Identification and quantification of benzimidazole resistance polymorphisms in Haemonchus contortus isolated in Northeastern Brazil

A systematic review of the molecular mechanisms related to anthelmintic resistance in Haemonchus contortus: A contemporary narrative

Haemonchus contortus is a gastrointestinal parasite that affects ruminants (cattle, sheep, etc.), having a significant welfare impact worldwide. The rise of anthelmintic resistance poses a growing challenge to adequate control, compromising the success of treatments. This study presents a systematic review of the molecular mechanisms involved in the resistance of H. contortus to anthelmintic drugs. Following an extensive literature search (9075 total articles/excluding duplications), 61 articles were examined. From these, benzimidazoles (BZD) and macrocyclic lactone (ML) were the most reported drug classes (17 and 29, respectively). The mutations in the β-tubulin gene were the primary mechanism of BZD resistance. Important comparisons from early reports of resistance mechanisms to ML (published before 2020) mainly based on parasite-population gene expression (e.g., ligand-gated chloride channels, LGCC, and P-glycoproteins, PGP) with more recent genomic and transcriptomic data (e.g., transcription factor, cky-1 gene) are highlighted. Additionally, resistance mechanisms to levamisole (LEV) and monepantel are discussed, showing evidence of polymorphisms in genes related to the nicotinic acetylcholine receptors (nAChR). Considering the available data, it is possible to divide the reports into two technological periods, evidencing that the availability of a chromosome-level genome for H. contortus in association with experiments based on controlled genetic crosses and transcriptome-wide data allowed for the visualization of genes and polymorphisms that were previously indistinguishable from unrelated genetic variation (i.e., genetic noise). Therefore, the study of anthelmintic resistance mechanisms is facing new possibilities, reflecting the large data banks and the speed at which this information is being processed. We suggest that new publications on drug resistance should adopt the approaches and refer to this new era of scientific discoveries. Consistent data interpretation, including artificial intelligence (AI) support, will help us to suggest novel biological mechanisms involved in drug resistance and predict its evolution, allowing a more comprehensible approach toward sustainable parasite control strategies.

Investigation on parasite infection and anthelmintic resistance of gastrointestinal nematodes in sheep in Hinggan league (City), China

BACKGROUND

Different areas of sheep infected with different types of parasites, all will cause serious harm to the local sheep, and the widespread use and repeated use of anthelmintics have produced different degrees of anthelmintic resistance (AR) in various regions. We re-investigated the infection of common parasites and AR of Gastrointestinal Nematodes (GINs) in sheep in Horqin Right Wing Front Banner, and first investigated the common parasite types and AR of GINs in sheep at other four areas in Hinggan league (city), China.

RESULTS

A total of 1770 fecal samples were collected from 1 prefecture-level city and 4 counties in Hinggan league, in which the infection rate of Coccidia ranged from 83.3% to 96.06%, that of Ascaris ovis ranged from 10.17% to 15.19%, that of Moniezia benedeni ranged from 0.6% to 1%, that of Moniezia expansa ranged from 0.33% to 8.15%. The infection rate of GINs was 100%, and Haemonchus contortus was still the dominant species. The AR results showed that only the closantel in Horqin Right Wing Middle Banner was low resiatant, and the other three regions had been resistant. Levamisole also occurred AR in the other four regions, the widely used ivermectin and albendazole had produced serious AR in five areas. The research shows that GINs are becoming more and more resistant to various anthelmintics, which has made the problem worse.

CONCLUSIONS

Understanding the dynamic changes of parasite infections and the development trend of AR in sheep in the region in this paper, the development trend seems to be more serious than imagined. Therefore only by deeply understanding the parasitic infections of sheep in this land can more reasonable medication guidance be carried out. It is expected to provide new ideas formore innovative, scientific and sustainable methods of preventing and controlling parasites.

Paraherquamides - A new hope and great expectations of anthelmintic agents: Computational studies

Nematode infections impose a significant health and economic burden, particularly as parasites develop resistance to existing treatments and evade host defenses. This study explores the efficacy of 48 paraherquamide analogs, a class of polycyclic spiro-oxindole alkaloids with unique structural features, as potential anthelmintic agents. Employing advanced computational methods, including molecular docking, MM-GBSA, and molecular dynamics simulations, we assessed the interaction of these analogs with the Ls-AchBP receptor, a model for nematode neurotransmission. Among the analogs studied, Paraherquamide K, Mangrovamide A, and Chrysogenamide A showed comparable docking and MM-GBSA scores to the native antagonist. Notably, their binding interactions exhibited slight distinction attributed to structural differences, such as the absence of a di-oxygenated 7-membered ring. Additionally, these analogs demonstrated robust binding stability in the molecular dynamic simulation studies and favorable pharmacokinetic properties in our in-silico ADME assessment. The insights gained from the study highlight the potential of these analogs as a basis for developing new therapeutics for nematode infections. The promising results from this computational analysis set the stage for subsequent in-vivo validations and pre-clinical studies, contributing to the arsenal against parasitic resistance.

Prevalence status and detection of benzimidazole resistance using AS-PCR in Haemonchus contortus of goats from Marathwada region, Maharashtra, India

This study examined Haemonchus contortus prevalence and benzimidazole resistance in eight districts of Marathwada, Maharashtra, India. A comprehensive investigation of 264 abomasa of goats collected from abattoirs and goats necropsied at the College of Veterinary Sciences and Animal Husbandry, Parbhani, revealed 21.21 % a prevalence of H. contortus. The incidence of H. contortus did not vary much across seasons and it was highest in summer (23.42 %), followed by monsoon (22.89 %), and lowest in winter (15.71 %). Statistically non-significant (p < 0.05) prevalence was observed in male and female animals. A detailed examination of 168 adult H. contortus worms from eight districts revealed the presence of all conceivable genotypes including homozygous resistant (rr), susceptible (SS), and heterozygous (Sr) BZ susceptible genotypes. The rr was the most frequent at 50 %, followed by SS at 27 % and Sr at 22 %. The presence of the SNP was observed in in all eight randomly selected and sequenced samples.

Expression of transporter genes in anthelmintic resistant isolates of Haemonchus contortus

ATP-binding cassette (ABC) transporters, including P-glycoproteins (PGP), have been implicated in drug resistance in different organisms including Haemonchus contortus. This study confirmed the resistance status of H. contortus isolates selected for ivermectin (IVM) and oxfendazole (OXF) resistances using the fecal egg count reduction test and evaluated the gene expression of seven ABC transporters using RT-qPCR for two biological scenarios: the effect of selection for anthelmintic resistance and the effect of drug exposure on gene expression. Gene expression results showed that selection for IVM resistance led to the significant upregulation of Hco-pgp-9a (1.5-fold), Hco-pgp-11 (3-fold) and Hco-haf-9 (1.5-fold) (p < 0.05). Similarly, selection for OXF resistance led to the significant upregulation of Hco-pgp-9a (3-fold), Hco-pgp-11 (4-fold) and Hco-haf-9 (2-fold) when comparing with the unselected ISE isolate (p < 0.05). Exposure of selected isolates to anthelmintics lead to no significant upregulation of the studied transporter genes. We also observed instances where there was strong intragroup variation regarding samples originating from parasites obtained from different individual hosts pointing that the interactions of the animal host with the tested anthelmintics may also play a role in the expression of the studied nematode genes.

