Prevalence of anthelmintic resistance on sheep and goat farms in the mid-Atlantic region and comparison of in vivo and in vitro detection methods

An Insight into Practices Associated with the Control of Internal Parasites in the Dairy Goat Herds of Romania: A Questionnaire Survey

The widespread and uncontrolled use of anthelmintic products has contributed to the emergence of anthelmintic resistance (AR). This phenomenon globally threatens the productivity and welfare of small ruminants. A questionnaire consisting of 34 questions was handed to 234 goat farmers across Romania to gain insight into control practices against internal parasites and the farmers' perception of the parasitic infections present in their herds and the efficacy of anthelmintic treatments. The majority of farmers (88.5%) admitted they had never submitted fecal samples for parasitological laboratory analysis, and 77.4% had treated the animals on their own. In general, the farmers dewormed their goats based on visual body weight estimation. Prophylactic anthelmintic treatment was practiced by more than 85% of the farmers. A traditional control approach based on treating the entire herd at fixed time intervals is widespread among Romanian goat and sheep farmers. The most commonly used anthelmintic drugs in the previous 3 years (2021-2023) were benzimidazoles (85.5%) and macrocyclic lactones (81.6%). Poor anthelmintic efficacy was suspected by 14.5% of farmers, and the minority (18.0%) considered internal parasites as a problem in their herds. Regarding the farmers' perception of the presence of parasites, there was a significant level of uncertainty. This is the first survey carried out in Romanian goat herds, and it provides up-to-date information on practices aimed at controlling internal parasites.

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

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

The identification of small molecule inhibitors with anthelmintic activities that target conserved proteins among ruminant gastrointestinal nematodes

Gastrointestinal nematode (GIN) infections are a major concern for the ruminant industry worldwide and result in significant production losses. Naturally occurring polyparasitism and increasing drug resistance that potentiate disease outcomes are observed among the most prevalent GINs of veterinary importance. Within the five major taxonomic clades, clade Va represents a group of GINs that predominantly affect the abomasum or small intestine of ruminants. However, the development of effective broad-spectrum anthelmintics against ruminant clade Va GINs has been challenged by a lack of comprehensive druggable genome resources. Here, we first assembled draft genomes for three clade Va species (Cooperia oncophora, Trichostrongylus colubriformis, and Ostertagia ostertagi) and compared them with closely related ruminant GINs. Genome-wide phylogenetic reconstruction showed a relationship among ruminant GINs structured by taxonomic classification. Orthogroup (OG) inference and functional enrichment analyses identified 220 clade Va-specific and Va-conserved OGs, enriched for functions related to cell cycle and cellular senescence. Further transcriptomic analysis identified 61 taxonomically and functionally conserved clade Va OGs that may function as drug targets for new broad-spectrum anthelmintics. Chemogenomic screening identified 11 compounds targeting homologs of these OGs, thus having potential anthelmintic activity. In in vitro phenotypic assays, three kinase inhibitors (digitoxigenin, K-252a, and staurosporine) exhibited broad-spectrum anthelmintic activities against clade Va GINs by obstructing the motility of exsheathed L3 (xL3) or molting of xL3 to L4. These results demonstrate valuable applications of the new ruminant GIN genomes in gaining better insights into their life cycles and offer a contemporary approach to discovering the next generation of anthelmintics.IMPORTANCEGastrointestinal nematode (GIN) infections in ruminants are caused by parasites that inhibit normal function in the digestive tract of cattle, sheep, and goats, thereby causing morbidity and mortality. Coinfection and increasing drug resistance to current therapeutic agents will continue to worsen disease outcomes and impose significant production losses on domestic livestock producers worldwide. In combination with ongoing therapeutic efforts, advancing the discovery of new drugs with novel modes of action is critical for better controlling GIN infections. The significance of this study is in assembling and characterizing new GIN genomes of Cooperia oncophora, Ostertagia ostertagi, and Trichostrongylus colubriformis for facilitating a multi-omics approach to identify novel, biologically conserved drug targets for five major GINs of veterinary importance. With this information, we were then able to demonstrate the potential of commercially available compounds as new anthelmintics.

The relationship between intraflagellar transport and upstream protein trafficking pathways and macrocyclic lactone resistance in Caenorhabditis elegans

Parasitic nematodes are globally important and place a heavy disease burden on infected humans, crops, and livestock, while commonly administered anthelmintics used for treatment are being rendered ineffective by increasing levels of resistance. It has recently been shown in the model nematode Caenorhabditis elegans that the sensory cilia of the amphid neurons play an important role in resistance toward macrocyclic lactones such as ivermectin (an avermectin) and moxidectin (a milbemycin) either through reduced uptake or intertissue signaling pathways. This study interrogated the extent to which ciliary defects relate to macrocyclic lactone resistance and dye-filling defects using a combination of forward genetics and targeted resistance screening approaches and confirmed the importance of intraflagellar transport in this process. This approach also identified the protein trafficking pathways used by the downstream effectors and the components of the ciliary basal body that are required for effector entry into these nonmotile structures. In total, 24 novel C. elegans anthelmintic survival-associated genes were identified in this study. When combined with previously known resistance genes, there are now 46 resistance-associated genes that are directly involved in amphid, cilia, and intraflagellar transport function.

