Haemonchus contortus: the then and now, and where to from here?

Inconsistency of in vitro exsheathment triggers for gastrointestinal nematode parasites of sheep, cattle and deer

Exsheathment is crucial in the transition from free-living to parasitic phase for most strongyle nematode species. A greater understanding of this process could help in developing new parasitic control methods. This study aimed to identify commonalities in response to exsheathment triggers (heat acclimation, CO2 and pH) in a wide range of species (Haemonchus contortus, Trichostrongylus spp., Cooperia spp., Oesophagostomum spp., Chabertia ovina, and members of the subfamily Ostertagiinae) from sheep, cattle and farmed deer. The initial expectation of similarity in pH requirements amongst species residing within the same organ was not supported, with unexpected pH preferences for exsheathment of Trichostrongylus axei, Trichostrongylus vitrinus, Trichostrongylus colubriformis and Cooperia oncophora. We also found differences between species in their response to temperature acclimation, with higher exsheathment in response to heat shock observed for H. contortus, Ostertagia ostertagi, T. axei, T. vitrinus and Oesophagostomum sikae. Furthermore, some species showed poor exsheathment under all experimental conditions, such as Cooperia curticei and the large intestinal nematodes C. ovina and Oesophagostomum venulosum. Interestingly, there were some significant differences in response depending on the host from which the parasites were derived. The host species significantly impacted on the exsheathment response for H. contortus, Teladorsagia circumcincta, T. vitrinus and T. colubriformis. Overall, the data showed variability between nematode species in their response to these in vitro exsheathment triggers, highlighting the complexity of finding a common set of conditions for all species in order to develop a control method based on triggering the exsheathment process prematurely.

Comparison of P-glycoprotein gene expression of two Haemonchus contortus isolates from Yucatan, Mexico, with resistant or susceptible phenotype to ivermectin in relation to a susceptible reference strain

The variability in the expression of different P-glycoprotein (P-gp) genes in parasitic nematodes of ruminants such as Haemonchus contortus (Hco-pgp) may be caused by different factors including nematode biology, geographical region and anthelmintic pressure. This study analysed the relative expression level of 10 P-gp genes in two H. contortus (Hco-pgp) field isolates from Yucatan, Mexico: 1) PARAISO (IVM-resistant) and 2) FMVZ-UADY (IVM-susceptible). These isolates were compared with a susceptible reference isolate from Puebla, Mexico, namely "CENID-SAI". In all cases H. contortus adult males were used. The Hco-pgp genes (1, 2, 3, 4, 9, 10, 11, 12, 14 and 16) were analysed for each isolate using the RT-qPCR technique. The Hco-pgp expressions were pairwise compared using the 2-ΔΔCt method and a t-test. The PARAISO isolate showed upregulation compared to the CENID-SAI isolate for Hco-pgp 1, 3, 9, 10 and 16 (P < 0.05), and the PARAISO isolate showed upregulation vs. FMVZ-UADY isolate for Hco-pgp 2 and 9 (P < 0.05), displaying 6.58- and 5.93-fold differences (P < 0.05), respectively. In contrast, similar Hco-pgp gene expression levels were recorded for FMVZ-UADY and CENID-SAI isolates except for Hco-pgp1 (P <0.1), which presented a significant upregulation (6.08-fold). The relative expression of Hco-pgp allowed confirming the IVM-resistant status of the PARAISO isolate and the IVM-susceptible status of the FMVZ-UADY isolate when compared to the CENID-SAI reference isolate. Therefore, understanding the association between the Hco-pgp genes expression of H. contortus and its IVM resistance status could help identifying the genes that could be used as molecular markers in the diagnosis of IVM resistance. However, it is important to consider the geographic origin of the nematode isolate and the deworming history at the farm of origin.

Inference of Essential Genes of the Parasite Haemonchus contortus via Machine Learning

Over the years, comprehensive explorations of the model organisms Caenorhabditis elegans (elegant worm) and Drosophila melanogaster (vinegar fly) have contributed substantially to our understanding of complex biological processes and pathways in multicellular organisms generally. Extensive functional genomic-phenomic, genomic, transcriptomic, and proteomic data sets have enabled the discovery and characterisation of genes that are crucial for life, called 'essential genes'. Recently, we investigated the feasibility of inferring essential genes from such data sets using advanced bioinformatics and showed that a machine learning (ML)-based workflow could be used to extract or engineer features from DNA, RNA, protein, and/or cellular data/information to underpin the reliable prediction of essential genes both within and between C. elegans and D. melanogaster. As these are two distantly related species within the Ecdysozoa, we proposed that this ML approach would be particularly well suited for species that are within the same phylum or evolutionary clade. In the present study, we cross-predicted essential genes within the phylum Nematoda (evolutionary clade V)-between C. elegans and the pathogenic parasitic nematode H. contortus-and then ranked and prioritised H. contortus proteins encoded by these genes as intervention (e.g., drug) target candidates. Using strong, validated predictors, we inferred essential genes of H. contortus that are involved predominantly in crucial biological processes/pathways including ribosome biogenesis, translation, RNA binding/processing, and signalling and which are highly transcribed in the germline, somatic gonad precursors, sex myoblasts, vulva cell precursors, various nerve cells, glia, or hypodermis. The findings indicate that this in silico workflow provides a promising avenue to identify and prioritise panels/groups of drug target candidates in parasitic nematodes for experimental validation in vitro and/or in vivo.

Reducing fecal egg count through selective breeding alters dorper lamb response to Haemonchus contortus in an artificial challenge trial

Infection by gastrointestinal nematodes (GIN), particularly Haemonchus contortus, can be detrimental to sheep health and performance. Genetic susceptibility to GIN varies between breeds, with those lacking high levels of natural resistance often requiring frequent anthelmintic treatment when facing parasitic challenge. Genetic technology can serve as a tool to decrease GIN susceptibility via selection for sheep with reduced fecal egg count (FEC) estimated breeding values (EBVs). However, the physiological changes that result from implementation of this strategy are not well described. Additionally, there is a need for comparison of animals from recent selective breeding against breeds with inherent GIN resistance. In this study we administered a challenge of H. contortus to Dorper x White Dorper (DWD; n = 92) lambs that have been genetically selected for either low (DWD-) or high (DWD+) FEC EBVs and Barbados Blackbelly x Mouflon (BBM; n = 19) lambs from a genetically resistant breed backgrounds. Lamb FEC, packed-cell volume (PCV) and serum IgG were measured at intermittent levels over 5 weeks. At day 21 and day 35, the selectively bred DWD- had a lower mean FEC compared to DWD+, but were higher than BBM. Reductions in both PCV and serum IgG from initial day 0 levels were observed in DWD lambs, but not in BBM. Furthermore, from a subset of lambs (n = 24) harvested at day 21, DWD- only tended (p = 0.056) to have lower mean worm counts than DWD+, with BBM having the lowest mean worm count. Differentially expressed genes (DEGs) identified via RNA-sequencing of abomasal tissue at day 21 indicate a more pronounced Th2 immune response and more rapid worm expulsion occurred in iBBM than iDWD- and iDWD+ lambs. However, gene expression in DWD- suggests an association between reduced FEC EBV and gastric acid secretion and the ability to limit worm fecundity. Ultimately, selection of Dorper sheep for low FEC EBV can reduce susceptibility to GIN, but it will likely require multiple generations with this trait as a breeding priority before presenting a similar resistance level to Caribbean breeds.

Association of β-globin polymorphisms and tolerance to haemonchosis in ewes and lambs of different sheep breeds

Gastrointestinal nematodes (GIN), especially Haemonchus contortus, represent a significant challenge for sheep production. Given the global concern about GIN anthelmintic resistance, alternative control methods able to reduce the dependence on these drugs are highly advisable. Since previous studies have shown that sheep carrying the Hb-A allele of β-globin are more resistant to H. contortus, this study aimed to investigate the relationship between the different haplotypes (Hb-AA, Hb-AB and Hb-BB) and phenotypes in Santa Inês (SI), Texel (TX) and White Dorper (DO) breeds infected with H. contortus. Blood samples were collected from 180 ewes and 123 lambs of the three breeds for DNA extraction followed by qPCR using a hydrolysis probe to identify the β-globin haplotypes. Phenotypic data, including fecal egg count (FEC), packed cell volume (PCV), FAMACHA score and body condition score for ewes and lambs, as well as weight gain for lambs, were collected. The genotypic frequencies of β-globin for ewes and lambs were, respectively: 21.7% and 21.4% Hb-AA, 50% and 50% Hb-AB and 28.3% and 28.6% Hb-BB in SI; 0% and 0% Hb-AA, 18.6% and 9.4% Hb-AB and 81.4% and 90.6% Hb-BB in TX; and 0% and 0% Hb-AA, 13.1% and 0% Hb-AB and 86.9% and 100% Hb-BB in DO. In ewes, mean PCV differed (p<0.05) between the three haplotypes, with higher PCV in Hb-AA animals, followed by Hb-AB and Hb-BB. When considering each breed separately, SI Hb-AA ewes presented higher PCV (p<0.05), highlighting that even in a breed already considered resistant, animals with Hb-AA haplotype showed superior performance. Lambs with the Hb-AA haplotype exhibited a higher (p<0.05) mean PCV compared to those with Hb-AB and Hb-BB. The same pattern was found in SI when analyzing each breed separately. No significant association was found between β-globin haplotypes and FEC, FAMACHA score, body condition score, or weight gain. Nevertheless, given that anemia is the major clinical sign of haemonchosis, our findings on PCV reinforce that sheep carrying the Hb-A allele of β-globin are more tolerant to haemonchosis. This study may support the development of a valuable tool, targeting genetic selection for GIN control, reducing the dependence on anthelmintics and boosting sheep production worldwide.

