Faecal Egg Count Reduction Test Research Articles

The first reported case of resistance of gastrointestinal nematodes to benzimidazole anthelmintic in goats in Poland

Fecal egg count reduction (FECR) test with albendazole and egg hatch test (EHT) with thiabendazole (TBZ) were performed in a dairy goat herd suspected of anthelmintic resistance to benzimidazoles. The herd had been regularly dewormed with fenbendazole for 5 previous years and despite that it remained infected with several species of gastrointestinal nematodes (Trichostrongylus colubriformis, Teladorsagia circumcincta, and Haemonchus contortus). Albendazole was administered per os at dose of 20 mg/kg to 10 goats (treated group), while 10 other goats remained untreated (control group). Fecal egg count (FEC) was determined using McMaster egg counting method before and 7 days after the treatment in the treated group, and once (at the latter moment) in the control group. EHT was performed on the pooled rectal sample collected from treated goats. EHT comprised the negative control and 7 consecutive concentrations of TBZ (0.05, 0.1, 0.2, 0.3, 0.5, 1.0, 2.0 μg/ml) according to the standard procedure. Two hundred eggs/larvae were counted to determine percentage of unhatched eggs, which was adjusted by the natural mortality. TBZ dose effective in preventing hatching of 50% of eggs (ED50) was determined using the log-probit transformation. Median FEC (range) before the treatment was 1000 (250–3450) epg in the treated group and dropped to 150 (50–500) epg after the treatment (p=0.005). Median FEC (range) after the treatment was also significantly lower in the treated than in control group (p=0.009), where it was 725 (0–5050) epg. FECR between the treated and control group was 81% (95% CI: 49%, 93%). FECR in the treated group was 83% and 74% based on average and individual approach, respectively. ED50 value of TBZ was 0.78 μg/ml. Only H. contortus persisted in the treated group after treatment. The results indicate resistance of H. contortus to a benzimidazole anthelmintic, which is the first such case reported in Polish goats.

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

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

Investigating anthelmintic efficacy against gastrointestinal nematodes in cattle by considering appropriate probability distributions for faecal egg count data

The Faecal Egg Count Reduction Test (FECRT) is the most widely used field-based method for estimating anthelmintic efficacy and as an indicator of the presence of anthelmintic resistant nematodes in cattle, despite never having been validated against the gold standard of controlled slaughter studies. The objectives of this study were to assess the normality of cattle faecal egg count (FEC) data and their transformed versions, since confidence intervals used to aid the interpretation of the FECRT, are derived from data assumed to be normally distributed, and violation of this assumption could potentially lead to the misclassification of anthelmintic efficacy. Further, probability distributions and associated parameters were evaluated to determine those most appropriate for representing cattle FEC data, which could be used to estimate percentage reductions and confidence limits. FEC data were analysed from 2175 cattle on 52 farms using a McMaster method at two different diagnostic sensitivities (30 and 15 eggs per gram (epg)) and a sensitive centrifugal flotation technique (SCFT) with a sensitivity of 1 epg. FEC data obtained from all egg count methods were found to be non-normal even upon transformation; therefore, it would be recommended that confidence or credible intervals be generated using either a Bootstrapping or Bayesian approach, respectively, since analyses using these frameworks do not necessarily require the assumption of normality. FEC data obtained using the SCFT method were best represented by distributions associated with the negative binomial and hence arithmetic means could be used in FECRT calculations.Where FEC data were obtained with less sensitive counting techniques (i.e. McMaster 30 or 15 epg), zero-inflated distributions and their associated central tendency were the most appropriate and would be recommended to use, i.e. the arithmetic group mean divided by the proportion of non-zero counts present; otherwise apparent anthelmintic efficacy could be misrepresented.

