Beneath the sea surface

The ocean is full of bacteria. So how do you know the seafood you eat is safe? Dr. Swapan Banerjee, Research Scientist at the Vibrio Laboratory at Health Canada’s Food Directorate, helps us understand what’s under the surface of the sea.

What are vibrios?

Vibrios are toxin-producing bacteria found naturally in water, fish and shellfish. There are different types of vibrios that can cause illness: salt-loving vibrios, which mainly live in marine environments, and freshwater vibrios, such as V. cholerae, which is associated with cholera, a century-old disease.

Vibrios are usually transferred to people when they consume contaminated foods or beverages. People who are infected with disease-causing vibrios may get sick from their food and symptoms can vary from mild to serious, depending on a variety of factors.

Foods contaminated with Vibrio species look, smell and taste normal. So how can people in Canada have confidence in eating seafood? That’s where Dr. Banerjee comes in!

See food differently

In 1998, Dr. Banerjee joined Health Canada’s Vibrio Laboratory, where he has put his passion and expertise in molecular biology to good use. As part of his work, Dr. Banerjee analyses seafood samples from across the country to ensure they are safe for consumption.

Two types of samples are analysed: harvested molluscs and retail samples. Dr. Banerjee’s laboratory analyses harvested molluscs hailing from the Atlantic region and Quebec for food safety and surveillance data. He maintains a database to analyse trends and to support safety assessments. The Canadian Food Inspection Agency collects retail samples for analysis from all over the country. Before being sold, retail products are independently processed by manufacturers to clean and lower their bacterial levels. Once arrived at the lab, they are analysed at random to ensure products on the retail market are safe for consumption.

While the lab and retailers try to minimize the risks to people in Canada as much as possible, a certain level of risk always remains. As such, when outbreaks of seafood-borne illness occur, Dr. Banerjee is prepared to quickly analyse suspected seafood to confirm whether Vibrio is to blame and—in collaboration with the Public Health Agency of Canada’s National Microbiology Laboratory in Winnipeg—to investigate the potential source of the outbreak. This double-pronged approach—proactively and reactively analysing samples—is how Dr. Banerjee contributes to keeping people in Canada safe and healthy.

A changing climate

Twenty years ago, vibrios were not of significant concern in Canada. The number of samples with Vibrio was quite low. However, in recent years, numbers have gone up. “This could be a result of climate change. As Canadian waters get warmer, tropical bacteria—which cannot survive in cold water—are suddenly finding a new hospitable and adaptable environment in which they can grow and survive. As a result, the odds of harmful vibrios finding their way in seafood and therefore onto Canadians’ plates are increasing.”

While more data and studies are needed to follow and establish the trend, Dr. Banerjee has already found a different pattern of Vibrio in seafood in Canada, meaning work at the Vibrio Laboratory is only just beginning. The research will soon have to continue without Dr. Banerjee however, as after more than 20 years of untiring work, he is winding down towards retirement. May his seafood be not under a microscope but safely on a dinner plate!