Fasciola hepatica is the causative agent of fasciolosis, a zoonosis with significant impact both in human and animal health. Understanding the basic processes of parasite biology, especially those related to interactions with its host, will contribute to control F. hepatica infections and hence liver pathology. Mucins have been described as important mediators for parasite establishment within its host, due to their key roles in immune evasion. In F. hepatica, mucin expression is upregulated in the mammalian invasive newly excysted juvenile (NEJ) stage in comparison with the adult stage. Here, we performed sequencing of mucin cDNAs prepared from NEJ RNA, resulting in six different cDNAs clusters. The differences are due to the presence of a tandem repeated sequence of 66 bp encoded by different exons. Two groups of apomucins one with three and the other with four repeats, with 459 and 393 bp respectively, were identified. These cDNAs have open reading frames encoding Ser-Thr enriched proteins with an N-terminal signal peptide, characteristic of apomucin backbone. We cloned a 4470 bp gene comprising eight exons and seven introns that encodes all the cDNA variants identified in NEJs. By real time polymerase chain reaction and high-resolution melting approaches of individual flukes we infer that fhemuc-1 is a single-copy gene, with at least two different alleles. Our data suggest that both gene polymorphism and alternative splicing might account for apomucin variability in the fhemuc-1 gene that is upregulated in NEJ invasive stage. The relevance of this variation in host–parasite interplay is discussed.

The effects of a range of FMRFamide-related peptides (FaRPs) on isometric contractility were tested using isolated muscle strips from the liver fluke, F. hepatica. The neuropeptides tested were the molluscan FaRPs, FMRFamide and FLRFamide, the turbellarian FaRPs, RYIRFamide and GYIRFamide, the cestode peptides, NPF and GNFFRFamide, and the nematode FaRPs, AF-1 (KNEFIRFamide), AF-2 (KHEYLRFamide), AF-8 (KSAYMRFamide), and PF-4 (KPNFIRFamide). Dose-response experiments were undertaken at a concentration range of 5 nM–5 μM for all of the neuropeptides tested. FMRFamide and AF-8 caused statistically significant increases in the amplitude and frequency of contractions at concentrations of 0·5 μM and 5 μM. FLRFamide and AF-2 also caused significant increases in contraction frequency at concentrations of 0·5 μM and 5 μM, although a significant increase in amplitude of contraction was observed only at a concentration of 5 μM. GYIRFamide increased both amplitude and frequency significantly at concentrations of 50 nM, 0·5 μM and 5 μM. RYIRFamide significantly increased frequency of contractions at concentrations of 0·5 μM and 5 μM, but failed to have a significant effect on contraction amplitude. AF-1 at a concentration of 5 μM increased contraction amplitude, but failed to have an effect on frequency at any of the concentrations used. PF-4 caused a statistically significant increase in both the amplitude and frequency of contractions at a concentration of 5 μM. NPF and GNFFRFamide had no effect on the in vitro motility of F. hepatica over the range of concentrations tested. The results are discussed in the light of possible structure–activity relationships in the FaRPs tested.