Molecular Detection of Blastocystis sp. in Insects and Other Invertebrates From China: Subtype Diversity and Potential Ecological Implications

Blastocystis sp. is widely detected in the intestinal tracts of vertebrates. To date, there are limited reports on its occurrence in invertebrate taxa and its interactions with invertebrates, which greatly hinders the ecological characterization of Blastocystis sp. This study employed morphological and molecular biological methods to analyze the distribution and diversity characteristics of Blastocystis sp. Carrier survey results revealed that among the 1387 collected invertebrates, including soil nematodes, earthworms, leeches, snails, slugs, ticks, woodlice, millipedes, and insects, insects were the invertebrate group in which Blastocystis sp. DNA was most frequently detected. Among insects, the highest detection rate was observed in Neuroptera (25%), followed by Hemiptera (5.66%), Orthoptera (4.76%), Diptera (4.73%), Hymenoptera (2.75%), and Coleoptera (2.63%). Only one tick was found positive, and no Blastocystis sp. DNA was detected in other invertebrate groups. The exploratory survey suggested that the living space, habitat environment, and feeding modes of insects may be associated with Blastocystis sp. detection. Subtype analysis revealed that only Blastocystis sp. ST1, ST2, and ST3 were detected in the surveyed insects. The three subtypes were isolated from bumblebees, lacewings, and houseflies, respectively, supporting the molecular identification results. Haplotype and genetic distance analyses, when performed separately by subtype, revealed substantial intra-subtype genetic diversity for ST1. These findings not only expand the range of arthropod taxa in which Blastocystis sp. DNA has been detected, but also raise the possibility that insects may participate in the environmental transmission cycle of the parasite, thereby contributing to a better understanding of its ecological niche.