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

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

Anthelmintic activity of European fern extracts against Haemonchus contortus

Most drugs used in the treatment of helminthiasis in humans and animals have lost their efficacy due to the development of drug-resistance in helminths. Moreover, since anthelmintics, like many pharmaceuticals, are now recognized as hazardous contaminants of the environment, returning to medicinal plants and their products represents an environmentally friendly way to treat helminthiasis. The goal of the present study was to test the anthelminthic activity of methanol extracts of eight selected European ferns from the genera Dryopteris, Athyrium and Blechnum against the nematode Haemonchus contortus, a widespread parasite of small ruminants. Eggs and adults of H. contortus drug-susceptible strain ISE and drug-resistant strain WR were isolated from experimentally infected sheep. The efficacy of fern extracts was assayed using egg hatch test and adults viability test based on ATP-level measurement. Among the ferns tested, only Dryopteris aemula extract (0.2 mg/mL) inhibited eggs hatching by 25% in comparison to control. Athyrium distentifolium, Dryopteris aemula and Dryopteris cambrensis were effective against H. contortus adults. In concentration 0.1 mg/mL, A. distentifolium, D. aemula, D. cambrensis significantly decreased the viability of females from ISE and WR strains to 36.2%, 51.9%, 32.9% and to 35.3%, 27.0%, 23.3%, respectively in comparison to untreated controls. None of the extracts exhibited toxicity in precise cut slices from ovine liver. Polyphenol's analysis identified quercetin, kaempferol, luteolin, 3-hydroxybenzoic acid, caffeic acid, coumaric acid and protocatechuic acid as the major components of these anthelmintically active ferns.

Anthelmintic resistance in sheep in the semiarid region of Minas Gerais, Brazil

Anthelmintic efficacy was evaluated among sheep that had become naturally infected with gastrointestinal nematodes in 17 flocks located in the semiarid region of Minas Gerais, Brazil. Feces were collected individually from 1021 hairy sheep to determine the number of eggs per gram of feces (EPG) and for coprocultures to identify nematode genera the nematodes. Only the animals that presented EPG counts greater than or equal to 200 were included in the study (totaling 381 sheep). The animals were divided into three treatment groups: albendazole, ivermectin and levamisole. Fourteen days after the administration of anthelmintics, fecal samples were taken from all animals. In each flock, the pre-treatment and post-treatment arithmetic mean EPG were used to calculate the efficacy (FECR) for each of the treatment groups and the lower 95% confidence limit. Data were analyzed with the "eggCounts 2.3" package in RStudio, using a Bayesian model for paired design. The anthelmintics were classified as being efficacious (when the FECR was both equal to or above 95% and the lower 95% confidence limit was equal to or above 90%) or as encountering anthelmintic resistance (when the FECR was below 95% and the lower 95% confidence limit was below 90%) or inconclusive (when none of the other criteria were fulfilled). Albendazole and ivermectin were not effective in any of the flocks. Levamisole was effective against gastrointestinal nematodes in 25% of the flocks studied. Haemonchus, Trichostrongylus and Oesophagostomum genera were identified in this study in a semiarid region of Minas Gerais, Brazil. The genus Haemonchus was the most prevalent, followed by Trichostrongylus and Oesophagostomum. After anthelmintic treatment, the most prevalent genus was Haemonchus, followed by Trichostrongylus; the genus Oesophagostomum was not detected. The highest percentage of Haemonchus larvae was observed after treatment with ivermectin, followed by albendazole and levamisole. This study revealed the existence of gastrointestinal nematodes in sheep that present multiple resistance to all three main classes of anthelmintic drugs.

Anthelmintic Efficacy in Sheep and Goats under Different Management and Deworming Systems in the Region of Lisbon and Tagus Valley, Portugal

Infections caused by gastrointestinal parasites have been described worldwide as one of the most important issues impacting small ruminant production. The systematic administration of anthelmintic (AH) drugs without following good practice principles has led to an increase in anthelmintic resistance (AR). There is scarce information regarding AH efficacy in small ruminants in Portugal. This study aimed to characterize by in vivo methods the presence and level of AR in four farms in the region of Lisbon and Tagus Valley. All four farms kept small herds in extensive management systems and used different deworming protocols. The active substances used were fenbendazole and a combination of mebendazole plus closantel in a dosage according to the manufacturers' instructions. On day 0 (T0), fecal samples were collected from all study animals, and animals in the treatment group (n = 40) were dewormed with the AH previously chosen by the assistant veterinarian. Animals in the control group (n = 30) did not receive any AH drug. The fecal sample collection was repeated on day 15 (T15), and the control group was treated. Egg counts were performed using the McMaster method for the eggs per gram (EPG), and AR was evaluated by the fecal egg count reduction test (FECRT) with a 95% confidence level (CL). The results from this experiment indicated that the four farms presented AR with two farms to fenbendazole (FECRT of 48% and 85%) and two farms to mebendazole plus closantel (FECRT of 66% and 79%). These results indicate that the gastrointestinal parasites of the four studied Portuguese farms are resistant to benzimidazoles, which suggests an increase in AR regarding nematodes in small ruminant production systems in Portugal.

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

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

Copper oxide wire particles effective against gastrointestinal nematodes in adult alpacas during a randomized clinical trial

OBJECTIVE

To determine whether copper oxide wire particles (COWP) administered as an oral bolus effectively decrease fecal gastrointestinal nematode (GIN) egg counts in adult alpacas.

