Blastocystis in raw vegetables from street markets in northern Thailand

Blastocystis is a stramenopile protist of controversial pathogenicity. The organism colonizes a broad range of vertebrate and invertebrate hosts. Blastocystis has also been found in the environment both in water and soil. Several routes of transmission have been proposed including human-to-human, animal-to-human and via contaminated food and water. In recent years, the presence of Blastocystis in vegetables has started to be explored. However, most studies have focused on microscopic detection. Moreover, works of this type from Asia are barely available. Hence, the aim of this preliminary study was to examine the occurrence of Blastocystis in raw vegetables sold in markets in northern Thailand. Fresh produce (n=20) commonly used in Thai cuisine (Lanna) was purchased from two street markets and screened for Blastocystis using qPCR. Blastocystis was detected in 45% of the samples with the dominant subtype being ST3. Produce growing underground, such as galangal, carrot and beetroot were positive for the organism suggesting soil or inadequately composted manure as the source of contamination. To our knowledge, our study is the first to perform subtyping of Blastocystis in vegetables. Our results hint towards fresh produce being an, as yet, not widely explored, transmission route of Blastocystis in the studied community. Looking forward, large-scale investigations should on the prevalence of this and other organisms under the One Health umbrella should be undertaken.