Public health risks associated with food‐borne parasites

Abstract

Parasites are important food‐borne pathogens. Their complex lifecycles, varied transmission routes, and prolonged periods between infection and symptoms mean that the public health burden and relative importance of different transmission routes are often difficult to assess. Furthermore, there are challenges in detection and diagnostics, and variations in reporting. A Europe‐focused ranking exercise, using multicriteria decision analysis, identified potentially food‐borne parasites of importance, and that are currently not routinely controlled in food. These are Cryptosporidium spp., Toxoplasma gondii and Echinococcus spp. Infection with these parasites in humans and animals, or their occurrence in food, is not notifiable in all Member States. This Opinion reviews current methods for detection, identification and tracing of these parasites in relevant foods, reviews literature on food‐borne pathways, examines information on their occurrence and persistence in foods, and investigates possible control measures along the food chain. The differences between these three parasites are substantial, but for all there is a paucity of well‐established, standardised, validated methods that can be applied across the range of relevant foods. Furthermore, the prolonged period between infection and clinical symptoms (from several days for Cryptosporidium to years for Echinococcus spp.) means that source attribution studies are very difficult. Nevertheless, our knowledge of the domestic animal lifecycle (involving dogs and livestock) for Echinoccocus granulosus means that this parasite is controllable. For Echinococcus multilocularis, for which the lifecycle involves wildlife (foxes and rodents), control would be expensive and complicated, but could be achieved in targeted areas with sufficient commitment and resources. Quantitative risk assessments have been described for Toxoplasma in meat. However, for T. gondii and Cryptosporidium as faecal contaminants, development of validated detection methods, including survival/infectivity assays and consensus molecular typing protocols, are required for the development of quantitative risk assessments and efficient control measures.

A Sensitive, One-Way Sequential Sieving Method to Isolate Helminths’ Eggs and Protozoal Oocysts from Lettuce for Genetic Identification

“…alveolar and cystic echinococcosis caused by E. multilocularis and E. granulosus s.l., respectively). Moreover, food is not the only source for parasites transmitted to humans, and so far quantitative estimations of the role of food in the transmission could not be established [20]. Overall, the role of food in the transmission of Echinococcus spp.…”

“…Therefore, a molecular approach is crucial for the correct identification of parasite stages and also for improving the sensitivity of the method. A variety of diagnostic procedures have been developed/validated in the last decades, mainly focusing on the monospecific detection of pathogens, with high potential to be used for food investigations [20]. However, a strategy with the potential of detecting simultaneously the full range of foodborne parasitic pathogens is still missing.…”

Monitoring of selected parasites and other foodborne microorganisms in vegetable products at point of sale

“…and G. intestinalis may be present in produce and can be identified as causes of foodborne diseases [11,2], there are only a few reports concerning their prevalence on produce. Most studies are from developing countries where poor hygiene is prevalent [12,13,14] and from north European countries where outbreaks connected with parasites were described in recent years [11,15,16].…”

“…The waterborne route and manure application to vegetable fields is the most important means of transmission of these parasites [16]. In some cases, transmission of these pathogens to vegetables were attributed to infected food-handlers [19].…”

Molecular Methods for the Detection of Toxoplasma gondii Oocysts in Fresh Produce: An Extensive Review

“…It has been estimated that 42–61% of acquired toxoplasmosis cases are foodborne [ 4 ]. The food- and waterborne transmission routes of T. gondii are numerous, including ingestion of infective tissue-dwelling stages of the parasite in raw or undercooked meat of infected animals and ingestion of oocysts, shed by infected felines and sporulated in the environment, in contaminated water or food, such as fresh produce (fruits, vegetables, and juice) [ 5 ].…”