February 4, 2013

LSU Engineering Professor Predicts Oyster Norovirus Outbreak in Cameron Parish

The Gulf Coast region is a national leader in oyster production. In 2010 alone, the region harvested about 15.5 million pounds of oysters[1], more than half of the national total. Consumption of raw oysters is certainly a Louisiana tradition, with more than 30 oyster-growing areas thriving along the Gulf Coast. However, as oyster season approaches, seafood contamination becomes a primary concern.

Dr. Zhiqiang Deng, associate professor of Water Resources and Coastal Engineering in the Department of Civil & Environmental Engineering, is using satellite data from the National Aeronautics and Space Administration (NASA) to develop better tools for predicting and preventing seafood contamination. In 2013, Deng and his research group became the first group of scientists in the world to predict oyster norovirus outbreaks in advance when they correctly predicted the outbreak in Cameron Parish Oyster Harvesting Area 30 weeks before it occurred. Deng’s research, conducted in collaboration with the Louisiana Department of Health and Hospitals (LDHH), is a major breakthrough in protecting public health.

Outbreaks of norovirus, a virus that causes acute stomach and intestinal inflammation with symptoms of vomiting and stomach pain in humans, have been a significant problem for the oyster farming industry. According to the Center for Disease Control (CDC), norovirus causes about 21 million illnesses annually.  The virus typically spreads through contaminated water or food, including seafood, but can also transfer from human to human.

“If your friend eats an infected oyster and gets infected by the norovirus, then you may also get sick,” Deng said. “That is why it is important to prevent the norovirus outbreak in the first place.”

Following a series of norovirus outbreaks in the spring of 2010, at least three oyster growing areas along the Gulf of Mexico were closed for more than a month. This January, the DHH closed a Cameron Parish molluscan shellfish harvesting area after nine people become ill after eating oysters harvested from the area. The closure of these highly productive oyster growing areas causes significant damages to the oyster industry in Louisiana, making it all the more important to determine outbreaks in advance.

Before Deng’s recent research accomplishments, decision-support tools for the management of oyster growing areas were lacking. Traditionally, the Louisiana Mollusk and Shellfish program, sponsored by the Louisiana Department of Natural Resources and the LDHH, takes water and oyster samples from Gulf Coast oyster growing areas monthly to determine potential health-related impacts of consumption.

“If the sampling staff notices that bacterial levels in a particular area are very high for at least three consecutive months, then they may close that area for potential public health risks,” Deng said.

Using this current detection process, it can take several months to determine the health-related risks in a particular area. The process is inefficient and costly, requiring at least two staff members to drive to each growing area to collect samples every month. Current sampling practices are also unable to prevent future outbreaks.

“An outbreak officially occurs when at least three people get sick,” Deng said. “In this case, people have already gotten sick before an area is closed, and we are unable to prevent health risks.”

Deng and his research group have contributed to oyster norovirus contamination research by developing an innovative model for predicting oyster norovirus outbreaks. The model involves prediction of future water quality conditions and bacteria levels.

“Norovirus outbreaks often occur 10 – 14 days after extremely low tide events during winter months or cold weather, when levels of fecal coliform, a bacterium that originates in feces, are high,” Deng said.

Deng’s research group uses images from NASA satellites that fly over Gulf of Mexico oyster growing areas daily to monitor water temperature and other environmental factors. Based on satellite remote sensing, Deng’s model can predict bacterial levels and associated norovirus outbreak conditions in oyster growing waters.

“Our predictive model is capable of producing an oyster norovirus outbreak alert a couple of weeks in advance,” Deng said. “If the model prediction shows that the probability of an outbreak will be high in a particular time period, then we can warn oyster management organizations like the LDHH to close certain harvesting areas,” Deng said.

In fact, on December 12, 2012, Deng’s model correctly predicted the latest norovirus outbreak in the Cameron Parish Oyster Harvesting Area. The outbreak prompted the LDHH to recall oysters and close the harvesting area. Deng’s group is still working to improve the model to provide even better predictions of oyster norovirus outbreaks in the future.

Deng’s group is also developing a website where government and public users can see real-time bacterial levels in oyster growing areas. Deng hopes to have a finished product website in the next few years, with the addition of surveillance cameras in growing areas to monitor harvesting activities. By linking his model to NASA data and a publically accessible website, Deng is helping oyster harvesters know in advance which oyster growing areas are safe for harvesting, and which are not.

“The most important thing is to protect the health of oyster consumers,” Deng said. “That is our job.”

For more info on Dr. Deng’s research, visit his webpage.


Article written by LSU Department of Research Communication Staff. 

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