The first molecular detection of benzimidazole resistance in Haemonchus contortus from sheep in Hejing and Minfeng counties of Southern Xinjiang

To understand the benzimidazole (BZ) resistance of Haemonchus contortus in Southern Xinjiang, three single nucleotide polymorphisms (SNPs) designated as F167Y, E198A, and F200Y, in the isotype-1 β-tubulin gene which are associated with BZ resistance, were investigated for H. contortus populations from sheep in Hejing and Minfeng counties of Southern Xinjiang. In brief, a total of 190 H. contortus adults were collected from 52 out of 70 slaughtered sheep in city abattoirs across two regions in Southern Xinjiang. The species identity of each adult worm was confirmed by PCR amplification of ITS-2 using H. contortus-specific primers targeting the ITS-2. The samples were then investigated for BZ-related SNPs at locus 167, 198, and 200, by PCR-sequencing of the isotype-1 β-tubulin gene. The results showed that only E198A and F200Y mutations were detected in the investigated H. contortus populations. The E198A mutation (homozygous and heterozygote resistant: found in 40% and 30% of sequenced samples from Minfeng and Hejing counties, respectively) was predominant compared with the F200Y mutation (homozygous and heterozygote resistant: found in 14% and 13.3% of sequenced samples from Minfeng and Hejing counties, respectively). The results indicate a high prevalence of BZ resistance in H. contortus populations from certain areas of Southern Xinjiang. Our findings provide valuable information for the prevention and control of H. contortus in areas with similar conditions.

Transcriptome reveals the roles and potential mechanisms of lncRNAs in the regulation of albendazole resistance in Haemonchus contortus

BACKGROUND

Haemonchus contortus (H. contortus) is the most common parasitic nematode in ruminants and is prevalent worldwide. H. contortus resistance to albendazole (ABZ) hinders the efficacy of anthelmintic drugs, but little is known about the molecular mechanisms that regulate this of drug resistance. Recent research has demonstrated that long noncoding RNAs (lncRNAs) can exert significant influence as pivotal regulators of the emergence of drug resistance.

RESULTS

In this study, transcriptome sequencing was conducted on both albendazole-sensitive (ABZ-sensitive) and albendazole-resistant (ABZ-resistant) H. contortus strains, with three biological replicates for each group. The analysis of lncRNA in the transcriptomic data revealed that there were 276 differentially expressed lncRNA (DElncRNA) between strains with ABZ-sensitive and ABZ-resistant according to the criteria of |log2Foldchange|≥ 1 and FDR < 0.05. Notably, MSTRG.12969.2 and MSTRG.9827.1 exhibited the most significant upregulation and downregulation, respectively, in the resistant strains. The potential roles of the DElncRNAs included catalytic activity, stimulus response, regulation of drug metabolism, and modulation of the immune response. Moreover, we investigated the interactions between DElncRNAs and other RNAs, specifically MSTRG.12741.1, MSTRG.11848.1, MSTRG.5895.1, and MSTRG.14070.1, involved in regulating drug stimulation through cis/trans/antisense/lncRNA‒miRNA-mRNA interaction networks. This regulation leads to a decrease (or increase) in the expression of relevant genes, consequently enhancing the resistance of H. contortus to albendazole. Furthermore, through comprehensive analysis of competitive endogenous RNAs (ceRNAs) involved in drug resistance-related pathways, such as the mTOR signalling pathway and ABC transporter signalling pathway, the relevance of the MSTRG.2499.1-novel-m0062-3p-HCON_00099610 interaction was identified to mainly involve the regulation of catalytic activity, metabolism, ubiquitination and transcriptional regulation of gene promoters. Additionally, quantitative real-time polymerase chain reaction (qRT-PCR) validation indicated that the transcription profiles of six DElncRNAs and six DEmRNAs were consistent with those obtained by RNA-seq.

CONCLUSIONS

The results of the present study allowed us to better understand the changes in the lncRNA expression profile of ABZ-resistant H. contortus. In total, these results suggest that the lncRNAs MSTRG.963.1, MSTRG.12741.1, MSTRG.11848.1 and MSTRG.2499.1 play important roles in the development of ABZ resistance and can serve as promising biomarkers for further study.

Evaluation of a combination of Citrus aurantium var. Dulcis essential oil and albendazole for the treatment of sheep gastrointestinal nematodes

Citrus fruits are consumed all over the world and their by-products are used for animal feed and essential oils production. This study aimed to evaluate the in vitro and in vivo activity of Citrus aurantium var. Dulcis essential oil (CaEO) combined with ABZ against benzimidazole resistant Haemonchus contortus. In vitro egg hatching assays (EHA) were performed using CaEO and ABZ to estimate the effective concentration to achieve 50% egg death (EC₅₀) values and calculate the test essential oil and drug combinations using a simplex-centroid mixture design. These concentrations were used for a second round of EHAs. Sixteen sheep were randomly allocated into two groups and treated with ABZ and the combination of CaEO and ABZ, and faecal egg count reduction tests were performed. In the first round of EHA, CaEO and ABZ showed EC₅₀ values of 0.57 and 0.0048 mg mL^-1, respectively. The H. contortus strain used in the study was shown to be highly benzimidazole resistant, with only 1.5% of parasites having susceptible ß-tubulin SNP genotypes. The ABZ reduced the shedding of nematode eggs by 78%, however, its combination with CaEO reduced faecal egg counts by only 9%. The present study is important to highlight the interferences of natural products in anthelmintic metabolism and consequently in drug efficacy.

Histidine acid phosphatase domain-containing protein from Haemonchus contortus is a stimulatory antigen for the Th1 immune response of goat PBMCs

Background

Histidine acid phosphatase (HAP), a member of the histidine phosphatase superfamily, is widely found in parasites and is also a potential vaccine antigen or drug target. However, the biological function of HAP in Haemonchus contortus is still unclear.

Methods

We cloned the HAP gene from H. contortus (Hc-HAP) and expressed the purified recombinant Hc-HAP (rHc-HAP) protein. The transcription of the Hc-HAP gene in the eggs, infective third-stage larvae (L3s), exsheathed third-stage larvae (xL3s) and adults (females/males) was analyzed by quantitative real-time-PCR (qPCR). An immunofluorescence assay was also used to detect the localization of Hc-HAP expression in adult worms. The effect of rHc-HAP on the function of peripheral blood mononuclear cells (PBMCs) was observed by co-culture of rHc-HAP protein with goat PBMCs.

Results

The qPCR results revealed that the Hc-HAP gene was transcribed at a higher level in the L3 and xL3 stages that there were gender differences in transcription at the adult stage, with females exhibiting higher transcription than males. Moreover, Hc-HAP was mainly expressed in adult intestinal microvilli. Additionally, western blot results revealed that rHc-HAP could be detected in goat sera artificially infected with H. contortus. In the experiments, rHc-HAP bound to goat PBMCs and released nitric oxide. The rHc-HAP also induced the expression of interferon gamma (IFN-γ) and the phosphorylated STAT 1 transcription factor, while inhibiting interleukin-4 expression.

Conclusions

The results shows that rHc-HAP stimulated the IFN-γ/STAT1 signaling pathway and enabled polarization of PBMCs toward T-helper 1 immune responses.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-022-05411-7.

