An Outbreak of Food-borne Botulism Caused by a Traditional Yogurt

Foodborne botulism (FB) is a potentially fatal and paralytic disease which can be prevented by the application of simple measures. FB outbreaks are usually the results of consuming contaminated canned vegetables or meat. However, in rare cases, dairy products can be their source of occurrence.

We report on nine cases of confirmed botulism who referred to our center on December 2019 with a common history of exposure to a type of traditional yogurt called “Poost yogurt” in local language. Patients presented with various combination of symptoms, 5 of them required ICU admission. All hospitalized patients fully recovered and discharged at a median of 14.5 days. In addition to these 9 cases, 60 patients were admitted and treated at Neyshabour University of Medical Sciences, as well. Totally, 69 patients in the area were diagnosed with FB with a definite history of “Poost yogurt” consumption and telltale symptoms of botulism.

Dairy products are a relatively uncommon source of FB. However, home-prepared cheese, and rarely yogurt, could bear contamination with clostridium botulinum, leading to intoxication due to improper refrigeration or incomplete heating. In this outbreak, the source of toxin was tracked down to a home-prepared Poost yogurt being sold at a dairy shop in Neyshabour. It is conceivable that improper refrigeration or incomplete heating of the milk, before fermentation, has led to spore vegetation and toxin production.

It is necessary to increase public awareness about traditional dairy products as a potential source of FB.