- 11 Φεβρουαρίου, 2015
- Posted by: jimfek
- Category:
Why wait for people to get sick from a foodborne illness when you can prevent it from happening in the first place?
Sounds logical enough. At least that’s the thinking behind a plan focusing on the pathogen Vibrio parahaemolyticus, which can infect oysters in some growing areas during the summer.
If adopted, the proposal will govern when oysters intended to be eaten raw can, and cannot, be harvested in Washington state. Or, to put it more bluntly, when certain oyster growing areas in the state will be closed — and when they can be reopened.
Under the plan, closures would primarily be based on air and water temperatures in an oyster-growing area instead of on illness outbreaks caused by eating raw oysters from the growing area.
This is in contrast to current policy in which the state waits until a certain number of people get sick from the pathogen before shutting down the growing area where the oysters came from.
While at first glance the proposal might seem a bit extreme, public health officials, as well as many oyster growers, agree that it’s critically important to come up with a plan that will do two things: protect people from becoming ill and help keep oyster growers in business.
What is Vibrio?
Raw oysters are especially popular in the summer, when V. parahaemolyticus bacteria tend to thrive.
According to the Centers for Disease Control and Prevention, V. parahaemolyticus is a naturally occurring bacterium that lives in brackish saltwater and causes gastrointestinal illness in humans. Most people become infected by this bacterium from eating raw or undercooked shellfish, particularly oysters, that are harvested when water temperatures rise to certain levels.
Last year, the Washington State Department of Health received 76 reports of V. parahaemolyticus-related illness.
CDC estimates that 4,500 cases of this type of Vibrio infection occur each year in the United States. However, the agency says that the number of cases actually reported is much lower because surveillance is complicated by underreporting.
For the most part, this type of Vibrio is not a statewide problem. But it can become a problem in inland coastal waters, such as Samish Bay, Hood Canal, and the south Sound region of Washington state because the waters in those growing areas tend to rise to higher temperatures in the summer than the waters do along the coast.
Under the state’s proposed plan, harvest closures would be put into place at 66 degrees F and last until 24 hours after the temperature drops.
Oyster harvesters would also have to cool shellfish to 50 degrees F or less within 5 hours. In addition, they would have to report water temperature and quantity of oysters harvested to the state health department.
As for other shellfish growing areas in the U.S, V. parahaemolyticus is no longer just a West Coast problem. According to CDC, since May 2013 there has been an increase in V. parahaemolyticus illnesses associated with consumption of raw or undercooked shellfish from several Atlantic coast harvest areas. Before 2012, infections from V. parahaemolyticus were rarely associated with shellfish from the Atlantic Coast.
The demand for raw oysters
According to CDC, this type of Vibrio, which is unrelated to pollution, naturally inhabits coastal waters in the U.S. and Canada and is present in higher concentrations during the summer. When the appropriate conditions occur with regard to salt content and temperature, V. parahaemolyticus thrives.
In other words, just when demand for raw oysters reaches its highest peak during the year, that’s when V. parahaemolyticus presents the most danger to human health.
Steven Blau (left) and Jed Schimke of Blau Oyster Co. on Samish Island, WA, display some freshly harvested oysters.
“Summer is the prime time for sales of oysters that will be eaten raw or grilled,” said Steven Blau of Blau Oyster Co. on Samish Bay in Western Washington. “That’s when they fly out the door.”
Bill Dewey, a shellfish grower and spokesman for Taylor Shellfish Farms, agrees about the popularity of raw oysters.
“Live oysters for the half-shell market are a huge percentage of our business and one of our fastest-growing markets,” he told Food Safety News, adding that Taylor Shellfish opened two new oyster bars in Seattle last summer to meet this demand.
Although Taylor Shellfish had to shut down its Samish Bay growing operation for two months last summer because of V. parahaemolyticus, it has farms in other parts of the state where it could harvest oysters intended for the raw market.
Under the proposed rule, shucked oysters — those that are taken out of their shells — are exempt because, for the most part, they’re cooked before they’re eaten. But all shell stock (oysters still in the shell) would fall under the control plan.