Population replacement of benzimidazole-resistant Haemonchus contortus with susceptible strains: evidence of changes in the resistance status

The spread of anthelmintic resistance (AR) in nematode populations threatens the viability of sheep production systems worldwide, and warrants the adoption of sensitive, practical, and standardized tests to detect AR. The aim of this study was to characterize the replacement of an Haemonchus contortus population resistant to benzimidazoles (BZDs) by a susceptible one, by means of both phenotypic and genotypic techniques. Phenotypic methods to assess BZD resistance included in vivo tests, such as the fecal egg count reduction test (FECRT), and in vitro tests, such as the egg hatch assay (EHA). Additionally, genotypification of polymorphisms associated with BZD resistance by sequencing a fragment of the isotype 1 β-tubulin gene was carried out. The initial, BZD-resistant population (initial Balcarce population) exhibited an egg count reduction (ECR) of 59.3%. Following refugium replacement, the final population (final Balcarce population) exhibited an ECR of 95.2%. For the initial Balcarce population, the median effective dose (ED₅₀) for the EHA was 0.607 μg thiabendazole (TBZ)/mL, with a rate of eclosion at a discriminating dose (E_DD) of 0.1 μg TBZ/mL of 76.73%. For the final Balcarce population, ED₅₀ was 0.02 μg TBZ/mL, and E_DD was 1.97%. In the initial population, 93% of the analyzed individuals exhibited genotypic combinations associated with BZD resistance (53% Phe/Phe₁₆₇-Tyr/Tyr₂₀₀, 37% Phe/Tyr₁₆₇-Phe/Tyr₂₀₀, and 3% Phe/Tyr₁₆₇-Glu/Leu₁₉₈). Conversely, no combination associated with resistance was found in individuals from the final population. All of the tests were useful for detecting AR to BZDs. The results from the genetic and phenotypical studies were consistent, and the resulting information greatly aided in interpreting the outcomes of the population replacement and the potential impact of this strategy on management of AR.

Nematicidal effect of a lectin preparation from Artocarpus heterophyllus (Moraceae) on larvae and adults of Haemonchus contortus

Haemonchus contortus is a hematophagous parasite that causes damage to ruminant production worldwide. This study reported the in vitro nematicidal effect of a lectin preparation (LP) isolated from Artocarpus heterophyllus seeds on larvae and adults of H. contortus. The protein extraction was in phosphate-buffered saline followed by protein precipitation with ammonium sulfate 70% and dialysis. The dialyzed protein fraction was chromatographed to obtain isolated LP. The LP was characterized by hemagglutinating activity (HA) assays, protein dosage and polyacrylamide gel electrophoresis. The motility index of H. contortus in the third larval stage (unsheathed L3 larvae) and adult stage was evaluated. The HA inhibition of LP by mannose and galactose as well as the electrophoretic profile indicated the presence of the lectins ArtinM and Jacalin. The motility index of H. contortus was significantly reduced (p < 0.001) during the first 8 h of LP exposure, both in larvae (lowest index 8.3% with LP at 1 mg mL-1) and female adults (lowest index 20% with LP at 500 μg mL-1; index 40% with LP at 1 mg mL-1). This research revealed that the LP has potential for being utilized in the development of natural nematicides.

Phenotypic and genotypic approaches for detection of anthelmintic resistant sheep gastrointestinal nematodes from Brazilian northeast

The aim of this study was to characterize the anthelmintic resistance (AR) of a sheep gastrointestinal nematode population, named Caucaia, from northeastern Brazil. Phenotypic tests performed were: egg hatch (EHT), larval development (LDT) and fecal egg count reduction (FECRT). Benzimidazoles (BZs) genotypic evaluation was by frequency of single nucleotide polymorphisms (SNPs) F200Y, F167Y and E198A, and for levamisole (LEV), by frequency of resistance alleles of Hco-acr-8 gene. The primers were designed specifically for Haemonchus contortus. Effective concentrations 50% (EC50) for BZs (EHT), and for macrocyclic lactones (MLs) and LEV (LDT) were 1.02 µg/mL, 1.81 ng/mL and 0.04 µg/mL, respectively. Resistance ratios for MLs and LEV were 0.91 and 3.07, respectively. FECRT efficacies of BZs, MLs, monepantel (MPTL) and LEV were 52.4; 87.0; 94.5 and 99.6%, respectively. qPCR for BZs demonstrated resistance allele frequencies of 0%, 26.24% and 69.08% for SNPs E198A, F200Y and F167Y, respectively. For LEV, 54.37% of resistance alleles were found. There was agreement between EHT, FECRT and qPCR for BZs, and agreement between LDT and qPCR for LEV. Thus, based on higher sensitivity of qPCR, and phenotypic evaluation, the Caucaia population was considered resistant to BZs, MLs, LEV and suspect for MPTL.

Haemonchus contortus Susceptibility and Resistance to Anthelmintics in Naturally Infected Egyptian Sheep

PURPOSE

Susceptibility and resistance of Haemonchus contortus to anthelmintic drugs, including ivermectin, levamisole, and albendazole in naturally infected sheep were investigated.

METHODS

Three sets of assays were conducted to detect drug efficacy. Firstly, in vivo estimation of drug resistance to H. contortus was explored in 80 sheep naturally infected with H. contortus. Sheep were divided into four equal groups (20 sheep for each group): the first group was treated with albendazole (5.00 mg/kg BW), the second with levamisole (7.50 mg/kg BW), the third with ivermectin (0.20 mg/kg BW), and the fourth group served as the untreated control. Fecal egg reduction test (FERT) was done at days 7 and 14 after treatment. Secondly, for in vitro egg hatching assay (EHA), H. contortus eggs from naturally infected sheep were collected and treated with 0.0002, 0.002, 0.02, 0.2, and 2.0 µg/mL albendazole. Thirdly, molecular detection of the albendazole resistance gene in adult male H. contortus worms and larvae from infected sheep was carried out using allele-specific PCR.

RESULTS

The FECRT results showed that the drug efficacy was 86.84% for albendazole and 100% for both levamisole and ivermectin. The result of EHA showed that eggs did not hatch at 2.0 µg/mL albendazole concentration. Molecular findings showed two forms, including H. contortus homozygous susceptible (SS) and heterozygous (RS) of "β-tubulin" gene at 200 sites, which were recorded in both single male worms and larvae.

CONCLUSION

H. contortus, which was susceptible to levamisole and ivermectin, had developed resistance to albendazole.

Castor cake as organic fertilizer to control gastrointestinal nematodes in pasture-raised sheep

Gastrointestinal parasitism is one of the factors that discourages farmers from raising small ruminants in cultivated pastures. To validate a soil treatment strategy to control the free-living stages of gastrointestinal nematodes (GIN), castor cake (CC) was used as a fertilizer on a pasture where sheep grazed on guinea grass under continuous stocking. On day zero, the pasture was divided into three paddocks, contaminated by GIN and treated, respectively, with CC divided into two applications (2CC1/2), CC in a single application (CC1) and organic compost in a single application (control). On day 21, eight GIN-free sheep were placed in each paddock. On day 58, significant differences (P<0.05) were observed: reduction of up to 66.10% in larvae.g-1 of dry mass in pastures fertilized with CC, decrease of up to 60.72% in infection rates among the animals in the groups treated with CC, higher average daily weight gain (over 185 g.day-1) and packed cell volume (over 26%) in the groups treated with CC, when compared to the control (128 g.day-1; 20.9%). In view of the results, the use of CC, mainly CC1, as a fertilizer for guinea grass pastures, under continuous stocking, proved to be promising, with 63.41% effectiveness in controlling worm infestations.

