Prevalence Of Anthelmintic Resistance Research Articles

Reduced anthelmintic use on 13 New Zealand sheep farms: farmer motivations and practical implementation

ABSTRACT Aims: To describe the personal drivers, sources of information and gastro-intestinal parasite control methods used by a group of New Zealand sheep farmers identified as low users of anthelmintic (AHC), and their perception of the efficacy and impacts of this approach. Methods: A convenience sample of 13 sheep farmers farming with a policy of reduced AHC use (no pre-determined routine treatments of ewes >19 months old and/or lambs not routinely treated at pre-determined intervals from weaning through to late autumn) were identified. Semi-structured interviews were conducted regarding their farming philosophy, motivations for reducing AHC use, perceptions of the impacts of farming with reduced AHC use, and parasite control practices. Semi-quantitative data were analysed using descriptive statistics for demographic data and categorising participants’ use of AHC and non-chemical control methods. Qualitative data regarding participants’ motivations, approaches and rationale were analysed by systematic analysis of the transcripts and distillation of key concepts. Results: Participants had been operating with reduced AHC use for 3 to ≥20 years. Key motivators for reducing AHC use were a diagnosis of anthelmintic resistance (AR) or concerns about AR developing. Parasite management information came from a wide range of sources. All respondents expressed overall positive views regarding the impacts of reduced AHC use but detailed information was not available. All identified that regular monitoring, based primarily on subjective animal and non-animal factors was important for their parasite control strategy. Most used faecal egg counts (FEC), often in an ad hoc manner. Five never treated adult ewes, two routinely treated ewes prior to lambing with short-acting AHC and the remainder occasionally treated a small number in low body condition. Four routinely treated some or all lambs at 28–30-day intervals from weaning to late autumn while the remainder based their treatment decisions for lambs on monitored information. All placed heavy emphasis on feeding sheep well, ensuring high post-grazing residuals, and cross-grazing. Conclusions: AR was a key motivator for participants to reduce AHC use, and a range of information sources and decision-making processes were used. Key parasite management practices were monitoring, primarily using subjective assessments, emphasis on feeding stock well and cross-grazing. Clinical relevance: The rising prevalence of AR will likely result in increasing the motivation for sheep farmers to reduce their AHC use. Veterinarians will play a key role in providing advice and assistance to facilitate changes in parasite management.

A national survey of anthelmintic resistance in ascarid and strongylid nematodes in Australian Thoroughbred horses

This study quantified the extent of anthelmintic resistance (AR) in ascarid and strongylid nematodes against commonly used anthelmintics in Australian Thoroughbred horses. Faecal egg count reduction tests (FECRTs, n = 86) and egg reappearance period (ERP) tests were conducted on 22 farms across Australia. Faecal egg counts (FECs) were determined using the modified McMaster technique, and percent faecal egg count reduction (%FECR) was calculated using the Bayesian hierarchical model and hybrid Frequentist/Bayesian analysis method. The results were interpreted using old (published in 1992) and new (2023) research guidelines of the World Association for the Advancement of Veterinary Parasitology (WAAVP). The species composition of strongylid nematodes was detected utilising a DNA-metabarcoding method using pre- and post-treatment samples. Resistance was observed in strongylid nematodes to commonly used single-active and combination anthelmintics, including ivermectin (IVM %FECR range: 82%–92%; 95% lower credible interval (LCI) range: 80%–90%), abamectin (ABM: 73%–92%; 65%–88%), moxidectin (MOX: 89%–91%; 84%–89%), oxfendazole (OFZ: 0%–56%; 0%–31%) and its combination with pyrantel (OFZ + PYR: 0%–82%; 0%–78%). Resistance in Parascaris spp. was observed to IVM (10%–43%; 0%–36%), ABM (0%; 0%) and MOX (0%; 0%). When the new thresholds recommended by the WAAVP were used, AR was detected in six additional FECRTs for strongylids and three more tests for Parascaris spp., introducing resistance to OFZ and OFZ + PYR in the latter. Shortened ERPs (4–6 weeks) of strongylids were observed in 31 FECRTs in which AR was not detected at 2 weeks post-treatment for all the anthelmintics tested. Among cyathostomins, Cylicocyclus nassatus, Cylicostephanus longibursatus and Coronocyclus coronatus were the most prevalent species at 2 weeks post-treatment, whereas the main species appearing at five weeks following treatments with macrocyclic lactones were Cylicocyclus nassatus, Cylicostephanus longibursatus and Cylicocyclus ashworthi. After treatment with OFZ + PYR, the latter three, plus Coronocyclus coronatus and Cyathostomum catinatum, were detected at 5 weeks post-treatment. Overall, the study highlights the prevalence of AR in both ascarids and strongylid nematodes against commonly used anthelmintic products to control worms in Australian horses. The results indicate that ML combination products provided acceptable efficacy at 2 weeks. However, ERP calculations suggest that products work less effectively than previously measured. It is suggested to regularly monitor the efficacy of the anthelmintics and consider changing the worm control practices to better manage worms and AR in Australian horses.

