Abstract
Different helminths and protozoa are transmitted to humans by oral uptake of environmentally resistant parasite stages after hand-to-mouth contact or by contaminated food and water. The aim of this study was to develop and validate a method for the simultaneous detection of parasite stages from fresh produce (lettuce) by a one-way isolation test kit followed by genetic identification (PCR, sequencing). Three sentinel zoonotic agents (eggs of Toxocara canis, Echinococcus multilocularis and oocysts of Toxoplasma gondii) were used to investigate the practicability and sensitivity of the method. The detection limits (100% positive results) in the recovery experiments were four Toxocara eggs, two E. multilocularis eggs and 18 T. gondii oocysts (in 4/5 replicates). In a field study, helminth DNA was detected in 14 of 157 lettuce samples including Hydatigera taeniaeformis (Syn. Taenia taeniaeformis) (four samples), T. polyacantha (three), T. martis (one), E. multilocularis (two) and Toxocara cati (four). Toxoplasma gondii was detected in six of 100 samples. In vivo testing in mice resulted in metacestode growth in all animals injected with 40–60 E. multilocularis eggs, while infection rates were 20–40% with 2–20 eggs. The developed diagnostic strategy is highly sensitive for the isolation and genetic characterisation of a broad range of parasite stages from lettuce, whereas the sensitivity of the viability tests needs further improvement.
Highlights
A plethora of helminths and protozoa are transmitted to humans by oral uptake of parasite stages which can survive harsh conditions for long periods of time in the environment
All replicates spiked with 20, and four taeniid eggs were positive for E. multilocularis in PCR (21 μm filter), while 2/5 and 3/5 were PCR positive for Taenia, respectively
No DNA amplification in both PCRs was observed in three control lettuce samples
Summary
A plethora of helminths and protozoa are transmitted to humans by oral uptake of parasite stages which can survive harsh conditions for long periods of time in the environment. The intestinal parasites occur mainly in tropical and subtropical regions, with insufficient access to clean water and inadequate or absent sanitation. Based on such epidemiological conditions, several studies depicting activities to improve water management, sanitation, and hygiene (WASH) have documented a reduction in the incidence of human soil-transmitted parasites [5]. A range of zoonotic parasites is transmitted to humans via environmental stages excreted in animal faeces. Intestinal zoonotic helminths and protozoa of free-roaming canids including domestic dogs and foxes as well as those from free-roaming domestic cats play a major role in contaminating the environment, including recreational areas, private kitchen
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