Tuesday, July 27, 2010

Sharks Bite Back Without Biting: study finds deadly bacteria

With only a few days remaining before the start of Discovery Network's annual Shark Week, circulating through several news agencies (even Discovery's own Discovery News) is word of a new wrinkle in shark predatory behavior, a new weapon in its arsenal as it were: deadly bacteria.

Detailed in an article in the Journal of Zoo and Wildlife Medicine, a study was conducted by researchers who examined nearly 200 of seven different species of shark (and one species of redfish) from Martha's Vineyard in Massachusetts to the Florida Keys, the Louisiana coast, and south to Belize. Taking swab samples from the fishes' cloaca (its genital opening), strong evidence of deadly Staphylococcus and E. coli along with a host of other bacteria was found. These are bacteria that are life-threatening as they have become highly drug-resistant over the years - one of the side effects of man's extensive use (some might say overuse) of antibiotics.

Drug-resistant diseases and bacteria have been an issue with the medical community for some time, but here is a documented study showing transference of these microbes to fish. The question is: how did they get there?

As reported in Discovery News, one of the researchers, Jason Blackburn at Florida Atlantic University, has some theories.
"Drugs given to humans could simply be excreted and eventually find their way into the ocean. Or bacteria in humans could acquire the resistance, be excreted, and then colonize fish that sharks eat, or the sharks, themselves. Some antibiotics are routinely dumped into aquaculture to help prevent infections -- that could be a source for some of the resistance."

The bacteria apparently is causing no harm to the sharks; perhaps the sharks are acting like host carriers, as occurs with other animals. But due to the drug-resistant nature of these bacteria, the
potential for harm to man by casual contact or perhaps through eating raw meat can not be discounted. The research team plans on another study to investigate that aspect of the problem.

Today, we are learning more and more about the way in which pollutants like methylmercury and other toxic substances can work their way up through the food chain and often collect in surprisingly strong levels in many of the ocean's large predators including sharks, tuna, dolphins and more.

"You don't expect to see multi drug resistance from these animals because they shouldn't be exposed to antibiotics," said Adam Schaefer, a co-researcher involved in the study. "These animals are at the top of the food chain; they reflect everything that's going on beneath them."

When I dive with sharks, I'm less concerned with their teeth than with their overall attitude and posturing. Looks like now I'll have to check to see if their running a temperature.

Read an abstract from the study in the Journal of Zoo and Wildlife Medicine.
Read the
article from Discovery News.

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