Gastrointestinal Nematode Parasites of Small Ruminants and Anthelmintics Efficacy Test in Sheep of Haramaya District, Eastern Ethiopia

The combination of cross-section and controlled field trail were carried out from December 2015 to June 2016 at Haramaya District, Eastern Hararhge, Ethiopia to evaluate the prevalence ofgastrointestinal nematodes and anthelmintic efficacy test in naturally infected small ruminants using faecal egg count reduction (FECR) test. From a total of 372 faecal samples examined using fecal flotation technique about 57% (212/372) samples were positive to gastrointestinal nematodes. Coprological investigation revealed that sheep and goats in district were infested with varieties of nematode parasites. The strongyles species were highly prevalent nematode parasites identified at about 22.3% (83/372) followed by trichuris 9.1% (34/372) and strongyloides 5.6% (21/372); whereas mixed infections of strongyles and strongyloides were recovered at lowest rate which accounted for about 5.1% (19/372). From considered risk factors age and kebele showed significant association (p&lt;0.05) with prevalence of nematodes parasites. The study revealed that 53.29% (97/182) of goats and 60.53% (115/190) sheep were found positive, while 58% (115/198) in female and 55.74% (97/174) in male and showed no significant difference (p&gt;0.05) between these factors. Mc Master egg counting in sheep harbored nematode parasites showed relatively similar percentage with no significant difference; but more of examined animals were classified in the range of moderate to heavy infections. The faecal egg count reduction test against albendazole, Tetraclozash and ivermectin indicated that 97.59%, 98.79% and 99.56% respectively which indicated an overall of very good state of efficacy against gastrointestinal nematodes of sheep. Therefore this study revealed that small ruminants of the study area harbored considerable level of gastrointestinal nematodes parasites which need further studies on species identification, larval ecology and strategic deworming with proper practice of available anthelmintics in small ruminants of the study area.

Anthelmintic resistance in ruminants: development, diagnostics, and procedures

Anthelmintic resistance of gastrointestinal nematodes in small ruminants, but also in cattle and horses, is now found worldwide. The reason for increasing anthelmintic resistance is, in particular, the extensive use of all the anthelmintic agents available on the market. A non-targeted use leads to the selection of naturally occurring resistance genes within parasite populations. The most practical method for evaluating the efficacy of an anthelmintic is the fecal egg-count reduction test. To reduce the rate of anthelmintic resistance development, the available active substances must be applied less and in a targeted manner. When applying targeted (selective) treatment, part of the herd is left untreated. Therefore, it is necessary to identify the animals that require treatment for health or economic reasons. To decide on anthelmintic treatment, findings can be collected from single animals or from a group of animals in a herd. To determine which groups of animals are to be treated within a herd (targeted treatment), pooled fecal samples (cattle and small ruminants), serum pepsinogen concentration (cattle), or Ostertagia ostertagi antibodies in the bulk milk (cattle) can be analyzed. For individual animal (targeted selective) treatment, criteria including fecal egg count (cattle and small ruminants), conjuctival color as an indicator for infection with Haemonchus contortus (FAMACHA®, small ruminants), body condition in adult animals (small ruminants), weight gain in juvenile animals (cattle and small ruminants), and the consistency of the feces (small ruminants) are used. These decision criteria can also be combined to enhance the informative value. Furthermore, an efficacy test of the anthelmintics used should be performed regularly at the beginning of the pasture season. During the pasture season, a low infection pressure should be maintained by pasture management strategies. The goal of sustainable parasite management is the reduction of anthelmintic treatment while maintaining the productivity and health of the animals and thus a longer effectiveness of the available drugs.

Resistant nematodes in cattle: Pharmaco-therapeutic assessment of the ivermectin- ricobendazole combination

