Newsletter: UP researchers caution against parasites in raw vegetables, seafood

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Scientists from the University of the Philippines (UP) are gently reminding the public to thoroughly wash and cook their market-bought fresh produce and seafood as a precautionary measure against parasites.

Toxoplasma gondii parasites (Photo credit: CDC-DPDx; see reference below)

The parasite that causes toxoplasmosis, called Toxoplasma gondii (T. gondii), is one of the most infectious parasites in the world: it affects almost a third of the world’s population, most especially vulnerable groups such as the pregnant and immunocompromised. While most people infected with the disease do not present any symptoms, some may suffer flu-like symptoms, such as fever, headache, and muscle aches. But in severe cases, toxoplasmosis can cause inflammation of the brain and blurry vision. Infected parents’ newborn infants may suffer from excessive fluid in the brain and developmental issues. Fortunately, treatments are available for toxoplasmosis, hence symptomatic individuals are advised to seek timely medical attention.

Cielo Emar M. Paraoan, Ren Mark D. Villanueva, and Marie Christine M. Obusan of the UP Diliman College of Science’s Institute of Biology (UPD-CS IB) found that T. gondii is fairly common in vegetables and oysters that they sampled from local markets in Central Luzon. Among the vegetables tested were lettuce, cabbage, carrots, cauliflower, and mung bean sprouts.

Six out of sixty (10%) collected vegetable samples contained traces of T. gondii, with leafy vegetables found to be more contaminated than root vegetables. Similarly, for oysters, 9.09%  or four out of 44 samples were also contaminated. The researchers noted that the T. gondii traces found on both vegetables and oysters are of Type I genotype. The researchers aim to investigate further the genotypes of T. gondii that will be detected in the country, as Asia is reported to have a high degree of genetic diversity.

The study provides evidence that T. gondii may be transmitted through vegetables and oysters that are being sold in supermarkets and public markets. However, the researchers noted that they only tested a small sample size, and more studies with bigger sample sizes must be conducted. At present, they have an ongoing study that detects the parasite in environmental samples.

The study also underscores the importance of adequately preparing fresh produce and seafood to eliminate not just T. gondii but also other parasites that may be present. The authors also emphasized the need for better management of biological pollutants. 

“The most sustainable approach for reducing the risk of T. gondii exposure through the consumption of seafood should focus on reducing T. gondii contamination at its source, as well as mitigating the flow of contaminated runoff to water bodies,” the authors said in their paper, published in the October 2023 issue of the Philippine Journal of Science.

References:

Paraoan CE et al. 2023. Molecular Detection and Prevalence of Toxoplasma gondii in Ready-to-eat Vegetables and Oysters in Central Luzon, Philippines. Philipp J Sci 152(5): 1989–1998. https://doi.org/10.56899/152.05.36

Centers for Disease Control and Prevention. (2023, June 9). CDC - toxoplasmosis. Centers for Disease Control and Prevention. https://www.cdc.gov/parasites/toxoplasmosis/index.html 

Mayo Clinic Staff. (2022, November 3). Toxoplasmosis. Mayo Clinic. https://www.mayoclinic.org/diseases-conditions/toxoplasmosis/symptoms-causes/syc-20356249 

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