Biochemical parameters, oxidative stress biomarkers, and anatomopathological changes in Wistar rats treated with 3'-demethoxy-6-O-demethylisoguaiacin and norisoguaiacin

Artemisia cina (Ac) is a plant with anthelmintic compounds such as 3'-demethoxy-6-O-demethylisoguaiacin (D) and norisoguaiacin (N). Three major objectives were proposed: (1) To evaluate biochemical parameters in blood (2) to determine the tissue oxidative stress by biomarkers as TBARS and glutathione peroxidase activity, and (3) to evaluate anatomopathological changes in organs such as the brain, liver, kidney, and lung after oral administration of n-hexane extract of Ac and D and N. D and N were administrated following the OECD guides for acute oral toxicity evaluation (Guide 420). Fifty Wistar rats were distributed into ten groups as follows: Group 1 (G1): 4 mg/Kg; G2: 40 mg/Kg; G3: 240 mg/Kg; G4: 1600 mg/Kg of n-hexane extract of Ac. G5: 2 mg/Kg; G6: 20 mg/Kg; G7: 120 mg/Kg; G8: 800 mg/Kg of D and N, G9: water and G10: polyvinylpyrrolidone at 2000 mg/Kg. At 14 days, the rats were euthanized, and the blood, liver, brain, kidney, and lung were taken for biochemical analysis, anatomopathological changes, and TBARS and GSH evaluation. Glucose, cholesterol, and phosphorus were altered. Histopathological analysis showed multifocal neuronal degeneration in the brain (G2). The kidney and lungs had changes in G7. The GSH and TBARS increased in G6 and G7. The TBARS activity was higher in G1 and G2. In conclusion, extract and D and N of Ac did not have damage at therapeutic doses. D, N, and n-hexane extract of A. cina do not cause histopathological damage at pharmaceutical doses. Still, the brain, kidney, and liver are related to biochemical parameters at higher doses. However, compounds are proposed as antioxidant agents.

Identification of genomic regions associated with resistance to gastrointestinal parasites in an indigenous sheep by single- and multiple-locus methods

We investigated the association between 157 SNPs located in 75 candidate genes involved in the immune system and proxy traits for resistance to gastrointestinal nematodes in sheep. A total of 211 lambs from eight flocks were sampled. Nematode eggs per gram were counted and classified as: (i) Strongyles, (ii) Nematodirus spp., (iii) Trichuris spp. and (iv) Marshallagia marshalli. Single- and multiple-locus models were used to test the marker-trait associations. Seven significant SNPs were identified on chromosomes OAR6, 15, 16, and 19. These findings provide insights for breeding nemarode-resistant traits in low-input production systems. General linear model, fixed and random model circulating probability unification, and Bayesian-information and linkage-disequilibrium iteratively nested keyway analyses identified a significant association between the eggs per gram of Strongyles nematodes and a specific variant of the PRLR gene.

A novel case of cutaneous, nasal and systemic fusariosis in a goat

The clinical findings associated with nasal, cutaneous and systemic fusariosis in a 3-year-old billy Boer goat are summarised. The clinical features, treatment, postmortem findings and laboratory diagnostics are reported and discussed in the context of existing knowledge on mycoses of small ruminants. The goat presented primarily for respiratory signs (inspiratory dyspnoea) with unilateral left-sided mucopurulent nasal discharge, and multifocal variably ulcerative and necrotic cutaneous nodules. Histopathology of nasal and cutaneous biopsies revealed necrotising pyogranulomatous inflammation with intralesional septate hyphal elements that correlated with culture of Fusarium oxysporum. The patient continued to deteriorate clinically during treatment with oxytetracycline and meloxicam, with the addition of sodium iodide and potassium iodide, and was humanely euthanased. Postmortem examination revealed multifocal nodular lesions throughout the kidneys, abdominal lymph nodes and lungs. These lesions were consistent with those identified antemortem from which F. oxysporum was cultured. Although treatment was unsuccessful, to the author's knowledge, no instance of rhinofacial or systemic caprine infection with Fusarium spp. has been documented in the veterinary literature, making this the first recognised instance of this form of infection in small ruminant species.

Predicting the risk and speed of drug resistance emerging in soil-transmitted helminths during preventive chemotherapy

Control of soil-transmitted helminths relies heavily on regular large-scale deworming of high-risk groups (e.g., children) with benzimidazole derivatives. Although drug resistance has not yet been documented in human soil-transmitted helminths, regular deworming of cattle and sheep has led to widespread benzimidazole resistance in veterinary helminths. Here we predict the population dynamics of human soil-transmitted helminth infections and drug resistance during 20 years of regular preventive chemotherapy, using an individual-based model. With the current preventive chemotherapy strategy of mainly targeting children in schools, drug resistance may evolve in soil-transmitted helminths within a decade. More intense preventive chemotherapy strategies increase the prospects of soil-transmitted helminths elimination, but also increase the speed at which drug efficacy declines, especially when implementing community-based preventive chemotherapy (population-wide deworming). If during the last decade, preventive chemotherapy against soil-transmitted helminths has led to resistance, we may not have detected it as drug efficacy has not been structurally monitored, or incorrectly so. These findings highlight the need to develop and implement strategies to monitor and mitigate the evolution of benzimidazole resistance.

First Report of Benzimidazole Resistance in Field Population of Haemonchus contortus from Sheep, Goats and Cattle in Bosnia and Herzegovina

Haemonchus contortus is a globally significant parasitic nematode in ruminants, with widespread resistance to benzimidazole due to its excessive and prolonged use. Given the extensive use of benzimidazole anthelmintics in Bosnia and Herzegovina, we hypothesized that resistance is prevalent. The aim of this study was to identify the presence of anthelmintic resistance to benzimidazole in H. contortus from naturally infected sheep, goats and cattle in Bosnia and Herzegovina through the detection of the Phe/Tyr polymorphism in the amino acid at position 200 of the β-tubulin protein. From 19 locations in Bosnia and Herzegovina, a total of 83 adult H. contortus were collected from the abomasum of ruminants. Among these, 45 H. contortus specimens were isolated from sheep, 19 from goats and 19 from cattle. Results showed that 77.8% of H. contortus in sheep exhibited homozygous resistant genotypes at position 200 of the β-tubulin gene, with 15.5% being heterozygous. In goats, all tested H. contortus (100%) were homozygous resistant, and no heterozygous resistant or homozygous sensitive genotypes were found. Cattle had 94.7% homozygous resistant H. contortus, with no heterozygous resistant genotypes detected. In H. contortus from sheep and cattle, 6.7% and 5.3%, respectively, displayed homozygous sensitive genotypes. This study, for the first time, highlights the presence of a resistant population of H. contortus in sheep, goats and cattle in Bosnia and Herzegovina, using the rt-qPCR method. The resistance likely spread from sheep or goats to cattle, facilitated by shared pastures and the practice of transhumance, indicating a widespread and growing issue of anthelmintic resistance.

