Shellfish Poisoning and Diseases
Types of Shellfish Poisoning
Shellfish diseases and poisoning affects seafood around the world.
In some cases, diseases affect the health of shellfish, but have not affect on humans that consume diseased seafood.
In other cases, shellfish may appear healthy, but can contain toxins which, if consumed, can cause illness and even death.
Toxins from red tides and other conditions can affect clams, oysters, mussels, scallops and other shellfish.
In North America, red tides can affect shellfish consumption. Shellfish taken from a red tide area can contain a toxin that causes paralytic shellfish poisoning. The toxin is not destroyed by cooking.
The phenomenon also occurs in the Pacific Northwest and other regions.
Domoic acid poisoning (DAP) and paralytic shellfish poisoning are linked to natural food sources for filter-feeding bivalve shellfish.
Domoic acid is produced by particular species of marine algae and accumulates in marine animals such as clams and mussels. The substance was identified as a shellfish toxin in 1987, after more than 100 people were sickened from eating contaminated mussels harvested off the Canadian province of Prince Edward Island.
According to NOAA, high-level exposure through eating contaminated seafood can be toxic, and can lead to amnesic shellfish poisoning, with symptoms such as seizures, short-term memory loss and, in rare cases, death. Since the early 1990s, shellfish monitoring has helped curb amnesic shellfish poisoning caused by high levels of domoic acid.
In North America, several diseases can affect oyster populations. One of the most famous shellfish epidemics in history occurred along North America's Atlantic Coast in the early 20th century.
Oysters, once incredibly abundant, began dying in large numbers. The source of the problem went un-diagnosed for many years as oysters died away in countless numbers.
Eventually, two diseases, MSX and dermo were identified as being a factor in the decline of oysters along the Atlantic Seaboard.
Although oyster populations have never recovered to historic levels, recent evidence suggests that in many areas, oysters have evolved that are resistant to these diseases.