ANIMALS

57 adult alpacas.

PROCEDURES

A double-blind clinical trial was performed during the months of April through August 2019. Adult alpacas enrolled in the trial were administered 2 g of COWP or a placebo control capsule PO on day 0 and day 45. On day 0 and at 15-day intervals, fecal samples were collected, and Modified McMaster fecal egg counts (FEC) were performed as well as physical examinations, including FAMACHA scoring and body condition scoring (BCS). Hematocrits were measured in 30-day intervals (days 0, 30, 60, and 90). Results were compared across groups.

RESULTS

A significant decrease in mean FEC was observed in the COWP-treated group over time, compared with the placebo group. Mean BCS, FAMACHA score, and Hct did not differ significantly between groups. No clinical evidence of copper toxicosis was observed.

CLINICAL RELEVANCE

Oral administration of COWP was determined to be a safe and effective method of reducing GIN FEC in adult alpacas.

Eucalyptus oil nanoemulsions against eggs and larvae of Haemonchus contortus

Haemonchus contortus is a highly pathogenic and prevalent helminth that causes many deaths in sheep herds. Anthelmintics are usually employed to overcome this issue; however, they do not guarantee immediate and lasting efficacy because of the occurrence of drug-resistant parasites. Among substances that are used in scientific studies for parasitic control, essential oils are known to have different pharmacological properties. However, they demonstrate instability owing to several factors, and therefore, nanoemulsification is considered an alternative to control the instability and degradability of these compounds. The objective of this study was to evaluate the cytotoxicity of nanoemulsions containing essential oil of Eucalyptus globulus against the blood of healthy sheep and to verify their activity against the parasite H. contortus in sheep. The results presented adequate nanotechnological characteristics (diameter 72 nm, PDI 0.2, zeta -11 mV, and acidic pH) and adequate morphology. Further, the corona effect and cytotoxic profiles of the free oil and nanoemulsion against blood cells from healthy sheep were evaluated. The tests results did not present a toxicity profile. For evaluating efficacy, we observed an important anthelmintic action of the nanoemulsion containing oil in comparison to the free oil; the results demonstrate a potential role of the nanoemulsion in the inhibition of egg hatchability and the development of larvae L1 to L3 (infective stage). Based on these results, we developed an important and potential anthelmintic alternative for the control of the parasite H. contortus.

In vitro anthelmintic activity of Dennettia tripetala G. Baker (Annonaceae) Fruits against Haemonchus contortus

Helminthosis is one of the greatest causes of parasitic disease and loss in animal productivity. As such, the control of helminth parasites is of critical importance. This study was aimed to investigate the in vitro anthelmintic activity of Dennettia tripetala G. Baker (Annonaceae) fruits against Haemonchus contortus. Using in vitro techniques, the anthelmintic activity of extracts and fractions of D. tripetala G. Baker (Annonaceae) was evaluated for ovicidal (Egg hatch inhibition test) and larvicidal (larval mortality test) activity. Besides, the maximum tolerated dose was determined in adult albino rats administered, 300, 400, and 500 mg/kg body weight of the CME fraction, and observed over a period of 48 h for signs of toxicity and mortality. Phytochemical screening uncovered the occurrence of flavonoids, steroids/triterpenes, cardiac glycosides, saponins, tannins, carbohydrates, and alkaloids in the crude methanol extract (CME), the ethyl acetate fraction (EAF), and butanol fraction. The maximum tolerated dose of the CME of D. tripetala did not produce observable signs of toxicity or death in all the rats given up to 500 mg/kg. The CME and EAF of D. tripetala fruits produced a significant ( p < 0.05 ) reduction in the hatchability of H. contortus eggs in a concentration-dependent manner, while the CME at concentrations between 12.5 and 100 mg/ml completely inhibited the hatching of H. contortus eggs. Similarly, EAF at doses of 25, 50, and 100 mg/ml completely inhibited the hatching of H. contortus eggs. The CME and EAF of D. tripetala fruits produced significant ( p < 0.05 ) larvicidal activity against L₃ of H. contortus in a concentration-dependent manner while the CME at concentrations between 6.25 and 100 mg/ml caused larval mortality of H. contortus L₃ larvae completely. This study suggests that methanol extract and fractions of D. tripetala fruits possess beneficial anthelmintic (ovicidal and larvicidal) activity against H. contortus, and may be a suitable alternative anthelmintic candidate for the control of nematodes.

Anthelmintic resistance status of goat gastrointestinal nematodes in Sing Buri Province, Thailand

Background and Aim:

Promotions of goat farming by both public and private sectors encouraged considerable goat raising in central Thailand. Gastrointestinal nematodes (GIN) infection is a major health and economic problem; however, evidence of resistance to broad-spectrum anthelmintics is frequently reported. Investigation of anthelmintic resistance (AR) status and identification of factors related to the development of AR is important components for sustainable GIN control. However, no information is available on this topic in the study area. The present study aimed to gather information on GIN control practices and to evaluate the effectiveness of albendazole, ivermectin, and levamisole for treating GIN infestation in goat herds in Sing Buri Province.