Non-coding RNA in the gut of the blood-feeding parasitic worm, Haemonchus contortus

The intestine of Haemonchus contortus is an essential tissue that has been indicated to be a major target for the prevention of haemonchosis caused by this parasitic nematode of small ruminants. Biological peculiarities of the intestine warrant in-depth exploitation, which can be leveraged for future disease control efforts. Here, we determined the intestinal ncRNA (lncRNA, circRNA and miRNA) atlas using whole-transcriptome sequencing and bioinformatics approaches. In total, 4846 novel lncRNA, 982 circRNA, 96 miRNA (65 known and 31 novel) and 8821 mRNA were identified from the H. contortus intestine. The features of lncRNA, circRNA and miRNA were fully characterized. Comparison of miRNA from the intestines and extracellular vesicles supported the speculation that the miRNA from the latter were of intestinal origin in H. contortus. Further function analysis suggests that the cis-lncRNA targeted genes were involved in protein binding, intracellular anatomical structure, organelle and cellular process, whereas the circRNA parental genes were mainly enriched in molecular function categories, such as ribonucleotide binding, nucleotide binding, ATP binding and carbohydrate derivative binding. The miRNA target genes were related to the cellular process, cellular response to stimulus, cellular protein modification process and signal transduction. Moreover, competing endogenous RNA network analysis revealed that the majority of lncRNA, circRNA and mRNA only have one or two binding sites with specific miRNA. Lastly, randomly selected circRNA, lncRNA and miRNA were verified successfully using RT-PCR. Collectively, these data provide the most comprehensive compilation of intestinal transcripts and their functions, and it will be helpful to decipher the biological and molecular complexity of the intestine and lay the foundation for further functional research.

Rapid, automated quantification of Haemonchus contortus ova in sheep faecal samples

Haemonchus contortus is one of the most pathogenic nematodes affecting small ruminants globally and is responsible for large economic losses in the sheep and goat industry. Anthelmintic resistance is rampant in this parasite and thus parasite control programs must account for drug efficacy on individual farms and, sometimes, whether H. contortus is the most prevalent trichostrongylid. Historically, coproculture has been the main way to determine the prevalence of H. contortus in faecal samples due to the inability to morphologically differentiate between trichostrongylid egg types, but this process requires a skilled technician and takes multiple days to complete. Fluoresceinated peanut agglutinin (PNA) has been shown to specifically bind H. contortus and thus differentiate eggs based on whether they fluoresce, but this method has not been widely adopted. The ParasightTM System (PS) fluorescently stains helminth eggs in order to identify and quantify them, and the H. contortus PNA staining method was therefore adapted to this platform using methodology requiring only 20 min to obtain results. In this study, 74 fecal samples were collected from sheep and analyzed for PNA-stained H. contortus, using both PS and manual fluorescence microscopy. The percentage of H. contortus was determined based on standard total strongylid counts with PS or brightfield microscopy. Additionally, 15 samples were processed for coproculture with larval identification, and analyzed with both manual and automated PNA methods. All methods were compared using the coefficient of determination (R2) and the Lin's concordance correlation coefficient (ρc). ParasightTM and manual PNA percent H. contortus results were highly correlated with R2 = 0.8436 and ρc = 0.9100 for all 74 fecal samples. Coproculture versus PS percent H. contortus were also highly correlated with R2 = 0.8245 and ρc = 0.8605. Overall, this system provides a rapid and convenient method for determining the percentage of H. contortus in sheep and goat fecal samples without requiring specialized training.

Cross infection of Haemonchus contortus between calves and lambs

Haemonchus contortus can frequently be found infecting pre-weaned beef calves on sheep and beef farms around the North Island of New Zealand. The purpose of this study was to determine whether parasites cycling in young cattle constitute a potentially important source of infection for sheep. A field isolate of H. contortus was cycled through either calves or lambs for 3 generations. The larvae resulting from the third cycle of infection were then used to infect both lambs and calves and the resulting faecal nematode egg count (FEC), worm burden, adult worm length and in utero egg count were measured. Larvae derived from lambs inoculated into calves exhibited lower establishment rates, the adult worms were shorter, had lower in utero egg counts, and the resulting faecal egg counts were also lower than when inoculated into lambs (p < 0.01). H. contortus' lack of ability to passage freely between lambs and calves indicates that large populations are unlikely to occur under mixed grazing, resulting in limited potential as a source of infection in sheep. However, indications of an ability to adapt to the alternative host suggest that some investigation of infection in cattle dominant farming operations in the north of the country might be warranted.

Characterization and population genetics of Haemonchus contortus in Merino sheep in Lesotho

Haemonchus contortus is the most pathogenic and economically restrictive gastrointestinal nematode in the small ruminant industry globally. Morbidity, poor cross-bodily state, and mortality of sheep in Lesotho suggest the presence of H. contortus. The present study investigated the morphological, molecular, and population genetics of H. contortus third-stage larvae infecting sheep in four ecological zones (EZ) of Lesotho. Coprocultures were prepared for larval morphological identification and PCR determination. Larvae were identified morphologically as 100% H. contortus. The Second Internal Transcribed Spacer (ITS-2) gene of the ribosomal DNA of H. contortus isolates in the present study revealed nucleotide homology ranging from 97 to 100% when compared with selected GenBank reference sequences. Pairwise evolutionary divergence among H. contortus isolates was low, with 0.01318 recorded as the highest in the present study. Five haplotypes resulted from 14 Lesotho sequences. Haplotype diversity and nucleotide diversity were 0.76923 and 0.00590, respectively. Genetic differentiation among isolates was low but not statistically significant. An analysis of molecular variance revealed that most molecular variation was distributed within topographic populations at 94.79% (FST = 0.05206, p > 0.05) and 5.21% among populations. There was high gene flow and no definite population genetic structure among Lesotho isolates.

Bacteria associated with ovine gut parasites Trichuris ovis and Haemonchus contortus

An associated microbiome of any host helps it in different metabolic processes ranging from the decomposition of food to the maturation of gametes. Organisms with a parasitic mode of life, though present at nutritious sites inside their host, maintain their own microbiome. Nevertheless, the comprehensive characterization and functionality of microbiome in parasitic organisms remain understudied. We selected two nematode parasites of Kashmir Merino sheep viz;Haemonchus contortus and Trichuris ovis based on their higher prevalence, difference in mode of nutrition, habitation site and effect on host. The objective of the study was to explore the bacteria associated with these parasitic nematodes of sheep. We adopted a 16S rRNA metagenomic sequencing approach to estimate and compare the bacterial communities present in these two nematode species. Nematode parasites from Kashmir Merino sheep were identified morphologically and confirmed with DNA characterization. H. contortus was dominated by phylum Proteobacteria (57%), Firmicutes (25%), Bacteroidota (15%) and Actinobacteriota (3%). Conversely, T. ovis showed Proteobacteria (78%) followed by Firmicutes (8%), Bacteroidota (8%), Actinobacteriota (1%), Fusobacteriota (1%) and other phyla (4%). This study provides a comprehensive account of the microbiome composition of H. contortus and T. ovis, both of which are highly prevalent among Kashmir Merino sheep. Additionally, T. ovis exhibited a greater bacterial diversity compared to H. contortus. Notably, these nematodes were found to harbor certain pathogenic bacteria. This study can further be carried forward in gaining insights into the complex relationship between the microbiota of a parasite and its pathogenicity, reproductive potential and host microbiome modification.

Natural Perylenequinone Compounds as Potent Inhibitors of Schistosoma mansoni Glutathione S-Transferase

The existing treatment strategy for Schistosomiasis centers on praziquantel, a single drug, but its effectiveness is limited due to resistance and lack of preventive benefits. Thus, there is an urgent need for novel antischistosomal agents. Schistosoma glutathione S-transferase (GST) is an essential parasite enzyme, with a high potential for targeted drug discovery. In this study, we conducted a screening of compounds possessing antihelminth properties, focusing on their interaction with the Schistosoma mansoni glutathione S-transferase (SmGST) protein. We demonstrated the unique nature of SmGST in comparison to human GST. Evolutionary analysis indicated its close relationship with other parasitic worms, setting it apart from free-living worms such as C. elegans. Through an assessment of binding pockets and subsequent protein-ligand docking, we identified Scutiaquinone A and Scutiaquinone B, both naturally derived Perylenequinones, as robust binders to SmGST. These compounds have exhibited effectiveness against similar parasites and offer promising potential as antischistosomal agents.

Medicinal plants as a source of antiparasitics: an overview of experimental studies

Despite advances in modern human and veterinary medicine, gastrointestinal (GI) parasitic infections remain a significant health issue worldwide, mainly in developing countries. Increasing evidence of the multi-drug resistance of these parasites and the side effects of currently available synthetic drugs have led to increased research on alternative medicines to treat parasitic infections. The exploration of potential botanical antiparasitics, which are inexpensive and abundant, may be a promising alternative in this context. This study summarizes the in vitro/in vivo antiparasitic efficacy of different medicinal plants and their components against GI parasites. Published literature from 1990-2020 was retrieved from Google Scholar, Web of Science, PubMed and Scopus. A total of 68 plant species belonging to 32 families have been evaluated as antiparasitic agents against GI parasites worldwide. The majority of studies (70%) were conducted in vitro. Most plants were from the Fabaceae family (53%, n = 18). Methanol (37%, n = 35) was the most used solvent. Leaf (22%, n = 16) was the most used plant part, followed by seed and rhizome (each 12%, n = 9). These studies suggest that herbal medicines hold a great scope for new drug discoveries against parasitic diseases and that the derivatives of these plants are useful structures for drug synthesis and bioactivity optimization.

