The Eradication of Blastocystis spp. Subtype 3 Improves the Course of Chronic Spontaneous Urticaria

Introduction: The role of Blastocystis spp. subtypes (STs) in chronic spontaneous urticaria (CSU) and the impact of the eradication are unclear. The aim of the study was to investigate the role of Blastocystis spp. STs in CSU and the impact of the eradication on disease activity.

Stool samples from 295 CSU patients and 38 healthy controls (HCs) were searched for Blastocystis spp. by direct microscopy. Fifty-seven samples from patients and 12 samples from HCs were analyzed for ST distribution by DNA sequencing. DNA sequencing was only performed in samples detected by real-time (RT) polymerase chain reaction (PCR). The patients and HCs with Blastocystis spp. formed groups A and B, respectively. Antiparasitic agents were used to eradicate the parasite in group A. Urticaria medication scores (MSs), urticaria activity score-7 (UAS7), blood eosinophil and basophil counts, total IgE values were compared between groups having different STs at the beginning and 6 months after the eradication. The subjects who were not taking any medication for the CSU such as antihistamine, montelukast, anti-IgE treatment, or cyclosporin had no active urticarial lesions during a 6-month period were considered to be in remission.

The parasite was detected in 45.7% (n = 135) of the CSU patients and 34.2% (n = 13) of the HCs. Fifty-seven samples (85.1%) in 67 CSU patients and 12 samples (92.3%) in 13 HCs revealed positive RT-PCR and formed groups A and B, respectively. ST3 was more frequent in group A (p < 0.001), whereas ST1 was more common in group B (p < 0.001). The patients having ST3 in group A formed subgroup A1 and other STs in group A formed subgroup A2. After the parasite eradication, the CSU remission rate was higher (p = 0.031) and the control values of UAS7, MSs were lower (p = 0.028, p = 0.049) in subgroup A1 than A2.

Although the presence of Blastocystis spp. ST3 does not worsen CSU, its eradication improves the CSU symptoms.