LAUSR

Simple Summary Blastocystis is a neglected enteric pathogen that is highly prevalent in humans and animals worldwide. Studies have reported that Blastocystis infection frequently coexists with other infectious pathogens in humans. However, dual infection by Blastocystis and Echinococcus multilocularis, which causes the severe parasitic disease echinococcosis has not been reported. In this study, the authors investigated the clinical prevalence, risk factors, and genotypes of Blastocystis in Tibetan patients with liver echinococcosis and Tibetan healthy controls from the Qinghai province in China, and also tested whether E. multilocularis infection increases host susceptibility to Blastocystis using a mouse model. The results found a significantly higher prevalence of genetically divergent Blastocystis in Tibetans with liver echinococcosis. E. multilocularis infection in Balb/c mice increased the host susceptibility to Blastocystis and aggravated intestinal pathology with higher disease severity and higher mortality. Taken together, these findings provide new insights into dual infections by Blastocystis and helminths in humans. Abstract Blastocystis is a common human intestinal protozoan parasite. Little is known about its prevalence in echinococcosis. This study tested whether Echinococcus multilocularis infection would increase host susceptibility to Blastocystis. A total of 114 fecal samples (68 hydatid disease patients and 46 healthy people) were collected from Tibetans in the Qinghai province in China. The presence of Blastocystis was identified by sequencing of the small subunit (SSU) rRNA gene. Balb/c mice were co-infected with Blastocystis and E. multilocularis and tested for host susceptibility to Blastocystis. The overall Blastocystis prevalence was 12.3%; 16.2% in the patients and 4.4% in healthy people (p < 0.05). Sequence analysis identified three known Blastocystis genotypes, including ST1, ST2, and ST3, and one unknown genotype. Experimental dual infection significantly reduced mouse survival rate (20%), induced more severe signs, and increased intestinal damages with a higher intestinal colonization level of Blastocystis. The mouse model showed that E. multilocularis infection increases host susceptibility to Blastocystis. Our study shows a significantly higher prevalence of Blastocystis in patients with liver echinococcosis and reveals that non-intestinal E. multilocularis infection increases host susceptibility to the Blastocystis. Our results highlight that E. multilocularis infection is associated with Blastocystis. These findings remind us that more attention should be paid to the gut health of the patients with a helminth infection during clinical patient care.