Detection of Echinococcus spp. and other taeniid species in lettuces and berries: Two international multicenter studies from the MEmE project

Abstract

Cystic and alveolar echinococcosis are severe zoonotic diseases characterized by long asymptomatic periods lasting months or years. Viable Echinococcus spp. eggs released into the environment through the feces of canids can infect humans through accidental ingestion via hand-to-mouth contact or consumption of contaminated food or water. Both Echinococcus multilocularis and Echinococcus granulosus sensu lato are considered as foodborne parasites. However, when considering possible pathways of human infection, it appears that food and waterborne related variables do not significantly increase the risk of infection. Providing evidence-based data for the presence of DNA and, potentially, eggs in fresh produce is crucial in understanding foodborne transmission of Echinococcus spp. to humans. Two multicenter and multicountry studies were conducted within the One Health EJP framework to estimate the proportion of lettuces and berries contaminated by E. multilocularis, E. granulosus sensu lato, and other taeniid DNAs from a total of 12 European countries, Tunisia and Pakistan. A total of 1117 lettuces, 71 others vegetables, 300 strawberries, 130 blueberries and 50 others berries samples were collected and analysed by washing, sequential sieving and real-time PCRs. E. multilocularis DNA was detected in 1.2 % (7/ 570) of lettuce samples tested from the seven European endemic countries (Denmark, France, Germany, Latvia, the Netherlands, Poland and Switzerland) and in 2 % (2/100) from Pakistan. E. granulosus sensu lato DNA was identified in 1.3 % of lettuces (9/695) collected in five European endemic countries (France, Italy, Latvia, Poland and Portugal) and in 12 % (9/75) and 4 % (4/100) from Tunisia and Pakistan, respectively. All E. granulosus sensu lato samples were identified as E. granulosus sensu stricto (20/22), except for two identified as E. canadensis (2/22) from Latvia and Pakistan. Regarding berries, E. multilocularis DNA was detected in 5.4 % (n =11/202) of strawberries, 7.3 % (6/82) of blueberries from the seven European endemic countries and 56 % (14/25) of blueberries from Pakistan. High contamination rates of E. granulosus sensu stricto were found outside of Europe, with 12.0 % (3/25) in blueberries from Pakistan and 81.3 %. (13/16) in strawberries from Tunisia. The total contamination rate of all taeniid species DNA in lettuces (5.3 %; 59/1117), others vegetables (5.6 %; 4/71) and berries (12.1 %; 58/480) suggests that the transfer of taeniid eggs from carnivore feces to food is not uncommon. Although we assume that eggs are the source of the DNA detected in this study, the viability of such eggs is unknown. The detection of Echinococcus species in lettuces and berries suggests a potential risk of foodborne human infection. The relative contribution of this risk remains to be estimated. Further studies on food and environmental contamination are necessary to cover different epidemiological contexts and social habits, leading to a better understanding of human infections by Echinococcus spp. eggs.