Materials and Methods:

Twenty-nine herds were randomly selected. Information on management practices was collected by face-to-face interview using a structured questionnaire. Three field experiments for routinely used anthelmintics, including albendazole, ivermectin, and levamisole were conducted from June 2019 to November 2019. Fecal samples were collected pre- and post-treatment and examined for fecal egg count reduction to determine the status of anthelmintic resistance of goat GIN.

Results:

Several improper practices were identified that lead to AR, especially chronic use of albendazole and ivermectin. All herds were considered resistant to albendazole and ivermectin, and levamisole resistant nematodes were detected in two herds. AR was strongly linked with the continuous use of anthelmintics.

Conclusion:

Levamisole, which was still effective in the province, should be used with caution to minimize the selection of resistant strains. Farmers should be provided with updated information for sustainable parasite control. Further, the efficacy of anthelmintics should be routinely monitored.

Anthelmintic Drug Resistance of Gastrointestinal Nematodes of Naturally Infected Goats in Haramaya, Ethiopia

Gastrointestinal parasites and their anthelmintic resistance are major constraints to goat production in Ethiopia. Experimental investigation by faecal egg count reduction test (FECRT) and larval cultures were used to assess the occurrence of anthelmintic resistance in naturally infected goats with gastrointestinal nematodes (GIN) in Haramaya, Ethiopia. One hundred goats with a minimum of 150 eggs per gram (EPG) count were selected and randomly divided into five groups, 20 goats in each group, four treated and one untreated group. The result of the faecal egg count reduction test percentage (FECRT%) and the lower 95% confidence limit showed the presence of anthelmintic resistance for all tested drugs except tetramisole. FECRT% and lower 95% confidence limit were 69.9% and 36.9 for albendazole, 84.3% and 66.1 for tetraclozan, 95.7% and 87.4 for tetramisole, and 71.1% and 38.2 for ivermectin, respectively. Trichostrongylus, Teladorsagia, and Haemonchus showed anthelmintic resistance for tested drugs. Coproculture from different treatment groups revealed Trichostrongylus (69.2% in ivermectin and 59.6% in albendazole) were the predominant nematode followed by Teladorsagia (21.9% in albendazole and 14.7% in ivermectin). In tetraclozan treatment group, Trichostrongylus (42%) and Teladorsagia (41.3%) were comparable, followed by Haemonchus (13%). In group treated with tetramisole, Teladorsagia (54.3%) were the most frequently detected nematode followed by Trichostrongylus (25.7%) and Haemonchus (11.4%). Therefore, this study demonstrated the presence of multidrug resistant nematodes that may limit the productivity of goats. Moreover, further studies covering wider areas of Ethiopia and mechanisms of nematode resistance need to be studied in the future.

Anthelmintic activity of methanol extract of Dennettia tripetala G. Baker (Annonaceae) fruits against Haemonchus contortus in red Sokoto goats

Haemonchosis is a gastrointestinal parasitic disease of economic importance in ruminants especially sheep and goats. In view of the rising costs of conventional veterinary anthelmintics and the development of resistance by Haemonchus contortus, there is a need to develop alternative ethnoveterinary therapies for the treatment and management of Haemonchosis. This study investigated the anthelmintic activity of Dennettia tripetala G. Baker (Annonaceae) fruits against Haemonchus contortus in red Sokoto goats. The maximum tolerated dose was determined in adult albino rats administered, 3000, 4000, and 5000 mg/kg body weight of the crude methanol extract (CME) fraction, and observed over a period of 48 h for signs of toxicity and mortality. The in vivo anthelmintic activity was evaluated using 20 kids infected with H. contortus and randomly allocated into 5 groups (1, 2, 3, 4, and 5). Kids in groups 1, 2, and 3 were treated with CME at doses of 1250, 2500, and 5000 mg/kg respectively for 3 consecutive days per os. Groups 4 and 5 were treated with albendazole (7.5 mg/kg) once and distilled water (5 ml) respectively and served as treated and untreated controls. Blood samples were collected for haematology. The maximum tolerated dose of the CME of D. tripetala did not produce observable signs of toxicity or death in all the rats given up to 5000 mg/kg. There was significant (P < 0.05) reduction in faecal egg count by CME at doses of 1250 mg/kg (91.6%), 2500 mg/kg (98.5%), and 5000 mg/kg (100%) at day 14 post-treatment. The total plasma protein (TPP) and FAMACHA© scoring values were significantly improved (P < 0.05) in the treated groups. These results indicate that methanol extract and fractions of D. tripetala fruits possess beneficial anthelmintic activity against H. contortus and may be a suitable alternative anthelmintic candidate for the control of haemonchosis in goats.

Newly identified parasitic nematode beta-tubulin alleles confer resistance to benzimidazoles

Infections by parasitic nematodes cause large health and economic burdens worldwide. We use anthelmintic drugs to reduce these infections. However, resistance to anthelmintic drugs is extremely common and increasing worldwide. It is essential to understand the mechanisms of resistance to slow its spread. Recently, four new parasitic nematode beta-tubulin alleles have been identified in benzimidazole (BZ) resistant parasite populations: E198I, E198K, E198T, and E198stop. These alleles have not been tested for the ability to confer resistance or for any effects that they might have on organismal fitness. We introduced these four new alleles into the sensitive C. elegans laboratory-adapted N2 strain and exposed these genome-edited strains to both albendazole and fenbendazole. We found that all four alleles conferred resistance to both BZ drugs. Additionally, we tested for fitness consequences in both control and albendazole conditions over seven generations in competitive fitness assays. We found that none of the edited alleles had deleterious effects on fitness in control conditions and that all four alleles conferred strong and equivalent fitness benefits in BZ drug conditions. Because it is unknown if previously validated alleles confer a dominant or recessive BZ resistance phenotype, we tested the phenotypes caused by five of these alleles and found that none of them conferred a dominant BZ resistance phenotype. Accurate measurements of resistance, fitness effects, and dominance caused by the resistance alleles allow for the generation of better models of population dynamics and facilitate control practices that maximize the efficacy of this critical anthelmintic drug class.