Haemonchus sp. in beef cattle in Brazil: species composition and frequency of benzimidazole resistance alleles

The aim of the present study was to investigate the occurrence of Haemonchus contortus and Haemonchus placei in beef cattle and the frequency of single nucleotide polymorphisms associated with benzimidazole (BZ)-resistance in Haemonchus spp. in Brazil. For such, fecal samples were collected from 61 beef cattle ranches in 11 Brazilian states. Third-stage larvae (L3) were produced for morphological species identification and DNA extraction. PCR was performed for the analysis of the isotype 1 β-tubulin gene and the products were sequenced to confirm the presence of H. placei and H. contortus. For each field population, pyrosequencing assays were performed to quantify the frequency of the F167Y, E198A and F200Y polymorphisms in the isotype-1 β-tubulin gene. The results of the morphometric analysis of 2345 larvae showed that H. placei was present on all ranches. The analysis of the isotype 1 β-tubulin gene confirmed 100% prevalence for H. placei and 23.7% for H. contortus. Pyrosequencing assays demonstrated single-nucleotide polymorphisms (SNPs) associated with BZ-resistance in all three codons (F167Y, E198A and F200Y) of the isotype 1 β-tubulin gene in H. placei field populations. Frequencies of resistance-associated alleles above background (≥ 15%) were found for at least one codon in 11.4% of the field isolates and maximum frequencies of 30, 21 and 29% were found for codons 167, 198 and 200, respectively, on individual ranches. This study confirms the presence of H. contortus in beef cattle in the major livestock farming states in Brazil and demonstrates that genotypes associated with BZ resistance are present in field populations of Haemonchus spp..

Characterization of benzimidazole resistance in Haemonchus contortus: integration of phenotypic, genotypic and proteomic approaches

The field strain of Haemonchus contortus has a long history of anthelmintic resistance. To understand this phenomenon, the benzimidazole resistance profile was characterized from the Malaysian field-resistant strain by integrating phenotypic, genotypic and proteomic approaches. The faecal egg count reduction test (FECRT) demonstrated that benzimidazole resistance was at a critical level in the studied strain. The primary resistance mechanism was attributed to F200Y mutation in the isotype 1 β-tubulin gene as revealed by AS-PCR and direct sequencing. Furthermore, the protein response of the resistant strain towards benzimidazole (i.e., albendazole) treatment was investigated via two-dimensional difference gel electrophoresis (2D-DIGE) and tandem liquid chromatography-mass spectrometry (LC-MS/MS). These investigations illustrated an up-regulation of antioxidant (i.e., ATP-binding region and heat-shock protein 90, superoxide dismutase) and metabolic (i.e., glutamate dehydrogenase) enzymes and down-regulation of glutathione S-transferase, malate dehydrogenase, and other structural and cytoskeletal proteins (i.e., actin, troponin T). Findings from this study are pivotal in updating the current knowledge on anthelmintic resistance and providing new insights into the defence mechanisms of resistant nematodes towards drug treatment.

Multiple anthelmintic resistance in gastrointestinal nematodes of Caprines on Mountain Research Centre for Sheep and Goat at Kashmir Valley, India

The study was conducted to evaluate the status of anthelmintic resistance in Gastro-Intestinal Nematodes (GINs) of goats at an organized farm located in Kashmir, as there is no report of resistance against these parasites of goats from this temperate region, although it has been reported worldwide including India. Caprines reared at this farm exhibited reduced efficacy to multiple anthelmintics following treatments with Fenbendazole (FBZ), Closantel and Ivermectin (IVM) in Faecal Egg Count Reduction Test (FECRT). The results suggested that the overall efficacy was highest for IVM at 83.5% and 90.0% on 7^th and 14^th day post-treatment, respectively and least for FBZ at 44.3% and 62.5%, respectively, whereas the corresponding figures for closantel were 68.3% and 86.2%, respectively. The pre-treatment faecal culture revealed Haemonchus contortus, Teladorsagia circumcincta and Trichostrongylus colubriformis as predominant strongyles, however, in post-treatment samples, only H. contortus was observed. Further, the infective larvae were subjected to Allele specific PCR (AS-PCR) for accurate diagnosis of BZ resistance. The AS-PCR revealed 52% of H. contortus were homozygous resistant (rr) and 17% were heterozygous (rS) on day “0” before treatment and 100% homozygous resistant (rr) on 7th day post treatment. In both T. colubriformis and T. circumcincta, 100% population was homozygous susceptible (SS) at day “0” before treatment. The overall frequency of resistant (r) allele for H. contortus was 60.5% and for susceptible allele (s) was 39.5%. For T. colubriformis and T. circumcincta the frequency of susceptible allele (s) was 100%. The survey indicated that the GINs of goats on the farm have developed multiple anthelmintic resistance to FBZ, closantel and IVM and the condition is alarming in the farm. Moreover surveillance studies about status of anthelmintic resistance in other farms (Govternment as well as Private) of Kashmir valley should be carried out at large scale to develop effective and sustainable control strategies against GI Nematodes.

Multiple anthelmintic resistance in gastrointestinal nematodes of small ruminants in Bangladesh

Anthelmintic resistance (AR) against gastrointestinal nematodes (GINs) of sheep and goats is a global concern. To address the problem, this study assessed the status of AR in different government and private sheep and goat farms in Bangladesh. We conducted fecal egg count reduction test (FECRT) and Egg hatch assay (EHA) experiments. For the detection of resistant larvae, pooled fecal samples from treated and non-treated groups were subjected to coproculture. Furthermore, 195 adult Haemonchus parasites were genotyped to ascertain benzimidazole (BZ) resistance allele from seven topographic zones of Bangladesh using allele specific PCR (AS-PCR). In FECRT, the percentage reduction along with 95% confidence intervals indicated that GINs were resistant to albendazole (ABZ), levamisole (LEV) and ivermectin (IVM). Coproculture revealed that Haemonchus spp., Oesophagostomum spp. and Trichostrongylus spp. were resistant to anthelmintics. ABZ resistance was also confirmed by in vitro EHA in all the farms except the private goat farm in Mymensingh. The genotype frequencies were 6% for homozygous resistant (rr), 59% for heterozygous (rS) and 35% for homozygous susceptible (SS) among different topographic zones. The allelic frequency of the mutation conferring resistance (r) ranged from 25% to 47% signifying resistance to BZ in nematodes of sheep/goats. The genotype frequencies (rr, rS and SS) and allelic frequencies (r and S) varied significantly (p˂0.05) in different zones in Bangladesh. Overall, the data suggest an alarming condition created by multiple AR in Bangladesh.

