Blastocystis hominis – Symptoms and Treatment Protocol Options
In 2022, approximately one billion individuals were infected with Blastocystis hominis worldwide, with prevalence rates ranging from 30% to 50% in developing regions and 1.5% to 10% in developed countries.1 Blastocystis hominis can be transmitted via the fecal-oral route, and human infection primarily results from the ingestion of cysts in contaminated water and food, such as improperly washed fruits and vegetables. Direct transmission may also occur through contact with animal reservoirs, including pets, livestock, and birds.1,2
In healthy individuals, infection with Blastocystis hominis (blastocystosis) is often mild or asymptomatic. However, immunocompromised individuals are more vulnerable and can develop blastocystosis with diarrhea and other symptoms. Animal models suggest that disease severity is exacerbated by impaired immunity.1
Symptoms of blastocystosis may include acute diarrhea, nausea, vomiting, abdominal pain, weight loss, anorexia, chronic diarrhea, bloating, and general weakness. Moreover, several non-gastrointestinal symptoms, such as rash, pruritus, urticaria, various food reactions, and joint pain, have been reported. In patients with significant immunosuppression or comorbidities, blastocystosis can be life-threatening.1,3
In vitro studies of pathogenesis demonstrate that Blastocystis hominis can:
- Attach to the intestinal mucosa
- Increase intestinal permeability (leaky gut) via the secretion of cysteine proteases
- Degrade secretory immunoglobulin A (sIgA)
- Induce the secretion of inflammatory cytokines, including interleukin-8 (IL-8)
- Contribute to the apoptosis of host cells3
Still, despite evidence of pathogenicity, many question whether it should be considered a pathogen or a commensal microorganism.3 The U.S. Centers for Disease Control and Prevention (CDC) describes Blastocystis hominis as “a genetically diverse unicellular parasite of unclear pathogenic potential.4 Nonetheless, the eradication of Blastocystis hominis is indicated in cases where it is the sole protist agent associated with symptoms.3 Furthermore, research is exploring the potential involvement of Blastocystis hominis in the pathogenesis of irritable bowel syndrome (IBS), colorectal cancer, and autoimmune diseases, including Hashimoto’s thyroiditis.1
Treatment protocols are presented in the document Blastocystis Treatment Protocols, available in your Provider Portal.
To test for Blastocystis hominis, order an Expanded GI Health Panel™ or a Comprehensive Ova and Parasites Panel™.
To place a test order, click here. DiagnosTechs will drop ship test kits directly to your patients. You may select this option at the top of the order form.
References:
- Pawelec-Pęciak O, Łanocha-Arendarczyk N, Grzeszczak K, et al. The Role of Blastocystis in the Etiology of Gastrointestinal and Autoimmune Diseases. Pathogens. 2025;14(4):313. doi:10.3390/pathogens14040313
- Jiménez PA, Jaimes JE, Ramírez JD. A summary of Blastocystis subtypes in North and South America. Parasit Vectors. 2019;12(1):376. doi:10.1186/s13071-019-3641-2
- Aykur M, Malatyalı E, Demirel F, et al. Blastocystis: A Mysterious Member of the Gut Microbiome. Microorganisms. 2024;12(3):461. doi:10.3390/microorganisms12030461
- CDC – DPDx – Blastocystis hominis. DPDx – Laboratory Identification of Parasites of Public Health Concern. October 21, 2019. Accessed June 13, 2025. https://www.cdc.gov/dpdx/blastocystis/index.html.