Maryland Warns Against Eating
Shellfish From Private Piers
ANNAPOLIS --- The growing proliferation of home based aquaculture projects and oyster gardens has lured some to eat the shellfish grown for water quality improvement initiatives. Due to the potential presence of pathogens, officials at the Maryland Department of the Environment (MDE) urge oyster growers against doing so.
Shellfish are filter-feeding organisms; they strain the surrounding water through their gills which trap and transfer food particles to their digestive tract. If the water they are housed in is contaminated with disease-causing organisms, these organisms are also trapped and consumed as food. Because shellfish pump large quantities of water through their gills each day, even low concentrations of harmful organisms from the waters can reach dangerous levels in the shellfish. If shellfish containing these organisms are eaten raw or partially cooked, illness may result.
Shellfish are bivalve mollusks such as clams, oysters, and mussels. [The term shellfish does not include crabs, lobsters, or shrimp.] Therefore, to protect public health, it is mandatory that shellfish be harvested from approved shellfish waters where protective standards have been met. MDE protects and classifies the state’s shellfish harvesting waters.
To protect public health, MDE does not permit the harvest of shellfish from marinas because of the potential for illegally discharged or unintentional discharge of boat waste. This restriction does not include blue crabs, which are crustaceans and do not filter-feed like oysters. MDE further recommends against consuming oysters grown from private piers. The area around a private dock or pier is near the shoreline in quiet waters, rather than out in the river where the oyster’s natural habitat is typically found. Activities such as the unexpected failure of a neighbor’s septic system, drainage of water from yards where pets are kept and other factors can introduce disease-causing organisms, which can be concentrated by oysters, posing a risk to people eating them.
In Maryland, the responsibility for the sanitary control of the shellfish industry is split among three state agencies: MDE, the Department of Health and Mental Hygiene (DHMH), and the Department of Natural Resources (DNR). MDE is responsible for identifying and eliminating pollution sources affecting Maryland’s shellfish harvesting waters, as well as determining whether the shellfish harvested are safe for human consumption. DHMH is responsible for any food control measures necessary to ensure that shellfish are harvested, processed, packaged and transported under sanitary conditions. DHMH also regulates shellfish dealers to assure compliance with the required sanitary standards. DNR is responsible for posting areas restricted to shellfish harvesting and for patrolling these areas to prevent illegal harvesting.
Diseases associated with shellfish consumption
There are a number of diseases that are caused by the transfer of fecal bacteria or viruses from human sanitation sources to raw shellfish. While these diseases do not infect the shellfish, oysters and clams may filter the disease-causing organisms out of the water and can accumulate enough of them to make consumers of raw or partially cooked shellfish ill.
Norwalk and Norwalk-like virus – The main reservoir for this virus is man. Symptoms include nausea, vomiting, diarrhea, abdominal cramps, and fever. The disease is usually self-limiting.
Hepatitis A virus – This virus causes weakness, fever, abdominal pain and yellow jaundice. It may result in damage to the liver. Although death is rare, it may occur among those with underlying diseases.
Salmonella – Several species of Salmonella are naturally found in the intestines of mammals, birds, amphibians, and reptiles. Salmonella can be transferred to shellfish by sewage pollution of coastal waters. Salmonella infections cause nausea, vomiting, abdominal cramps, and fever. One species causes typhoid fever.
Shigella –This bacterium causes symptoms very similar to Salmonella. Shigella is found only in the human intestinal tract and is not a result of contamination by animal species.