GLIN==> Scientists Find Bird and Human E. coli in Wild Fish

["Marie E. Zhuikov" <mzhuikov@d.umn.edu>]

                        MN SEA GRANT
                        NEWS RELEASE
7/1/08
Contact: Marie Zhuikov, mzhuikov@umn.edu, (218) 726-7677

        Scientists Find Bird and Human E. coli in Wild Fish

Scientists at the University of Minnesota have found that some of the 
potentially harmful bacteria in the Duluth-Superior Harbor come from an 
unlikely source: the fishes. It's not the fishes' fault, though. They 
are just carrying around bacteria that are already in their environment.

University of Minnesota researchers Dennis Hansen, John Clark, Satoshi 
Ishii, Michael Sadowsky, and Randall Hicks are the first to discover 
the sources of E. coli (Escherichia coli) in several species of wild 
fish. They collected carp, brown bullheads, Eurasian ruffe, round 
gobies, white perch, and rock bass from the Duluth-Superior Harbor as 
part of a Minnesota Sea Grant-funded study to determine the sources of 
bacteria that result in local beach closures.

In a peer-reviewed paper recently published in the Journal of Great 
Lakes Research, the scientists describe that most of the E. coli were 
found in bottom-dwelling fishes (brown bullheads, ruffe, carp, and 
round gobies) and the genetic matches were most similar to E. coli 
found in bottom sediments, Canada geese, mallard ducks, and human 
wastewater. The researchers didn't test the bacteria for pathogencity.

"We didn't find the bacteria in the fish meat  -- it's carried in their 
intestine," said Randall Hicks, biology professor at the University of 
Minnesota Duluth. "Anglers shouldn't worry about using the fish as 
food. They should just be careful not to cut open a fish's intestine."

If an angler happens to cut open fish intestines during cleaning, Jeff 
Gunderson, associate director with Minnesota Sea Grant, suggests they 
thoroughly wash the fish with clean water and cook it fully.

E. coli is an indicator of potential pollution. Levels of it are used 
to determine whether local beaches should be posted with "no water 
contact" advisories. There are a variety of types of E. coli. The most 
worrisome for humans is usually the E. coli from other humans (often 
from sewage overflows). While many strains are harmless, some cause 
gastrointestinal illnesses. Symptoms include vomiting, diarrhea, or 
other more serious conditions people would not want as a reminder of a 
fun day at the beach.

"Fish probably acquire E. coli when they eat food contaminated with 
feces," said Hicks. Researchers don't expect E. coli to flourish in 
cold-blooded fish, since the bacterium is more common in warm-blooded 
animals. "However, it is possible that fish may reintroduce E. coli 
bacteria into waterways when they excrete their own waste," Hicks said.

"Currently, it's probably more appropriate to consider fish as carriers 
of E. coli from other sources, rather than a new source of 
contamination in our waterways," Hicks added.

Until 1966, E. coli was thought to survive only in warm-blooded animals 
such as birds and mammals but it has since been discovered in the 
intestines of wild fish. The source of the bacteria in these 
cold-blooded animals was thought to be from polluted water and food, 
but researchers did not attempt to trace it.

Subsequently, E. coli was discovered in the intestines of farm-raised 
tilapia and rainbow trout. The fish were not the source for the E. 
coli, rather, the suspect was their food, which had been contaminated 
by pigeon droppings.

For more information on this project, order the free journal article: 
Sources and Sinks of Escherichia coli in Benthic and Pelagic Fish, from 
Minnesota Sea Grant by visiting 
http://www.seagrant.umn.edu/publications/JR544 or calling (218) 
726-6191. Ask for JR 544.
                                       ###

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