Nematodicidal combinations have been proposed as a valid strategy to achieve effective nematode control in the presence of drug resistance. The goals of this study were: (1) to compare the clinical efficacy (therapeutic response) of ivermectin (IVM) and ricobendazole (RBZ) given subcutaneously either by separate or combined administration to calves naturally infected with gastrointestinal nematodes resistant to IVM, and (2) to evaluate the potential pharmacokinetic (PK) and/or pharmacodynamic (PD) interactions occurring after the co-administration of both anthelmintics. Sixty male calves naturally infected with gastrointestinal nematodes resistant to IVM were randomly allocated into four groups (n=15). Untreated control: animals not receiving anthelmintic treatment; IVM alone: animals treated with IVM by subcutaneous (SC) injection (0.2mg/kg); RBZ alone: animals received RBZ by the SC route (3.75mg/kg); IVM+RBZ: animals treated with IVM and RBZ (0.2 and 3.75mg/kg, respectively), by SC injection in two separates sites. Eight animals of each treated group were randomly selected to perform the PK study. Plasma samples were taken from those animals up to 28days post-treatment. IVM and RBZ plasma concentrations were quantified by HPLC. The therapeutic response was determined by faecal egg count reduction test (FECRT). The proportions of third-stage larvae (L3) recovered from coprocultures were used to calculate the efficacy against the main parasite genera. The daily total egg deposition for each experimental group was estimated. Similar pharmacokinetic trends were obtained for both IVM and RBZ allying the single-drug and the combined treatments, which indicates the absence of PK interactions between both anthelmintics. The observed overall clinical drug efficacies were 48% (IVM alone), 94% (RBZ alone) and 98% (IVM+RBZ). Haemonchus spp. and Cooperia spp. were recovered in the coproculture after IVM treatment, suggesting that resistance to IVM includes both genera. In fact, the efficacy against Cooperia spp. was 83% (IVM), 98% (RBZ) and 98% (IVM+RBZ), while the efficacy against Haemonchus spp. was 0% (IVM), 97% (RBZ) and 100% (IVM+RBZ). The combination was the only treatment that achieved 100% clinical efficacy against IVM-resistant Haemonchus spp. The total egg excretion was reduced to 49.9% (IVM alone group), 6.3% (RBZ alone group) and 1.8% (IVM+RBZ combined group) compared to the untreated control. Although the combined treatment did not significantly increase the overall clinical efficacy in the current natural field conditions, an additive effect was achieved against IVM-resistant nematodes. In fact, the combination obtained significantly higher efficacy against IVM-resistant Haemonchus spp. than RBZ alone. Additionally, the epidemiological relevance of the reduction in the number of eggs excreted following the combined treatment is not negligible and should be taken into account in future studies. Further work is required to understand the advantages of nematodicidal combinations in different natural anthelmintic resistance scenarios.

Homeopathic Treatment with a Complex of Cina9 CH and Colocynthis CH in Horses Naturally Infected with Intestinal Strongyles

<p class=MsoNormal style=margin-bottom:0in;margin-bottom:.0001pt;text-align: justify;line-height:150%> The aim of this study was to evaluate the efficacy of homeopathic and allopathic treatments on gastrointestinal parasites in horses. Eighteen clinically healthy and regularly trained Standard bred horses were used with the informed consent of the owners. The horses were randomly divided into 3 equally groups: Group A was treated with ivermectin, Group B received daily treatment with an homeopathic combination of Cina 9CH and Colocynthis 9CH, and Group C (Control Group) received treatment with placebo. Directly after the first faecal sampling, the horses were treated with anthelmintic drugs (day 0). All horses were observed daily to record for any clinical signs of side-effects (e.g., sweating, mydriasis, colics) caused by the products. Body Condition Score (BCS) measurement was performed on horses before (d0) and after the end of experimental period (d35). The collection of faecal samples was carried out from each animal before (d0) and after 3 (d3), 7 (d7), 10 (d10), 13 (d13), 16(d16), 20 (d20), 27 (d27), and 35 (d35) days the start of experimental period. Fecal egg count reduction (FECR) tests were performed to evaluate the efficacy of allopathic and homeopathic treatment. Two-way repeated measures analysis of variance (ANOVA) was applied to determine significant effects of treatment and time on BCS values. Differences on efficacy of treatment were found among groups. In particular, the efficacy of ivermectin on Group A based on FECR was of 98.8%. Egg count reduction after homeopathic treatment were lower than 10%,although the parasite eggs showed altered morphological aspect with thinned and coerced walls. Whereas, the Group C had no reduction in FECR and parasite eggs showed no morphological alterations. A statistically significant effect of time was found on the BCS values in group A (P<0.05) and B (P<0.001). Moreover, Groups B showed higher BCS values respect to Group A and Group C. The homeopathic treatment evaluated in the present study did not prove effective in controlling gastrointestinal nematodes in the conditions that it was tested as demonstrated by the lack of FECR. <p class=MsoNormal style=margin-bottom:0in;margin-bottom:.0001pt;text-align: justify;line-height:150%> Keywords: Homeopathic treatment, Horse, Ivermectin, Gastrointestinal parasites

