Vibrio parahaemolyticus food poisoning, also known as halophilic bacteria food poisoning, is caused by consuming food contaminated with this bacterium, primarily seafood. Clinically, it is characterized by sudden onset, abdominal pain, vomiting, diarrhea, and watery stools as the main symptoms.

bubble_chart Epidemiology

(1) Source of Pestilence The source of pestilence is patients. During collective outbreaks, only a few severe cases are hospitalized, while the majority of untreated patients may become sources of pestilence. However, since patients excrete the most bacteria during the initial stage [first stage] of the disease, bacterial excretion rapidly decreases afterward. Therefore, widespread epidemics due to bacterial dissemination by patients are unlikely.

(2) Transmission Routes The disease is transmitted through food, primarily seafood or salt-preserved products. Common sources include crabs, cuttlefish, jellyfish, fish, and mud snails, followed by eggs, meat, or vegetables. Cases caused by consuming meat or vegetables are often due to contamination of food containers or cutting boards.

(3) Susceptible Populations People of all ages and genders can contract the disease, but young adults are the most affected. Immunity after infection is weak, allowing repeated infections.

The disease frequently occurs in coastal areas during summer and autumn, often leading to collective outbreaks. In recent years, there has been an increasing trend of cases in coastal regions.

bubble_chart Pathogen

Vibrio parahaemolyticus is a Gram-negative, pleomorphic bacillus or slightly curved vibrio. This bacterium is halophilic and acid-sensitive, unable to grow on salt-free culture media, but reproduces rapidly in 3–6% saline solution with a cycle of 8–9 minutes. Growth ceases in solutions with less than 0.5% or more than 8% salt. It dies within 1–3 minutes in vinegar, is inactivated by heating at 56°C for 5–10 minutes, and dies in 1% hydrochloric acid within 5 minutes.

V. parahaemolyticus is known to have 12 O antigens and 59 K antigens, and can be classified into 5 types based on its fermentation of sugars. Various vibrios exhibit strong virulence toward humans and animals, with pathogenic substances primarily including thermostable direct hemolysin (TDH) with a molecular weight of 42,000 and TDH-related hemolysin (TRH) with a molecular weight of 48,000, both possessing hemolytic activity, enterotoxicity, and lethal effects.

Ingestion of more than 100,000 live bacteria can cause illness, with some cases presenting as septicemia. This bacterium has invasive properties, and the TDH and TRH it produces share similar antigenicity and immunogenicity, both exhibiting hemolytic activity and enterotoxin effects, which can lead to intestinal loop swelling, congestion, and fluid retention, causing diarrhea. TDH has a specific cardiotoxic effect, leading to perianal abscess, atrial fibrillation, premature contractions, or myocardial damage. Recent studies have found that urease is associated with diarrhea in this disease. Patients' constitution and immunity vary, resulting in a wide range of clinical manifestations. Inhabitants from mountainous or inland areas who become infected in coastal regions tend to have more severe and typical symptoms, while cases in coastal areas are generally milder.

bubble_chart Pathological Changes

The main pathological changes include grade I erosion in the jejunum and ileum, gastric mucosal inflammation, and congestion of internal organs (liver, spleen, lungs).

bubble_chart Clinical Manifestations

The incubation period ranges from 1 hour to 4 days, with the majority being around 10 hours.

The onset is abrupt, often accompanied by abdominal pain, diarrhea, vomiting, dehydration, fear of cold, and fever. Abdominal pain is mostly paroxysmal colicky pain, frequently located in the upper abdomen, around the navel, or in the ileocecal region. Diarrhea occurs 3 to over 20 times a day, with varied stool characteristics, mostly yellow watery or pasty stools. Approximately 2–16% present with typical bloody or meat-washing-water-like stools, while some patients may have pus-blood or mucus-blood stools, but tenesmus is rare. Due to vomiting and diarrhea, patients often experience dehydration; those with grade III dehydration may exhibit hoarseness and muscle spasms, and in some cases, blood pressure drops, complexion turns pale or cyanotic, even leading to unconsciousness. Fever is generally less severe than in bacillary dysentery, but dehydration is more common. Recent domestic reports on Vibrio parahaemolyticus food poisoning show varied clinical manifestations, which can be typical, gastroenteritis-type, dysentery-type, toxic shock-type, or the rare chronic enteritis-type.

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bubble_chart Auxiliary Examination

(1) White Blood Cell Count The total count is mostly above 10,000/mm³, with elevated neutrophils.

(2) Stool Examination Microscopic examination may reveal white blood cells or pus cells, often accompanied by red blood cells, which can be easily misdiagnosed as bacillary dysentery. Stool culture can detect Vibrio parahaemolyticus, with the vast majority turning negative rapidly, and only a few remaining positive for 2 to 4 days.

bubble_chart Diagnosis

During the epidemic season of Vibrio parahaemolyticus food poisoning, clinical diagnosis can be established based on the following characteristics: consumption of suspicious food (such as pickled products or seafood), collective outbreaks, short incubation period with acute onset, fever and abdominal pain being more severe than other intestinal pestilence diseases, bloody watery diarrhea, and frequent dehydration. Culturing suspicious food may sometimes isolate the same Vibrio parahaemolyticus found in feces.

This disease should be differentiated from staphylococcal food poisoning, enterotoxigenic large intestine bacillus, Salmonella food poisoning, acute bacillary dysentery, and cholera.

bubble_chart Treatment Measures

(1) Supportive and symptomatic treatment: Patients with dehydration require intravenous infusion of normal saline or glucose saline, or oral rehydration salts to correct fluid loss. For those with decreased blood pressure, in addition to replenishing blood volume and correcting acidosis, vasoactive drugs may be used as appropriate.

(2) Antibacterial drugs: Mild cases may not require antibacterial drugs, while more severe cases can be treated with compound formula sulfamethoxazole, gentamicin, amikacin, or fluoroquinolone antibiotics such as norfloxacin.

bubble_chart Prognosis

Preventive measures are similar to those for other bacterial infections.

(1) Animal-based foods should be thoroughly cooked before consumption.

(2) Leftovers from previous meals should be reheated adequately before eating.

(3) Prevent cross-contamination between raw and cooked foods during handling.

(4) Aquatic products such as swimming crabs, fiddler crabs, and jellyfish should be preserved by soaking in saturated salt (with vinegar added for flavoring and sterilization), and rinsed repeatedly with cold boiled water before consumption.