Genome-Wide Analysis of Haemonchus contortus Proteases and Protease Inhibitors Using Advanced Informatics Provides Insights into Parasite Biology and Host-Parasite Interactions

Biodiversity within the animal kingdom is associated with extensive molecular diversity. The expansion of genomic, transcriptomic and proteomic data sets for invertebrate groups and species with unique biological traits necessitates reliable in silico tools for the accurate identification and annotation of molecules and molecular groups. However, conventional tools are inadequate for lesser-known organismal groups, such as eukaryotic pathogens (parasites), so that improved approaches are urgently needed. Here, we established a combined sequence- and structure-based workflow system to harness well-curated publicly available data sets and resources to identify, classify and annotate proteases and protease inhibitors of a highly pathogenic parasitic roundworm (nematode) of global relevance, called Haemonchus contortus (barber's pole worm). This workflow performed markedly better than conventional, sequence-based classification and annotation alone and allowed the first genome-wide characterisation of protease and protease inhibitor genes and gene products in this worm. In total, we identified 790 genes encoding 860 proteases and protease inhibitors representing 83 gene families. The proteins inferred included 280 metallo-, 145 cysteine, 142 serine, 121 aspartic and 81 "mixed" proteases as well as 91 protease inhibitors, all of which had marked physicochemical diversity and inferred involvements in >400 biological processes or pathways. A detailed investigation revealed a remarkable expansion of some protease or inhibitor gene families, which are likely linked to parasitism (e.g., host-parasite interactions, immunomodulation and blood-feeding) and exhibit stage- or sex-specific transcription profiles. This investigation provides a solid foundation for detailed explorations of the structures and functions of proteases and protease inhibitors of H. contortus and related nematodes, and it could assist in the discovery of new drug or vaccine targets against infections or diseases.

Biases in parasite biodiversity research: why some helminth species attract more research than others

As the number of known and described parasite species grows every year, one might ask: how much do we actually know about these species beyond the fact they exist? For free-living taxa, research effort is biased toward a small subset of species based on their properties or human-centric factors. Here, using a large data set on over 2500 helminth parasite species described in the past two decades, we test the importance of several predictors on two measures of research effort: the number of times a species description is cited following its publication, and the number of times a species' name is mentioned in the scientific literature. Our analysis highlights some taxonomic biases: for instance, descriptions of acanthocephalans and nematodes tend to receive more citations than those of other helminths, and species of cestodes are less frequently mentioned in the literature than other helminths. We also found that helminths infecting host species of conservation concern receive less research attention, perhaps because of the constraints associated with research on threatened animals, while those infecting host species of human use receive greater research effort. Intriguingly, we found that species originally described by many co-authors subsequently attract more research effort than those described by one or few authors, and that research effort correlates negatively with the human population size of the country where a species was discovered, but not with its economic strength, measured by its gross domestic product. Overall, our findings reveal that we have conducted very little research, or none at all, on the majority of helminth parasite species following their discovery. The biases in study effort we identify have serious implications for future research into parasite biodiversity and conservation.

Refugia or reservoir? Feral goats and their role in the maintenance and circulation of benzimidazole-resistant gastrointestinal nematodes on shared pastures

Gastrointestinal nematodes threaten the productivity of grazing livestock and anthelmintic resistance has emerged globally. It is broadly understood that wild ruminants living in sympatry with livestock act as a positive source of refugia for anthelmintic-susceptible nematodes. However, they might also act as reservoirs of anthelmintic-resistant nematodes, contributing to the spread of anthelmintic resistance at a regional scale. Here, we sampled managed sheep and cattle together with feral goats within the same property in New South Wales, Australia. Internal transcribed spacer 2 (ITS-2) nemabiome metabarcoding identified 12 gastrointestinal nematodes (Cooperia oncophora, Cooperia punctata, Haemonchus contortus, Haemonchus placei, Nematodirus spathiger, Ostertagia ostertagi, Teladorsagia circumcincta, Oesophagostomum radiatum, Oesophagostomum venulosum, Trichostrongylus axei, Trichostrongylus colubriformis and Trichostrongylus rugatus). Isotype-1 β-tubulin metabarcoding targeting benzimidazole resistance polymorphisms identified 6 of these nematode species (C. oncophora, C. punctata, H. contortus, H. placei, O. ostertagi and T. circumcincta), with the remaining 3 genera unable to be identified to the species level (Nematodirus, Oesophagostomum, Trichostrongylus). Both ITS-2 and β-tubulin metabarcoding showed the presence of a cryptic species of T. circumcincta, known from domestic goats in France. Of the gastrointestinal nematodes detected via β-tubulin metabarcoding, H. contortus, T. circumcincta, Nematodirus and Trichostrongylus exhibited the presence of at least one resistance genotype. We found that generalist gastrointestinal nematodes in untreated feral goats had a similarly high frequency of the benzimidazole-resistant F200Y polymorphism as those nematodes in sheep and cattle. This suggests cross-transmission and maintenance of the resistant genotype within the wild ruminant population, affirming that wild ruminants should be considered potential reservoirs of anthelmintic resistance.

Low-cost molecular methods to characterise gastrointestinal nematode co-infections of goats in Africa

BACKGROUND

Veterinary diagnostics aid intervention strategies, track zoonoses, and direct selective breeding programs in livestock. In ruminants, gastrointestinal nematode (GIN) parasites are a major cause of production losses, but morphologically similar species limit our understanding of how specific GIN co-infections impact health in resource-limited settings. To estimate the presence and relative abundance of GINs and other helminths at the species level, we sought to develop a low-cost and low-resource molecular toolkit applied to goats from rural Malawi smallholdings.

METHODS

Goats were subjected to health scoring and faecal sampling on smallholdings in Lilongwe district, Malawi. Infection intensities were estimated by faecal nematode egg counts with a faecal subsample desiccated for DNA analysis. Two DNA extraction methods were tested (low-resource magbead kit vs high-resource spin-column kit), with resulting DNA screened by endpoint polymerase chain reaction (PCR), semi-quantitative PCR, quantitative PCR (qPCR), high-resolution melt curve analysis (HRMC), and 'nemabiome' internal transcribed spacer 2 (ITS-2) amplicon sequencing.

RESULTS

Both DNA isolation methods yielded comparable results despite poorer DNA purity and faecal contaminant carryover from the low-resource magbead method. GINs were detected in 100% of samples regardless of infection intensity. Co-infections with GINs and coccidia (Eimeria spp.) were present in most goats, with GIN populations dominated by Haemonchus contortus, Trichostrongylus colubriformis, Trichostrongylus axei, and Oesophagostomum columbianum. Both multiplex PCR and qPCR were highly predictive of GIN species proportions obtained using nemabiome amplicon sequencing; however, HRMC was less reliable than PCR in predicting the presence of particular species.

CONCLUSIONS

These data represent the first 'nemabiome' sequencing of GINs from naturally infected smallholder goats in Africa and show the variable nature of GIN co-infections between individual animals. A similar level of granularity was detected by semi-quantitative PCR methods, which provided an accurate summary of species composition. Assessing GIN co-infections is therefore possible using cost-efficient low-resource DNA extraction and PCR approaches that can increase the capacity of molecular resources in areas where sequencing platforms are not available; and also open the door to affordable molecular GIN diagnostics. Given the diverse nature of infections in livestock and wildlife, these approaches have potential for disease surveillance in other areas.

