Assay aims to solve oyster toxin problem

11-Jun-2013 - Last updated on 12-Jun-2013 at 07:21 GMT

Oyster larvae have been threatened by a bacterial disease. (Photo by Lynn Ketchum, courtesy of Oregon State University)

An assay has been developed to detect a disease which caused millions of dollars in losses to the oyster industry a few years ago.

The assay can detect the toxin secreted by Vibrio tubiashii, a bacterial disease that caused devastation in the Pacific Northwest in 2007.

The aim, when it is perfected and commercialised, is to give oyster growers an early warning sign to tell when they have a problem with high levels of the toxin and actions is needed.

When the bacteria and the toxin it produces reach unacceptably high levels, they can kill the tiny seed oysters before they have a chance to grow, according to scientists in the College of Veterinary Medicine at Oregon State University.

Work still to do

“We still need to improve the sensitivity of the test and better quantify results, but it should provide information in about 30 minutes that used to take three or four days," said Frances Biel, a faculty research assistant in the OSU Department of Biomedical Sciences.

"That type of rapid detection will let oyster growers know they have a problem while they can still do something about it."

Besides oysters, this bacteria and toxin can also affect shrimp, clams and other marine species important to aquaculture.

"Shockingly little was known about V. tubiashii at first, and the toxins that it produces," said Claudia Hase, an OSU associate professor of veterinary medicine.

"It secretes a zinc-metalloprotease compound that's toxic to shellfish, and that's what our new assay is able to detect."

Test approach

The new assay uses a "dipstick" that has proven superior to another approach which was tested, and conceptually it's similar to a human pregnancy test. It uses monoclonal antibodies that recognize the particular toxic protein of concern.

The oyster die-offs that began happening in the late 2000s appear to have various causes, researchers said, including changes in ocean acidification.

Some measures were taken to help deal with the acidification, but widespread die-offs continued to occur that couldn't be linked to that problem and the vibriosis disease caused by the bacteria was found to be a major concern.

Source: Journal of Microbiological Methods

Online ahead of print, DOI: 10.1016/j.mimet.2013.05.009

“Development of monoclonal antibody-based assays for the detection of Vibrio tubiashii zinc-metalloprotease (VtpA)”

Authors: Dima N. Gharaibeh, Frances M. Biel, Claudia C. Hase