Vibrio parahaemolyticus infection

Notification requirement for Vibrio parahaemolyticus infection

From 1 April 2025, Vibrio parahaemolyticus infection is a routine notifiable condition in Victoria. Pathology services must provide written notification of Vibrio parahaemolyticus detection or isolation in a clinical specimen to the Department of Health within 5 working days. This is a Victorian statutory requirement.

Exclusion for Vibrio parahaemolyticus infection

Cases with Vibrio parahaemolyticus gastroenteritis are required to be excluded from children's services centre or primary school until there is no loose bowel motions for 24 hours, or 48 hours in an outbreak setting.

Food handlers, childcare workers and healthcare workers, including age and disability workers should be excluded from work until 48 hours after cessation of diarrhoea.

Cases with Vibrio parahaemolyticus wound infections do not require exclusion.

Infectious agent of Vibrio parahaemolyticus

Vibrio parahaemolyticus is one of several bacteria of the genus Vibrio that occurs naturally in marine environments. Environmental factors such as warm low-salinity seawater can influence Vibrio abundance.

Identification of Vibrio parahaemolyticus infection

Clinical features

Gastrointestinal symptoms associated with Vibrio parahaemolyticus infection are:

• Watery diarrhoea (occasionally bloody diarrhoea)
• Abdominal cramps
• Nausea
• Vomiting
• Fever
• Headache

Most cases are mild to moderate, and illness lasts around 3 days (ranging from 8 hours to 12 days).

Symptoms associated with Vibrio parahaemolyticus wound infections are:

• Pain
• Redness
• Warmth
• Pus or discharge

Diagnosis

Testing for Vibrio parahaemolyticus is via stool culture.

Testing for Vibrio parahaemolyticus wound infections is via a wound swab.

Incubation period of Vibrio parahaemolyticus

Symptoms of Vibrio parahaemolyticus usually develop within 24 hours of consuming contaminated foods or water, but this can range from 4 to 96 hours.

Public health significant and occurrence of Vibrio parahaemolyticus

There has been an increasing incidence of sporadic cases and outbreaks of Vibrio parahaemolyticus infections linked to contaminated seafood ingestion in multiple regions around the world.

In Australia, outbreaks have been linked to locally grown oysters with significant implications for human health, the economy and international trade.

Reservoir of Vibrio parahaemolyticus

Vibrio parahaemolyticus is a bacterium that occupies coastal marine environments. Marine waters, shellfish and other marine organisms can act as reservoirs.

Mode of transmission of vibriosis

Infections with Vibrio parahaemolyticus occur most commonly through ingestion of raw or undercooked shellfish such oysters, mussels and clams, or drinking contaminated water.

It can also be associated with ingestion of other raw or undercooked seafood such as fish, prawns, crab or lobster.

Period of communicability of Vibrio parahaemolyticus

Vibrio parahaemolyticus is not usually spread from person-to-person.

Susceptibility and resistance to Vibrio parahaemolyticus

People of all ages are susceptible to Vibrio parahaemolyticus infection. Most infections are mild and self-limiting. Risks factors for developing severe disease include underlying chronic illness, being immunocompromised, consumption of antibiotics and medications that reduce stomach acid levels.

Control measures for Vibrio parahaemolyticus

Preventive measures

Good food hygiene and hand hygiene practices can help prevent Vibrio parahaemolyticus infections. These include:

• purchasing shellfish and oysters from reputable seafood suppliers
• ensuring you refrigerate these foods immediately after purchasing them
• keeping raw seafood away from ready to eat or cooked foods
• always washing hands with soap and water after handling raw shellfish
• avoiding consumption of raw or undercooked seafood such as oysters, especially during warm summer periods or if at increased risk of severe disease (such as people with immune suppression)
• avoiding the use of seawater in food preparation methods which do not involve cooking (such as washing vegetables)
• avoiding exposure of open wounds to seawater. If wounds are exposed, then wash with soap and clean water.

Control of case

Treatment is supportive, however in cases with more severe or prolonged illness, antibiotic treatment may be required.

Wounds should be protected from further exposure to seawater and covered with an appropriate dressing.

Local Public Health Units are following up cases of Vibrio parahaemolyticus infection to identify possible food sources.

Control of contacts

Consider the diagnosis of Vibrio parahaemolyticus infection in contacts of the case with a possible common exposure.

Outbreak measures for Vibrio parahaemolyticus

Two or more cases of Vibrio parahaemolyticus with a common exposure are suggestive of an outbreak. An outbreak investigation is commenced by Local Public Health Units (LPHUs) with the Department of Health, local council and other stakeholders to rapidly identify the source and prevent further cases.

Epidemiological, environmental and laboratory investigations are undertaken as per the Guidelines for the investigation of gastroenteritis. A risk assessment is undertaken to inform the appropriate level or response and coordination/management arrangements.