Ex-vivo efficacy of commercially available anthelmintics against blood feeding stomach worm Haemonchus contortus of ruminants

Haemonchus contortus is the most prevalent and pathogenic gastrointestinal nematodes (GINs) in ruminants causing extensive economic losses. It is essential to estimate the efficacy of common commercially available anthelmintics against Haemonchus contortus parasite. Here, we standardized an ex-vivo culture platform for H. contortus and evaluated the efficacy of commonly used anthelmintics namely, albendazole (ABZ), levamisole (LVM), ivermectin (IVM), closantel (CLS) and rafoxanide (RFX). Adult worms were collected from abomasa of slaughtered animals, cultured in MEM, DMEM, M199 or RPMI with or without 20% FBS for up to 72 h. Cultured worms were incubated with ABZ, LVM, IVM, RFX or CLS in DMEM supplemented with 20% FBS at different concentrations (0.5-50 µg/ml) in triplicates and examined at 0, 3, 6, 12, 24, 36 and 48 h post treatment. Of the culture conditions, DMEM supplemented with 20% FBS supported the survival of H. contortus for (P < 0.001) longer period of time which was used in the evaluation of anthelmintics. The efficacy of CLS and RFX were significantly (P < 0.001) higher than other drugs and 100% mortality was observed at 2 µg/ml of CLS and RFX within 12 h post treatment. However, ABZ, LVM, and IVM showed significant effect at the concentration of 50 µg/ml with 48, 36, and 24 h, respectively. Morphological changes included severe cuticle disruption around the buccal cavity, posterior region and vulva as well as loss of cuticle structure integrity coupled with expulsion and fragmentation of digestive components of parasites when treated with 50 µg/ml of ABZ, LVM, and IVM and 2 µg/ml of RFX and CLS. Collectively, DMEM supplemented with 20% FBS can be used as ex-vivo culture platform for maintenance of H. contortus, and RFX and CLS can be used as the promising drugs for the prevention, control and treatment of H. contortus infections.

Assembly and Analysis of Haemonchus contortus Transcriptome as a Tool for the Knowledge of Ivermectin Resistance Mechanisms

Haemonchus contortus (Hc) is an important parasitic nematode of small ruminants. In this study we assembled the transcriptome of Hc as a model to contribute to the knowledge about the profile of the differential gene expression between two Mexican Hc strains under different anthelmintic resistance statuses, one susceptible and the other resistant to ivermectin (IVMs and IVMr, respectively), in order to improve and/or to have new strategies of control and diagnosis. The transcript sequence reads were assembled and annotated. Overall, ~127 Mbp were assembled and distributed into 77,422 transcript sequences, and 4394 transcripts of the de novo transcriptome were matched base on at least one of the following criteria: (1) Phylum Nemathelminthes and Platyhelminthes, important for animal health care, and (2) ≥55% of sequence identity with other organisms. The gene ontology (GO) enrichment analysis (GOEA) was performed to study the level of gene regulation to IVMr and IVMs strains using Log Fold Change (LFC) filtering values ≥ 1 and ≥ 2. The upregulated-displayed genes obtained via GOEA were: 1993 (for LFC ≥ 1) and 1241 (for LFC ≥ 2) in IVMr and 1929 (for LFC ≥ 1) and 835 (for LFC ≥ 2) in IVMs. The enriched GO terms upregulated per category identified the intracellular structure, intracellular membrane-bounded organelle and integral component of the cell membrane as some principal cellular components. Meanwhile, efflux transmembrane transporter activity, ABC-type xenobiotic transporter activity and ATPase-coupled transmembrane transporter activity were associated with molecular function. Responses to nematicide activity, pharyngeal pumping and positive regulation of synaptic assembly were classified as biological processes that might be involved in events related to the anthelmintic resistance (AR) and nematode biology. The filtering analysis of both LFC values showed similar genes related to AR. This study deepens our knowledge about the mechanisms behind the processes of H. contortus in order to help in tool production and to facilitate the reduction of AR and promote the development of other control strategies, such as anthelmintic drug targets and vaccines.

An informatic workflow for the enhanced annotation of excretory/secretory proteins of Haemonchus contortus

Major advances in genomic and associated technologies have demanded reliable bioinformatic tools and workflows for the annotation of genes and their products via comparative analyses using well-curated reference data sets, accessible in public repositories. However, the accurate in silico annotation of molecules (proteins) encoded in organisms (e.g., multicellular parasites) which are evolutionarily distant from those for which these extensive reference data sets are available, including invertebrate model organisms (e.g., Caenorhabditis elegans - free-living nematode, and Drosophila melanogaster - the vinegar fly) and vertebrate species (e.g., Homo sapiens and Mus musculus), remains a major challenge. Here, we constructed an informatic workflow for the enhanced annotation of biologically-important, excretory/secretory (ES) proteins ("secretome") encoded in the genome of a parasitic roundworm, called Haemonchus contortus (commonly known as the barber's pole worm). We critically evaluated the performance of five distinct methods, refined some of them, and then combined the use of all five methods to comprehensively annotate ES proteins, according to gene ontology, biological pathways and/or metabolic (enzymatic) processes. Then, using optimised parameter settings, we applied this workflow to comprehensively annotate 2591 of all 3353 proteins (77.3%) in the secretome of H. contortus. This result is a substantial improvement (10-25%) over previous annotations using individual, "off-the-shelf" algorithms and default settings, indicating the ready applicability of the present, refined workflow to gene/protein sequence data sets from a wide range of organisms in the Tree-of-Life.

Comparative Metabolome Analyses of Ivermectin-Resistant and -Susceptible Strains of Haemonchus contortus

Resistance to anthelmintics such as ivermectin (IVM) is currently a major problem in the treatment of Haemonchus contortus, an important parasitic nematode of small ruminants. Although many advances have been made in understanding the IVM resistance mechanism, its exact mechanism remains unclear for H. contortus. Therefore, understanding the resistance mechanism becomes increasingly important for controlling haemonchosis. Recent research showed that the metabolic state of bacteria influences their susceptibility to antibiotics. However, little information is available on the roles of metabolites and metabolic pathways in IVM resistance of H. contortus. In this study, comparative analyses of the metabolomics of IVM-susceptible and -resistant adult H. contortus worms were carried out to explore the role of H. contortus metabolism in IVM resistance. In total, 705 metabolites belonging to 42 categories were detected, and 86 differential metabolites (17 upregulated and 69 downregulated) were identified in the IVM-resistant strain compared to the susceptible one. A KEGG pathway analysis showed that these 86 differential metabolites were enriched in 42 pathways that mainly included purine metabolism; the biosynthesis of amino acids; glycine, serine, and threonine metabolism; and cysteine and methionine metabolism. These results showed that amino acid metabolism may be mediated by the uptake of IVM and related with IVM resistance in H. contortus. This study contributes to our understanding of the mechanisms of IVM resistance and may provide effective approaches to manage infection by resistant strains of H. contortus.

The Immune Response to Nematode Infection

Nematode infection is a major threat to the health of humans, domestic animals and wildlife. Nematodes vary in their effect on the host and in the mechanisms underlying immunity but the general features are becoming clear. There is considerable variation among individuals in resistance to infection and much of this variation is due to genetic variation in the immune response. The major histocompatibility complex has a strong influence on resistance to infection but other genes are collectively more important. Resistant individuals produce more IgA, eosinophils, IgE and mast cells than susceptible individuals and this is a consequence of stronger type 2 (Th2) immune responses. A variety of factors promote Th2 responses including genetic background, diet, molecules produced by the parasite and the location of the infection. A variety of cells and molecules including proteins, glycolipids and RNA act in concert to promote responses and to regulate the response. Nematodes themselves also modulate the host response and over 20 parasite-derived immunomodulatory molecules have been identified. Different species of nematodes modulate the immune response in different ways and probably use multiple molecules. The reasons for this are unclear and the interactions among immunomodulators have still to be investigated.

In vitro culture of parasitic stages of Haemonchus contortus

Haemonchus contortus is a constraint to sheep production. Seeking to reduce the use of hosts and produce parasitic stages in large-scale, a 42-day in vitro culture protocol of H. contortus third-stage larvae was optimized using Dulbecco's modified Eagle's medium (DMEM). In cell-free culture, larvae were maintained at 39.6°C, in acidic media (pH 6.1) for 3 or 6 days with Δ4-dafachronic acid followed by DMEM pH 7.4 supplemented or not with Fildes' reagent. In DMEM pH 7.4 at 37°C, supplementation with Caco-2 cells was compared to Fildes. On Day 14, fourth-stage larvae (L4) development rates in acidic media supplemented (86.8-88.4%) or not (74.4-77.8%) with Fildes and in Caco-2 cell co-culture (92.6%) were similar, and superior to DMEM pH 7.4 with Fildes (0.0%). On Day 21, Caco-2 cell co-culture resulted in higher larvae differentiation (25.0%) and lower degeneration (13.9%) compared to acidic media (1.5-8.1% and 48.6-69.9%, respectively). This is the first report of prolonged in vitro culture of H. contortus larvae using commercial media in co-culture with Caco-2 cells. Although no progression to the adult stage, Caco-2 cell co-culture resulted in morphological differentiation of H. contortus L4 and larval viability for up to 28 days.

