Blastocystis and the Microbiome
Is Blastocystis a pathogen? Should we eradicate it? How to eradicate it? Does it have any benefits?
General:
Review, Aug 2022: The regulatory function of Blastocystis spp. on the immune inflammatory response in the gut microbiome https://www.frontiersin.org/articles/10.3389/fcimb.2022.967724/full - unclear whether pathogen or not.
There are several sub-genera of blastocystis, some are pathogenic, and some are not. Here is a useful blog on Blasto by a Danish scientist: https://www.blastocystis.net/p/me-and-my-research.html
A quote from his blog:
There is no known efficient eradication strategy for Blastocystis.
Eradication of Blastocystis Carriage With Antimicrobials: Reality or Delusion? (Review, 2010)
Studies have reported the discovery of several novel subtypes, such as ST33 and ST34 in horses, and ST35 to ST38 in various mammalian hosts. These findings suggest that Blastocystis has a diverse genetic makeup, which may influence its pathogenic potential and interactions with hosts https://www.nature.com/research-intelligence/blastocystis-infections-and-intestinal-parasites
FMT:
First Blastocystis Transmission to FMT Recipients Reported. Lack of adverse effects may warrant removing parasite from stool donor exclusion criteria, researchers say (Nov 2019) https://www.medpagetoday.com/gastroenterology/generalgastroenterology/83443. Human transmission of Blastocystis by Fecal Microbiota Transplantation without development of gastrointestinal symptoms in recipients.
In the United States, stool donors are no longer screened for Blastocystis hominis, and CHUV (Lausanne University Hospital) has adopted the same practice. (2023) https://smw.ch/index.php/smw/article/view/3472/5739#d119e205
Transient colonization with Blastocystis spp. after transmission via fecal microbiota transplantation (2025) https://link.springer.com/article/10.1007/s10096-025-05124-6 "We present the first long-term data on viable Blastocystis spp. transmission via fresh FMT in three cases. Transient colonization with Blastocystis spp. was observed, without serious FMT-related adverse events"
Harms:
One subtype of the common gut eukaryote Blastocystis directly kills off the good gut bacterium Bifidobacterum, and is linked with reduced numbers of another good microbiome bacterium, Lactobacillus (2019): https://www.genengnews.com/news/gut-microbiome-eukaryote-causes-death-of-good-bacteria/ - Interactions between a pathogenic Blastocystis subtype and gut microbiota: in vitro and in vivo studies.
Presence of Blastocystis in gut microbiota is associated with cognitive traits and decreased executive function (Jun 2022) https://www.nature.com/articles/s41396-022-01262-3
Evaluation of association with subtypes and alleles of Blastocystis with chronic spontaneous urticaria (Apr 2022, n=189) https://www.sciencedirect.com/science/article/abs/pii/S0001706X22001474 "the presence of Blastocystis ST3 allele 34 significantly associated with chronic spontaneous urticaria"
Benefits:
Stool Microbiota Diversity Analysis of Blastocystis-Positive and Blastocystis-Negative Individuals (Jan 2022, n=1285) https://www.mdpi.com/2076-2607/10/2/326 "Individuals with Blastocystis-positive stools appear to have gut microbiomes associated with eubiosis unlike those with Blastocystis-negative stools, whose gut microbiomes are similar to those associated with dysbiosis"
Experimental colonization with Blastocystis ST4 is associated with protective immune responses and modulation of gut microbiome in a DSS-induced colitis mouse model (Apr 2022) https://link.springer.com/article/10.1007/s00018-022-04271-9
Blastocystis subtype 4 linked to gut microbiota stability (Aug 2022) https://www.thelancet.com/journals/lanmic/article/PIIS2666-5247(22)00196-3/fulltext
Intestinal Blastocystis is linked to healthier diets and more favorable cardiometabolic outcomes in 56,989 individuals from 32 countries (Jul 2024, n=1124) https://forum.humanmicrobiome.info/threads/intestinal-blastocystis-is-linked-to-healthier-diets-and-more-favorabl.476/