Zero-inflated hierarchical models for faecal egg counts to assess anthelmintic efficacy

The prevalence of anthelmintic resistance has increased in recent years, as a result of the extensive use of anthelmintic drugs to reduce the infection of parasitic worms in livestock. In order to detect the resistance, the number of parasite eggs in animal faeces is counted. Typically a subsample of the diluted faeces is examined, and the mean egg counts from both untreated and treated animals are compared. However, the conventional method ignores the variabilities introduced by the counting process and by different infection levels across animals. In addition, there can be extra zero counts, which arise as a result of the unexposed animals in an infected population or animals. In this paper, we propose the zero-inflated Bayesian hierarchical models to estimate the reduction in faecal egg counts. The simulation study compares the Bayesian models with the conventional faecal egg count reduction test and other methods such as bootstrap and quasi-Poisson regression. The results show the Bayesian models are more robust and they perform well in terms of both the bias and the coverage. We further illustrate the advantages of our proposed model using a case study about the anthelmintic resistance in Swedish sheep flocks.

Anthelmintic resistance status of gastrointestinal nematodes of sheep to the single or combined administration of benzimidazoles and closantel in three localities in Mexico

Veterinaria Mexico OA ISSN: 2448-6760 Cite this as: Alcala Canto Y, Sumano Lopez HS, Ocampo Camberos L, Gutierrez L. Anthelmintic resistance status of gastrointestinal nematodes of sheep to the single or combined administration of benzimidazoles and closantel in three localities in Mexico. Veterinaria Mexico OA. 2016;3(4). doi: 10.21753/vmoa.3.4.374 Sheep production requires the constant assessment of parasitic burden and the efficacy of existing treatments for proper management. In this study, the administration of five different treatments was evaluated for the reduction of the percentage of eggs per gram of feces (EPG) shed by gastrointestinal nematodes (GIN) from sheep on three different sheep-breeding farms in Mexico (Texcoco, Estado de Mexico; Hueytamalco, Puebla; and Tlaltizapan de Zapata, Morelos). In these farms, ivermectin and benzimidazole derivatives had been routinely administered for two consecutive years. To determine whether drugs with different pharmacological properties decreased GIN fecal egg excretion, the treatments closantel (CLOS), albendazole (ABZ) and fenbendazole (FBZ) were administered alone and in combinations of CLOS + ABZ and CLOS + FBZ, to five groups of sheep, with an additional untreated control group on each farm (n = 28 per flock). Anthelmintic resistance was determined using Fecal Egg Count Reduction Tests (FECRT) as recommended in the guidelines of the World Association for the Advancement of Veterinary Parasitology. Fecal samples were collected 14 and 21 days after treatment. The anthelmintic resistance status was determined based on the reduction in the fecal egg count arithmetic mean and 95 % confidence limits. According to the FECRT, resistance developed to CLOS, ABZ, FBZ and CLOS + FBZ because the mean percentage of EPG reduction was ≤ 95 % with a lower confidence limit of ≤ 90 %. By contrast, nematode susceptibility was confirmed for the CLOS + ABZ combination, as it reduced the percentage of GIN fecal egg output by 96.46 ± 3.04 % (day 14) and 96.88 ± 3.04 % (day 21). Based on the morphometric identification of larvae, Haemonchus spp., Cooperia spp. and Teladorsagia spp. were the most abundant genera on all farms before the administration of these five treatments. In conclusion, the use of the anthelmintic combination of closantel plus albendazole may reduce the development of anthelmintic resistance in gastrointestinal nematodes. Figure 1. Marginal means ± SD of the percentage reduction in egg count on days 14 and 21 after treatment of sheep on three farms (n = 28 per flock) with fenbendazole (FBZ), closantel (CLOS), albendazole (ABZ), closantel + fenbendazole (CLOS + FBZ) and closantel + albendazole (CLOS + ABZ).

