that is depleting the striped bass population in the Chesapeake Bay, say researchers at the University of Maryland College of Veterinary Medicine. They report their findings in the February 2001 issue of the Journal of Clinical Microbiology. In the early 1980s the Chesapeake Bay suffered a collapse of some of its fish stocks including the striped bass. Restrictions on fishing activity improved the fish populations in the early 1990s, but by the end of the decade there was again a noticeable decline in the striped bass population. After closely monitoring the health of the striped bass population, officials discovered that many of the fish suffered from systemic mycobacteriosis.

"This was the first time that mycobacteriosis had been detected in the Chesapeake Bay and represents the first reported case of mycobacteriosis in wild fish on the Atlantic coast," say the researchers, who have isolated the bacterium responsible and suggest that it is a new species of mycobacterium, the family of bacteria that is also responsible for tuberculosis in humans.

In fish, mycobacteriosis is a chronic, progressive disease and may take years to develop. Affected fish may lose their appetite and have impaired growth. In some cases skin lesions in the form of blisters or ulcers may develop. Although mycobacteriosis is an old disease and exists worldwide, there have been very few reports of its occurrence in the wild and very little is known about its prevalence and impact on wild fisheries.

"With the knowledge of the unique sequences in this new isolate, PCR assays can be designed for the specific identification of this isolate of Mycobacterium," say the researchers. This will enable investigation of future outbreaks as well as epidemiological studies to determine reservoirs of infection and possible routes of transmission.

(R.A. H
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Contact: Jim Sliwa
jsliwa@asmusa.org
202-942-9297
American Society for Microbiology
21-Feb-2001