Vegetables, fresh fruit and mushrooms represent a potential source of infection by a variety of pathogens including the tapeworms, Echinococcus granulosus and E. multilocularis. E. multilocularis causes alveolar cystic echinococcosis (AE) in which multiple small cysts are formed that spread throughout the internal organs. The disease progresses slowly and can be asymptomatic for as long as 15 years, but eventually produces disorders similar to liver cancer. It is extremely pathogenic with a fatality rate reaching over 50%.
In 2015 a study, conducted by Anna Lass and colleagues, focused on the Varmia-Masuria Province in Poland. Here the prevalence of E. multilocularis in foxes is as high as 50% and the area has the highest number of cases of AE in Poland. The transmission routes of this tapeworm were unknown.
One hundred and three samples of fruits (various berries) vegetables and mushrooms were collected from kitchen gardens, forests and plantations and analysed for the presence of E. multilocularis DNA.
Initial work, performed by artificial contamination of purchased fruit and vegetables, suggested that many eggs were lost during preparation for DNA extraction, amplification and sequencing, as their previous work showed they could detect the presence of a single isolated egg.
Nevertheless, when their protocol was used with samples collected from the wild, the tapeworm DNA was detected in 23.3% of samples from gardens, forests and plantations. The highest proportion of contaminated samples being those collected from kitchen gardens.
Interestingly the authors noted a large increase in the fox population had been occurring in Varmia-Masuria Province at that time, and people living there often consumed their own home grown fruit and vegetables and also collected fruits and mushrooms from the forest. They concluded that consumption of fresh fruits, vegetables and mushrooms could pose a risk of infection by this highly pathogenic tapeworm.
Findings challenged
Their findings have recently been challenged by Lucy Robertson and colleagues. These researchers recognise that Poland has a relatively higher incidence of AE than other Baltic countries. However, they propose that the inferences with respect to the danger posed by eating fresh, raw produce from the area, that were made in the 2015, paper may have been too dramatic and cause undue concern.