Benzimidazoles Pharmacodynamics in Equine Strongyles

Our research aimed to assess the effectiveness of four benzimidazoles: albendazole, fenbendazole, mebendazole and thiabendazole against equine strongyles. The tests were performed between March 2015 and May 2016, on samples collected from 20 horses and 8 donkeys living in Harghita County. In vivo, Faecal Egg Count Reduction Test (FECRT) was used to evaluate fenbendazole pharmacodynamics. In vitro, Egg hatch assay (EHA) and Larval development assay (LDA) were used to evaluate the effectiveness of albendazole, fenbendazole, mebendazole and thiabendazole. The predominance of small strongyle species was observed, mostly Cyathostomum type A. In the horse group, before treatment, the average intensity was 1595.5 EPG, the maximum value being 4000, and extensivity 55%. Tested again at 14 days after treatment, all samples were negative. In the donkey group, before treatment, the total number was 6550 EPG, intensity of 935.7 and extensivity of 87.5%. 14 days after treatment, the average intensity was 150 and the extensivity 50%. In the horse group, EHA proved the efficacy of fenbendazole (0.0192%), albendazole (0.3740%) and thiabendazole (11.62%) and a major risk of inducing adaptive phenomena for mebendazole (Y parameter 1009.92). In the donkey group, all benzimidazoles had limited effectiveness: thiabendazole (73.93%), mebendazole (87.51%), fenbendazole (94.05%), albendazole (111.67%). All benzimidazoles inhibited larval development. For all tested benzimidazoles, the resistance induction predictive comparative risk analysis highlighted the benefit of their use, provided that the treatment protocol allows sufficient contact time.

Efficacy of ivermectin against gastrointestinal nematodes of cattle in Denmark evaluated by different methods for analysis of faecal egg count reduction

The efficacy of ivermectin (IVM) against gastrointestinal nematodes in Danish cattle was assessed by faecal egg count reduction test (FECRT). Six cattle farms with history of clinical parasitism and avermectin use were included. On the day of treatment (Day 0), 20 naturally infected calves per farm (total n = 120) were stratified by initial faecal egg counts (FEC) and randomly allocated to a treatment group dosed with 0.2 mg IVM kg−1 body weight s.c. (IVM; n = 10) or an untreated control group (CTL; n = 10). Individual FEC were obtained at Day 0 and Day 14 post-treatment and pooled faeces by group were cultured to isolate L3 for detection of Ostertagia ostertagi and Cooperia oncophora by qPCR. Treatment efficacies were analysed using the recommended WAAVP method and two open-source statistical procedures based on Bayesian modelling: ‘eggCounts’ and ‘Bayescount’. A simulation study evaluated the performance of the different procedures to correctly identify FEC reduction percentages of simulated bovine FEC data representing the observed real data. In the FECRT, reduced IVM efficacy was detected in three farms by all procedures using data from treated animals only, and in one farm according to the procedures including data from treated and untreated cattle. Post-treatment, O. ostertagi and C. oncophora L3 were detected by qPCR in faeces of treated animals from one and three herds with declared reduced IVM efficacy, respectively. Based on the simulation study, all methods showed a reduced performance when FEC aggregation increased post-treatment and suggested that a treatment group of 10 animals is insufficient for the FECRT in cattle. This is the first report of reduced anthelmintic efficacy in Danish cattle and warrants the implementation of larger surveys. Advantages and caveats regarding the use of Bayesian modelling and the relevance of including untreated cattle in the FECRT are discussed.

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.

Confirmation of ivermectin resistance in Ostertagia ostertagi in cattle in New Zealand

