A multiplex PCR-based method to identify strongylid parasite larvae recovered from ovine faecal cultures and/or pasture samples

World Association for the Advancement of Veterinary Parasitology (W.A.A.V.P.): Third edition of the guideline for evaluating efficacy of anthelmintics in ruminants (bovine, ovine, caprine)

This guideline is aimed at those who are involved in the assessment of anthelmintic efficacy in ruminant livestock species (bovine, ovine and caprine). The intent is to provide a framework that can be adopted worldwide for the testing of anthelmintics in ruminants, such that studies carried out in different countries can be compared and thereby unnecessary duplication can be reduced. Recommendations are made for the selection, housing and feeding of study animals, the type of studies required, the method used to conduct those studies, the assessment of results and the standards for defining anthelmintic efficacy.

A molecular assessment of Ostertagia leptospicularis and Spiculopteragia asymmetrica among wild fallow deer in Northern Ireland and implications for false detection of livestock-associated species

BACKGROUND

Wild deer populations utilizing livestock grazing areas risk cross-species transmission of gastrointestinal nematode parasites (GINs), including GINs with anthelmintic resistance (AR) traits. Wild deer have been shown to carry problematic GIN species such as Haemonchus contortus and Trichostrongylus species in the UK, but the presence of livestock GINs in Northern Ireland deer populations is unknown. Also, is it not known whether AR traits exist among GINs of deer such as Ostertagia leptospicularis and Spiculopteragia asymmetrica in pastureland where anthelmintics are heavily used.

METHODS

Adult-stage GIN samples were retrieved from Northern Irish wild fallow deer abomasa. Individual specimens were subject to a species-specific PCR analysis for common sheep and cattle GIN species with ITS-2 sequence analysis to validate species identities. In addition, the beta-tubulin gene was subject to sequencing to identify benzimidazole (BZ) resistance markers.

RESULTS

ITS-2 sequencing revealed O. leptospicularis and S. asymmetrica, but species-specific PCR yielded false-positive hits for H. contortus, Teladorsagia circimcincta, Trichostrongylus axei, T. colubriformis, T. vitrinus and Ostertagia ostertagi. For beta-tubulin, O. leptospicularis and S. asymmetrica yielded species-specific sequences at the E198 codon, but no resistance markers were identified in either species at positions 167, 198 or 200 of the coding region.

DISCUSSION

From this report, no GIN species of significance in livestock were identified among Northern Ireland fallow deer. However, false-positive PCR hits for sheep and cattle-associated GINs is concerning as the presence of deer species in livestock areas could impact both deer and livestock diagnostics and lead to overestimation of both GIN burden in deer and the role as of deer as drivers of these pathogens. ITS-2 sequences from both O. leptospicularis and S. asymmetrica show minor sequence variations to geographically distinct isolates. AR has been noted among GINs of deer but molecular analyses are lacking for GINs of wildlife. In producing the first beta-tubulin sequences for both O. leptospicularis and S. asymmetrica, we report no BZ resistance in this cohort.

CONCLUSIONS

This work contributes to genetic resources for wildlife species and considers the implications of such species when performing livestock GIN diagnostics.

Role of Silver Nanoparticles for the Control of Anthelmintic Resistance in Small and Large Ruminants

Helminths are considered a significant threat to the livestock industry, as they cause substantial economic losses in small and large ruminant farming. Their morbidity and mortality rates are also increasing day by day as they have zoonotic importance. Anthelmintic drugs have been used for controlling these parasites; unfortunately, due to the development of resistance of these drugs in helminths (parasites), especially in three major classes like benzimidazoles, nicotinic agonists, and macrocyclic lactones, their use is becoming very low. Although new anthelmintics are being developed, the process is time-consuming and costly. As a result, nanoparticles are being explored as an alternative to anthelmintics. Nanoparticles enhance drug effectiveness, drug delivery, and target specificity and have no resistance against parasites. Different types of nanoparticles are used, such as organic (chitosan) and inorganic (gold, silver, zinc oxide, iron oxide, and nickel oxide). One of them, silver nanoparticles (AgNPs), has unique properties in various fields, especially parasitology. AgNPs are synthesized from three primary methods: physical, chemical, and biological. Their primary mechanism of action is causing stress through the production of ROS that destroys cells, organs, proteins, and DNA parasites. The present review is about AgNPs, their mode of action, and their role in controlling anthelmintic resistance against small and large ruminants.

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.

Prevalence and molecular identification of gastrointestinal nematodes in Qinghai-Tibetan Plateau of China

BACKGROUND

Gastrointestinal nematodes (GINs) have seriously affected the production and earnings of animal husbandry in various countries, while some species of GINs infect humans. At present, little is known about the species and prevalence of GINs in Qinghai-Tibetan Plateau (QTP).

METHODS

In this study, 528 fresh faecal samples were collected from typical areas in different altitudes with seven species of livestock in Qinghai, Tibet, Gansu and Yunnan Provinces. ITS-2 rRNA gene of nematodes was employed to detect by PCR and sequencing analysis. Phylogenetic analysis of related sequences was performed using MEGA 6.0 software.

RESULTS

The overall prevalence of GINs was 80.3% with 20 species of GINs detected, while Teladorsagia circumcincta was the dominant one, and four of which were zoonotic species such as Trichostrongylus colubriformis, Trichostrongylus axei, Trichostrongylus vitrinus and Oesophagostomum stephanostomum.

CONCLUSION

The study provided panoptic information on the prevalence and species diversity of GINs in QTP area, which is useful and valuable for reference of measure formulation in livestock husbandry and public health concerns. The parasites of T. circumcincta, Cylicocyclus nassatus, Strongylus edentatus, Cylicostephanus longibursatus, Telephlebia brevicauda, Cyathostomum catinatum, Mecistocirrus digitatus, Cooperia punctata, Cylicodontophorus bicoronatus, Nematodirus oiratianus and Oesophagostomum asperum were firstly reported the presence in QTP area. The study also showed that horse could be infected by T. circumcincta, goat could be infected by C. nassatus, cattle could be infected by S. edentatus and C. bicoronatus,and O. stephanostomum could infect yak, cattle and Mongolian sheep in worldwide. Nevertheless, more investigations are needed, such as microscopic examination, to accurately determine the species in the region.

Molecular identification and phylogenetic analysis of gastrointestinal nematodes in different populations of Kazakh sheep

Gastrointestinal nematode (GIN) infection in sheep has been recognized globally as a major problem challenging animal health and production. The objective of this study is to use a molecular diagnosis of the prevalence for gastrointestinal nematode (GIN) dominant species of Kazakh sheep and its hybrid (Kazakh × Texel). The internal transcribed spacer 2 (ITS-2) sequences of ribosomal DNA (rDNA) were used as the target sequence. In the study, three dominant species of nematodes, namely Haemonchus contortus, Trichostrongylus spp., and Teladorsagia (Ostertagia) circumcincta from the Kazakh sheep and the F1 and F2 generations of Texel × Kazakh sheep hybrids were subjected to molecular identification and phylogenetic analysis. The fecal and single larva genomic DNA were extracted and amplified by PCR using specific primers to determine the infection rate of the three nematode species. In addition, the PCR products were sequenced and analyzed using bioinformatics methods to construct a phylogenetic tree. The results showed that all the three species had their ITS-2 specific amplified. According to the sequence homology analysis of PCR products, the results showed a high homology (above 98.5% homology) with H. contortus, Trichostrongylus spp., T. circumcincta ITS-2 sequences in GenBank. Phylogenetic analysis showed that the ITS-2 sequences of the three species were on the same branch as the ITS-2 sequences of the same species in NCBI. And on different branches from those of the ITS-2 sequences of different families, genera and species. Sequences carried out on three species from different samples showed a close relationship and little genetic difference in phylogenetic tree. The infection rates based on fecal DNA were 35.59, 25.55, and 11.24% for H. contortus, Trichostrongylus spp., and T. circumcincta, respectively. While the infection rates based on larva DNA, were 24.07, 18.89, and 13.26% for H. contortus, Trichostrongylus spp., and T. circumcincta, respectively. The seasonal prevalence of the three dominant species in spring was significantly higher than that in autumn and winter. And there was no significant difference between Kazakh, F1 and F2 sheep considering the infection rate of the studied three species of nematodes. This study provides valuable molecular approaches for epidemiological surveillance and for assisting in the control of Nematodirus infection in sheep.