Anthelmintic activity of nanoencapsulated carvacryl acetate against gastrointestinal nematodes of sheep and its toxicity in rodents

The objective of this study was to evaluate the efficacy of carvacryl acetate (CVA) and nanoencapsulated CVA (nCVA) on gastrointestinal nematodes of sheep. The CVA was nanoencapsulated with chitosan/gum arabic and the efficacy of nanoencapsulation (EE), yield, zeta potential, nanoparticle morphology and release kinetics at pH 3 and 8 were analyzed. Acute and subchronic toxicity were evaluated in rodents and reduction of egg counts in the faeces (FECRT) of sheep. The sheep were divided into four groups (n = 10): G1, 250 mg/kg CVA; G2, 250 mg/kg nCVA; G3, polymer matrix and G4: 2.5 mg/kg monepantel. EE and nCVA yield were 65% and 57%, respectively. The morphology of the nanoparticles was spherical, size (810.6±286.7 nm), zeta potential in pH 3.2 (+18.3 mV) and the 50% release of CVA at pHs 3 and 8 occurred at 200 and 10 h, respectively. nCVA showed LD50 of 2,609 mg/kg. CVA, nCVA and monepantel reduced the number of eggs per gram of faeces (epg) by 57.7%, 51.1% and 97.7%, respectively. The epg of sheep treated with CVA and nCVA did not differ from the negative control (P>0.05). Nanoencapsulation reduced the toxicity of CVA; however, nCVA and CVA presented similar results in the FECRT.

In vitro anthelmintic activity of Lippia gracilis Schauer essential oil against egg-hatching of goat gastrointestinal nematodes

ABSTRACT Since drug-resistant nematodes became a common problem in sheep and goat industries, alternative methods using natural products have emerged as a viable and sustainable anthelmintic treatment option. Here, the in vitro effect of essential oil extracted from Lippia gracilis Schauer was assessed on the hatching process of nematodes recovered from naturally infected goats. Essential oil at concentrations of 0.08% (0.008 μL/mL), 0.12% (0.012 μL/mL), and 0.16% (0.016 μL/mL) was able to induce an average inhibition of 74.7, 84 and 93%, respectively. The effective concentration required to inhibit egg hatching in 50% of eggs (EC50) was 0.03452%. Therefore, essential oil of L. gracilis showed promisor in vitro anthelmintic results against egg-hatching of goat gastrointestinal nematodes.

Drug Screening for Discovery of Broad-spectrum Agents for Soil-transmitted Nematodes

Soil-transmitted nematodes (STNs), namely hookworms, whipworms, and ascarids, are extremely common parasites, infecting 1-2 billion of the poorest people worldwide. Two benzimidazoles, albendazole and mebendazole, are currently used in STN mass drug administration, with many instances of low/reduced activity reported. New drugs against STNs are urgently needed. We tested various models for STN drug screening with the aim of identifying the most effective tactics for the discovery of potent, safe and broad-spectrum agents. We screened a 1280-compound library of approved drugs to completion against late larval/adult stages and egg/larval stages of both the human hookworm parasite Ancylostoma ceylanicum and the free-living nematode Caenorhabditis elegans, which is often used as a surrogate for STNs in screens. The quality of positives was further evaluated based on cheminformatics/data mining analyses and activity against evolutionarily distant Trichuris muris whipworm adults. From these data, two pairs of positives, sulconazole/econazole and pararosaniline/cetylpyridinium, predicted to target nematode CYP-450 and HSP-90 respectively, were prioritized for in vivo evaluation against A. ceylanicum infections in hamsters. One of these positives, pararosaniline, showed a significant impact on hookworm fecundity in vivo. Taken together, our results suggest that anthelmintic screening with A. ceylanicum larval stages is superior to C. elegans based on both reduced false negative rate and superior overall quality of actives. Our results also highlight two potentially important targets for the discovery of broad-spectrum human STN drugs.

Strategic vaccination of hair sheep against Haemonchus contortus

In this study, we evaluated in two trials a protocol designed to protect hair sheep using Barbervax®, a vaccine containing Haemonchus contortus gut membrane glycoprotein antigens. Results indicated that naturally infected vaccinated sheep had significant egg count reductions (90.2 ± 4.03%) compared with controls, although blood parameters remained relatively unchanged probably because the level of challenge was low. Vaccination prevented the periparturient rise in egg shedding of ewes, as well as egg shedding in lambs (37.1%). In the second trial, sheep which were experimentally exposed to higher artificial challenge also showed an efficient response to the vaccine as confirmed by high antibody levels and reduced egg counts and worm burdens (87 ± 5.4% and 79%) respectively. Thus, we believe that the vaccine should be integrated with other management practices for meat hair sheep as it has the advantages of adequate efficacy, reducing anthelmintic utilization and avoiding milk and environmental contamination with chemical residues.

Anthelmintic resistance in hair sheep farms in a sub-humid tropical climate, in the Huasteca Potosina, Mexico

This is the first report about anthelmintic resistance (AR) in hair sheep farms determined in a sub-humid tropical climate, in an area known as Huasteca Potosina, Mexico. Faecal egg count reduction tests (FECRT) and egg hatch in vitro tests were conducted to identify the level of AR against benzimidazole (BZ) in parasitic gastrointestinal nematode (GIN) populations. An allele-specific polymerase chain reaction (AS-PCR) was performed to obtain a 250 bp band, indicating resistance, and a 550 bp band, indicating susceptibility to BZ. Macrocyclic lactones (ML) and imidazothiazole (IMZ) drugs were also tested with the FECRT. A PROBIT analysis was conducted using SAS to determine the 50% lethal doses (LD₅₀) of the drugs according to the egg hatch in vitro test. Resistance to BZ and ML was found on all farms (0-70% effectiveness), whereas the susceptibility of nematodes to IMZ was detected with the FECRT (93-100% effectiveness). The LD₅₀ was higher than the discriminating dose (0.1 μg ml^-1) for BZ and confirmed AR to this anthelmintic; we also confirmed a high AR frequency with AS-PCR. Therefore, we suggest that strategic deworming should be performed to avoid the development of resistance to imidazothiazole.

A detection of benzimidazole resistance-associated SNPs in the isotype-1 β-tubulin gene in Haemonchus contortus from wild blue sheep (Pseudois nayaur) sympatric with sheep in Helan Mountains, China

Background

Benzimidazole (BZ) resistance is an increasingly serious problem due to the excessive use of this anthelmintic for controlling Haemonchus contortus, which is one of the major gastrointestinal nematodes infecting small ruminants worldwide. Three known single nucleotide polymorphisms (SNPs), F167Y (TAC), E198A (GCA) and F200Y (TAC), in the isotype-1 β-tubulin gene of H. contortus are associated with BZ resistance. Comprehending the spread and origins of BZ resistance-associated SNPs has important implications for the control of this nematode.

Results

Twenty-seven adult H. contortus were harvested from wild blue sheep (Pseudois nayaur), small wild ruminants sympatric with domestic ruminants, inhabiting the Helan Mountains, China, to monitor the status of BZ resistance. In addition, 20 adult H. contortus from domestic sheep sympatric with this wild ruminant and 36 isotype-1 β-tubulin haplotype sequences of H. contortus (two of these haplotypes, E198A3 and E198A4, possessed resistance-associated SNP E198A (GCA) from domestic ruminants in eight other geographical regions of China were used to further define the origins of BZ resistance-associated SNPs within the worms collected from blue sheep. The BZ resistance-associated SNP E198A was detected, whereas SNPs F167Y (TAC) and F200Y (TAC) were not found within the worms collected from blue sheep, and the frequency of homozygous resistant E198A (GCA) was 7.40%. The evolutionary tree and network showed consistent topologies for which there was no obvious boundary among the worms from the wild and domestic hosts, and two haplotypes (E198A1 and E198A2) possessing E198A from the wild blue sheep had two different independent origins. E198A1 had the same origin with E198A3 but E198A2 had a different origin with them. Population genetic analyses revealed a low level of Fst values (ranging from 0 to 0.19749) between all H. contortus worm groups in China.