Six suspected cases of ivermectin resistance in Ostertagia spp. in cattle were investigated after routine anthelmintic efficacy testing on commercial farms. On four farms a comprehensive faecal egg count reduction test (FECRT) was undertaken using oral formulations of ivermectin (0.2mg/kg), albendazole (10mg/kg) and levamisole (7.5mg/kg) while on two farms only ivermectin was tested. The proportions of Ostertagia spp. in the untreated control and post-treatment larval cultures were used to apportion egg counts to genera and determine efficacy against this genus.Isolates of Ostertagia spp. recovered from three of the farms were each used to infect 18 six month old calves. The efficacy of oral formulations of ivermectin and moxidectin, both at 0.2mg/kg, was determined against each isolate by slaughter and worm count.The efficacy of ivermectin against Ostertagia spp., based on differentiated FECRT for each of the farms varied from 0% to 88%. The efficacy of ivermectin based on worm counts in the slaughter trial varied from 13% to 75% but moxidectin was >99% effective against all isolates. In addition, in the FECRT albendazole, at a dose rate of 10mg/kg, failed to achieve 95% efficacy against Ostertagia spp. on two farms (82% and 85%). Levamisole consistently failed to achieve 95% efficacy against Ostertagia spp. which is consistent with its known lesser efficacy against this parasite.These results confirm the presence of macrocyclic lactone resistant O. ostertagi in cattle in New Zealand and the likely presence of dual resistance, to macrocyclic lactones and albendazole, in some isolates. Resistant populations of this highly pathogenic parasite are probably not uncommon in New Zealand and pose a significant threat to animal production and welfare in the future.

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

Despite strong economic opportunities and incentives for small ruminant production, their health and productivity are often severely affected by parasitic disease. To combat these effects, most farms administer anthelmintics to their animals at frequent intervals, and without consideration to principles of sustainable integrated parasite management (SIPM). This has led to growing problems caused by the development of drug-resistant populations of gastrointestinal nematodes (GIN) in much of the world, particularly in Haemonchus contortus. The objectives of this research were to characterize levels of anthelmintic resistance on small ruminant farms located in the mid-Atlantic US and to compare the fecal egg count reduction test (FECRT) and larval development assay (LDA) for detecting resistance. To achieve these objectives, the DrenchRite® LDA was used to evaluate resistance status to benzimidazoles, ivermectin, moxidectin, and levamisole on 20 goat and 14 sheep farms in the Mid-Atlantic US over a 2-year period. A FECRT was also conducted on 14 of the same farms and on 2 additional farms in which the LDA was not completed. For the LDA and coprocultures, fecal samples were collected rectally from a minimum of 10 individual animals, pooled, and express-mailed to the University of Georgia for analysis. For the FECRT, albendazole, ivermectin, moxidectin, and/or levamisole were tested on each farm. Animals were allocated randomly based on FAMACHA© scores to 2–5 treatment groups, which included an untreated control group. The number of treatment groups on a farm depended on the number of qualified animals present. Haemonchus contortus was the most common parasite recovered from fecal cultures; the mean level across all farms was 79%. Results of the LDA indicated resistance to benzimidazoles, ivermectin, moxidectin, and levamisole on 100%, 82%, 47%, and 24% of farms, respectively. Multi-drug resistance to all 3 drug classes was detected for H. contortus on 18% of farms (1 sheep and 5 goat farms). Of the 16 farms tested by FECRT, resistance to albendazole was present on 8/10 farms, to ivermectin on 4/4 farms, to moxidectin on 7/9 farms and to levamisole on 2/5 farms tested. Results obtained from the FECRT and the LDA (p=0.51) were similar. The prevalence of resistance found in this study in the mid-Atlantic region of the US is very similar to that reported in an earlier survey of resistance performed in the Southern US, demonstrating that anthelmintic resistance in GIN is a serious problem on small ruminant farms throughout the Eastern US.

Resistance of Haemonchus sp. to monepantel and reduced efficacy of a derquantel / abamectin combination confirmed in sheep in NSW, Australia

Early in 2015, sheep in a summer rainfall area of NSW, Australia, displayed signs of haemonchosis despite treatment with monepantel. A faecal egg count reduction test (FECRT) was performed on yearlings with natural field infections using various anthelmintics. Only a four-way combination drench achieved a reduction in faecal egg count (FEC) greater than 95%. The combination contained abamectin, albendazole, levamisole and closantel. Treatments with a derquantel/abamectin combination, monepantel and moxidectin reduced FECs by 93, 31, and 30% respectively. Sheep treated with abamectin displayed an increase in FEC of 22%. Larval differentiation counts conducted 10days post-treatment showed that 100% of survivors were Haemonchus sp. This result confirms for the first time monepantel resistant Haemonchus in sheep in NSW, and is amongst the first of the Australian cases in sheep not associated with goats. A second FECRT was performed using sheep from the moxidectin and abamectin treatment groups in the first FECRT. In this second FECRT, monepantel treatment reduced FECs by 51% and 29% in the sheep previously treated with moxidectin and abamectin respectively. This suggests monepantel, in combination with moxidectin, may give some control against severely abamectin resistant Haemonchus.

