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Water Parasite Found in Supermarket Pre-Washed Vegetables

Fruits and vegetables at a supermarket.
Credit: Jacopo Maia/ Unsplash
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Cryptosporidium has been discovered in pre-washed vegetables from major supermarkets in Kent by researchers in the School of Biosciences.

The water-borne and food-borne parasite Cryptosporidium, which has most recently been identified for contaminating drinking water in areas of the UK, was found in over 17% of samples of pre-washed vegetables analysed by the scientists.

Cryptosporidium is a parasite that causes an infection called cryptosporidiosis, affecting people and farm animals with symptoms such as diarrhoea, vomiting, stomach pains and fever. Cryptosporidium is typically found in lakes, streams, rivers and untreated drinking water.

Cryptosporidiosis is contagious and most notably transferred from another person or animal by touching faeces, or by swimming in or drinking contaminated water. While occasionally people can be infected by eating and drinking contaminated food such as unpasteurised milk, under cooked meat and offal (liver, kidneys, and heart), there was limited research into the presence of Cryptosporidium in pre-washed and ready to eat vegetables in the UK.

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While pre-washed and ready-to-eat vegetables undergo more thorough washing with water containing chlorine disinfectants compared to unpackaged vegetables, Cryptosporidium particles (oocysts) are actually resistant to disinfection with chlorine and can only be reliably removed by boiling water or filtration. So, they are expected to be free from parasites and ready to eat straight from the packaging, but some oocysts remain and are likely to cause illness.

Dr Anastasios Tsaousis, Reader in Molecular and Evolutionary Parasitology and the research lead, said: ‘Whilst our 2023 study cannot distinguish between live and inert Cryptosporidium, it is nevertheless important in that the presence of Cryptosporidium in pre-washed vegetables could mean revisiting the sanitation methods employed by suppliers along the chain of production such as improved hygiene measures during harvesting, processing, packaging, transportation and storage.

‘There is also a need for increased awareness among consumers on the adequate storage of vegetables and handwashing before eating.’

Reference: Suleiman AJ, Mavrides DE, Maxamhud S, Gentekaki E, Tsaousis AD. Presence of Cryptosporidium parvum in pre-washed vegetables from different supermarkets in South East England: A pilot study. Parasitol Res. 2024;123(6):230. doi: 10.1007/s00436-024-08250-w

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