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Four newly identified parasitic nematode beta-tubulin alleles confer benzimidazole resistance.

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The four newly identified alleles do not confer deleterious fitness consequences.

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Five beta-tubulin alleles confer recessive benzimidazole resistance.

First Report of Anthelmintic Resistance in Gastrointestinal Nematodes in Goats in Romania

Currently, there are three classes of anthelmintics most commonly used in small ruminants: the benzimidazoles (BZs), macrocyclic lactones (MLs) and cholinergic agonists (especially levamisole; LEV). The widespread use of those products has led to the emergence of drug-resistant parasite strains which represents a serious threat to the livestock industry. In the present study, we describe for the first time a case of resistance to anthelmintics in goats in Romania. The study was carried out in 2021 in a dairy goat herd from the Transylvania region. Two types of diagnostic methods were used to confirm anthelmintic resistance (AR). First, the faecal egg count reduction test (FECRT), an in vivo AR diagnostic method, was used to evaluate the efficacy of eprinomectin (EPM). The results of this test were analysed applying two different calculative methods that are used only in treated animals (without the control group). Furthermore, two in vitro methods were used: the egg hatch test (EHT) for the detection of resistance to BZs, and the larval development test (LDT) for detection of resistance to all three classes of anthelmintics. The results of FECRT indicate the resistance of gastrointestinal nematodes (GINs) to EPM in both calculative methods (FECR₁ = -88% and FECR₂ = -202%). In addition, the results obtained for ivermectin aglycone (IVM-AG) in LDT also indicate resistance to drugs from MLs group, especially avermectins. Similarly, the results of in vitro methods (EHT and LDT) indicate resistance to BZs in this herd. LEV was the only drug that stopped the development of L3 larvae 100% (LDT). H. contortus was the only nematode species found in coproculture after EPM treatment. Furthermore, H. contotus L3 larvae was the only species found in the wells with the highest concentrations of thiabendazole (TBZ) and IVM-AG in LDT. This suggests that resistance to both BZs and MLs was present for that species.

Anthelmintic resistance of Haemonchus contortus from sheep flocks in Brazil: concordance of in vivo and in vitro (RESISTA-Test©) methods

This study evaluated the resistance status of Haemonchus contortus from sheep flocks in the state of São Paulo, Brazil, through comparison between the fecal egg count reduction test (FECRT) and the larval development test (LDT). For the FECRT, 35 sheep were selected in each of five flocks and divided into groups treated with: benzimidazole, levamisole, ivermectin, monepantel and control. Feces were collected for EPG and fecal cultures. The LDT was performed using thiabendazole (TBZ), levamisole (LEV), ivermectin aglycone (IVM-A) and Zolvix (ZLV). Resistance to all drugs was detected using FECRT in 100% of the flocks, except in relation to ZLV (40% resistant and 20% suspected of resistance). LDT indicated resistance to TBZ and IVM-A in all flocks, to LEV in 80% of flocks and to ZLV in 10%. Total agreement was obtained between the two tests for TBZ and IVM (k = 1.0), while for LEV (k = 0.8) and ZLV (k = 0.9), substantial and almost perfect agreement were obtained, respectively. The concordance between the tests was significant, thus showing that it is possible to use the outcome of the LDT to predict the FECRT, and hence validating the former as a fast diagnostic test for use by sheep farmers in Brazil.

Prevalence of anthelmintic resistance of gastrointestinal nematodes in Polish goat herds assessed by the larval development test

Background

Helminthic infections, in particular those caused by gastrointestinal nematodes (GIN), are found worldwide and are among the most economically important diseases of goats. Anthelmintic resistance (AR) in GIN of goats is currently present worldwide, and single- or multidrug resistant species are widespread. The aim of this study was to determine the prevalence of AR to benzimidazoles (BZ), macrocyclic lactones (ML) and imidazothiazoles represented by levamisole (LEV) in the Polish goat herds by using an in vitro larval development test, which is useful especially in large-scale epidemiological surveys.

Results

This cross-sectional study was conducted from September 2018 to June 2019 and enrolled 42 dairy goat herds scattered over the entire country. The most commonly used anthelmintic class in goat herds in Poland were BZ (92%), followed by ML (85%) and LEV (13%). BZ-resistant GIN populations were found in 37 herds (88%, CI 95%: 75 to 95%), ML-resistant GIN populations in 40 herds (95%, CI 95, 84 to 99%), and LEV-resistant GIN populations in 5 herds (12%, CI 95%: 5 to 25%). Multidrug resistance involving all three anthelmintic classes was found in 5 herds (12%, CI 95, 5 to 25%). Based on the morphological features of stage 3 larvae the main resistant GIN turned out to be Haemonchus contortus and Trichostrongylus spp. The use of BZ and frequency of anthelmintic treatments were significantly related to the presence of AR to BZ in Polish goat herds.

