Researchers have described the first reported outbreak of botulism in Vietnam that was associated with vegetarian pâté in recent months.

At least 13 people fell ill after eating Minh Chay brand pâté, which was recalled earlier this year.

A study published by Wellcome Open Research covers six patients who contracted botulism after eating the commercially made pâté. Clinical diagnosis was confirmed by identification of Clostridium botulinum type B from the suspected food source made by Loi Song Moi Company.

Botulinum antitoxin was not available in Vietnam during the outbreak in July and August. It was provided by the World Health Organization at the beginning of September.

Initial and ongoing treatment
In July 2020, a Taiwanese 36-year-old man went to the Department of Tropical Diseases, Cho Ray hospital in Ho Chi Minh City. He had been referred from his local hospital in Khanh Hoa province, where he had been admitted four days previously with a one-day history of nausea and vomiting.

He reported consumption of seafood one day prior to onset of original symptoms. Because of this, the initial diagnosis was saxitoxin, brevetoxin or tetrodotoxin poisoning.

The second case was his wife. She was a Vietnamese 36 year old in the second trimester of pregnancy and accompanied her husband to hospital. She had the same seafood as him, and similar gastrointestinal symptoms one day later. She had not previously been assessed but mentioned blurred vision and swallowing difficulties.

Three days following hospital admission their conditions had deteriorated with worsening respiratory function. Foodborne botulism was suspected and dietary history re-explored from their relatives. This revealed the couple had eaten the same brand of vegetarian mushroom pâté produced in Vietnam 20 to 36 hours before the first symptoms occurred.

The next three patients were Vietnamese women aged 20, 24 and 26, also referred from local hospitals at the end of July. The trio were friends with no social link to the first two patients. They had a history of gastrointestinal symptoms of nausea, vomiting and abdominal pain, followed by development in the next two days of neurological issues, difficulty breathing and limb weakness.

Because of the similarity to cases one and two, a history of food consumption was taken. They had eaten the same brand of vegetarian pâté as the previous couple between 24 and 48 hours before onset of symptoms.

Samples of remaining pâté from patients’ houses were taken. Presence of Clostridium botulinum in the food samples of all cases was confirmed and diagnosis of botulism  established. Clostridium botulinum was not isolated from these patients but it was detected in the stool of two other cases.

Stock of antitoxin for rare diseases
The vegetarian pâté contained almond, walnuts and cashews, as well as mushroom, and came in metal containers which provided the anaerobic conditions needed for bacterium growth and toxin production.

The last case was a 54-year-old Vietnamese man who went to the department in August, three weeks after the first five cases. He gave a history of dizziness, nausea, vomiting and abdominal pain which occurred 24 hours after eating the same brand of vegetarian pâté. Over the next 24 hours, he developed other symptoms including double and blurred vision.

All six cases required intubation and mechanical ventilation. The time to this following consumption of the pâté ranged from four to nine days.

Given that botulinum antitoxin was not accessible, and their severe status, all patients received a trial of plasma exchange therapy, but no clear benefit was seen. Delay in diagnosis and lack of specific treatment are likely to result in worse clinical outcomes.

“The logistics of maintaining stocks of costly antitoxin for what are rare diseases is a challenge; cross-border cooperatives with rapid dissemination of stocks as needed may be one solution,” said researchers.

The first five cases stayed in hospital for four to five weeks before referral to their local hospitals for ICU care. All patients required ongoing invasive mechanical ventilation when discharged. The sixth patient remained in intensive care in Cho Ray hospital as of late October.

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