Detection of anthelmintic resistance in sheep and goat against fenbendazole by faecal egg count reduction test.

Anthelmintic resistance against commonly used anthelmintic fenbendazole was evaluated by employing faecal egg count reduction test (FECRT) in naturally occurring gastrointestinal (GI) nematodes in the semi organized sheep and goat farms of Ludhiana and Amritsar districts. A total of 80 animals (20 each for sheep and goat in both districts) were randomly selected and their faecal samples were examined by qualitative and quantitative parasitological techniques. Results indicate presence of high level of resistance against fenbendazole in both sheep and goat population of Ludhiana and Amritsar districts. More resistance was observed in the GI nematodes from animals reared in Amritsar district as compared to Ludhiana district. The level of anthelmintic resistance observed was apparently more in sheep than goats.

Influence of sustained deworming pressure on the anthelmintic resistance status in strongyles of sheep under field conditions.

Anthelmintic resistance (AR) status in Madras Red sheep from selected field flocks of a government funded scheme, covered by regular, sustained anthelmintic treatment for more than 10years was determined. Parameters such as fecal egg count reduction test (FECRT), larval paralysis assay (LPA), and allele-specific-PCR (AS-PCR) were used to test the efficacy of fenbendazole, tetramisole, and ivermectin at recommended doses, in two seasons. Sheep belonging to non-beneficiary farmers were used as controls. Mean FECRT values of beneficiary group during winter and summer seasons were 77.77 and 76.04, 93.65 and 92.12, and 95.37 and 98.06%, respectively, for fenbendazole, tetramisole, and ivermectin. In the non-beneficiary groups, the corresponding values were 74.82 and 81.09%, 96.05 and 97.40%, and 97.26 and 98.23%, respectively. The results revealed resistance to fenbendazole, suspect resistance to tetramisole and susceptibility to ivermectin in beneficiary flock. In non-beneficiary flock, while resistance was noticed against fenbendazole, both tetramisole and ivermectin were effective. FECR values were found to be significantly different between beneficiary and non-beneficiary groups against tetramisole. The results of LPA confirmed this finding, as 50% of the Haemonchus contortus larvae were paralyzed at the concentration of 0.0156μg/ml in the beneficiary group, while those of non-beneficiary groups required lower concentrations of 0.0078μg/ml. AS-PCR revealed the predominance of heterozygous susceptible population of H. contortus in the beneficiary group. In this study, resistance to fenbendazole was confirmed in both the beneficiary and non-beneficiary groups and this could be attributed to frequent use of benzimidazoles as seen from the deworming records. Emergence of tetramisole resistance was detected in the beneficiary group, where the drug was used continuously for 4years. Ivermectin was found to be effective in all the flocks. It is recommended that the practice of routine deworming of three to four times a year should be avoided, as it can lead to emergence of anthelmintic resistance.

The efficacy and plasma profiles of abamectin plus levamisole combination anthelmintics administered as oral and pour‐on formulations to cattle