While many of the unshucked oysters are bought to be grilled, especially in the summer months, Laura Johnson, a spokesperson for the state health department’s Office of Shellfish and Water Protection, said even then the oysters are not always thoroughly cooked. (Waiting until the shells to open is not a reliable guide. They actually have to be cooked to an internal temperature of 145 degrees F for 15 seconds before being eaten.)
It’s only logical
That’s what most of the oyster growers say about the state’s proposed plan. Many of them worked with the state in coming up with the proposal.
Describing it as a “proactive approach,” Dewey told Food Safety News that the draft rule uses a new approach based on water and air temperature data coupled with historic illness data from all the various harvest areas — instead of waiting until illnesses are confirmed.
He said that the information that has been gathered has been used to establish criteria for stopping harvest proactively when environmental conditions suggest that Vibrio risks are high.
“Ultimately, we believe it will result in either similar and maybe shorter closure periods for our harvest areas — and most importantly, far fewer illnesses,” he said.
The health department’s Johnson pointed to one of the obvious shortcomings of the current rule: Most of the closures take place in August and September despite the fact that most illnesses occur in July and August.
Margaret Barrette, executive director of the Pacific Coast Shellfish Growers Association, told Food Safety News that Washington is the first state “out of the gate” with a plan that looks for environmental factors to close down shellfish farms instead of illnesses.
“It’s very proactive and very out of the box,” she said. “I’m sure Oregon and other shellfish growing states will be carefully watching this and will possibly be following suit.”
She said that Washington state leads the nation in farmed shellfish acres, primarily because a significant portion of the tidelands is in private hands.
But when it comes to production, that’s not so clear, mainly because producers haven’t been required to divulge that information. Under Washington state’s proposal, however, that would happen, which will give the state and the growers a better idea of what percentage is harvested for the raw market
“More people are getting sick with Vibrio, but that could be because raw oysters are getting more popular,” said Blau. “Now we’ll pay attention to how many are sold instead of just how many illnesses are reported.”
Dewey said that Taylor’s has not had any Vibrio-related lawsuits and he’s not aware of any other company, at least on the West Coast, that has. He also said he checked with health department officials and that they were not aware of any lawsuits either.
What’s going on here?
Jed Schimke of Blau Oyster Co. on Samish Island, WA, holds some freshly harvested oysters.
If the state can monitor and shut down shellfish beds that test positive for pathogens such as E. coli and norovirus, why can’t it do the same for V. parahaemolyticus?
It turns out that monitoring is ineffective at preventing illness, Dewey said, explaining that only certain strains will cause illness and detecting them has proven to be elusive.
“We can have high total Vibrio numbers and no illnesses — and no indication of virulent strains present and still have illnesses,” he said. “This has been very frustrating.”
That’s why the growers see the state’s proposed plan as a positive step forward.
“On paper, it’s looking like it will be a good way to go,” Blau said.
“The science part of it makes sense to us,” said his coworker Jed Schimke. “Without a shadow of a doubt, Vibrio parahaemolyticus needs the right temperature to thrive.”
“It’s important to move in this direction to protect people from getting sick,” Johnson from the state health department told Food Safety News.
What it’s not
It’s important to know that V. parahaemolyticus is NOT Vibrio vulnificus, a potentially fatal bacterium that lives in brackish saltwater and seawater, for the most part in warmer states such as Florida and Louisiana. According to CDC, V. vulnificus can cause disease with potentially fatal complications in people whose immune systems are compromised, particularly those with chronic liver disease.
Like V. parahaemolyticus, V. vulnificus is part of a group of Vibrios that require salt and are present in higher concentrations in warmer waters.
About the proposed rule
The Washington State Department of Health is accepting public comments on the proposal through March 11. Go here to review the plan.
Comments can be mailed to Laura Johnson, Washington State Department of Health, P.O. Box 47824, Olympia, WA, 98504-6824. They can also be emailed to Laura.Johnson@doh.wa.gov or faxed to her at 360-236-2257.
A public hearing on the proposal is scheduled for March 11 in Tumwater, WA.
If the state legislature approves the updated plan, it would go into effect on May 1, 2015. The plan was last updated in 2009.
© Food Safety News