Modelling bodyweight to avoid anthelmintic underdosing of goats in resources-limited settings

Improved management of livestock in resource-limited settings can provide a means towards improved human nutrition and livelihoods. However, gastrointestinal nematodes (GIN) are a significant production-limiting factor. Anthelmintics play a role in GIN management; however, few anthelmintic classes are available in many low-middle-income countries. Utilising a limited range of classes may increase selection for anthelmintic resistance; therefore, strategies to reduce other selective pressures are of heightened importance. Avoiding anthelmintic underdosing is one such strategy, but it can be challenging without access to accurate bodyweight measurement. Many previous studies have used thoracic girth as a practical proxy for bodyweight in goats; however, they have rarely considered the potential impact of natural variation on therapeutic doses. Here, the relationship between bodyweight and thoracic girth was modelled using data from 820 goats from three Malawian biomes in two seasons, with the specific aim of avoiding underestimation of bodyweight. The internally cross-validated linear regression (∛Weight ~ 0.053 + 0.040*Girth, R² = 0.92, rounded up to the nearest 5 kg) was validated against data from an additional 352 Malawian goats (1.4% of goats allocated an underdose and 10.2% allocated a dose > 200% of bodyweight). The equation was further externally validated using an historical dataset of 150 goats from Assam, India (2.7% of goats were allocated to an underdose and 24.8% allocated to a > 200% of bodyweight). These results suggest that a more globally generalisable approach may be feasible, provided the accuracy of the estimate is considered alongside the therapeutic index of the pharmaceutical.

Haemonchus contortus: an overview

This focus article was prepared by Amanda Carson, Rudolf Reichel, Suzie Bell, Rachael Collins and Jasmine Smith of the APHA Small Ruminant Species Expert Group, and Dave Bartley from the Moredun Research Institute.

The microbial community associated with Parascaris spp. infecting juvenile horses

Background

Parasitic nematodes, including large roundworms colloquially known as ascarids, affect the health and well-being of livestock animals worldwide. The equine ascarids, Parascaris spp., are important parasites of juvenile horses and the first ascarids to develop widespread anthelmintic resistance. The microbiota has been shown to be an important factor in the fitness of many organisms, including parasitic nematodes, where endosymbiotic Wolbachia have been exploited for treatment of filariasis in humans.

Methods

This study used short-read 16S rRNA sequences and Illumina sequencing to characterize and compare microbiota of whole worm small intestinal stages and microbiota of male and female intestines and gonads. Diversity metrics including alpha and beta diversity, and the differential abundance analyses DESeq2, ANCOM-BC, corncob, and metagenomeSeq were used for comparisons.

Results

Alpha and beta diversity of whole worm microbiota did not differ significantly between groups, but Simpson alpha diversity was significantly different between female intestine (FI) and male gonad (MG) (P= 0.0018), and Shannon alpha diversity was significantly different between female and male gonads (P = 0.0130), FI and horse jejunum (HJ) (P = 0.0383), and FI and MG (P= 0.0001). Beta diversity (Fig. 2B) was significantly different between female and male gonads (P = 0.0006), male intestine (MI) and FG (P = 0.0093), and MG and FI (P = 0.0041). When comparing organs, Veillonella was differentially abundant for DESeq2 and ANCOM-BC (p < 0.0001), corncob (P = 0.0008), and metagenomeSeq (P = 0.0118), and Sarcina was differentially abundant across four methods (P < 0.0001). Finally, the microbiota of all individual Parascaris spp. specimens were compared to establish shared microbiota between groups.

Conclusions

Overall, this study provided important information regarding the Parascaris spp. microbiota and provides a first step towards determining whether the microbiota may be a viable target for future parasite control options.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-022-05533-y.

Importance of TGFβ in Cancer and Nematode Infection and Their Interaction-Opinion

Historically, there has been little interaction between parasitologists and oncologists, although some helminth infections predispose to the development of tumours. In addition, both parasites and tumours need to survive immune attack. Recent research suggests that both tumours and parasites suppress the immune response to increase their chances of survival. They both co-opt the transforming growth factor beta (TGFβ) signalling pathway to modulate the immune response to their benefit. In particular, there is concern that suppression of the immune response by nematodes and their products could enhance susceptibility to tumours in both natural and artificial infections.

In Vitro Anthelmintic Activity of a Hydroalcoholic Extract from Guazuma ulmifolia Leaves against Haemonchus contortus

The purpose of the present study was to assess the ovicidal and larvicidal activity of a hydroalcoholic extract (HAE) and their fractions (aqueous, Aq-F and organic, EtOAc-F) from Guazuma ulmifolia leaves using Haemonchus contortus as a biological model. The egg hatching inhibition (EHI) and larval mortality against infective larvae (L3) tests were used to determine the anthelmintic effect of the treatments. The extract and fractions were tested at different concentrations against eggs and L3. Additionally, distilled water and methanol were used as negative controls and ivermectin as a positive control. The extract and fractions were subjected to HPLC analysis to identify the major compounds. The HAE displayed the highest ovicidal activity (100% EHI at 10 mg/mL). Fractionation of the HA extract allowed increasing the nematicidal effect in the EtOAc-F (100% EHI at 0.62 mg/mL and 85.35% mortality at 25 mg/mL). The phytochemical analysis of the extract and fractions revealed the presence of kaempferol, ethyl ferulate, ethyl coumarate, flavonol, luteolin, ferulic acid, luteolin rhamnoside, apigenin rutinoside, coumaric acid derivative, luteolin glucoside, and quercetin glucoside. These results suggest that G. ulmifolia leaves could be potential candidates for the control of H. contortus or other gastrointestinal parasitic nematodes.

Castor bean cake for the control of parasites in pasture-finished sheep

The purpose of this study was to evaluate castor bean cake as alternative input in the control of gastrointestinal parasites in sheep raised on irrigated pasture under continuous stocking. The treatments consisted of sheep supplemented with standard diet and pasture fertilized with urea; sheep supplemented with alternative diet and pasture fertilized with urea; sheep supplemented with standard diet and pasture fertilized with in natura castor bean cake; and sheep supplemented with alternative diet and pasture fertilized with in natura castor bean cake. A randomized complete block design (CBD) was used, with 16 replications (sheep), with repeated measures over time, the plots being the treatments, and the subplots the collection times. Infective nematode larvae in the pasture (L3.g DM⁻¹), number of eggs per gram of feces (EPG), globular volume (GV), and total plasma protein (TPP) were evaluated. For adult gastrointestinal parasite counts, CBD was also used with six replications. Except for FAMACHA^© grade, all variables had effect (P < 0.01) of the time factor. The average number of L3.g DM⁻¹ and EPG were 126 and 841, respectively, with no effect (P > 0.05) of the treatment factor. The values observed for GV and TPP were higher than 25.9% and 6.4 g·dL⁻¹, respectively, which were considered normal. As organic fertilizer, the fractionated application of in natura castor bean cake does not reduce the contamination of pastures by nematode larvae. The evaluated feeds improve the resilience of the sheep to infection by gastrointestinal parasites. The treatments using castor bean cake reduced the adult parasites present in the abomasum of sheep.

MULTIPLE ANTHELMINTIC RESISTANCE AMONG DORPER SHEEP DETECTED WITH PHENOTYPIC MARKERS AGAINST PARASITIC GASTROENTERITIS

Parasitic gastroenteritis (PGE) is a significant disease that affects small ruminant production. PGE is controlled exclusively by chemical anthelmintics but restricted by anthelmintic resistance. Hence, dependence on anthelmintics needs to be reduced. This study aimed to investigate the anthelmintic resistance status of a Dorper sheep farm while determining the phenotypic markers of resistance to PGE. Sheep that met the criteria of the Faecal Egg Count Reduction Test (FECRT) were divided into a control and four treatment groups of 11 to 13 animals per group. Faecal and blood samples at pre- and post-treatments were subjected to faecal egg counts (FEC), faecal culture, packed cell volume (PCV) and peripheral eosinophil counts (PEC). The data were analysed by Spearman rank correlation and two-way ANOVA. FECRT showed resistance towards albendazole, levamisole, fenbendazole and ivermectin which was predominated by Haemonchus contortus. Significant negative correlations were observed between FEC and PCV in control (r=-0.88, p<0.01), fenbendazole (r=-0.58, p<0.01) and ivermectin (r=-0.69, p<0.01) groups. Significant positive correlations were detected between FEC and PEC in control (r=0.95, p<0.01) and levamisole (r=0.56, p<0.01) groups. This study shows multiple anthelmintic resistance with promising resistant characteristics against PGE among sheep.

