Background: Studies of human intestinal microbiota have focused mainly on bacteria and scarce information on how eukaryotic parasites fit in the gut context or its role in human health and disease. Objectives: This is an approach to explore if intestinal parasites represent a significant factor concerning the treatment-decisions or disease activity in inflammatory conditions such as SpA Methods: A Cross-sectional study including 65 patients with SpA according to ASAS classification criteria was performed. Clinical evaluation was made by rheumatologists and gastroenterologists. Stool samples were collected and microscopically analyzed by direct saline, Mini Parasep concentration and Kato Katz. Most prevalent protozoa in Colombia were also analyzed using PCR/qPCR. Lab tests included fecal calprotectin, CRP, ESR, and HLA-B*27. The association between intestinal parasite infection and clinical/treatment variables were evaluated using the Chi-square or Fisher’s exact test. (Ethical/Cod.2017-023) Results: SpA patients had a mean age of 43.9±11.5 years, 61.5% were male, 52.5% were positive for HLA-B*27 and 87.7% had axial involvement. In total, 67.7% of the patients were receiving biological treatment, 64.6% had ASDAS-CRP ≥2.1. In total, 75.4% of patients were positive for ≥2 gastrointestinal symptoms with a predominance of abdominal pain (66.2%), abdominal inflammation (63.1%), diarrhea (47.7%) and intolerance to some food (58.5%). Interestingly, 21.3% have high levels of calprotectin, 20% of patients with high calprotectin were receiving biological treatment against IL-17 (p=0.086) and 80% of these patients had BASDAI >4 (p=0.017) and ASDAS-VSG >2.1 (p=0.03). The parasites found in SpA patients were Endolimax nana (98%), Blastocystis ssp. (63.8%), Entamoeba coli (8.6%), Entamoeba histolytica (6.9%), Chilomastix mesnili (6.4%), E. dispar/moshkovskii (1.7%) and Giardia intestinalis (3.7%). Patients positive for E coli (80%) were treated with NSAIDs (p=0.003). 3/4 of patients positive for E histolytica presented HLAB*27:05:02 positive. Likewise, the only patient who was positive for G intestinalis expressed this allele. 5/7 of patients treated with Sulfasalazine presented Blastocystis ssp and 33.3% E coli . The presence of intestinal parasites in SpA patients was not associated with gastrointestinal symptoms, either disease-activity measures. Conclusion: The intestinal parasitism in the tropical countries as Colombia have shown an interesting pattern in SpA patients. The treatment may modulate the presence of some parasites; however, the presence of intestinal parasites in SpA does not seem to influence clinical disease activity Acknowledgments: The Government Institute of Science, Technology,and Innovation,Francisco Jose de Caldas—COLCIENCIAS(Grant No. 130877757442). Universidad El Bosque (PCI-2018-10091),Hospital Militar Central (Grant 2017-023), Clínicos IPS, Gastroadvanced, Fundación Instituto de Reumatología Fernando Chalem-Bogota,Colombia and Biomedicina de Chihuahua, México Disclosure of Interests: None declared