Molecular and phylogenetic characterization of zoonotic Trichostrongylus species from goats for the first time in Bangladesh

BACKGROUND

Trichostrongylus is one of the most important nematodes infecting animals and humans. The current study was designed to identify the Trichostrongylus species infecting goats by multiplex PCR and phylogenetic analysis.

METHODS

A total of 124 goats' viscera were collected from different abattoirs of Mymensingh division. Trichostrongylus species were isolated and characterized based on morphometry, multiplex PCR and phylogenetic analysis.

RESULTS

Among 124 viscera of goats, 39 were positive with two species, Trichostrongylus colubriformis and Trichostrongylus vitrinus, revealing an overall 31.45% prevalence. Morphological identification of Trichostrongylus species was confirmed by multiplex PCR amplification of the ITS2 gene and sequencing. Partial sequencing of the ITS2 gene of two species revealed seven single nucleotide polymorphisms (three transitions and four transversions) in this study. The neighbor-joining phylogenetic tree demonstrated that T. colubriformis and T. vitrinus isolates were clustered together with the reference sequences that belong to the clade A and B without any geographical boundaries.

CONCLUSIONS

This is the first report on molecular and phylogenetic analysis of Trichostrongylus species from ruminants in Bangladesh. These results provide the baseline data for understanding the zoonosis and epidemiology of this parasite in Bangladesh and global perspectives.

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.

Preliminary results of the recombinase polymerase amplification technique for the detection of Haemonchus contortus from Hungarian field samples

Haemonchus contortus is a parasitic nematode of small ruminants responsible for significant economic losses and animal health concerns globally. Detection of gastrointestinal nematode (GIN) infection in veterinary practice typically relies on microscopy-based methods such as the faecal egg count and morphological identification of larval culture. However, mixed co-infections are common and species-specific identification is typically time-consuming and expertise-intensive. Compounded by increasing anthelmintic resistance, there is an urgent need to implement the molecular diagnosis of GIN in the livestock industry, preferably in field settings. Advances in isothermal amplification techniques including recombinase polymerase amplification (RPA) assays could improve this. Yet, constraints in RPA kit availability and amplicon detection systems limit the use of this technology in point of care settings. In this study, we present an early-stage, proof-of-concept demonstration of RPA targeting the internal transcribed spacer (ITS2) region of H. contortus. Having tested against eight closely related nematodes and also against five farm isolates in Eastern Hungary, preliminary results derived from a comparative analysis of 3 primer sets showed the assay detects H. contortus DNA and has a limit of detection of 10^-5 ng/μl. We also tested an end-result naked eye detection system using various DNA binding dyes, of which EvaGreen® dye was successful for a qualitative RPA detection that could be adaptable at farm sites.

Multi-Omic Profiling, Structural Characterization, and Potent Inhibitor Screening of Evasion-Related Proteins of a Parasitic Nematode, Haemonchus contortus, Surviving Vaccine Treatment

The emergence of drug-resistant parasitic nematodes in both humans and livestock calls for development of alternative and cost-effective control strategies. Barbervax^® is the only registered vaccine for the economically important ruminant strongylid Haemonchus contortus. In this study, we compared the microbiome, genome-wide diversity, and transcriptome of H. contortus adult male populations that survived vaccination with an experimental vaccine after inoculation in sheep. Our genome-wide SNP analysis revealed 16 putative candidate vaccine evasion genes. However, we did not identify any evidence for changes in microbial community profiling based on the 16S rRNA gene sequencing results of the vaccine-surviving parasite populations. A total of fifty-eight genes were identified as significantly differentially expressed, with six genes being long non-coding (lnc) RNAs and none being putative candidate SNP-associated genes. The genes that highly upregulated in surviving parasites from vaccinated animals were associated with GO terms belonging to predominantly molecular functions and a few biological processes that may have facilitated evasion or potentially lessened the effect of the vaccine. These included five targets: astacin (ASTL), carbonate dehydratase (CA2), phospholipase A2 (PLA2), glutamine synthetase (GLUL), and fatty acid-binding protein (FABP3). Our tertiary structure predictions and modelling analyses were used to perform in silico searches of all published and commercially available inhibitor molecules or substrate analogs with potential broad-spectrum efficacy against nematodes of human and veterinary importance.

Depicting Fecal Microbiota Characteristic in Yak, Cattle, Yak-Cattle Hybrid and Tibetan Sheep in Different Eco-Regions of Qinghai-Tibetan Plateau

The gut microbiota is closely associated with the health and production performance of livestock. Partial studies on ruminant microbiota are already in progress in the Qinghai-Tibetan Plateau Area (QTPA) in China, but large-scale and representative profiles for the QTPA are still lacking. Here, 16S rRNA sequencing was used to analyze 340 samples from yak, cattle, yak-cattle hybrids, and Tibetan sheep, which lived in a shared environment from 4 eco-regions of the QTPA during the same season, and aimed to investigate the fecal microbiota community composition, diversity, and potential function. All samples were clustered into 2 enterotypes, which were derived from the genera Ruminococcaceae UCG-005 and Acinetobacter, respectively. Environment, human activity, species, and parasitization all affected the fecal microbiota. By assessing the relationship between the fecal microbiota and the above variables, we identified a scattered pattern of fecal microbiota dissimilarity based more significantly on diet over other factors. Additionally, gastrointestinal nematode infection could reduce the capacity of the bacterial community for biosynthesis of other secondary metabolites, carbohydrate metabolism, and nucleotide metabolism. Ultimately, this study provided a fecal microbiota profile for ruminants living in 4 eco-regions of the QTPA and its potential future applications in developing animal husbandry regimes. IMPORTANCE Cattle, yak, and sheep reside as the main ruminants distributed throughout most regions of Qinghai-Tibetan Plateau Area (QTPA) in China. However, there is a lack of large-scale research in the QTPA on their fecal microbiota, which can regulate and reflect host health as an internalized "microbial organ." Our study depicted the fecal microbiota community composition and diversity of yak, cattle, yak-cattle hybrids, and Tibetan sheep from 4 eco-regions of the QTPA. Additionally, our results demonstrated here that the ruminant samples could be clustered into 2 enterotypes and that diet outweighed other factors in shaping fecal microbiota in the QTPA. This study provided a basis for understanding the microbiota characteristic of ruminants and its possible applications for livestock production in the QTPA.

