Update on Blastocystis: highlights from the Fourth International BlastocystisConference

While the stramenopile Blastocystis, first discovered in 1911, is considered the most prevalent enteric protist in humans, its biology remains largely unexplored. Clinical studies have only recently begun investigating the role of Blastocystis in the gut and its relationship with the gut microbiome, and whether it plays a pathogenic role in human and animal health. Aiming to gather leading researchers in the field to encourage and stimulate cross-disciplinary dialogue while fostering long-term international collaborations, the Fourth International Blastocystis Conference was hosted from the 17 ^th to the 19 ^th of September 2024 in Heraklion (Crete, Greece). The event was mainly supported by the COST Action CA21105, " Blastocystis under One Health", and the Microbiology Society. The multi- and interdisciplinary conference programme covered all aspects related to Blastocystis evolutionary biology and advances in omics, intestinal ecology (gut microbiome), clinical significance and association with disease, diagnosis and molecular characterisation, as well as epidemiology and One Health. The high-quality presentations discussed at the conference provided researchers with a synthesis of recent advancements, while key research questions, knowledge gaps, and future steps in Blastocystis research were identified. Herein, we aim to provide a thorough overview of the presentations at the congress. The COST Action CA21105, 'Blastocystis under One Health,' will build on the insights and collaborations fostered during the conference, promoting integrative research approaches, advancing our understanding of Blastocystis, and driving future efforts to translate these findings into improved public health strategies.

Blastocystis, first identified in 1911, is one of the most common intestinal microorganisms found in humans; yet, little is known about its biology. Only recently have scientists started to investigate the role of Blastocystis in the gut microbiome and whether it causes disease in humans and animals. The Fourth International Blastocystis Conference, which was hosted in Heraklion (Crete, Greece) from the 17 ^th to the 19 ^th of September 2024, aimed to gather researchers from within the field to advance understanding and foster collaboration. The event was mainly supported by the COST Action CA21105, " Blastocystis under One Health", and the Microbiology Society. The event brought together research from various fields to discuss topics such as Blastocystis' biology, its role in the gut microbiome, links to disease, methods of diagnosis, and its global impact. Presentations highlighted recent advancements in the fields, identified unanswered questions and outlined future research priorities. In this summary, we aim to provide a thorough overview of the presentations at the congress. The COST Action CA21105, 'Blastocystis under One Health,' will build on the insights and collaborations formed during the conference, to advance our understanding of Blastocystis and better understand its implications for public health.