Increase in locally acquired Vibrio Parahaemolyticus infections

02 November 2021

The Communicable Disease Control Branch has identified an increase in locally acquired Vibrio parahaemolyticus infections with 15 cases reported since 1 September 2021, compared with no cases reported in 2020, and eight cases in 2019 (of which seven were acquired overseas). Cases reported since 1 September 2021 include nine females and six males, with a range in age of 23 to 81 years (median age of 51 years). Fourteen cases have reported consuming oysters during their incubation period.

Vibrio parahaemolyticus is a Gram-negative bacterium that is naturally found in South Australian marine, coastal and tidal waters. There are two patterns of infection, gastroenteritis and wound infections. Symptoms of V. parahaemolyticus gastroenteritis include: watery diarrhoea, abdominal pain, nausea, vomiting, fever and headache. Symptoms of V. parahaemolyticus wound infection include: wound pain, redness, warmth and discharge.

Gastroenteritis is associated with eating raw or undercooked seafood such as oysters, fish, crustaceans and the use of contaminated seawater in food preparation methods. Cross contamination with other food can occur especially with poor food handling practices. V. parahaemolyticus does not usually spread from person to person, however, person-to-person spread is possible if there is poor personal hygiene.

Symptoms of gastroenteritis usually occur within 24 hours of eating contaminated food. Symptoms are usually mild to moderate in severity and last around 3 days (range 8 hours to 12 days). However, the infection can be severe in people with comorbid disease, particularly liver disease, excessive alcohol consumption, use of antacid medication, and immunocompromise.

Medical practitioners are advised to:

  • Advise pregnant women, persons with immunosuppression, and the elderly to refrain from eating raw or undercooked seafood.

  • Consider V. parahaemolyticus as a differential diagnosis in individuals presenting with a gastroenteritis type illness, especially when the illness occurs after consuming seafood.

  • Request stool testing in persons who present with suspected food poisoning. Request Vibrio parahaemolyticus in addition to M, C & S and write ‘suspected food poisoning’ in the clinical notes. V. parahaemolyticus is not routinely tested for in some laboratories.

  • Manage patient with V. parahaemolyticus gastroenteritis as per other forms of gastroenteritis. Antibiotics are not usually required for V. parahaemolyticus gastroenteritis, but treat severe or persistent disease with antibiotics as per the Therapeutic Guidelines: Antibiotic.

  • Exclude the patient from work/school/childcare until there has been no diarrhoea for at least 24 hours (48 hours for commercial food handlers).

  • Notify suspected and confirmed cases V. parahaemolyticus to the Communicable Disease Control Branch on 1300 232 272 or 

Dr Louise Flood – Director, Communicable Disease Control Branch