Untargeted Multimodal Metabolomics Investigation of the Haemonchus contortus Exsheathment Secretome

In nematodes that invade the gastro-intestinal tract of the ruminant, the process of larval exsheathment marks the transition from the free-living to the parasitic stages of these parasites. To investigate the secretome associated with larval exsheathment, a closed in vitro system that effectively reproduces the two basic components of an anaerobic rumen environment (CO2 and 39 °C) was developed to trigger exsheathment in one of the most pathogenic and model gastrointestinal parasitic nematodes, Haemonchus contortus (barber‘s pole worm). This study reports the use of multimodal untargeted metabolomics and lipidomics methodologies to identify the metabolic signatures and compounds secreted during in vitro larval exsheathment in the H. contortus infective third-stage larva (iL3). A combination of statistical and chemoinformatic analyses using three analytical platforms revealed a panel of metabolites detected post exsheathment and associated with amino acids, purines, as well as select organic compounds. The major lipid classes identified by the non-targeted lipidomics method applied were lysophosphatidylglycerols, diglycerides, fatty acyls, glycerophospholipids, and a triglyceride. The identified metabolites may serve as metabolic signatures to improve tractability of parasitic nematodes for characterizing small molecule host–parasite interactions related to pathogenesis, vaccine and drug design, as well as the discovery of metabolic biomarkers.

Estimation of the impact of three different bioinformatic pipelines on sheep nemabiome analysis

Background

Next-generation sequencing (NGS) has provided an alternative strategy to study the composition of nematode communities with increased resolution and sensitivity. However, the handling and processing of gigabytes worth of amplicon sequence data produced by an NGS platform is still a major hurdle, limiting the use and adoption of faster and more convenient analysis software.

Methods

In total 32 paired, fecal samples from Swedish sheep flocks were cultured and the larvae subsequently harvested subjected to internal transcribed spacer 2 (ITS2) amplicon sequencing using the PacBio platform. Samples were analyzed with three different bioinformatic pipelines, i.e. the DADA2, Mothur and SCATA pipelines, to determine species composition and richness.

Results

For the the major species tested in this study (Haemonchus contortus, Teladorsagia circumcinta and Trichostrongylus colubriformis) neither relative abundances nor species diversity differed significantly between the three pipelines, effectively showing that all three analysis pipelines, although different in their approaches, yield nearly identical outcomes. In addition, the samples analyzed here had especially high frequencies of H. contortus (90–95% across the three pipelines) both before and after sample treatment, followed by T. circumcinta (3.5–4%). This shows that H. contortus is the parasite of primary importance in contemporary Swedish sheep farms struggling with anthelmintic resistance. Finally, although on average a significant reduction in egg counts was achieved post-treatment, no significant shifts in major species relative frequencies occurred, indicating highly rigid community structures at sheep farms where anthelmintic resistance has been reported.

Conclusions

The findings presented here further contribute to the development and application of NGS technology to study nemabiome compositions in sheep, in addition to expanding our understanding about the most recent changes in parasite species abundances from Swedish sheep farms struggling with anthelmintic resistance.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-022-05399-0.

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.

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.

Combined Molecular and Lectin Binding Assays to Identify Different Trichostrongyle Eggs in Feces of Sheep and Goats from Egypt

BACKGROUND

Trichostrongyles are common causes of parasitic gastroenteritis in sheep and goats worldwide. Accurate identification of these nematodes to the genus and/or species level is important for therapy selection and control strategies. In the present study, molecular and egg-lectin binding approaches were employed to identify the most economically important trichostrongyles circulating in sheep and goat herds from six districts in Dakahlia governorate, Egypt.

MATERIALS

Fecal samples from 653 and 205 goats reared within 17 herds were collected and tested for the trichostrongyle eggs using the modified Wisconsin sucrose flotation method. For identification of the trichostrongyle(s) present, eggs from 75 (63 sheep and 12 goats) samples which had high egg count (EPG) and pooled eggs (n = 19 pools, 15 sheep and 4 goats) from samples with moderate or low EPGs were examined. Molecular examination was conducted amplifying the ITS2 region of the rDNA for six different trichostrongyles in individual PCR reactions. For egg-lectin bindings, 4 fluorescently-labeled specific lectins were used; peanut agglutinin (PNA) for Haemonchus contortus, Aleuria aurantia agglutinin (AAL) for Trichostrongylus species, Lens culinaris agglutinin (LCA) for Teladorsagia circumcnicta and Lotus tetragonolobus lectin (LTL) for Cooperia species.

RESULTS

Fourteen (82.3%) herds were found infected, of which trichostrongyle eggs were detected in fecal samples of 26.5% (173/653) of sheep and 10.2% (21/205) of goats. Results of the PCR and lectin bindings were compatible and 4 trichostrongyles were detected: H. contortus, T. circumcincta, Trichostrongylus axei and Trichostrongylus colubriformis. Haemonchus contortus eggs were found in all the infected herds, and as the single species in 21 and 5 of sheep and goat samples, respectively. Lectin stained smears demonstrated the dominance of H. contortus eggs over eggs of the other detected trichostrongyles. Eleven herds were found infected with T. axei as the second most prevalent trichostrongyle; however, few AAL-stained eggs were noticed in the positive samples. Mixed infections were frequently detected as H. contortus-T. axei combination. Infections with T. circumcincta were noted in sheep samples from two herds, but not in any sample from the goats. No Ostertagia leptospicularis, Cooperia curticei or Nematodirus species were noted among the tested samples.

CONCLUSIONS

This is the first molecular and lectin binding survey to determine the species composition of trichostrongyles infecting sheep and goats from Egypt. Haemonchus contortus plays the principal role in small ruminant trichostrongylosis in Egypt. Egg-lectin staining shows promise for future for its application in routine diagnosis as a rapid and simple technique. Findings of the earlier reports from Egypt are tabulated and reviewed.

Triple lectin staining of trichostrongyle eggs from naturally infected small ruminants

Trichostrongyle nematodes can be a major threat to the profitability of small ruminant producers depending of the species and intensity of trichostrongyles parasitizing their herd. Haemonchus contortus, Teladorsagia circumcincta, and Trichostrongylus colubriformis are typically the most common and clinically important species. Three lectins (PNA, LCA and AAL) have been reported to bind specifically to eggs from these three genera and therefore could be used to quantify the intensity of each species in individual animals. Peanut agglutinin (PNA) has been the most commonly tested lectin because it selectively binds intensely to eggs of the most pathogenic species, H. contortus. Lens culinaris agglutinin (LCA) and Aleuria aurantia agglutinin (AAL) have shown specificity to T. circumcincta and Trichostrongylus spp. respectively, however, these lectins have only been evaluated using eggs harvested directly from adult females, and not from fecal samples. The purpose of the present study is to describe a method to sequentially stain H. contortus, T. circumcincta and Trichostrongylus spp. fecal eggs with PNA, LCA and AAL, and then evaluate the resultant staining patterns seen with eggs collected from a naturally infected goat shown with PCR to contain H. contortus, T. circumcincta, Ostertagia leptospicularis, Trichostrongylus colubriformis and Trichostrongylus axei eggs. These results were also compared with patterns observed with eggs stained with single lectins and double combinations of lectins. The various patterns were then compared to those seen with egg samples collected from an ewe shown to only contain H. contortus. PNA bound intensely and uniformly to all eggs from samples containing only H. contortus eggs; however, some eggs additionally bound LCA and AAL in localized patches of varying size, and a few eggs exhibited intense and uniform binding of all three lectins. Single PNA-staining of goat samples containing the five trichostrongyles species identified most eggs as H. contortus, and triple-staining showed patterns consistent with those seen for H. contortus. Binding of AAL to non-Haemonchus eggs was uniform but showed significant variations in intensity. Lesser staining eggs tended to also stain intensely with LCA, which is consistent with published binding pattern for T. circumcincta. Most eggs that AAL bound intensely to did not bind with LCA, which is consistent with published binding pattern for Trichostrongylus spp. Autofluorescence was observed with the DAPI filter-cube among most non-Haemonchus eggs. This study demonstrates the need for additional field studies to further validate the specificity of these three lectins for use in identifying eggs from the three species of trichostrongyles.

