Food safety: seasonal influence on parasitic contamination of lettuce (Lactuca sativa L.) commercialized in street markets in Belém, Pará, Brazil

Abstract The consumption of fresh vegetables in Brazil and in the world has been increasing significantly. Of these foods, lettuce (Lactuca sativa L.) is the vegetable most consumed in Brazil, since it is suitable for several types of diet and presents a low caloric value. Nevertheless, the preference for this type of food and its benefits may expose consumers to the risk of contracting infections due to various pathogens. The objective of the present study was to evaluate the influence of seasonality on the parasitic contamination of lettuces commercialized in four street markets in the city of Belém-PA, Brazil. One hundred and twenty lettuce specimens were obtained from municipal street markets in Belém during the dry and rainy seasons, and then processed and analysed individually by the spontaneous sedimentation method. The level of contamination of the vegetables was found to be similar in the different seasonal periods, being 36.7% during the dry season and 38.7% in the rainy season. Mixed parasitic contamination, detected especially in the rainy season, suggests that the rainfall indices may influence the increase in the number of parasite species potentially affecting the population. The results showed elevated contamination by parasitic agents in all the street markets that commercialized the vegetable. The main parasitic species detected were Ascaris sp., Ancylostoma sp., Strongyloides sp., Enterobius vermicularis, Taenia sp., Toxoplasma gondii oocyst, and other dirt. The study identified a moderate rate of contamination by helminths and protozoans in the lettuces sold in the street markets of the city of Belém, showing evidence of the continuous risk of parasitic infections to humans from the consumption of raw vegetables, which justifies the implementation of measures that allow for an improvement in the hygienic-sanitary quality.