Conclusions

This cross-sectional study demonstrates the existence of AR to BZ, ML and LEV on Polish goat farms. Resistance to BZ and ML is widespread, while AR to LEV is currently at a low level. A considerable proportion of herds harbours multidrug resistant GIN, which requires further consideration. An effective anthelmintic treatment strategy, reasonable preventive measures and better understanding of the resistance-related management practices by farmers and veterinarians may delay further development of AR.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12917-020-02721-9.

Isolation of pure Trichostrongylus colubriformis strains from naturally infected sheep using two methodologies

Two methodologies were tested to isolate pure Trichostrongylus colubriformis strains from naturally infected sheep. Also, the in vitro susceptibility status to commercial anthelmintic (AH) drugs was determined in these strains. These methods were performed in a tropical region of Mexico where naturally infected sheep and goats host Haemonchus contortus, T. colubriformis and Oesophagostomum columbianum. For the first strain, a group of 6 naturally infected lambs from the "Paraiso" farm were treated with closantel (subcutaneous (SC), 10 mg/kg). On day 10 post-treatment, the eggs per gram (EPG) of faeces were determined with the McMaster technique. The faeces from the two lambs with the highest EPG were used for coprocultures (4 days, 28 °C). The L₃ larvae were recovered and identified as T. colubriformis (69%) and O. columbianum (31%). The latter was removed by 10-day refrigeration (4-5 °C) followed by sieving (25 μm), resulting in 100% T. colubriformis (PARAISO strain). The second strain was isolated using repeated doses of levamisole (LEV, SC 7.5 mg/kg) in an 8-year-old sheep. The sheep had 1700 EPG before the LEV treatments and maintained 1300 EPG after both LEV treatments (day 10). The coproculture (4 days, 28 °C) after the second treatment contained 100% T. colubriformis (FMVZ-UADY strain). The in vitro AH susceptibility was determined using the egg hatch test for benzimidazole (BZ), and the larval migration inhibition test for ivermectin (IVM) and LEV. The PARAISO strain was BZ- and LEV-susceptible, and IVM-resistant. Meanwhile, the FMVZ-UADY strain was BZ- and IVM-susceptible, and LEV-resistant. The conditions where these two protocols could be used in other parts of the world were discussed.

Caribbean small ruminant importation requirements in an era of widespread anthelmintic resistance

Resistance of small ruminant gastrointestinal parasites to available classes of anthelmintic drugs is a widespread problem. As such, use of these drugs needs to be applied in a judicious manner in order to protect animal health. Herein, a case of drug-resistant gastrointestinal nematodes imported to the Cayman Islands is outlined. In order to explore the potential for similar occurrences within the region, a survey was undertaken in March 2017 to assess the importation requirements for small ruminants to English-speaking Caribbean countries. The survey showed that universal administration of anthelmintics to small ruminants is a common pre-requisite for importation to the Caribbean region, though very few countries require any proof of drug efficacy. Such requirements are discordant with current recommendations for judicious anthelmintic use in domestic animal species and promote the continued development of anthelmintic resistance. While this survey focused on small ruminants, similar policies are often in place for the importation of a variety of animal species, including cattle, horses, and companion animals. Given that anthelmintic resistance is also recognized in parasite populations that impact these species, it may be time for the international community to revisit live animal importation requirements in the age of anthelmintic resistance. Some recommendations and considerations are put forward to help preserve animal health, animal welfare, and developing animal agricultural industries.

High energy levels in the diet reduce the parasitic effect of Haemonchus contortus in Pelibuey sheep

Nutritional aspects modulate the parasitological and immune response in infected sheep. The aim of the present study was to evaluate the parasitological and humoral immune response of Pelibuey sheep experimentally infected with Haemonchus contortus that were fed diets with two different energy (n = 12) and protein (n = 12) levels. Twenty-four Pelibuey lambs infected with H. contortus were evaluated over 12 weeks. An additional six animals were considered as a control group. Fecal egg count (FEC) was determined, in addition to packed cell volume (PCV), total plasma protein (TPP), and immunoglobulin levels (IgA, IgG, and IgM) by indirect enzyme-linked immunosorbent assay (iELISA). Data were analyzed by repeated measures over time. The lambs that received a high-energy (HighE) diet had the lowest FEC (P < 0.01) regardless of whether they received a high (HighP) or low (LowP) level of protein. The effect of energy level was also observed over time: FEC values decreased and PCV and TPP values increased. Higher immunoglobulin levels were obtained for females (P < 0.05) than males yet, overall, the energy and protein levels of the diets did not affect the response of the immunoglobulins. Over time, however, an increase in IgG and IgM was observed, whereas the IgA level remained basal.

