UNASSIGNED: Anisakis are globally distributed, marine parasitic nematodes that can cause human health problems, including symptoms such as vomiting, acute diarrhea, and allergic reactions. As parasitic nematodes that primarily affect the patient\'s digestive tract, intestinal helminths can interact directly with the host microbiota through physical contact, chemicals, or nutrient competition. It is widely accepted that the host microbiota plays a crucial role in the regulation of immunity.
UNASSIGNED: Nematodes collected from the abdominal cavity of marine fish were identified by molecular biology and live worms were artificially infected in rats. Infection was determined by indirect ELISA based on rat serum and worm extraction. Feces were collected for 16S rDNA-based analysis of microbiota diversity.
UNASSIGNED: Molecular biology identification based on ITS sequences identified the collected nematodes as A. pegreffii. The success of the artificial infection was determined by indirect ELISA based on serum and worm extraction from artificially infected rats. Microbiota diversity analysis showed that a total of 773 ASVs were generated, and PCoA showed that the infected group was differentiated from the control group. The control group contained five characterized genera (Prevotellaceae NK3B31 group, Turicibacter, Clostridium sensu stricto 1, Candidatus Stoquefichus, Lachnospira) and the infected group contained nine characterized genera (Rodentibacter, Christensenella, Dubosiella, Streptococcus, Anaeroplasma, Lactococcus, Papillibacter, Desulfovibrio, Roseburia). Based on the Wilcoxon test, four processes were found to be significant: bacterial secretion system, bacterial invasion of epithelial cells, bacterial chemotaxis, and ABC transporters.
UNASSIGNED: This study is the first to analyze the diversity of the intestinal microbiota of rats infected with A. pegreffii and to determine the damage and regulation of metabolism and immunity caused by the infection in the rat gut. The findings provide a basis for further research on host-helminth-microbe correlationships.

Studying the genetic diversity of nematode parasite populations is crucial to gaining insight into parasite infection dynamics and informing parasite phylogeography. Anisakiasis is a zoonotic disease caused by the consumption of infectious third-stage larvae (L3) of Anisakis spp. carried by marine fish. In the present study, a total of 206 mitochondrial DNA sequences (cytochrome c oxidase 2, cox2) were used to study the genetic diversity, genetic structure, and historical demography of twelve A. pegreffii populations from Trichiurus japonicas along the coast of mainland China and Taiwan. Two distinct evolutionary lineages of A. pegreffii and no significant genealogical structures corresponding to sampling localities suggested that isolation in the marginal seas shaped their patterns of phylogeographic distribution along the coast of mainland China and Taiwan during glaciation with lower sea levels. Furthermore, pairwise FST values and AMOVA did not indicate any significant genetic differentiation among groups with no relation to the geographic area, which might be attributed to fewer barriers to gene flow as well as large population sizes. The results of the neutrality test, mismatch distribution, and Bayesian skyline plot analyses showed that entire population underwent population expansion during the late Pleistocene. Analysis of the demographic history revealed that A. pegreffii underwent historical lineage diversification and admixture due to secondary contact based on ABC analysis. The present research represents the first definitive population structure and demographic history across sampling locations of A. pegreffii along the coast of mainland China and Taiwan.

To better understand the molecular mechanisms underlying allergens and parasite immunity and discover the stage-enriched gene expression of fish-borne zoonotic nematodes in the stomach, we used RNA-seq to study the transcriptome profiles of Anisakis pegreffii (Nematoda: Anisakidae, AP) in simulated gastric juice. Mobile L3 larvae were incubated in simulated medium at 37 °C in 5% CO2 (AP-GJ) and the control group larvae were collected in PBS under the same conditions (AP-PBS). We found that the sequences of A. pegreffii were highly similar to Toxocara canis sequences. Among the transcripts, there would be 138 up-regulated putative genes and 251 down-regulated putative genes in AP-GJ group. Several lipid binging-related genes were more highly expressed in AP-GJ larvae. Moreover, 17 allergen genes were up-regulated and 29 were down-regulated in AP-GJ larvae. Eleven allergen genes belonged to one or more of the following three categories: biological process, cellular component, and molecular function. According to KEGG analysis, the main pathways that were represented included protein processing in transcription, immune system, cancer, and infectious disease. In particular, the most significant changes in the expression of parasite-derived allergen products occurred in AP-GJ larvae. This study helps us to extend our understanding of the biology of the fish-borne zoonotic parasite A. pegreffii and could be helpful for more precise risk assessment and providing guidelines for allergic consumers.