Public Health has noted a recent increase in food-borne illness caused by Vibrio parahaemolyticus infections among BC residents, above what we usually expect at this time of year. These have occurred across the province but the majority of cases reside in or have visited coastal areas.
Source of Vibrio parahaemolyticus, a naturally occurring marine bacterium that proliferates during the summer in BC’s coastal waters, is typically from accumulation in filter-feeding shellfish such as oysters, clams, scallops, and mussels. Its numbers increase when water temperature rises.
People can be infected through
- Consumption of raw or undercooked shellfish, particularly oysters, which may have been purchased at restaurants and stores or that have been harvested from beaches;
- Inadvertent ingestion or contact with ocean water.
Clinically, the vast majority of infections present as acute mild to moderately-severe gastrointestinal illness, 4 to 96 hours after exposure. Patients may complain of watery diarrhea, abdominal cramps, nausea, vomiting, fever, and headache. Some also have bloody or mucoid diarrhea. Symptoms typically last between 1 and 7 days. Rarely, Vibrio parahaemolyticus can also infect wounds. Systemic illness and death are extremely rare.
Diagnosis typically occurs through a culture of stool or other relevant sample. In some parts of BC, a PCR test may be conducted on stool instead.
Treatment is supportive. In the vast majority of cases, no treatment is required other than oral rehydration. If illness is severe, prolonged or in immunocompromised patients, consider antibiotic therapy.
Prevention should be pursued by reminding patients to keep shellfish refrigerated, to cook shellfish thoroughly, and to limit the inadvertent swallowing of ocean water during the months of June to September in BC.