Gastrointestinal nematodes of sheep and cattle: Biology and control

Identification of a novel methyltransferase-type 12 protein from Haemonchus contortus and its effects on functions of goat PBMCs

Background

Methyltransferases (MTFs) are broad range of enzymes, which are ubiquitously expressed in diverse organisms ranging from bacteria to animals. MTFs proteins have been associated with various biological/cellular processes including transcriptional regulation, subcellular protein and RNA localization, signal transduction and DNA-damage repair. However, the role of MTFs in immune mechanism during host–parasite interaction has not been addressed yet.

Results

An open reading frame (764 bp) of methyltransferase-type 12 gene of H. contortus denoted as HcMTF-12, was successfully cloned using reverse transcriptase-polymerase chain reaction (RT-PCR) followed by prokaryotic expression in Escherichia coli BL21 (DE3 strain). The recombinant HcMTF-12 protein (rHcMTF-12) was about 47 kDa along with a fusion vector protein of 18 kDa. Immunoblot results identified the native protein MTF-12 with antibodies produced in rats against rHcMT-12, whereas rHcMTF-12 protein was recognized with sera of goat experimentally infected with H. contortus. Immunohistochemical analysis revealed that the native MTF-12 protein was mainly located in the periphery (cuticle) of parasite sections as well as within the pharynx and intestinal region. An immunofluorescence assay validated that rHcMTF-12 attached to the surface of goat PBMCs. Furthermore, the cytokines transcription of IL-2, IFN-γ and IL-4 transcripts of PBMCs incubated with rHcMTF-12 were enhanced in a dose-dependent manner. The secretion of TGF-β1 and IL-10 was significantly decreased. However, IL-6 production was not significantly different as compared to the control groups. Moreover, the migration activity and nitric oxide (NO) production by PBMCs were induced considerably, whereas the proliferation of PBMCs cells was negatively affected when incubated with the rHcMTF-12 protein.

Conclusions

Our findings suggest that HcMTF-12 significantly mediated the functions of PBMCs, and it might be a potential candidate for therapeutic interventions against haemonchosis.

Detection of genomic regions underlying resistance to gastrointestinal parasites in Australian sheep

BACKGROUND

This study aimed at identifying genomic regions that underlie genetic variation of worm egg count, as an indicator trait for parasite resistance in a large population of Australian sheep, which was genotyped with the high-density 600 K Ovine single nucleotide polymorphism array. This study included 7539 sheep from different locations across Australia that underwent a field challenge with mixed gastrointestinal parasite species. Faecal samples were collected and worm egg counts for three strongyle species, i.e. Teladorsagia circumcincta, Haemonchus contortus and Trichostrongylus colubriformis were determined. Data were analysed using genome-wide association studies (GWAS) and regional heritability mapping (RHM).

RESULTS

Both RHM and GWAS detected a region on Ovis aries (OAR) chromosome 2 that was highly significantly associated with parasite resistance at a genome-wise false discovery rate of 5%. RHM revealed additional significant regions on OAR6, 18, and 24. Pathway analysis revealed 13 genes within these significant regions (SH3RF1, HERC2, MAP3K, CYFIP1, PTPN1, BIN1, HERC3, HERC5, HERC6, IBSP, SPP1, ISG20, and DET1), which have various roles in innate and acquired immune response mechanisms, as well as cytokine signalling. Other genes involved in haemostasis regulation and mucosal defence were also detected, which are important for protection of sheep against invading parasites.

CONCLUSIONS

This study identified significant genomic regions on OAR2, 6, 18, and 24 that are associated with parasite resistance in sheep. RHM was more powerful in detecting regions that affect parasite resistance than GWAS. Our results support the hypothesis that parasite resistance is a complex trait and is determined by a large number of genes with small effects, rather than by a few major genes with large effects.

Gastrointestinal nematodes infections and anthelmintic resistance in grazing sheep in the Eastern Inner Mongolia in China

Gastrointestinal nematodes (GIN) are a crucial restraint to grazing sheep production worldwide. This study was conducted to determine the infections and anthelmintic resistance (AR) of GIN in pasture-based sheep in the Eastern Inner Mongolia, China. GIN eggs were tested from 600 grazing sheep feces of 10 farms using saturated saline flotation method and McMaster's method. The egg hatch test (EHT) and the faecal egg count reduction test (FECRT) were used to evaluate resistance of GIN to anthelmintics. We found that the average infection rate was 79.2% (range: 45%-100%). The grand mean faecal egg count (FEC) was 1813.2 eggs per gram (EPG) (range: 0-32400 EPG). There were significant differences in GIN infection among different breeds of sheep. The sequence of infection intensity and infection rate were Small fat tail > Ujimqin > Ju Ud (p<0.05). The 50% effective doses (ED50) of albendazole(ABZ) and levamisole (LMS) for expelling were 5.670 µg/mL and 0.302 µg/mL, respectively. The percentage reductions of avermectin (AVM), ivermectin (IVM), ABZ and LMS were 81.28%, 86.49%, 76.21% and 96.59%, respectively. The most predominant parasite genus in all four anthelmintics was Haemonchus. In these tested areas, mixed infections of GIN in grazing sheep were very common. AR, especially in Haemonchus, was a serious problem in these sheep flocks. Thus, actions are urgently required to taken to mitigate the worsening situation.