Haemonchus contortus Parasitism in Intensively Managed Cross-Limousin Beef Calves: Effects on Feed Conversion and Carcass Characteristics and Potential Associations with Climatic Conditions

The objectives of the study were: (a) to study the effect of Haemonchus spp. on the growth performance characteristics of fattening calves, (b) to assess any potential effects on carcass characteristics and (c) to investigate the potential role of climatic conditions in the process of the infection. The study was conducted for 201 days in an intensively managed cross-Limousin herd. The animals were divided into two equal groups: those receiving anthelmintic treatment (AT) and the untreated (C) controls. The same nutritional regime was applied to both groups and the feed consumption was calculated daily. Standard parasitological examinations were performed at weekly intervals. At slaughter, carcasses were weighed and assessed for conformation and fat cover classes. Climatic variables were obtained for the location of the farm and a temperature-humidity index was calculated. Before anthelmintic treatment with ivermectin, there was no difference in parasitic burdens between the two groups: 544 (AT) vs. 554 (C) epg, whilst after it, counts were 0 and 450–700 epg, respectively, with over 96% of larvae identified as Haemonchus spp. and, later, confirmed as Haemonchus contortus. It was concluded that treated animals had a higher average total bodyweight gain, higher feed conversion ratio and carcass yield of superior quality than controls. There was a difference between the two groups in the pattern of reduction of dry matter intake as the temperature-humidity index increased.

Allele specific PCR for a major marker of levamisole resistance in Haemonchus contortus

Haemonchus contortus is a haematophagous parasitic nematode that infects small ruminants and causes significant animal health concerns and economic losses within the livestock industry on a global scale. Treatment primarily depends on broad-spectrum anthelmintics, however, resistance is established or rapidly emerging against all major drug classes. Levamisole (LEV) remains an important treatment option for parasite control, as resistance to LEV is less prevalent than to members of other major classes of anthelmintics. LEV is an acetylcholine receptor (AChR) agonist that, when bound, results in paralysis of the worm. Numerous studies implicated the AChR sub-unit, ACR-8, in LEV sensitivity and in particular, the presence of a truncated acr-8 transcript or a deletion in the acr-8 locus in some resistant isolates. Recently, a single non-synonymous SNP in acr-8 conferring a serine-to-threonine substitution (S168T) was identified that was strongly associated with LEV resistance. Here, we investigate the role of genetic variation at the acr-8 locus in a controlled genetic cross between the LEV susceptible MHco3(ISE) and LEV resistant MHco18(UGA2004) isolates of H. contortus. Using single worm PCR assays, we found that the presence of S168T was strongly associated with LEV resistance in the parental isolates and F3 progeny of the genetic cross surviving LEV treatment. We developed and optimised an allele-specific PCR assay for the detection of S168T and validated the assay using laboratory isolates and field samples that were phenotyped for LEV resistance. In the LEV-resistant field population, a high proportion (>75%) of L₃ encoded the S168T variant, whereas the variant was absent in the susceptible isolates studied. These data further support the potential role of acr-8 S168T in LEV resistance, with the allele-specific PCR providing an important step towards establishing a sensitive molecular diagnostic test for LEV resistance.

In vitro effect of three tropical plants on adult Haemonchus placei, an haematophagous nematode from cattle

Background

Vernonia amygdalina (leaf), Garcinia kola (seed), and Leucaena leucocephala (seed) are three well-known tropical plants used in African ethnomedicine to reduce parasitic worm burdens and are potential sources of alternative solution for controlling parasitic helminths infection in grazing livestock. This study investigated extracts from these plants for anthelmintic activity against adult Haemonchus placei, an haematophagous nematode from cattle abomasa. Powdered plant materials were macerated in acetone and the crude acetone extracts evaluated for anthelmintic activity using H. placei adult worm motility assay. Afterwards, fresh sample of V. amygdalina was macerated successively in chloroform and acetone and the extracts evaluated for anthelmintic activity. The chloroform extract was subjected to phytochemical and FT-IR analyses and fractionated by vacuum liquid chromatography. Anthelmintic data were fitted to a nonlinear regression equation (Log [extract or fraction] vs. lethality; variable slope) to produce best-fit sigmoidal curves and LC50 values computed with associated uncertainty.

Results

Of the three tropical plants, only V. amygdalina was active against adult H. placei with best-fit LC50 of 6.51 mg/mL (95% CI: 5.32–7.75). Evaluation of the two extracts obtained by successive maceration showed that chloroform extract (LC50, 2.46 mg/mL, 95% CI: 1.87–3.28) was 11 times as potent as acetone extract (LC50, 27.01 mg/mL, 95% CI: 21.32–48.57) (α < 0.0001). Chromatographic fractionation of the chloroform extract yielded four fractions (FA-FD) with FB (LC50, 2.38 mg/mL, 95% CI: 1.76–3.28) 2.19 times as potent as FC (LC50, 5.21 mg/mL, 95% CI: 4.40–5.79) against H. placei, while FA and FD were inactive. Phytochemical evaluation of the chloroform extract revealed the presence of saponins, steroids, terpenoids, cardiac glycosides, and the absence of tannins, flavonoids, alkaloids, and anthraquinones. FT-IR structural analysis of chloroform extract indicated the presence of key functional groups which are chemical fragments/ structural motifs known to be present in the two major classes of bioactive compounds (sesquiterpene lactones and steroid glucosides) reportedly to be found in V. amygdalina.

Conclusions

The findings showed that chloroform extract of V. amygdalina leaf possessed relatively good anthelmintic activity against adult H. placei. This could be indicative of its potential usefulness as an anthelmintic phytomedicine to control gastrointestinal nematodes infection in cattle.

Key highlights

Graphical abstract

A Review: Haemonchus contortus Infection in Pasture-Based Sheep Production Systems, with a Focus on the Pathogenesis of Anaemia and Changes in Haematological Parameters

Simple Summary

Infection with Haemonchus contortus parasites (haemonchosis) is an important cause of anaemia in sheep. Haemonchosis is a global problem, although sheep that are kept in warm, high rainfall environments are at the greatest risk of infection due to the favourable conditions for H. contortus survival. Following ingestion, the parasites develop in the abomasum of sheep. Various factors such as age, breed, health, nutritional status, and larval challenge influence the severity of clinical disease. Hyperacute, acute, and chronic haemonchosis are reviewed, focusing on the pathophysiology of haemonchosis, associated clinical signs, and haematological and biochemical findings.

Abstract

Haemonchosis is an important cause of anaemia in sheep worldwide, particularly those that are kept in pasture-based systems in warm, high rainfall environments. Potential outcomes vary based on the severity of infection and the sheep’s immune response, however, in some sheep infection can lead to death. The consequences of Haemonchus contortus infection mean that it has been well-studied in a range of different farming systems. However, to our knowledge, there has not been a recent review focused on the pathophysiology of anaemia caused by haemonchosis. Thus, this review provides an in-depth discussion of the literature related to the pathophysiology of haemonchosis and associated clinical signs for hyperacute, acute, and chronic haemonchosis. Additionally, haematological and biochemical findings are presented, and various diagnostic methods are assessed.

Comparative analysis on transcriptomics of ivermectin resistant and susceptible strains of Haemonchus contortus

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 Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-022-05274-y.

The production costs of Haemonchus contortus and other nematode parasites in pre-weaned beef calves in New Zealand

Haemonchus contortus can frequently be found infecting pre-weaned beef calves on sheep and beef farms around the North Island of New Zealand. The purpose of this study was to consider whether the presence of this parasite alone, or as part of a mixed infection, could be impacting growth rates of young animals, on three commercial farms in the North Island of New Zealand. Trials were conducted on commercial sheep and beef farms in each of the Northland, King Country and Gisborne regions, in late summer/autumn (February to April) of 2016 to measure the effect of treatment with narrow and broad spectrum anthelmintics on liveweight gain of spring-born calves pre-weaning. Each farm was chosen based on the presence of Haemonchus and that it was a beef cow/calf system with the cows and calves grazing the same pastures as sheep at some stage. Three sampling visits were made to each farm with the animals being weighed, faecal sampled and treated with one of two anthelmintics (Closantel alone to remove only Haemonchus or a triple combination containing moxidectin, levamisole and oxfendazole to remove all nematodes) or left untreated, on each of the first two visits. There was no significant difference in liveweight gain between any of the treatment groups, hence there was no evidence for an impact of Haemonchus alone, or a mixed nematode infection, on pre-weaned calf growth rates on these farms. It remains unclear whether there may be a justification to consider treatment of calves should they constitute a significant source of pasture larval infestation with H. contortus, in an integrated cattle-sheep system.