In phase I, faecal egg count reduction tests (FECRT) were conducted on six commercial cattle farms to compare the performance of two pour‐on and one oral combination anthelmintic. Groups of 12–15 calves were sampled for faecal nematode egg count (FEC) before treatment with either abamectin oral, levamisole oral, an abamectin+levamisole oral combination or one of two abamectin+levamisole combination pour‐ons. Samples were collected again 14days after treatment to calculate the percentage reduction in FEC. The proportions of infective stage larvae (L3) in faecal cultures were used to apportion egg counts to, and calculate efficacy against, the main parasite genera.Abamectin oral was effective against Ostertagia except on one farm where resistance was indicated, but had reduced efficacy against Cooperia on four farms. Levamisole oral was effective against Cooperia on all farms, but had variable efficacy against Ostertagia. The abamectin+levamisole oral was effective against both species on all farms. The abamectin+levamisole pour‐ons were effective on some farms but not on others. In particular, pour‐on 2 failed to achieve 95% efficacy in 45% of evaluations, 4/6 against Cooperia and 1/5 against Ostertagia. On some farms the combination pour‐ons were less effective than their constituent actives administered alone as orals.In phase II, 8 groups of 6 calves, grazing parasite-free pasture, were infected with putatively ML‐resistant isolates of Cooperia oncophora and Ostertagia ostertagi. Once infections were patent groups were treated with oral or pour‐on formulations of abamectin alone, levamisole alone, abamectin+levamisole (two pour‐ons) or remained untreated. Blood samples were collected for analysis and after 8days all calves were euthanized and abomasa and intestines recovered for worm counts.All treatments were effective against O. ostertagi and all treatments containing levamisole were effective against C. oncophora. Animals treated with the oral combination had higher Cmax and AUC values for abamectin in plasma than animals treated orally with abamectin alone. In contrast, animals treated with the combination pour-ons tended to have lower plasma levels for abamectin than those treated with abamectin alone as a pour-on, with differences in the Cmax and AUC values approaching statistical significance (p-values ≤0.07). There were no differences detected in plasma concentrations of levamisole.The inconsistent and sometimes poor efficacy of the combination pour‐ons on-farm is likely due to reduced levels of abamectin in the plasma and hence less active reaching the target worms in the gut.

Efficacy of ivermectin, closantel and fenbendazole against gastrointestinal nematodes of sheep in Kashmir valley.

The present work was undertaken to evaluate the therapeutic efficacy of ivermectin, closantel and fenbendazole under field conditions against Gastrointestinal Nematodes (GIN) of cross bred merino sheep in Budgam area of Kashmir Valley. A total of 115 sheep having Egg per gram of faeces (EPG) greater than or equal to 150 (mean EPG 258.89) were selected. The animals were randomly divided into four groups comprising of 30 animals each in three treatment groups (ivermectin, closantel and fenbendazole) and twenty-five in fourth untreated infected control group. Faecal samples from the selected animals were collected on day '0' pre treatment and on days 8th and 14th post treatment. Based on Faecal Egg Count Reduction Test (FECRT), ivermectin was found to be 98.80% effective against strongyles on 8th day post treatment, however an efficacy of 100% was seen against strongyle worms on 14th day post treatment. 98.80 and 100% efficacy was observed on day 8th post treatment against strongyles in case of closantel and fenbendazole respectively, however efficacy decreased to 97.60 and 98.8% respectively on 14th day post treatment. There was no evidence of development of resistance by GIN of cross bred merino sheep in District Budgam of Kashmir Valley to ivermectin, closantel and fenbendazole.

Cross-resistance to moxidectin and ivermectin on a meat sheep farm in France

Resistance to ivermectin and moxidectin was explored by a faecal egg count reduction test in two sheep flocks with suspected anthelmintic resistance. The FECRT confirmed one suspicion, with a mean percentage of reduction in egg excretion within the treated groups of 0% for ivermectin (CI 95%: −228 to 58) and 13% for moxidectin (CI 95%: −152 to 70). This was further explored by a controlled efficacy test. An experimental infection of 18 naïve lambs was set up using infective larvae isolated from this flock (5000 L3/lamb). Compared to the control group, abomasal worm burdens (Teladorsagia circumcincta) were reduced by 90% [CI 95%: 81.5–94.8] and 85% [CI 95%: 72.4–92.2] after ivermectin (p<0.05) and moxidectin (p<0.05) treatment respectively. Again, compared to the control group, there was a reduction for intestinal strongyles (Trichostrongylus colubriformis) of 100% and 99% [CI 95%: 97.5–99.7] for ivermectin and moxidectin respectively. No difference was found between the efficacy of moxidectin and ivermectin. Pharmacokinetic values indicated that the strongyles were submitted to anthelmintic concentrations usually lethal to them. This trial demonstrated the first multiple resistance of ovine strongyles in France.