Phylogenetic analysis of Trichostrongylus vitrinus isolates from southwest Iran

Background

Trichostrongylus is one of the most important zoonotic trichostrongylid nematodes, infecting mostly livestock. Data on its genetic characteristics are lacking in Iran.

Methods

We determined the phylogenetic relationships of Trichostrongylus species in three counties of Kohgiloyeh and Boyerahmad (K-B) province, southwest Iran. Small intestine and abomasum of 70 sheep and goats were investigated.

Results

A total of 35 isolates of Trichostrongylus worms were detected and all were genetically identified as Trichostrongylus vitrinus. Analysis of 321 bp of the internal transcribed spacer 2 (ITS2) of ribosomal DNA revealed 16 genotypes. All genotypes were single nucleotide polymorphisms, including some hypervariable points. All sequences were trimmed to 170 bp, compared with sequences on GenBank including short sequences from other endemic foci of Iran and other countries and all isolates were used to generate a maximum likelihood phylogenetic tree, which consisted of two clades A and B. Clade A included isolates from Iran, Russia, New Zealand, Australia and the UK; clade B only contained South African isolates. Most clade A isolates (north, southwest and west Iran, Russia, New Zealand, Australia and UK) were in a similar phylogenetic position. One subclade was detected in clade A (isolates from Southwest Iran, New Zealand and UK).

Conclusions

We hypothesize that drug resistant T. vitrinus may account for its exclusive detection in our samples. The high similarity of genotypes from Iran, New Zealand and UK may be due to their close political relationships during the colonial era. More research is needed to understand better the phylogeny of T. vitrinus and its relationship with drug resistance and human transmission.

Molecular identification of different Trichostrongylus species infecting sheep and goats from Dakahlia governorate, Egypt

Nematodes of genus Trichostrongylus can cause remarkable economic losses in the small ruminant`s industry and some species have a zoonotic potential. Since the most common source for human infection is the infected animals, accurate identification of different Trichostrongylus species in animals would reflect the species that can infect humans from the same area. The objective of the present study is to identify common Trichostrongylus species infecting small ruminants in Dakahlia governorate, Egypt using molecular-based techniques. Fecal samples from 340 sheep and 115 goats from rural areas in 3 cities of Dakahlia governorate and 2 cities at its borders were collected, and the strongyle-type eggs were detected in 33.2% and 14.7% of sheep and goats, respectively. PCR amplification of the internal transcribed spacer of the ribosomal DNA (ITS2 rDNA) for 3 Trichostrongylus spp.; T. axei, T. colubriformis and T. vitrinus was conducted for eggs harvested from 25 sheep and 16 goat samples. Two species were detected; T. axei (in 16 sheep and 14 goats) and T. colubriformis (in 2 sheep but no goats). This is the first report of T. colubriformis in sheep from Dakahlia governorate, where this species was reported earlier from humans. No T. vitrinus was detected in any tested sample of sheep or goats. Purified PCR products of T. axei isolates were successfully sequenced and revealed 3 haplotypes; 2 from sheep and 1 from goats, and the isolates are related genetically to T. axei isolates from camels in Egypt. Phylogenetic analysis of the Genbank-retrieved ITS2-amplified T. axei isolates worldwide suggested the existence of genetic variants. Earlier reports on the identified Trichostrongylus spp. in different animals from Egypt as well as African and Arabian countries are tabulated.

A survey of gastrointestinal nematode species in red deer (Cervus elaphus) farms in New Zealand using PCR

Gastrointestinal nematodes are recognised as an animal health issue for farmed red deer. The aim of this study was to explore the range of species infecting farmed deer herds and their farm-level prevalence in New Zealand. Faecal samples were collected from 12-24-month-old deer (n = 6-26; mean 19) on 59 farms located in the North (n = 25) and South (n = 34) Islands. Sub-samples of faeces were pooled by farm and cultured to recover third stage larvae. Twenty four larvae were randomly selected and identified to species using a multiplex PCR (total = 1217 larvae). At farm-level the most prevalent nematodes were Oesophagostomum venulosum 83% (n = 49) and the deer-specific nematodes in the subfamily Ostertagiinae (=Ostertagia-type) including, Spiculoptera asymmetrica 73% (n = 43), Ostertagia leptospicularis 47% (n = 28), Spiculoptera spiculoptera 47% (n = 28). The recently identified Trichostrongylus askivali was present on 32% (n = 19) of the farms and Oesophagostomum sikae on 17% (n = 10). In the analysis of the total number of larvae identified, the proportion was in similar order, 45% (n = 548) were O. venulosum, 14% (n = 173) S. asymmetrica, 10% (n = 124) S. spiculoptera, 9% (n = 114) O. leptospicularis, T. askivali, 3% (n = 40) and only 2% were O. sikae (n = 20). This study is the first to show the farm-level prevalence of nematode species in deer in New Zealand and the first to use PCR as a diagnostic tool. It provides data consistent with cross-infection from sheep/cattle to deer, and provided tentative insights into the proportions of the main GIN species across the deer population including O. sikae and T. askivali which have only recently been identified in New Zealand.

Diarrhoea associated with gastrointestinal parasites in grazing sheep

Diarrhoea is a common, widespread and frustrating reality for sheep enterprises in most sheep producing regions globally and of particular concern in Australia as the major risk factor for breech flystrike. Parasitic disease has long been recognised as an important factor in diarrhoea in sheep, particularly the gastrointestinal nematodes (Trichostrongylus and Teladorsagia species). This review focuses on the role of parasitic infections in causing diarrhoea in sheep, with emphasis on the epidemiology of diarrhoea outbreaks related to worms and opportunities to manage the risk of diarrhoea outbreaks in sheep related to parasitic infections. Parasitic nematodes damage the gastrointestinal tract via a complex relationship between direct impacts from worms, such as physical changes to the gut mucosa, and indirect effects largely associated with the host response. Diarrhoea associated with large worm burdens is most efficiently managed through integrated parasite management programs. Despite some limitations, measuring faecal worm egg counts remains a mainstay for assessing the contribution of worms to outbreaks of diarrhoea in sheep. Larval hypersensitivity scouring is emerging as a significant cause of worm-related diarrhoea in sheep without large adult worm burdens in some geographic locations. The syndrome describes a heightened inflammatory response to the ingestion of trichostrongylid infective larvae seen in the gut of sheep with diarrhoea, and is most effectively addressed through selecting sheep for low breech soiling ('dag scores'), as worm resistant sheep may show an increased propensity for diarrhoea, even with low rates of larval challenge. Importantly, dag should be considered as a separate trait to WEC in breeding indexes. Outbreaks of diarrhoea in young sheep are often multifactorial, and co-infections with nematodes and other infectious agents associated with diarrhoea are common. This presents challenges for the field investigation of diarrhoea in grazing sheep.

