Background: Ivermectin (IVM) is one of the most important and widely used anthelmintics in veterinary medicine. However, its efficacy is increasingly compromised by widespread resistance, and the exact mechanism of IVM resistance remains unclear for most parasitic nematodes, including Haemonchus contortus, a blood-sucking parasitic nematode of small ruminants. Methods: In this study, an H. contortus IVM-resistant strain from Zhaosu, Xinjiang, China, was isolated and assessed by the control test, faecal egg count reduction test (FECRT) and the larval development assay (LDA). Subsequently, comparative analyses on the transcriptomics of IVM-susceptible and IVM-resistant adult worms of this parasite were carried out using RNA sequencing (RNA-seq) and bioinformatics. Results: In total, 543 (416 known, 127 novel) and 359 (309 known, 50 novel) differentially expressed genes (DEGs) were identified in male and female adult worms of the resistant strain compared with those of the susceptible strain, respectively. In addition to several previously known candidate genes which were supposed to be associated with IVM resistance and whose functions were involved in receptor activity, transport, and detoxification, we found some new potential target genes, including those related to lipid metabolism, structural constituent of cuticle, and important pathways such as antigen processing and presentation, lysosome, autophagy, apoptosis, and NOD1-like receptor signalling pathways. Finally, the results of quantitative real-time polymerase chain reaction confirmed that the transcriptional profiles of selected DEGs (male: 8 genes, female: 10 genes) were consistent with those obtained by the RNA-seq. Conclusions: Our results indicate that IVM has multiple effects, including both neuromuscular and non-neuromuscular targets, and provide valuable information for further studies on the IVM resistance mechanism in H. contortus. Graphical

Background: The Smad proteins function in TGF-β signalling transduction. In the model nematodeCaenorhabditis elegans, the co-Smad, DAF-3 mediates R-Smads and performs a central role in DAF-7 signal transduction, regulating dauer formation and reproductive processes. Considering the divergent evolutionary patterns of the DAF-7 signalling pathway in parasitic nematodes, it is meaningful to explore the structure and function of DAF-3 in parasitic nematodes, such asHaemonchus contortus.Methods: Adaf-3gene (Hc-daf-3) and its predicted product (Hc-DAF-3) were identified fromH. contortusand characterised using integrated genomic and genetic approaches. In addition to immunohistochemistry employed to localiseHc-DAF-3 within adult worm sections, real-time PCR was conducted to assess the transcriptional profiles in different developmental stages ofH. contortusand RNA interference (RNAi) was performedin vitroto assess the functional importance ofHc-daf-3in the development ofH. contortus.Results: Hc-DAF-3 sequences predicted fromHc-daf-3displayed typical features of the co-Smad subfamily. The nativeHc-DAF-3 was localised to the gonad and cuticle of adult parasites. In addition,Hc-daf-3was transcribed in all developmental stages studied, with a higher level in the third-stage larvae (L3) and adult females. Moreover, silencingHc-daf-3by RNAi retarded L4 development.Conclusion: The findings of the present study demonstrated an important role ofHc-DAF-3 in the development ofH. contortuslarvae.

Background: In most multicellular organisms, the transforming growth factor-β (TGF-β) signalling pathway is involved in regulating the growth and stem cell differentiation. Previous studies have demonstrated the importance of three key molecules in this pathway in the parasitic nematode Haemonchus contortus, including one TGF-β type I receptor (Hc-tgfbr1), one TGF-β type II receptor (Hc-tgfbr2), and one co-Smad (Hc-daf-3), which regulated the developmental transition from the free-living to the parasitic stages of this parasite. However, almost nothing is known about the function of the TGF-β ligand (Hc-tgh-2) of H. contortus. Methods: Here, the temporal transcription profiles of Hc-tgh-2 at eight different developmental stages and spatial expression patterns of Hc-TGH-2 in adult female and male worms of H. contortus have been examined by real-time PCR and immunohistochemistry, respectively. In addition, RNA interference (RNAi) by soaking was employed to assess the importance of Hc-tgh-2 in the development from exsheathed third-stage larvae (xL3s) to fourth-stage larvae (L4s) in H. contortus. Results: Hc-tgh-2 was continuously transcribed in all eight developmental stages of H. contortus studied with the highest level in the infective third-stage larvae (iL3) and Hc-TGH-2 was located in the muscle of the body wall, intestine, ovary of adult females and testes of adult males. Silencing Hc-tgh-2 by the specific double-stranded RNA (dsRNA), decreased the transcript level of Hc-tgh-2 and resulted in fewer xL3s developing to L4s in vitro. Conclusions: These results suggested that the TGF-β ligand, Hc-TGH-2, could play important roles in the developmental transition from the free-living (L3s) to the parasitic stage (L4s). Furthermore, it may also take part in the processes such as digestion, absorption, host immune response and reproductive development in H. contortus adults.

Parasitic nematodes are important pathogens that infect animals, causing significant economic losses globally. Current repeated treatments have led to widespread anthelmintic resistance in nematode populations, so vaccine development offers an alternative control approach. However, only one effective vaccine (named Barbervax) has been developed to protect animals against one of the most pathogenic nematodes of ruminants—Haemonchus contortus (the barber’s pole worm). This vaccine contains a dominant component, Concanavalin A (Con A) purified H11 antigen, which has been shown to induce high levels (>85%) of immune protection in sheep breeds, but in goat breeds, the immunoprotection test of this native protein is still lacking. Here, we evaluated the protective efficacy of low-dose Con A-purified proteins for controlling the H. contortus infection in goats. Four-month-old Boer goats were equally divided into two vaccinated groups of 5 μg and 10 μg native proteins, and one adjuvant control. Each goat was immunized subcutaneously thrice and then challenged with 7000 infective third-stage larvae (L3s). The fecal egg count (FEC), degree of anemia, antibody levels of serum and abomasum mucosa, as well as worm burdens, were detected in experimental goats. Our results showed that both 5 μg and 10 μg vaccinated groups induced the effective protection in goats, reduced mean FEC by 71.8% and 68.6%, and mean worm burdens by 69.8% and 61.6%, respectively, compared to the adjuvant control. In addition, we detected that the serum antibody responses to the Con A-purified proteins were dominated by the IgG subtype, but the mucosal antibody responses were not detected. These data demonstrate Con A-purified proteins induced effective immunoprotection in goats, and underline their significance for controlling this widespread parasite.

The complete mitochondrial (mt) genome of Trichuris skrjabini has been determined in the current study and subsequently compared with closely related species by phylogenetic analysis based on concatenated datasets of mt amino acid sequences. The whole mt genome of T. skrjabini is circular and 14,011 bp in length. It consists of a total of 37 genes including 13 protein coding genes (PCGs), two ribosomal RNA (rRNA) genes, 22 transfer RNA (tRNAs) genes, and two non-coding regions. The gene arrangement and contents were consistent with other members of the Trichuridae family including Trichuris suis, Trichuris trichiura, Trichuris ovis, and Trichuris discolor. Phylogenetic analysis based on concatenated datasets of amino acids of the 12 PCGs predicted the distinctiveness of Trichuris skrjabini as compared to other members of the Trichuridae family. Overall, our study supports the hypothesis that T. skrjabini is a distinct species. The provision of molecular data of whole mt genome of T. skrjabini delivers novel genetic markers for future studies of diagnostics, systematics, population genetics, and molecular epidemiology of T. skrjabini.