Produce parasite role ‘unlikely’ Finds Norwegian assessment

A risk assessment in Norway has supported previous findings showing it is unlikely that Echinococcus multilocularis will be imported into the country via contaminated produce.

The Norwegian Scientific Committee for Food and Environment (VKM) reviewed data on the contamination of fresh produce with the parasite, the spread of Echinococcus multilocularis in Sweden and other countries, and the monitoring of foxes and wolves in Norway. The findings update a previous VKM assessment from 2012.

The agency said the series of events required for fresh produce to be contaminated, imported, and reach the consumer is complex and appears unlikely.

Echinococcus multilocularis is also known as the fox tapeworm. Rodents are the main intermediate hosts, but parasites can also infect humans. The disease, alveolar echinococcosis, is rare, extremely severe, and difficult to treat. Without treatment, it is typically fatal within 10 years. It is of public health significance as people may act as accidental dead-end intermediate hosts if they ingest eggs via contaminated foods or water or from contact with infected hosts or their feces.

A decade after its identification in Sweden in 2011, the prevalence of Echinococcus multilocularis is still low, with limited distribution. This indicates a slow rate of spread. The parasite has not been detected in mainland Norway and analysis of imported fresh produce has not found Echinococcus multilocularis DNA.

Only nine cases have been diagnosed in Sweden since 2012. A 2020 study on six cases of alveolar echinococcosis reported that the location and route of infection could not be determined.

Produce contamination

Since the previous VKM opinion, various surveys have been undertaken in Europe regarding the contamination of fresh produce with Echinococcus multilocularis eggs. A 2015 study in Poland reported that more than 23 percent of produce samples were contaminated with Echinococcus multilocularis DNA. However, another study challenged these findings.

A survey of mixed salads and berries in 2021 found Echinococcus multilocularis DNA on one RTE salad sample grown in Italy; this finding was backed up by microscopy, in which another lab reported a taeniid egg in the same sample. Echinococcus multilocularis is established in Poland and Italy. DNA detection does not necessarily indicate that one or more infectious eggs are present on the fresh produce, nor does it present a risk of infection.

In other work, four of 30 strawberries were positive in Latvia, and five of 30 strawberry samples were positive in Estonia. In Norway, a survey of 820 imported and locally grown berry samples sold between August 2019 and November 2020 were analyzed using the same method as the one used in the Italian survey, and Echinococcus multilocularis DNA was not detected. Thirty fresh produce samples analyzed at the Norwegian reference laboratory for parasites at the Norwegian University of Life Sciences in 2023 and 2024 were negative for Echinococcus multilocularis DNA.

VKM said the previous assessment that it was unlikely Echinococcus multilocularis will be imported to Norway via contaminated berries, fruits, and mushrooms was still valid.

“Although this scenario could have a direct effect on human health, and thus may be of concern to consumers, it is nevertheless almost impossible to result in the establishment of Echinococcus multilocularis in Norway as the contaminated berries would have to be consumed by an appropriate intermediate host, which, in turn, would need to be consumed by an appropriate definitive host, which would then spread the parasite further,” added the agency.

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