Development and field evaluation of a species-specific mt-COI targeted SYBR-Green Real Time PCR for detection and quantification of Haemonchus contortus in cattle in Turkey

Haemonchus contortus is one of the most important gastrointestinal nematodes (GINs) infecting sheep, goats, and cattle worldwide. We developed a SYBR Green real-time PCR (qPCR) assay for detection and quantification of H. contortus by using specific primers based on a conserved region of the mitochondrial cytochrome oxidase subunit I (mt-COI) gene, and evaluated this technique in the detection of H. contortus infections in cattle in Central Anatolia Region of Turkey. The newly developed qPCR assay successfully discriminated H. contortus from other GIN species infecting cattle in the specificity evaluations, with a specific melt peak of 77.5 °C. Our results revealed the efficient amplification of the proposed target COI region within the range of plasmid copies, from 2 × 10⁶ to 2 × 10¹ per μl, with 96.9 % efficiency, R² value of 0.999, and a slope of -3.398. Among the 920 cattle fecal samples from the field, 58 samples (6.3 %) were positive with qPCR assay, whereas 45 samples (4.9 %) were positive, as determined by larval culture, suggesting the utility of SYBR Green qPCR. Phylogenetic characterization of the partial COI gene of H. contortus isolates was also evaluated for 100 eggs and third stage larvae recovered from positive cattle faecal samples, which were verified with the qPCR assay prior to analyses. COI sequences were classified into three haplotypes (THC1 to THC3) with intraspecific nucleotide differences of 0.50 to 0.76 %. Phylogenetic analyses revealed that the haplotypes grouped with H. contortus isolates from several countries in a monophyletic cluster, with evidence of at least two main haplogroups. Overall, the SYBR Green qPCR assay was highly specific and sensitive, suggesting that it can be used for screening of H. contortus infections in livestock populations in epidemiological studies and the control of this important parasite.

Validation of ITS-2 rDNA nemabiome sequencing for ovine gastrointestinal nematodes and its application to a large scale survey of UK sheep farms

We have validated ITS-2 rDNA nemabiome next-generation amplicon sequencing to determine relative species abundance of gastrointestinal nematode species in ovine fecal samples. In order to determine species representation biases, ITS-2 rDNA amplicon sequencing was applied to mock communities or field populations with known proportions of L3 for eight of the major ovine gastrointestinal nematode species: Teladorsagia circumcincta, Trichostrongylus vitrinus, Haemonchus contortus, Cooperia curticei, Trichostrongylus axei, Trichostrongylus colubriformis, Chabertia ovina and Oesophagostumum venulosum. Correction factors, calculated from this data, were shown to reduce species representation biases when applied to an independent set of field samples of known composition. We compared ITS-2 rDNA amplicon sequencing data that was generated from harvested eggs, freshly hatched L1 or L3 larvae following fecal culture and no statistically significant differences were found for the more abundant parasite species. We then applied the validated ITS-2 rDNA nemabiome amplicon sequencing assay to a set of archived L1 gastrointestinal nematode populations, collected in 2008 from fecal samples from 93 groups of 20 ewes and 61 groups of 20 lambs derived from 99 UK sheep farms. The presence of the major gastrointestinal nematode species had previously been determined on this large sample set by species-specific PCR. We show how the ITS-2rDNA amplicon sequencing data provided much more detailed information on species abundance than the previous species-specific PCR. This new data represents the most comprehensive overview of the relative abundance of the major gastrointestinal nematode species across UK sheep farms to date. Substantial variance in the relative abundance of both T. circumcincta and T. vitrinus between farms was revealed with the former species being of statistically significantly higher abundance in all three regions sampled (England, Scotland and Wales). The data also revealed that the relative abundance of T. circumcinta was statistically significantly higher in ewes than in lambs with the opposite pattern being the case for T. vitrinus. The nemabiome sequencing data also clearly illustrated the sporadic nature and skewed distribution of H. controtus across UK sheep farms as well as a higher relative abundance on farms from England compared to Wales and Scotland. The nemabiome survey also provides the first widescale data on the relative abundance of the two major large intestinal nematodes C. ovina and O. venulosum. This work validates ITS-2 rDNA nemabiome sequencing for use in sheep and illustrates the power of the approach for large scale surveillance of ovine gastrointestinal nematodes.

Molecular screening approach to identify protozoan and trichostrongylid parasites infecting one-humped camels (Camelus dromedarius)

Little is known about the diversity of many parasites infecting camels, with most relying on morphological parameters. DNA extracted from different tissues (n = 90) and fecal samples (n = 101) from dromedary camels (Camelus dromedarius) in Egypt were screened for multiple parasites using different molecular markers. Screening of tissue samples (heart) for Toxoplasma gondii and Sarcocystis spp. was performed using B1 and 18S rRNA gene markers, respectively. T. gondii was further genotyped using multiplex multilocus nested PCR-RFLP (Mn-PCR-RFLP). Sarcocystis was analyzed using PCR-RFLP characterization (XbaI and MboI restriction enzymes). A taxonomically challenging but important group of nematodes (Trichostrongylidae family) were screened using the ITS-2 ribosomal DNA (rDNA) species-specific markers. Furthermore, nested PCR was used for the detection of Cryptosporidium spp. (SSU rRNA gene) and positive samples were genotyped after RFLP (SspI and VspI) and sequencing. Cryptosporidium parvum isolates were subtyped by sequence analysis of the 60-kDa glycoprotein gene. This study revealed that many parasites infect the investigated camels, including T. gondii (1.1%), Sarcocystis spp. (64.4%), Cryptosporidium spp. (5.9%) and Trichostrongylidae nematodes (22.7%). The species contribution for nematodes was as follows: Haemonchus spp. (95.6%), Trichostrongylus axei (26%), Trichostrongylus colubriformis (65.2%) and Cooperia oncophora (60.8%). Mn-PCR-RFLP typing for Toxoplasma was only successful for three markers: 5'-SAG2 (type II), 3'-SAG2 (type II) and alt. SAG2 (type II). PCR-RFLP using XbaI showed possible mixed Sarcocystis infection. Moreover, the Cryptosporidium genotypes detected were C. parvum (IIdA19G1 and IIaA15G1R1), Cryptosporidium rat genotype IV and a novel genotype (camel genotype). This approach revealed the unique Cryptosporidium genotypes infecting the investigated camels, and the high genetic diversity of the investigated parasites.

The Genome Sequence of the Anthelmintic-Susceptible New Zealand Haemonchus contortus

Internal parasitic nematodes are a global animal health issue causing drastic losses in livestock. Here, we report a H. contortus representative draft genome to serve as a genetic resource to the scientific community and support future experimental research of molecular mechanisms in related parasites. A de novo hybrid assembly was generated from PCR-free whole genome sequence data, resulting in a chromosome-level assembly that is 465 Mb in size encoding 22,341 genes. The genome sequence presented here is consistent with the genome architecture of the existing Haemonchus species and is a valuable resource for future studies regarding population genetic structures of parasitic nematodes. Additionally, comparative pan-genomics with other species of economically important parasitic nematodes have revealed highly open genomes and strong collinearities within the phylum Nematoda.

The current status of anthelmintic resistance in a temperate region of Australia; implications for small ruminant farm management

Widespread anthelmintic resistance in small ruminants is a constraint on the profitability of the meat/wool industry. Limited published data is available on the prevalence and efficacy of anthelmintics, particularly in Australia where parasites affecting ruminant systems vary greatly between geographic regions. This paper reports on the anthelmintic resistance status in a temperate region of Victoria, Australia, a major sheep producing state largely affected by Trichostrongylus species and Teladorsagia circumcincta. The prevalence of anthelmintic resistance to any product was high (71%), with farms reporting varying levels of drug efficacies (21-100%). Resistance to older chemical groups (i.e. fenbendazole and levamisole) and single active macrocyclic lactone treatments was higher than newer chemical groups and combination treatments. This report provides clarity on anthelmintic resistance in the temperate region of Victoria and more importantly suggests that more comprehensive, regional specific anthelmintic resistance studies are required to understand the real level of chemical resistance threatening the effective control of worms.

