Detection of taeniid ( Taenia spp., Echinococcus spp.) eggs contaminating vegetables and fruits sold in European markets and the risk for metacestode infections in captive primates

Abstract

Due to frequent cases of alveolar echinococcosis (AE) in captive primates in Europe, 141 samples of food, which consisting of vegetables and fruits, were investigated for contamination with egg-DNA of taeniids. Each sample consisted of at least 40 heads of lettuce as well as various vegetables and fruits. The samples were purchased at different times of the year: either from September to November (autumn), originating from greenhouses or fields in the Basel region in the North of Switzerland, or in April and May (spring) when fruit and vegetables are sourced from throughout Europe from various wholesalers. Each sample was washed, and the washing water sieved through mesh apertures of 50 μm and 21 μm, respectively. The debris, including taeniid eggs, collected on the 21 μm sieve were investigated by a multiplex PCR-analysis followed by direct sequencing. In 17 (18%) of the 95 samples collected in autumn, taeniid-DNA was detected (Taenia hydatigena in four, Taenia ovis in three, Taenia polyacantha in two and Hydatigera (Taenia) taeniaeformis in five cases). Similarly, in 13 (28%) of the 46 samples collected during spring taeniid-DNA was detected (Echinococcus granulosus s.l. in two, Taenia crassiceps in one, T. hydatigena in two, Taenia multiceps/Taenia serialis in two, Taenia saginata in one and H. taeniaeformis in five cases). Although DNA of Echinococcus multilocularis was not found specifically in this study, the detection of other fox taeniids reveals that vegetables and fruit fed to the primates at the Zoo Basel at different times of the year and from different origin are contaminated with carnivore's faeces and therefore act as a potential source of AE infections.

The European Union summary report on trends and sources of zoonoses, zoonotic agents and food‐borne outbreaks in 2016

“…multilocularis and E. granulosus s.l. is still ongoing (Federer et al., ; Lass et al., ; Robertson et al., ). Two recent reviews and meta‐analyses suggested that the chance of AE and CE transmission through the ingestion of food and water contaminated with E .…”

“…In addition, the debate on the importance of unwashed contaminated fresh fruit, vegetables and mushrooms in the transmission of E. multilocularis and E. granulosus s.l. is still ongoing (Federer et al, 2016;Lass et al, 2016;Robertson et al, 2016). Two recent reviews and meta-analyses suggested that the chance of AE and CE transmission through the ingestion of food and water contaminated with E. multilocularis and E. granulosus eggs does exist, but potential risk factors associated with foodborne and waterborne transmission do not significantly increase the risk of infection to humans Conraths et al, 2017).…”

Knowledge, Attitudes, and Practices of 50 Patients with Surgically Treated Cystic Echinococcosis from Basrah Province, Iraq

“…A similar study in Jordan involving 55 patients infected with CE, revealed that, in addition to contact with animals through their occupation, many also consumed raw vegetables [35]. Eating unwashed vegetables is a risky practice that potentially increases exposure to Echinococcus, as well as other canine zoonotic diseases [36,37]. A study in Turkey identified a variety of canine parasite eggs on unwashed vegetables, including Taenia spp.…”

Assessing the Contamination of Food and the Environment With Taenia and Echinococcus Eggs and Their Zoonotic Transmission

“…It was estimated that a single taeniid egg (T. hydatigena) contains around 7000 mitochondrial targets, and the detection limit of PCRs targeting the mitochondrial DNA was estimated at 33 copies [10•]. In our lab, a reliable method combining sieving (eggs retained in a 20-μm sieve), microscopy, multiplex PCR on DNA from taeniid-positive samples (egg-DNA PCR) and optionally confirmatory sequencing was developed [10•, 51] aiming to differentiate eggs of E. granulosus s.l., E. multilocularis and other taeniids, and the method has extensively been used for individual diagnosis (e.g., [54,60,61]) and in studies investigating field-collected specimens (see below). However, molecular analyses of taeniid eggs can also be performed after isolation with classical diagnostic sedimentation/flotation procedures [62,63].…”

“…e, f Immature eggs showing a thin embryophore and no oncosphere; e was stored for 8 months in saline solution at 4°C and f was freshly removed from an adult specimen of E. multilocularis infecting a fox from the ground [92], though such a contamination cannot be excluded as flies were shown to transmit such eggs [26]. A second investigation on the presence of cestode eggs in feed (vegetables, fruits) [60] was triggered by frequent cases of alveolar echinococcosis in primates kept in captivity at a Zoo. Egg-DNA PCR using multiplex PCR/sequencing [10•] on filtered samples revealed non-zoonotic Taenia spp.…”