Conclusions

Results of the current study of the three BZ resistance-associated SNPs of H. contortus from wild blue sheep suggested that only E198A (GCA) was present within the worms collected from the wild ruminants and had multiple independent origins.

Electronic supplementary material

The online version of this article (10.1186/s12917-019-1838-4) contains supplementary material, which is available to authorized users.

Anthelmintic effect of thymol and thymol acetate on sheep gastrointestinal nematodes and their toxicity in mice

Thymol is a monoterpene and acetylation form of this compound can reduce the toxicity and enhance its biological effects. The objective of this study was to evaluate the effect of thymol and thymol acetate (TA) on egg, larva and adult Haemonchus contortus and the cuticular changes, acute toxicity in mice and the efficacy on sheep gastrointestinal nematodes. In vitro tests results were analyzed by analysis of variance (ANOVA) and followed by comparison with Tukey test or Bonferroni. The efficacy of in vivo test was calculated by the BootStreet program. In the egg hatch test (EHT), thymol (0.5 mg/mL) and TA (4 mg/mL) inhibited larval hatching by 98% and 67.1%, respectively. Thymol and TA (8 mg/mL) inhibited 100% of larval development. Thymol and TA (800 µg/mL) reduced the motility of adult worms, by 100% and 83.4%, respectively. Thymol caused cuticular changes in adult worm teguments. In the acute toxicity test, the LD50 of thymol and TA were 1,350.9 mg/kg and 4,144.4 mg/kg, respectively. Thymol and TA reduced sheep egg count per gram of faeces (epg) by 59.8% and 76.2%, respectively. In in vitro tests thymol presented better anthelmintic activity than TA. However TA was less toxic and in in vivo test efficacy was similar.

Status of benzimidazole resistance in intestinal nematode populations of livestock in Brazil: a systematic review

Background

Benzimidazoles (BZ) are a class of drugs widely used in veterinary and human medicine, creating a great selection pressure and the emergence of BZ resistance. We conducted a systematic review to assess the status of resistance and/or effectiveness reduction of BZ drugs in animal nematodes in Brazil, and make information accessible to the scientific community, as many studies are published in Portuguese. PubMed, SciELO Brasil, LILACS/Bireme, GNTD database, and Google Scholar were searched with no language restrictions.

Results

A total of 40 studies met our eligibility criteria (from the year 1989 forward). Sheep was the host most frequently analysed, and albendazole was the most frequently drug studied. The majority of studies (75.7%) showed that BZ drugs are insufficiently active (FECRT <80%) against nematode parasites of livestock. The mean FECRT for fenbendazole, thiabendazole, albendazole, mebendazole, oxfendazole, and ricobendazole were 71.8%, 71.8%, 58.6%, 53.9%, 46.9%, and 41.5%, respectively. It was observed through linear regression that FECRT is significantly reduced over time between 2007 and 2014 (R = −0.653 p = 0.021) for the treatment of cattle with BZ, suggesting progressive loss of effectiveness and increased resistance for these hosts.

Conclusions

The scenario of BZ resistance in nematode populations in Brazil is not favourable. Given the high cost of drug discovery and development, it is urgent to implement control measures and to monitor the effectiveness/resistance to nematodes in livestock in Brazil.

Genotypic profile of benzimidazole resistance associated with SNP F167Y and F200Y beta-tubulin gene in Brazilian populations of Haemonchus contortus of goats

Benzimidazoles are the most common anthelminthic used for control of gastrointestinal nematodes of goats in the Brazilian semi-arid region. Resistance to these compounds in the nematode Haemonchus contortus has been associated with single nucleotide polymorphisms (SNP) in codons 167 (F167Y) and 200 (F200Y) on the β-tubulin isotype 1 gene. To determine the resistance profile to benzimidazoles of populations of H. contortus of goats of Brazilian semi-arid region, larvae of 29 populations of these nematodes were individually genotyped by real time PCR using a Taqman assay. The percentage of larvae homozygous (RR) for SNP F200Y was relatively low (18.9%), particularly when compared to SNP F167Y (32.7%), indicating that the latter has more relevance in this region. However, the associations between these two SNP demonstrate percentages of resistance ranging from 34.7% to 100% between populations, being the highest percentages for homozygous individuals resistant for the mutation 167 and susceptible to mutation 200 (RR-F167Y/F200Y-SS: 26.7%), followed by combination of heterozygous for both mutations (F167Y-SR/F200Y-SR: 22.8%). These results indicate high levels of resistance in populations of H. contortus of goats in the Brazilian semi-arid region, and thus ineffective antiparasitic control with the use of benzimidazoles in the region.

Genotypic and phenotypic evaluation for benzimidazole resistance or susceptibility in Haemonchus contortus isolates

Haemonchus contortus isolates were evaluated for benzimidazole (BZ) resistance or susceptibility by allele-specific PCR based on β-tubulin isotype 1 gene polymorphisms at the F167Y, E198A, and F200Y sites. Two isolates, one presumed susceptible from wild pronghorn antelope (PH) and one known to be resistant from goats (VM), were also assayed phenotypically for BZ resistance or susceptibility in the larval development assay (Drenchrite®). The BZ EC50 was 0.198 μM (intermediate between susceptible and weak resistant) for PH with critical well 5 (intermediate between susceptible and weak resistant) and 1.456 μM (intermediate weak resistant and resistant) for VM with critical well 8.5 (resistant). Genotypically, DNA extracted from pooled VM L3 larvae in the Drenchrite® wells with the highest BZ concentration was homozygous susceptible (SS) at the F167Y and E198A sites and homozygous resistant (RR) at the F200Y site by PCR, and sequence analysis bore this out. PH L3 larvae DNA from a control well (no BZ) was SS at all three sites by PCR, confirmed by sequence analysis. All single adult worm samples (N = 21) from PH, VM, Egypt goat (EG), and a Texas llama were SS at F167Y and E198A by PCR; however, only 3 PH worms and 1 EG worm were SS at F200Y. Three additional PH worms were RS and upon cloning two clones were identified as resistant by sequencing and two as susceptible. Clones from single adult worms VM, llama, and EG samples that were RR by PCR at F200Y were sequence verified as resistant. In this study, F200Y was the most frequently found genotypic marker for BZ resistance or susceptibility in the different Haemonchus isolates.