Abomasal nematode species differ in their in vitro response to exsheathment triggers

A crucial step in the infection process of grazing ruminants by gastro-intestinal nematodes is the exsheathment of the infective third-stage larva following ingestion. Recently, heat shock was shown to play an important role in the carbon dioxide (CO₂)-dependent exsheathment response in Haemonchus contortus. The current in vitro study set out to evaluate the role of heat shock in other abomasal species. In rumen fluid, all species tested exsheathed rapidly and efficiently in response to heat shock and CO_2. This response was significantly higher compared to slow temperature changes, supporting the hypothesis that heat shock plays an important role in vivo. However, in artificial buffer, the effect of heat shock was species-dependent. For H. contortus and Ostertagia leptospicularis, the response in artificial buffer was similar to rumen fluid. In contrast, Ostertagia ostertagi and Teladorsagia circumcincta exsheathment was significantly lower and/or slower in artificial buffer, and there was no benefit of heat shock. For these two species, it appears that there are co-factors in the rumen fluid, in addition to heat shock and CO₂, contributing to exsheathment. Overall, the data indicate that there are significant differences between abomasal species in their response to exsheathment triggers.

Emergence and the spread of the F200Y benzimidazole resistance mutation in Haemonchus contortus and Haemonchus placei from buffalo and cattle

Benzimidazoles have been intensively (for over 40 years) used in the livestock sector, particularly in small ruminants. This has been led to the widespread emergence of resistance in a number of small ruminant parasite species, especially Haemonchus contortus. In many countries benzimidazole resistance has severely compromised the control of H. contortus in small ruminants; but there is a little information on benzimidazole resistance in H. contortus infecting buffalo and cattle. Resistance to benzimidazoles have also been reported in the large ruminant parasite, Haemonchus placei, but again there is relatively little information on its prevalence. Hence it is very important to understand how resistance-conferring mutations emerge and spread in both parasites in buffalo and cattle hosts in order to develop approaches for the recognition of the problem at an early stage of its development. The present study suggests that the F200Y (TAC) mutation is common in H. contortus, being detected in 5/7 populations at frequencies between 7 and 57%. Furthermore, 6/10 H. placei populations contained the F200Y (TAC) mutation, albeit at low frequencies of between 0.4 and 5%. The phylogenetic analysis suggests that the F200Y (TAC) mutation in H. contortus has emerged on multiple occasions in the region, with at least three independent emergences across the populations. In contrast, the F200Y (TAC) resistance-conferring mutation in H. placei is only seen on a single haplotype. A high level frequency of the resistance haplotypes in the region, suggests that the unique resistance conferring-mutation has spread from a single emergence; likely by anthropogenic animal movement. Overall, these results provide the first clear genetic evidence for the spread of benzimidazole resistance-conferring mutations to multiple different locations from a single emergence in H. placei; while being consistent with previous small ruminant-based observations of multiple emergence of resistance mutations in H. contortus.

Droplet digital polymerase chain reaction (ddPCR) as a novel method for absolute quantification of major gastrointestinal nematodes in sheep

In this paper, we present for the first time a new tool, based on Droplet Digital™ Polymerase Chain Reaction (ddPCR), for absolute quantification of key genera of gastrointestinal (GI) nematode parasites of grazing livestock. Four combinations of primers/probe sets targeting the internal transcribed spacer region 2 (ITS2) of the ribosomal RNA gene array were designed using the Primer3 software, following in silico analysis of nucleotide sequences from nematodes of interest downloaded from common databases. The amplified regions include both a universal region for detection of any strongylid gastrointestinal parasite and three different genus specific regions, making it possible to differentiate between the most important GI nematodes of sheep in Sweden: Haemonchus, Teladorsagia and Trichostrongylus. Analysis of samples containing serial dilutions and different mixtures of genomic DNA extracted from different species of adult worms proved useful in assessment of different threshold settings with the QuantaSoft software. Analysis of template DNA from these worms indicated that ddPCR is a viable choice for detection and absolute quantification of the different genera and also in samples with multiple species. Interpretation of the ddPCR results was straightforward and choice of analytical approach had little influence on the final results. Thus, the results obtained in the different analytical approaches seemed to be robust and the concentrations determined were uniform. Furthermore, the linear range of the Haemonchus ddPCR assay was similar to that of real-time PCR (qPCR). Taken together, our data confirm the suitability of ddPCR for detection and absolute quantification of three major sheep pathogens when tested on larval cultures from pooled ovine faeces. The results also indicate that ddPCR can be a useful complement to applications based on conventional egg counting methods such as the faecal egg reduction test (FECRT).

Hidden in plain sight - Multiple resistant species within a strongyle community

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PCR speciation highlighted parasite species diversity on a commercial UK sheep farm.

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Species diversity confounded interpretation of faecal egg count data and bioassays.

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These tests detected only moderate resistance to benzimidazoles and ivermectin.

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Post-treatment populations were composed almost entirely of Teladorsagia circumcincta.

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Ivermectin strongly selected for a highly dual-resistant and pathogenic species.

Ovine parasitic gastroenteritis is a complex disease routinely treated using anthelmintics. Although many different strongyle species may contribute to parasitic gastroenteritis, not all are equally pathogenic: in temperate regions, the primary pathogen is Teladorsagia circumcincta. In this study we investigated benzimidazole and ivermectin resistance on a commercial sheep farm in southeast Scotland. We assessed the impact of species diversity on the diagnosis of resistance using the faecal egg count reduction test and in vitro bioassays, and correlated the results with the frequency of benzimidazole resistance-associated genotypes measured in the T. circumcincta population by pyrosequencing of the β-tubulin isotype-1 gene.

Faecal egg count reduction test results showed efficacies of 65% for albendazole and 77% for ivermectin, indicating moderate resistance levels on the farm. However, PCR speciation of the same populations pre- and post-treatment revealed that removal of susceptible species had masked the presence of a highly resistant population of T. circumcincta. Less than 25% of individuals in the pre-treatment populations were T. circumcincta, the remainder consisting of Cooperia curticei, Chabertia ovina, Oesophagostomum venulosum and Trichostrongylus spp. In contrast, post-treatment with albendazole or ivermectin, the majority (88% and 100% respectively) of the populations consisted of T. circumcincta. The egg hatch test for benzimidazole resistance and the larval development test for ivermectin resistance were carried out using eggs obtained from the same populations and the results were broadly consistent with the faecal egg count reduction test. Thirty individual T. circumcincta from each sampling time point were assessed for benzimidazole resistance by pyrosequencing, revealing a high frequency and diversity of resistance-associated mutations, including within the population sampled post-ivermectin treatment.

These results highlight the potential diversity of parasite species present on UK farms, and their importance in the diagnosis of anthelmintic resistance. On this particular farm, we demonstrate the presence of a highly dual-resistant population of T. circumcincta, which was strongly selected by treatment with either benzimidazoles or ivermectin, while other potentially less pathogenic species were removed.