Experimental evidence for the lack of sensitivity of in vivo faecal egg count reduction testing for the detection of early development of benzimidazole resistance

The objective of this study was to compare the results of an in vitro egg hatch test (EHT), micro-agar larval development test (MALDT) and in vivo faecal egg count reduction test (FECRT) between worm strains obtained from goats and sheep identically infected with the gastrointestinal parasitic nematode Haemonchus contortus. Results from the in vivo and in vitro tests were compared with benzimidazole (BZ)-resistance-associated β-tubulin allele frequencies determined using Pyrosequencing™. BZ resistance was not detected by the in vivo FECRT, where reductions of > 99% for both the resistant and the susceptible H. contortus strains were detected in both species. Discriminating doses in EHT and MALDT for the resistant strain indicated a low level (approx. 25%) of resistant individuals. Genotyping indicated that the susceptible strain had 10% BZ-resistant β-tubulin codon 200 alleles and the resistant strain had 26% respective resistant alleles. The in vitro tests and allele-frequency distribution suggested low levels of resistance in both strains; however, the FECRT did not support the evidence of resistant individuals of either strain in either species, suggesting a potential underestimation of low-level resistance in sheep and goats when employing this test.

Quantitative benzimidazole resistance and fitness effects of parasitic nematode beta-tubulin alleles

Infections by parasitic nematodes inflict a huge burden on the health of humans and livestock throughout the world. Anthelmintic drugs are the first line of defense against these infections. Unfortunately, resistance to these drugs is rampant and continues to spread. To improve treatment strategies, we must understand the genetics and molecular mechanisms that underlie resistance. Studies of the fungus Aspergillus nidulans and the free-living nematode Caenorhabditis elegans discovered that a beta-tubulin gene is mutated in benzimidazole (BZ) resistant strains. In parasitic nematode populations, three beta-tubulin alleles, F167Y, E198A, and F200Y, have long been correlated with resistance. Additionally, improvements in sequencing technologies have identified new alleles - E198V, E198L, E198K, E198I, and E198Stop - also correlated with BZ resistance. However, none of these alleles have been proven to cause resistance. To empirically demonstrate this point, we independently introduced the F167Y, E198A, and F200Y alleles as well as two of the newly identified alleles, E198V and E198L, into the BZ susceptible C. elegans N2 genetic background using the CRISPR-Cas9 system. These genome-edited strains were exposed to both albendazole and fenbendazole to quantitatively measure animal responses to BZs. We used a range of concentrations for each BZ compound to define response curves and found that all five of the alleles conferred resistance to BZ compounds equal to a loss of the entire beta-tubulin gene. These results prove that the parasite beta-tubulin alleles cause resistance. The E198V allele is found at low frequencies along with the E198L allele in natural parasite populations, suggesting that it could affect fitness. We performed competitive fitness assays and demonstrated that the E198V allele reduces animal health, supporting the hypothesis that this allele might be less fit in field populations. Overall, we present a powerful platform to quantitatively assess anthelmintic resistance and effects of specific resistance alleles on organismal fitness in the presence or absence of the drug.

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Beta-tubulin alleles from parasitic nematodes were introduced into drug-susceptible C. elegans using CRISPR-Cas9.

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Beta-tubulin variants are strongly selected in albendazole competitive fitness assays.

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The E198V allele confers a fitness cost in control conditions as compared to other alleles.

The first report of multidrug resistance in gastrointestinal nematodes in goat population in Poland

Background

Prophylactic anthelmintic treatment with one of three basic classes of anthelmintics (benzimidazoles, macrocyclic lactones and imidazothiazoles) is still the mainstay of control of gastrointestinal nematode infections in small ruminants worldwide. As a consequence, anthelmintic resistance is a serious threat to small ruminant health and production. While the resistance to one class of anthelmintics has already been reported in most of countries, the newly-emerging problem is the resistance to two or even all of classes referred to as multidrug resistance. This study aimed to evidence the presence of multidrug resistance of gastrointestinal nematodes in goats in Poland.

Results

The combination of one in vivo method (fecal egg count reduction test) and two in vitro methods (egg hatch test and larval development test) performed in two goat herds in the southern Poland showed the presence of gastrointestinal nematodes resistant to fenbendazole and ivermectin in both herds. Moreover, in one herd it revealed the development of resistance to the last effective anthelmintic, levamisole, in response to one-year intensive use. Haemonchus contortus was the most prevalent gastrointestinal nematode in samples in which resistance to benzimidazoles and ivermectin was found, whereas Trichostrongylus colubriformis predominated when resistance to levamisole was observed.

Conclusion

This study shows for the first time that multidrug resistance of gastrointestinal nematodes to three basic classes of anthelmintics is already present in goat population in Poland. Moreover, it may indicate that different species or genera of gastrointestinal nematodes are responsible for the resistance to specific anthelmintics.

Sustainable Approaches to Parasite Control in Ruminant Livestock

It is increasingly difficult to manage and control gastrointestinal nematode parasites in pasture-based ruminant livestock operations because of the high prevalence of anthelmintic resistance. Anthelmintics should be combined with alternative forms of control. Sustainable tools include copper oxide wire particles and condensed tannin-rich plants, which target primarily Haemonchus contortus in small ruminants. Nematophagous fungi reduce larvae on pasture and target nematode larvae in feces of most livestock species. In addition, and perhaps most importantly, genetic selection focuses on parasite resistance. Producers should use as many tools as possible to minimize the need for pharmaceutical interventions and optimize animal production.

