An outbreak linked to alfalfa sprouts last year was the first identified Salmonella Havana occurrence in Australia, according to researchers.
During June 2018, an increase in Salmonella Havana was detected through routine surveillance by the Communicable Disease Control Branch (CDCB) of South Australia (SA) Health. During 2013 to 2017, three to 14 cases were reported annually to CDCB. No previous outbreaks had been attributed to this Salmonella strain in Australia.
A total of 31 cases were reported to the CDCB in June and July 2018 as part of the outbreak investigation. They were 19 females and 12 males with an age range of 22 to 87 years old. Days unwell ranged from two to 23 and there was a high hospitalization rate with 13 people going to hospital.
“This suggests that either there might have been a high dose of contamination on the alfalfa sprouts or the outbreak strain might be more pathogenic than other Salmonella strains, thus leading to a higher burden of disease for this specific strain,” said researchers.
Sprouts from a hotel and retail
Hypothesis-generating interviews with 17 people identified eight with the same hotel as a common exposure but no meals were shared between them. Five people who did not eat at the hotel identified having alfalfa sprouts from either a supermarket, bakery, fruit and vegetable store, or health food store.
Environmental health officers inspected the hotel in mid-June and identified alfalfa sprouts were served as a garnish on all hot meals, with snow pea shoots and mesclun lettuce. The hotel used alfalfa sprouts supplied by a local distributer who sourced them from SA Sprouts, a sprouts producer.
Trace-back of alfalfa sprouts implicated by those not linked to the hotel identified they were from the one sprouts producer.
Food safety issues at SA Sprouts included vermin control as an inspection identified vermin feces underneath pallets in the bulk storage area storing seeds.
Three alfalfa sprouts samples from the hotel and five samples from retail were positive for Salmonella Havana. Eleven positive results were found on sprout product samples from the producer, with six being Salmonella Havana and five Salmonella Oranienburg. No cases of Salmonella Oranienburg had been notified in SA since April 2018.
Contaminated seeds and pest control
Eighteen infected people and 54 controls were included in a case-control study. Increased risk of illness was shown for alfalfa sprouts. They are considered a high-risk product due to risk of microbial contamination in sprout seeds, and being produced in an environment ideal for growth of bacterial pathogens. Also, they are usually consumed raw which increases the risk of infection.
An emergency order was served on the producer to stop distributing products, which were only available in SA, and a recall of all alfalfa products from the supply chain was issued. It was unclear when in the production of alfalfa sprouts contamination occurred. However, contaminated seeds and poor pest control are the most likely causes.
Authorities did not find a breakdown in the production process but several structural deficiencies were identified. SA Sprouts committed to cease production of sprout products and to rectify issues.
Researchers said the investigation highlighted the importance of ensuring producers comply with legislation and standards for primary production and food safety and that equipment is adequately maintained to reduce the likelihood of contamination.
“To minimize future outbreaks linked to alfalfa sprouts and other sprouts, it is suggested that sprouts producers take appropriate action to minimize the likelihood of contaminated product, including using a decontamination step to minimize the bacterial load on sprout seeds and in the sprouting process and ensuring they comply with legislation and standards for primary production and food safety.”
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