Fecal parasite identification by microscopy and PCR in scimitar-horned oryx, Oryx dammah, managed at two sites

The scimitar-horned oryx, Oryx dammah, an endangered species extinct in the wild, is managed in various captive management programs and is the focus of reintroduction efforts. Management variability can contribute to substantial parasite load differences, which can affect deworming programs and potentially transfer parasites to different regions with translocations. Parasite studies in O. dammah are lacking. In this study, we determined fecal egg/oocyst counts of O. dammah in two captive herds, Fossil Rim Wildlife Center (FRWC) and Kansas City Zoo (KCZ). Fecal egg counts (FEC) were performed on O. dammah feces collected seasonally using the modified McMaster method, and microscopy provided additional identification of parasite genera ova and oocysts. To identify parasites to species level, homogenized fecals provided DNA subjected to the polymerase chain reaction (PCR) using genus specific primers. Microscopy and sequencing results indicated the presence of Strongylus (Strongylus vulgaris, Angiostrongylus cantonensis), Trichostrongylus (Haemonchus contortus, Camelostrongylus mentulatus), Trichuris (T. leporis, T. ovis, and T. discolor), Isospora (Isospora gryphoni) and Eimeria (E. zuernii and E. bovis), with Strongylus being the most common. Nematodirus was identified through microscopy at FRWC. Fecal egg counts were significantly higher in (FRWC) than in (KCZ) in all samplings (P = <0.001). No significant difference was seen between parasite load and seasons (P = 0.103), nor site and season (P = 0.51). Both study sites maintained most animals within commonly accepted FEC levels found in domestic livestock. Individuals with high numbers of EPG or OPG were subordinate males, pregnant females, or neonates. Several significant interactions were found between genera of parasites, age, sex, season, and pregnancy status in the FRWC herd. Sampling limitations prevented further analysis of the KCZ herd. Understanding interactions between parasite loads and physiological, environmental, and regional differences can help determine inter-specific transfer of parasites, and establish appropriate anthelmintic programs for O. dammah herds.

Chilling requirements for hatching of a New Zealand isolate of Nematodirus filicollis

The eggs of some species of the parasitic nematode Nematodirus require a period of chilling before they can hatch; N. filicollis is one such species. This study investigated this requirement for chilling in a New Zealand strain of this species. Eggs of N. filicollis were extracted from lamb's faeces and incubated at 20°C to allow development to the third stage larvae within the egg. These eggs were then placed into tissue culture plates and incubated at: 2.7°C (±0.99), 3.6°C (±0.90), 4.7°C (±0.35), 6.4°C (±0.37), 8.0°C (±1.54) or 9.9°C (±0.14) for up to 224 days. At 14day intervals until day 84, then every 28 days, one plate was removed from each temperature and placed at 13.1°C (±0.44) for 14 days. Eggs were then assessed for hatching. From this data, chill units were calculated by subtracting the culture temperature from a constant threshold of 11°C and multiplying by the number of days for which the sample was cultured; then the Gompertz model fitted. Even though hatching overall was low, a greater proportion of eggs hatched with chill accumulation. Maximum hatching of eggs required 800-1000 chill units. Consequently in the field, more than one season of chilling would be required before hatching. As such a generation time could take more than one year to complete. This is different to the hatching dynamics of N. spathiger, the other main species found in New Zealand sheep, which does not display this requirement for chilling and hatches immediately once the third stage larvae are developed.

Diagnosis, Treatment and Management of Haemonchus contortus in Small Ruminants

Haemonchus contortus is a highly pathogenic, blood-feeding nematode of small ruminants, and a significant cause of mortalities worldwide. Haemonchosis is a particularly significant threat in tropical, subtropical and warm temperate regions, where warm and moist conditions favour the free-living stages, but periodic outbreaks occur more widely during periods of transient environmental favourability. The clinical diagnosis of haemonchosis is based mostly on the detection of anaemia in association with a characteristic epidemiological picture, and confirmed at postmortem by the finding of large numbers of H. contortus in the abomasum. The detection of impending haemonchosis relies chiefly on periodic monitoring for anaemia, including through the 'FAMACHA' conjunctival-colour index, or through faecal worm egg counts and other laboratory procedures. A range of anthelmintics for use against H. contortus is available, but in most endemic situations anthelmintic resistance significantly limits the available treatment options. Effective preventative programmes vary depending on environments and enterprise types, and according to the scale of the haemonchosis risk and the local epidemiology of infections, but should aim to prevent disease outbreaks while maintaining anthelmintic efficacy. Appropriate strategies include animal management programmes to avoid excessive H. contortus challenge, genetic and nutritional approaches to enhance resistance and resilience to infection, and the monitoring of H. contortus infection on an individual animal or flock basis. Specific strategies to manage anthelmintic resistance centre on the appropriate use of effective anthelmintics, and refugia-based treatment schedules. Alternative approaches, such as biological control, may also prove useful, and vaccination against H. contortus appears to have significant potential in control programmes.

Effect of anthelmintic treatment strategy on strongylid nematode species composition in grazing lambs in Scotland

Background

Refugia based anthelmintic protocols aim to reduce the rate of development of anthelmintic resistance in gastrointestinal nematodes (GIN). Previous studies have illustrated the impact of different drenching regimes on drug efficacy and animal growth; however, the impact on nematode populations has yet to be characterised within natural infections. This study investigated the changes in species composition of GIN throughout the grazing season, following implementation of four different ivermectin drenching regimes over six years: neo-suppressive monthly treatment (NST), targeted selective treatment (TST), strategic prophylactic treatment (SPT) and treatment upon observation of clinical signs (MT).

Methods

Lambs were grazed on one of eight replicate paddocks each grazing season following treatment regimes assigned in year 1. Faecal samples were collected fortnightly from all animals and hatched to first stage larvae (L₁). DNA was extracted from individual L₁ and a multiplex PCR assay targeting the internal transcribed spacer 2 (ITS2) region of Teladorsagia circumcincta, Trichostrongylus spp. and Haemonchus contortus conducted. Other species were identified using species-specific PCR. Worm-naïve tracer lambs were grazed on the paddocks at the start and end of each grazing season and adult worms recovered at post mortem to investigate the parasite population on pasture.

Results

Results showed an overall decrease in species diversity in egg output from the NST group which occurred within a single grazing season and was consistent throughout the experiment. Species diversity was protected over six years in groups implementing TST, SPT and MT treatment regimes, designed to offer refugia. The expected shift in species prevalence throughout the season from Teladorsagia to Trichostrongylus was observed in all but the NST group where only Teladorsagia spp. were recovered from trial lambs by the end of the experiment. Worm burdens indicated the presence of several species at relatively low abundance on pasture in the NST group in 2011. However, these species were not represented in egg output from trial lambs, probably due to the frequent anthelmintic treatment administered throughout the grazing season.

Conclusion

The molecular methods utilised here worked well. The comparable results of the three refugia-based treatment regimes suggest that nematode diversity can be maintained using part or whole group treatments if a rich supra-population of parasites are available to re-infect animals post treatment.

Benzimidazole resistance in Nematodirus spathiger and N. filicollis in New Zealand

AIM

To determine the prevalence of benzimidazole resistance in Nematodirus spathiger and N. filicollis from a sample of New Zealand farms.

METHODS

The efficacy of albendazole (ABZ) against Nematodirus spp. was assessed by faecal nematode egg count reduction (FECR) tests undertaken in lambs aged 3-8 months old on 27 sheep farms throughout New Zealand. On each farm, groups of 10-16 lambs were either treated with ABZ (4.75 mg/kg) or remained as untreated controls. Faecal samples were collected from all animals at the time of treatment and 7-10 days later. Faecal nematode egg counts (FEC) were performed using a modified McMaster technique. Larvae were cultured from pooled faecal samples, collected 7-10 days after treatment from each group, by incubation at 20°C for 6 weeks, 4°C for 26 weeks then 13°C for 2 weeks. The resulting third stage larvae were identified to species using a multiplex PCR assay, that identified species-specific sequences in the second internal transcribed spacer region of ribosomal DNA. The efficacy of ABZ for N. spathiger and N. filicollis was calculated from the proportion of the two species in culture and the group mean FEC before and after treatment. Only farms with a mean of 10 epg for each species in untreated samples were included for analysis. Resistance was defined as an efficacy <95%.