Biology, Epidemiology, and Control of Gastrointestinal Nematodes of Small Ruminants

Strongylid gastrointestinal nematodes are an important cause of disease and economic loss in small ruminants. These parasites are important in most of the United States, with the bloodsucking parasite Haemonchus contortus being the predominant species of concern. Sheep and goats are infected while grazing, and the biology of infective larvae on pastures is important in the design of parasite management programs. Widespread resistance to anthelmintics requires strategies designed to preserve remaining drug activity; these include combination treatments with multiple classes of anthelmintics and targeted treatments.

Biology, Epidemiology, Diagnosis, and Management of Anthelmintic Resistance in Gastrointestinal Nematodes of Livestock

Control of gastrointestinal nematodes has been based on anthelmintics. However, this strategy is unsustainable owing to anthelmintic resistance. Parasitic nematodes have biologic and genetic features that favor the development of drug resistance, making the emergence of resistant nematodes inevitable. The rate of resistance development is affected controllable factors. There is a need to change the paradigm of how gastrointestinal nematodes are controlled to decrease the rate at which resistance develops. This article reviews the biology and prevalence of anthelmintic resistance, and provides recommendations for diagnosing resistance and for strategies that should be implemented to reduce the development of resistance.

Harnessing the gut microbiome in the fight against anthelminthic drug resistance

Intestinal helminth parasites present major challenges to the welfare of humans and threaten the global food supply. While the discovery of anthelminthic drugs empowered our ability to offset these harms to society, the alarming rise of anthelminthic drug resistance mitigates contemporary efforts to treat and control intestinal helminthic infections. Fortunately, emerging research points to potential opportunities to combat anthelminthic drug resistance by harnessing the gut microbiome as a resource for discovering novel therapeutics and informing responsible drug administration. In this review, we highlight research that demonstrates this potential and provide rationale to support increased investment in efforts to uncover and translationally utilize knowledge about how the gut microbiome mediates intestinal helminthic infection and its outcomes.

Caffeoyl and coumaroyl derivatives from Acacia cochliacantha exhibit ovicidal activity against Haemonchus contortus

ETHNOPHARMACOLOGY RELEVANCE

Acacia cochliacantha is a small tree whose foliage is traditionally used in Mexico for treatment of kidney pain, gastrointestinal illnesses and to kill intestinal parasites. In recent decades, the study of vegetal extracts has offered other possible alternatives for the control of Haemonchus contortus. Considering that this nematode affects dramatically the health and productivity of small ruminants, the aim of this study was to identify the anthelmintic compounds from A. cochliacantha hydro-alcoholic extract (HA-E) through an ovicidal test.

MATERIAL AND METHODS

In vitro egg hatch assay was conducted to determinate the anthelmintic effects of a HA-E (60g). Liquid-liquid ethyl acetate/water extraction gave two fractions (EtOAc-F, 1.92g; Aq-F; 58.1g). The less polar compounds from ethyl acetate fraction were extracted by addition of dichloromethane offering a precipitate phase (Mt-F, 1.25g) and a soluble mixture (DCMt-F 1.15g). All fractions were evaluated for ovicidal activity obtaining the egg hatching inhibition (EHI, 0.07-25mg/mL). Ivermectin (0.5mg/mL) was used as a reference drug (positive control), and distilled water, 2.5% DMSO and 2% methanol were used as negative controls. The isolated compounds from the most active fractions were subjected to spectroscopic (¹H NMR) Spectrometric (MS) and UV HPLC analysis in order to identify the bioactive compounds.

RESULTS

The less polar treatments (AcOEt-F, DCMt-F, DCMt-P) showed the highest ovicidal activities (98-100% EHI; at 0.62-1.56mg/mL) and the major compounds found in these fractions were identified as caffeoyl and coumaroyl derivatives, including caffeic acid (1), p-coumaric acid (2), ferulic acid (3), methyl caffeate (4), methyl-p-coumarate (5), methyl ferulate (6) and quercetin. In case of the less active fractions (Aq-F, Mt-F) were constituted principally by glycosylated flavonoids.

CONCLUSION

These results show that caffeoyl and coumaroyl derivatives from Acacia cochliacantha leaves had promising anthelmintic activity against Haemonchus contortus. This leguminous may offer an alternative source for the control of gastrointestinal nematodes of small ruminants.

Evaluation of benzimidazole resistance status in Ascaridia galli

Susceptability of Ascaridia galli to benzimidazole (BZ) was investigated using faecal egg count reduction test (FECRT), in ovo larval development test (LDT) and genetic markers (mutations at codons 167, 198 and 200 of β-tubulin gene). Six flocks (F1−F6) of a commercial laying hen farm with different number of exposure to BZ were recruited. The FECR was calculated by analyzing individual faeces (F1, F2, F4 and F5) before and 10 days after treatment. The LDT was performed on parasite eggs from pooled samples from F1 to F6 and LC50 and LC99 were calculated. DNA was extracted from 120 worms and sequenced for β-tubulin gene. In all flocks, the FECRs were above 95% (lower CI above 90%). No significant difference was observed (p > 0·05) among obtained LC50 (F1/F4 and F2/F5 vs F3/F6) in the LDT. However, LC50 and LC99 were higher than suggested values for declaration of resistance in other nematode species. No variation was observed in codon positions involved in BZ resistance. Overall, our results indicated lack of evidence of resistance to BZ in A. galli. More research is needed to confirm these results and to further optimize the existing tools for detection and monitoring of anthelmintic resistance in A. galli.