Two benzimidazole resistance-associated SNPs in the isotype-1 β-tubulin gene predominate in Haemonchus contortus populations from eight regions in China

Haemonchus contortus is one of the most important parasitic nematodes of small ruminants around the world, particularly in tropical and subtropical regions. The control of haemonchosis relies mainly on anthelmintics, but the excessive and prolonged use of anthelmintics is causing serious drug resistance issues in many countries. As benzimidazole (BZ) anthelmintics have been broadly used in China, we hypothesized that resistance is widespread. Given the link between three known single nucleotide polymorphisms (SNPs, designated F167Y, E198A and F200Y) in the isotype-1 β-tubulin gene and BZ resistance, our goal here was to explore the presence of these mutations in H. contortus from small ruminants (sheep and goats) from eight provinces in China using PCR-coupled sequencing. In addition, the genetic diversity and genetic relationship of isotype-1 β-tubulin sequence haplotypes were also investigated. Among 192 H. contortus adult individuals representing the eight populations, we identified six distinct sequence types, five of which had SNP E198A (GCA) and/or F200Y (TAC). Sequence analysis showed that the frequencies of SNPs E198A and F200Y were 0-70% and 0-31%, respectively. SNP F167Y (TAC) was not detected in any population. In addition, high haplotype diversities (0.455-0.939) and nucleotide diversities (0.018-0.039) were calculated. A network analysis of the isotype-1 β-tubulin gene sequences showed that SNPs E198A and F200Y occurred in multiple distinct groupings, suggesting multiple independent origins of these SNPs. The findings of this first study of SNPs in the isotype-1 β-tubulin gene of H. contortus populations suggest that BZ resistance is prevalent in some regions of China, and that any control strategy might focus on monitoring BZ resistance in this country.

Benzimidazole resistance survey for Haemonchus, Teladorsagia and Trichostrongylus in three European countries using pyrosequencing including the development of new assays for Trichostrongylus

Resistance to benzimidazoles (BZs) in trichostrongyloid nematodes is a worldwide problem for livestock production, particularly regarding small ruminants. Sensitive and reliable methods are required to assess anthelmintic resistance status. Currently available methods for BZ resistance detection can be divided into three main groups, in vivo (e.g. faecal egg count reduction test), in vitro (e.g. egg hatch assay) and molecular tests. Three single nucleotide polymorphisms (SNPs) in the isotype-1 β-tubulin gene of various nematode species correlate with BZ resistance. While PCR-based methods have been reported for the three most economically important nematodes of sheep, namely, Trichostrongylus, Haemonchus and Teladorsagia, pyrosequencing assays are so far only available for the latter two. Here, the design and evaluation of pyrosequencing assays for isotype-1 and isotype-2 β-tubulin genes of Trichostrongylus colubriformis are described. PCR fragments carrying the susceptible and corresponding resistant genotype were combined in defined ratios to evaluate assay sensitivity and linearity. The correlation between the given and the measured allele frequencies of the respective SNPs (codons F167Y, E198A and F200Y) was very high. Pyrosequencing assays for Haemonchus, Teladorsagia and Trichostrongylus were subsequently used for a BZ resistance survey, carried out in the three European countries, namely Ireland, Italy and Switzerland. Larval cultures obtained from field survey samples in 2012 and 2013 were used for pyrosequencing. The test was applied when the target species represented at least 10% of the sample. Trichostrongylus and Teladorsagia were detected in all countries' samples whereas Haemonchus was not detected in samples from Ireland. SNPs in isotype-1 associated with resistance were detected for all three species, with frequencies at codon F200Y far exceeding those at codons F167Y and E198A. Elevated SNP frequencies in isotype-2 of Trichostrongylus were only rarely detected. Farms with BZ resistance-associated SNP frequencies above 10% were most often found in Switzerland followed by Ireland and Italy.

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Successful development of a pyrosequencing assay for Trichostrongylus.

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Resistance survey revealed high number of SNPs present in all three countries.

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SNP at codon 200 most prevalent in European trichostrongyloid populations.

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Low number of SNPs found in Italy corresponds to FECRT data.

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Pyrosequencing successfully employed as a tool for large scale surveys.

The development of anthelmintic resistance with best practice control of nematodes on commercial sheep farms in the UK

Antimicrobial resistance threatens the effective prevention and treatment of an ever-increasing range of infections. The widespread development of anthelmintic resistance is a major global issue affecting the effective control of parasite diseases in grazing livestock production. Sustainable control strategies that reduce dependence on antimicrobials have the potential to slow the further development of resistance but there is little data on the effect of control strategies on resistance development in the field. This report documents a study undertaken to measure the temporal effect of the UK sustainable control of parasites in sheep (SCOPS) guidelines on the development of anthelmintic resistance. Farms carrying out SCOPS or traditional worm control (TRADITIONAL) were tested for resistance to the benzimidazole and imidazothiazole anthelmintics in vitro using a discriminating dose (dd) larval development test (LDT) in year 1 and then 7 years later. In years 5 and 7, resistance was also measured using a dose-response LDT assay. There was a significant increase in Teladorsagia survivors at the benzimidazole dd assay between year 1 and year 7 for both treatment groups, but the increase in survivors was greater for the farms carrying out their traditional worm control compared to the SCOPS farms. There was also a significant difference between benzimidazole dd results generated across years for Trichostrongylus, but the year and treatment interaction was not significant. Only one of the farm Teladorsagia populations had survivors in the imidazothiazole dd assay in years 1 and 7 and none of the Trichostrongylus populations survived in year 1 compared to isolates from three of the farms in year 7. Dose-response data showed a significant effect for time for both the benzimidazole and imidazothiazole anthelmintics and the increase was again significantly higher for the Teladorsagia populations in the TRADITIONAL group compared to the SCOPS group. This data suggests an increased sensitivity both to detect and to measure changes in response to anthelmintics with the dose-response assay compared to the dd and this is important particularly when allele frequencies are low as might be the case when novel compounds are released to the market. Anthelmintic use across years 5-7 was significantly lower for the farms in the SCOPS group compared to the TRADITIONAL group and farmers in the SCOPS group had selected products from the benzimidazole group less often than farmers in the TRADITIONAL group. Both groups had made minimal use of the imidazothiazole anthelmintic classes and the majority of ewe treatments were selected from the macrocyclic lactone class. Further research is required to determine the effect of these anthelmintic choices on the development of resistance to the macrocyclic lactones.

F200Y polymorphism of the β-tubulin isotype 1 gene in Haemonchus contortus and sheep flock management practices related to anthelmintic resistance in eastern Amazon

The objective of the present study was to determine the frequency of the F200Y polymorphism in the β-tubulin isotype 1 gene of Haemonchus contortus from various sheep flocks in eastern Amazon, and to identify management practices that may favor the emergence of resistance to anthelmintic drugs in the same area. In total, 305 specimens of H. contortus were collected from sheep at 12 farms located in the state of Pará. An allele-specific PCR was performed to detect the F200Y polymorphism, and questionnaires were used to obtain information about the farms and flocks. All genotypes were detected as follows: 31% of the parasites were RR, 37% of the parasites were SR, and 32% were SS. The completed questionnaires revealed that all farms employed semi-intensive farming systems, performed suppressive anthelmintic treatment, and based their choice of drug on cost and availability rather than on any knowledge regarding drugs that remained effective on their property. It can thus be concluded that the SNP in codon 200 of the β-tubulin isotype 1 gene is present in the H. contortus populations from eastern Amazon, and that a series of management practices that favor the emergence of anthelmintic resistance are employed on these farms.

