Wrong Bacteria Framed for Oyster Disaster

For the last several years, large oyster hatcheries in the Pacific Northwest were thought to be facing massive declines due to infections of the bacteria Vibrio tubiashii. Now researchers are saying that experts may have framed the wrong guy, with the real bacterial killer still on the loose.

The oyster die offs began back in 2005, when dramatic losses were first seen in Netarts Bay, Oregon. These mass deaths soon moved to other oyster hatcheries in the northwestern United States, hitting the industry hard for the next several years.

Since then, thanks to tighter controls of factors like water acidity, the hatchery industry has largely recovered. However, it is now a near certainty that the suspected killer, Vibrio tubiashii, may have been the victim in a classic case of relative mix up.

That's because a new study published in the journal Applied and Environmental Microbiology details how V. tubiashii did not show significant pathogenicity to Pacific oysters. However, the bacteria's close cousin, Vibrio coralliilyticus, proved highly infectious, even boasting a mortality rate similar to that seen during the hatchery die-offs.

So how was this missed? V. coralliilyticus didn't really fit the profile, as it isn't known to be an oyster killer.

"V. coralliilyticus was believed to primarily infect warm water corals and contributes to coral bleaching around the world," researcher Claudia Häse explained in a recent statement. "It shares some gene sequences with V. tubiashii, but when we finally were able to compare the entire genomes, it became apparent that most of what we're dealing with in the Pacific Northwest is V. coralliilyticus."

This means that the stomping grounds of this true killer are far more widespread than previously believed, and its taste in victims is far more diverse.

"Although we've largely addressed the problems the hatcheries face, these bacteria continue to pose threats to wild oysters," Häse added.

And that's worrisome, as "V. coralliilyticus, in particular, has a very powerful toxin delivery system, and vibrios are some of the smartest of all bacteria. They can smell, sense things and swim toward a host."

The researcher and her colleagues argue that better and more accurate diagnostics could help researchers avoid future suspect mix-ups, and get the jump on other killers.