RESULTS

On farms that met the threshold of 10 epg in faecal samples, benzimidazole resistance was found on 20/21 (95%) farms for N. spathiger compared with 4/10 (40%) farms for N. filicollis (p<0.05). In samples collected following treatment, a mean of 83 (min 46, max 100)% of Nematodirus spp. larvae recovered from the untreated groups were N. spathiger, compared with 94 (min 45, max 100)% in the ABZ treated groups (p=0.03). This change in percentage was not influenced by the overall efficacy of treatment based on the FECR test (p=0.324).

CONCLUSION

The results confirm the high level of resistance in N. spathiger in New Zealand and that benzimidazole resistance was more common in N. spathiger than N. filicollis. While resistance to benzimidazole anthelmintics has been reported previously in New Zealand, this is the first report of N. filicollis being resistant to benzimidazole anthelmintics.

The Identification of Haemonchus Species and Diagnosis of Haemonchosis

Diagnosis is often equated with identification or detection when discussing parasitic diseases. Unfortunately, these are not necessarily mutually exclusive activities; diseases and infections are generally diagnosed and organisms are identified. Diagnosis is commonly predicated upon some clinical signs; in an effort to determine the causative agent, identification of genera and species is subsequently performed. Both identification and diagnosis play critical roles in managing an infection, and involve the interplay of direct and indirect methods of detection, particularly in light of the complex and expanding problem of drug-resistance in parasites. Accurate and authoritative identification that is cost- and time-effective, based on structural and molecular attributes of specimens, provides a foundation for defining parasite diversity and changing patterns of geographical distribution, host association and emergence of disease. Most techniques developed thus far have been grounded in assumptions based on strict host associations between Haemonchus contortus and small ruminants, that is, sheep and goats, and between Haemonchus placei and bovids. Current research and increasing empirical evidence of natural infections in the field demonstrates that this assumption misrepresents the host associations for these species of Haemonchus. Furthermore, the capacity of H. contortus to utilize a considerably broad spectrum of ungulate hosts is reflected in our understanding of the role of anthropogenic forcing, the 'breakdown' of ecological isolation, global introduction and host switching as determinants of distribution. Nuanced insights about distribution, host association and epidemiology have emerged over the past 30years, coincidently with the development of increasingly robust means for parasite identification. In this review and for the sake of argument, we would like to delineate the diagnosis of haemonchosis from the identification of the specific pathogen. As a foundation for exploring host and parasite biology, we will examine the evolution of methods for distinguishing H. contortus from other common gastrointestinal nematodes of agriculturally significant and free-ranging wild ruminants using morphological, molecular and/or immunological methods for studies at the species and genus levels.

Hemoparasites in a wild primate: Infection patterns suggest interaction of Plasmodium and Babesia in a lemur species

Hemoparasites can cause serious morbidity in humans and animals and often involve wildlife reservoirs. Understanding patterns of hemoparasite infections in natural populations can therefore inform about emerging disease risks, especially in the light of climate change and human disruption of natural ecosystems. We investigated the effects of host age, sex, host group size and season on infection patterns of Plasmodium sp., Babesia sp. and filarial nematodes in a population of wild Malagasy primates, Verreaux's sifakas (Propithecus verreauxi), as well as the effects of these infections on hematological variables. We tested 45 blood samples from 36 individuals and identified two species of Plasmodium, one species of Babesia and two species of filarial nematodes. Plasmodium spp. and Babesia sp. infections showed opposite patterns of age-dependency, with babesiosis being prevalent among young animals, while older animals were infected with Plasmodium sp. In addition, Babesia sp. infection was a statistically significant negative predictor of Plasmodium sp. infection. These results suggest that Plasmodium and Babesia parasites may interact within the host, either through cross-immunity or via resource competition, so that Plasmodium infections can only establish after babesiosis has resolved. We found no effects of host sex, host group size and season on hemoparasite infections. Infections showed high prevalences and did not influence hematological variables. This preliminary evidence supports the impression that the hosts and parasites considered in this study appear to be well-adapted to each other, resulting in persistent infections with low pathogenic and probably low zoonotic potential. Our results illustrate the crucial role of biodiversity in host-parasite relationships, specifically how within-host pathogen diversity may regulate the abundance of parasites.

A combined parasitological molecular approach for noninvasive characterization of parasitic nematode communities in wild hosts

Most hosts are concurrently or sequentially infected with multiple parasites; thus, fully understanding interactions between individual parasite species and their hosts depends on accurate characterization of the parasite community. For parasitic nematodes, noninvasive methods for obtaining quantitative, species-specific infection data in wildlife are often unreliable. Consequently, characterization of gastrointestinal nematode communities of wild hosts has largely relied on lethal sampling to isolate and enumerate adult worms directly from the tissues of dead hosts. The necessity of lethal sampling severely restricts the host species that can be studied, the adequacy of sample sizes to assess diversity, the geographic scope of collections and the research questions that can be addressed. Focusing on gastrointestinal nematodes of wild African buffalo, we evaluated whether accurate characterization of nematode communities could be made using a noninvasive technique that combined conventional parasitological approaches with molecular barcoding. To establish the reliability of this new method, we compared estimates of gastrointestinal nematode abundance, prevalence, richness and community composition derived from lethal sampling with estimates derived from our noninvasive approach. Our noninvasive technique accurately estimated total and species-specific worm abundances, as well as worm prevalence and community composition when compared to the lethal sampling method. Importantly, the rate of parasite species discovery was similar for both methods, and only a modest number of barcoded larvae (n = 10) were needed to capture key aspects of parasite community composition. Overall, this new noninvasive strategy offers numerous advantages over lethal sampling methods for studying nematode-host interactions in wildlife and can readily be applied to a range of study systems.

Evidence for reversion towards anthelmintic susceptibility in Teladorsagia circumcincta in response to resistance management programmes

Maintaining production and economic viability in the face of resistance to multiple anthelmintic actives is a challenge for farmers in many countries. In this situation, most farmers in New Zealand rely on the use of combination products, containing multiple actives with similar spectra of activity, in order to maintain control. However, there are concerns that use of combinations, once resistance has already developed to the individual actives, could rapidly lead to complete failure of all actives. This study followed seven farms, previously diagnosed with resistance to at least two classes of anthelmintic, which were implementing a tailored programme of 'best practice parasite management'. The aim was to ascertain whether the programmes, which included the almost exclusive use of combination anthelmintics, were able to prevent resistance from developing further. Strategies implemented on each farm varied, but had consistent underlying principles i.e. to avoid over-use of anthelmintics; to minimise parasite challenge to susceptible stock; to maintain refugia of susceptibility and to ensure that only effective anthelmintics were used. Annual faecal egg count reduction tests (FECRT) were undertaken in lambs on all farms to monitor anthelmintic efficacy over 5 years. The efficacy of albendazole, ivermectin and levamisole was calculated and the changes in efficacy against Teladorsagia circumcincta assessed. Overall, there was a significant improvement in the effectiveness of both levamisole and ivermectin against T. circumcincta, and a positive but non-significant trend in efficacy of albendazole, i.e. there was evidence for reversion towards susceptibility. Hence, the almost exclusive use of combination anthelmintics, integrated with other resistance management strategies, did not result in further resistance development despite all farms exhibiting resistance to multiple actives at the outset. What-is-more, the measured increases in anthelmintic efficacy suggests that adoption of best practice management strategies may extend the useful life of anthelmintics even after resistance has been diagnosed.