Three-year evaluation of best practice guidelines for nematode control on commercial sheep farms in the UK

Anthelmintics are commonly used on the majority of UK commercial sheep farms to reduce major economic losses associated with parasitic diseases. With increasing anthelmintic resistance worldwide, several countries have produced evidence-based, best practice guidelines with an example being the UK's Sustainable Control of Parasites in Sheep (SCOPS) initiative. In 2012, a pilot study demonstrated that SCOPS-managed farms used fewer anthelmintic treatments than traditionally managed farms, with no impact on lamb productivity and worm burden. Building on these results, we collected data for three consecutive years (2012-2014) with the following aims: (1) To compare the effects of traditional and SCOPS-based parasite management on lamb productivity and worm burden; (2) To evaluate the effect of region and farm type on lamb productivity and worm burden; (3) To compare the frequency and patterns of use of anthelmintic treatment on traditional and SCOPS-managed farms. The study was carried out on 16 farms located in the North east and the South west of England and Wales. Lamb productivity was assessed by quantifying birth, mid-season and finish weights and calculating daily live-weight gains and time to finish in a cohort of 40-50 lambs on each farm. Five annual faecal egg counts were carried out on each farm to assess worm burden. No differences in lamb productivity and worm burdens were found between farms that adopted SCOPS guidelines and traditional farms across the three years. However, mean infection levels increased for both the SCOPS and the traditional groups. Lamb production was not significantly different for farm type and region but the effect of region on infection was significant. For both ewes and lambs, SCOPS farms carried out significantly fewer anthelmintic treatments per year, and used fewer anthelmintic doses/animal than traditional farms. The data suggest a trend to increasing use of anthelmintics in ewes on traditional but not on the SCOPS farms and a decreasing use of anthelmintics in lambs on both SCOPS and traditional farms. Across time, an increasing number of SCOPS farmers left their ewes and lambs untreated and the reverse was true for traditional farmers. Overall, farms implementing SCOPS guidelines used less anthelmintic treatments and less frequently than traditionally managed farms, without loss of animal performance or increased worm burden. Implementing SCOPS guidelines might have economic benefits for farmers, help reduce development of anthelmintic resistance on farms and decrease any environmental impact of anthelmintics. Furthermore, these data suggest some important epidemiological trends that should be investigated in long-term studies.

In vitro effects of Eucalyptus staigeriana nanoemulsion on Haemonchus contortus and toxicity in rodents

Strategies for controlling gastrointestinal nematodes have been developed based on the use of numerous alternative methods, including the use of phytotherapy. New formulations of essential oils with anthelmintic activity have been proposed as a means to optimize their biological effects. Thus, the objective of this study was to formulate a nanoemulsion to optimize the nematicide effect of Eucalyptus staigeriana essential oil (EsEO). Initially, physico-chemical analyses were performed to verify the stability of the E. staigeriana nanoemulsion (EsNano). In vitro tests were conducted to evaluate the ovicidal and larvicidal activities of both EsNano and EsEO against Haemonchus contortus, and toxicology tests were then performed on rodents. The EsEO content in the nanoemulsion was 36.4% (v/v), and the mean particle size was 274.3 nm. EsNano and EsEO inhibited larval hatching by 99% and 96.3% at 1 and 2mg/ml concentrations, respectively, and inhibited larval development by 96.3% and 97.3% at 8 mg/ml concentrations. The acute toxicity test revealed that the EsNano and EsEO doses required to kill 50% of the mice (LD50) were 1,603.9 and 3,495.9 mg/ml, respectively. EsNano did not alter the hematological parameters in the rats after treatment.

Evaluation of 'best practice' (SCOPS) guidelines for nematode control on commercial sheep farms in England and Wales

Parasitic diseases are a major constraint to optimum livestock production and are the major cause of economic loss in UK sheep flocks, with farmers remaining dependant on anthelmintics for control. In the UK, research and evidence based, "best practice" guidelines for sustainable control of parasites in sheep (SCOPS) were first produced in 2004 and have been regularly updated since. This study was designed to evaluate the effect of these best practice guidelines for worm control on lamb production and infection levels, compared with more traditional management. Sixteen farms were selected based on a 2 cube factorial design with 3 factors known to affect worm epidemiology: control regimen; farm type; and climatic region. A formalised plan for worm control using 7 potential resistance-delaying practices was prepared for each of the 8 best practice (SCOPS) farms, in conjunction with the farms veterinarians. The 8 farms in the traditional management group (CONTROL farms) were selected based on ongoing evidence of them using worm control strategies deemed to be "higher-risk". A cohort of 40-50 study lambs at each farm was monitored from birth to finishing, allowing evaluation of lamb productivity, worm infection levels and for comparison of numbers of anthelmintic treatments. Birth and mid-season weights were used to calculate daily live-weight gain. Birth and finish dates were used to calculate time to finish and finish weights were also compared. Faecal egg counts, larval culture and species differentiation were undertaken throughout the year to assess the impact of the control strategies on worm burdens. There was no significant difference in results for any of the 3 production responses when comparing predicted means accounting for the differences in birth weight. In fact SCOPS farms had, on average, a higher daily weight gain and finish weight than CONTROL farms when comparing observed means. Statistical analysis of infection levels clearly showed no significant effect according to farm type (p=0.71) or treatment (p=0.81). In contrast the effect of region (p=0.08), although not significant, had a much larger effect size (standardised mean difference) with lower parasite burdens based on faecal egg counts on Northern farms compared to Southern farms. For both ewes and lambs, significantly fewer treatments were carried out on the SCOPS farms. The data collected from this study suggests that farms implementing SCOPS principles use less anthelmintic than other farms, without loss of animal performance or increased worm burden.

Estudo da atividade anti-helmíntica do extrato etanólico de Jatropha mollissima (Pohl) Baill. (Euphorbiaceae) sob Haemonchus contortus em ovinos no semiárido paraibano

Objetivou-se com o presente trabalho, avaliar o efeito anti-helmíntico de Jatropha mollissima por meio de experimentos in vitro e in vivo. Inicialmente foi investigada a concentração de extrato com efeito bioativo, pelo teste de evolução da toxicidade do extrato etanólico de J. mollissima sobre o microcrustáceo Artemia salina, obtendo uma CL50 de 660,80µg/ml, que foi testada em coproculturas contendo larvas infectantes de Haemonchus contortus e em animais para a verificação da redução do OPG. Para o teste in vivo o extrato foi dissolvido em água para se obter as concentrações 660,80µg/ml e 1321,6µg/ml, foram coletadas fezes semanalmente e sangue quinzenalmente. Como resultados dos testes in vitro, o extrato etanólico do caule de Jatropha mollissima mostrou-se tóxico sobre A. salina, com CL50 abaixo de 1000 µg/ml e inibiu a eclosão de ovos e o desenvolvimento de larvas de H. contortus, apresentando uma eficiência de 70,77%. O teste in vivo revelou que o extrato é também eficaz em ovinos, com redução significativa na contagem de OPG após 28 dias de experimento, 47 e 44% de redução nos grupos tratados com o extrato, 7,5% no grupo de animais não tratados e 40,6% com a ivermectina. Mesmo parasitados, os animais permaneceram clinicamente saudáveis e sem anemia. O extrato etanólico do caule de Jatropha mollissima pode representar uma alternativa ao controle da verminose ovina, pois retarda a resistência parasitária.