Immunization With Recombinant Haemonchus contortus Y75B8A.8 Partially Protects Local Crossbred Female Goats From Haemonchus contortus Infection

Haemonchus contortus Y75B8A.8 (Hc8) derived from H. contortus excretory–secretory (ES) products was identified as a functional inhibitor of goat interleukin 2 (IL-2). It may act as a vaccine candidate for the development of therapeutic strategies against H. contortus infection. In this research, recombinant Hc8 (rHc8) and goat anti-rHc8 polyclonal antibodies were employed to evaluate the protective capacities of Hc8 antigen against H. contortus infections via active and passive immunization trials, respectively. In both trials, local crossbred female goats aged 9–12 months old were randomly divided into three groups, five in each group, respectively. Parasitological examinations, including fecal egg counts (FEC), cumulative FEC (cFEC), and worm burdens, were performed. In addition, antibody levels in mucosal homogenate (MH) samples and hematological and immunological parameters were detected. In the passive trial, goats were intravenously immunized with 5 mg total IgG containing anti-rHc8 goat polyclonal antibodies. After twice immunization, compared with the challenged control group, cFEC was reduced by 39%. In addition, there was a 46% reduction of worm burdens compared with the challenged controls. In the active immunization trials, 500 μg of recombinant Hc8 protein was given subcutaneously twice to 9–12-month-old local crossbred female goats with a 2-week interval, resulting in the generation of high levels of antigen-specific circulating antibodies. Besides, cFEC and abomasal worm burden were reduced by 70 and 55%, respectively, compared with the challenged control group. In addition, immunized goats had higher mucosal homogenate IgA and hemoglobin levels than the challenged controls in both passive and active immunization trials. These preliminary results demonstrated the immunoprophylactic effects of Hc8 antigen and will inform new studies on ES proteins in developing subunit recombinant vaccines against H. contortus.

Increasing resistance to multiple anthelmintic classes in gastrointestinal nematodes on sheep farms in southwest England

Background

Anthelmintic resistance (AR) in gastrointestinal nematodes (GIN) is increasing globally, and farmers are encouraged to adopt sustainable control measures. Haemonchus contortus is increasingly reported in the UK, potentially complicating effective GIN control.

Methods

Faecal egg count reduction tests (FECRT) were conducted on 13 farms in north Devon, England, UK in 2016. Relative abundance of H. contortus was quantified using peanut agglutinin staining and used to estimate faecal egg count reduction percentages (FECR%) using the eggCounts R package.

Results

On average, farms had GIN resistance to three anthelmintic classes. No farms had susceptibility to all anthelmintics tested. AR was more prevalent in 2016 than on the same farms in 2013. H. contortus was present on 85% of the farms tested and comprised on average 6% (0%–52%) of GIN eggs before treatment. Resistance or suspected resistance to all anthelmintics tested was observed in this species on different farms.

Conclusion

The results demonstrate diversity of AR profiles on farms, apparent progression of AR within a 3‐year period, and challenges detecting AR in mixed‐species infections. Where possible, interpretation of mixed‐species FECRT should take into account the relative abundance of species pre‐ and post‐treatment to identify pragmatic treatment options targeting individual genera.

Variants Within Genes EDIL3 and ADGRB3 are Associated With Divergent Fecal Egg Counts in Katahdin Sheep at Weaning

Gastrointestinal nematodes (GIN) pose a severe threat to sheep production worldwide. Anthelmintic drug resistance coupled with growing concern regarding potential environmental effects of drug use have demonstrated the necessity of implementing other methods of GIN control. The aim of this study was to test for genetic variants associated with resistance or susceptibility to GIN in Katahdin sheep to improve the current understanding of the genetic mechanisms responsible for host response to GIN. Linear regression and case-control genome-wide association studies were conducted with high-density genotype data and cube-root transformed weaning fecal egg counts (tFEC) of 583 Katahdin sheep. The case-control GWAS identified two significant SNPs (P-values 1.49e-08 to 1.01e-08) within introns of the gene adhesion G protein-coupled receptor B3 (ADGRB3) associated with lower fecal egg counts. With linear regression, four significant SNPs (P-values 7.82e-08 to 3.34e-08) were identified within the first intron of the gene EGF-like repeats and discoidin domains 3 (EDIL3). These identified SNPs were in very high linkage disequilibrium (r² of 0.996–1), and animals with alternate homozygous genotypes had significantly higher median weaning tFEC phenotypes compared to all other genotypes. Significant SNPs were queried through public databases to identify putative transcription factor binding site (TFBS) and potential lncRNA differences between reference and alternate alleles. Changes in TFBS were predicted at two SNPs, and one significant SNP was found to be within a predicted lncRNA sequence with greater than 90% similarity to a known lncRNA in the bovine genome. The gene EDIL3 has been described in other species for its roles in the inhibition and resolution of inflammation. Potential changes of EDIL3 expression mediated through lncRNA expression and/or transcription factor binding may impact the overall immune response and reduce the ability of Katahdin sheep to control GIN infection. This study lays the foundation for further research of EDIL3 and ADGRB3 towards understanding genetic mechanisms of susceptibility to GIN, and suggests these SNPs may contribute to genetic strategies for improving parasite resistance traits in sheep.

Selection of genome-wide SNPs for pooled allelotyping assays useful for population monitoring

Parasitic worms are serious pests of humans, livestock and crops worldwide. Multiple management strategies are employed in order to reduce their impact, and some of these may affect their genome and population allelic frequency distribution. The evolution of chemical resistance, ecological changes, and pest dispersal have allowed an increasing number of pests to become difficult to control with current management methods. Their lifestyle limits the use of ecological and individual-based management of populations. There is a need to develop rapid, affordable, and simple diagnostics to assess the efficacy of management strategies and delay the evolution of resistance to these strategies. This study presents a multi-locus, equal-representation, whole genome pooled SNPs selection approach as a monitoring tool for the ovine nematode parasite Haemonchus contortus. The SNP selection method used two reference genomes of different quality, then validated these SNPs against a high-quality recent genome assembly. From over 11 million high-quality SNPs identified, 334 SNPs were selected, of which 262 were species-specific, yielded similar allele frequencies when assessed as multiple individuals or as pools of individuals, and suitable to distinguish mixed nematode isolate pools from single isolate pools. As a proof-of-concept, 21 Australian H. contortus populations with various phenotypes and genotypes were screened. This analysis confirmed the overall low-level of genetic differentiation between populations collected from the field, but clearly identifying highly inbred populations, and populations showing genetic signatures associated with chemical resistance. The analysis showed that 66% of the SNPs were necessary for stability in assessing population genetic patterns, and SNP pairs did not show linkage according to allelic frequencies across the 21 populations. This method demonstrates that ongoing monitoring of parasite allelic frequencies and genetic changes can be achieved as a management assessment tool to identify drug-treatment failure, population incursions, and inbreeding signatures due to selection. The SNP selection method could also be applied to other parasite species.

Drug resistant parasites and fungi from a one-health perspective: A global concern that needs transdisciplinary stewardship programs

Antimicrobials including antibiotics, antiparasitic, and antifungals, are subjected to resistance. In this context, Public Health Organizations called for a One Health approach because antimicrobials used to treat different infectious diseases in animals and plants may be the same than those used in humans. Whereas mechanisms of resistance transmission from animals or environment to humans should be considered differently if related to prokaryotic or eukaryotic pathogens, their impact can be considered as a whole. In that respect, we discussed the use of anti-parasitic in animals including anticoccidials, anthelmintics, and insecticides-acaricides, and the use of azoles in the environment that may both favor the development of drug resistance in humans. In light of the current situation, there is an urgent need for a transdisciplinary approach through anti-parasitic and antifungal stewardship programs in humans, animals, and environment, especially in the era of COVID-19 pandemic that will probably aggravate antimicrobial resistance.

Point of care colourimetric and lateral flow LAMP assay for the detection of Haemonchus contortus in ruminant faecal samples

In this study, we present an optimised colourimetric and a lateral flow LAMP assay for the detection of Haemonchus contortus in small ruminant faecal samples. Using a previously published LAMP primer set, we made use of commercially available colourimetric LAMP and lateral flow kits and combined this into an optimised diagnostic assay which was then tested on field faecal samples from Eastern and South-Eastern Hungary as well as a pure H. contortus egg faecal sample from Košice, Slovakia. Both assays showed no conflicts in visual detection of the results. Additionally, we modified and tested several centrifuge-free DNA extraction methods and one bead-beating egg lysis DNA extraction method to develop a true point of care protocol, as the source of the starting DNA is the main rate-limiting step in farm-level molecular diagnosis. Out of the various methods trialed, promising results were obtained with the magnetic bead extraction method. Sample solutions from the Fill-FLOTAC® technique were also utilised, which demonstrated that it could be efficiently adapted for field-level egg concentration to extract DNA. This proof of concept study showed that isothermal amplification technologies with a colourimetric detection or when combined with a lateral flow assay could be an important step for a true point of care molecular diagnostic assay for H. contortus.