Foodborne botulism survey in Northern Italy from 2013 to 2020: Emerging risk or stable situation?

Italy has one of the highest incidence rates of foodborne botulism in Europe. It is a neuro-paralytic disease caused by ingesting ready-formed botulinum neurotoxins (BoNTs) produced by some spore-forming clostridia. Due to its severity and epidemic potential, foodborne botulism is included in the list of notifiable diseases, and botulism cases are managed based on collaboration among public health authorities providing food inspections, formal analysis, and supporting hospitals in rapid diagnosis. This study aimed to conduct a survey for investigating BoNT-producing clostridia occurrences in foods from Northern Italy between 2013 and 2020. In total, 2187 food samples were provided by food business operators for their own control protocols, and the presence of BoNT-producing clostridia was investigated using multiplex real-time PCR. Sixteen food samples (0.73%, 95% CI 0.45–1.19) were found positive for the presence of BoNT-producing clostridia, including dairy products, fruit, vegetables, sauces, bakery products, gastronomic preparations, meat products, and spices and flavourings, with the target genes bont/A and bont/B being the only targets found in this survey. Collaboration with local hospitals was carried out through analysis of biological samples in suspected foodborne botulism cases using a mouse bioassay for identifying the toxin involved. When available, food residues related to the suspected cases were also analysed. Among 52 patients with suspected symptoms of foodborne botulism, 18 patients were confirmed to be positive, showing the presence of BoNT/A, BoNT/B, and BoNT/E. In five cases, food residues were identified, mostly as homemade products. Our study highlights that foodborne botulism continues to be a public health concern in both industrial processing and homemade products, stressing the importance of consumer education to avoid hazardous botulism outbreaks.