Comparison of FECPAKG2, a modified Mini-FLOTAC technique and combined sedimentation and flotation for the coproscopic examination of helminth eggs in horses

BackgroundDue to high prevalence of anthelmintic resistance in equine helminths, selective treatment is increasingly promoted and in some countries a positive infection diagnosis is mandatory before treatment. Selective treatment is typically recommended when the number of worm eggs per gram faeces (epg) exceeds a particular threshold. In the present study we compared the semi-quantitative sedimentation/flotation method with the quantitative methods Mini-FLOTAC and FECPAKG2 in terms of precision, sensitivity, inter-rater reliability and correlation of worm egg counts to improve the choice of optimal diagnostic tools.MethodsUsing sedimentation/flotation (counting raw egg numbers up to 200), we investigated 1067 horse faecal samples using a modified Mini-FLOTAC approach (multiplication factor of 5 to calculate epgs from raw egg counts) and FECPAKG2 (multiplication factor of 45).ResultsFive independent analyses of the same faecal sample with all three methods revealed that variance was highest for the sedimentation/flotation method while there were no significant differences between methods regarding the coefficient of variance. Sedimentation/flotation detected the highest number of samples positive for strongyle and Parascaris spp. eggs, followed by Mini-FLOTAC and FECPAKG2. Regarding Anoplocephalidae, no significant difference in frequency of positive samples was observed between Mini-FLOTAC and sedimentation/flotation. Cohen’s κ values comparing individual methods with the combined result of all three methods revealed almost perfect agreement (κ ≥ 0.94) for sedimentation/flotation and strong agreement for Mini-FLOTAC (κ ≥ 0.83) for strongyles and Parascaris spp. For FECPAKG2, moderate and weak agreements were found for the detection of strongyle (κ = 0.62) and Parascaris (κ = 0.51) eggs, respectively. Despite higher sensitivity, the Mini-FLOTAC mean epg was significantly lower than that with FECPAKG2 due to samples with > 200 raw egg counts by sedimentation/flotation, while in samples with lower egg shedding epgs were higher with Mini-FLOTAC than with FECPAKG2.ConclusionsFor the simple detection of parasite eggs, for example, to treat foals infected with Parascaris spp., sedimentation/flotation is sufficient and more sensitive than the other two quantitative investigared in this study. Mini-FLOTAC is predicted to deliver more precise results in faecal egg count reduction tests due to higher raw egg counts. Finally, to identify animals with a strongyle epg above a certain threshold for treatment, FECPAKG2 delivered results comparable to Mini-FLOTAC.Grpahical

Anthelmintic efficacy of fenbendazole and levamisole in native fowl in northern Iran

BackgroundWith the increasing number of free-range domestic chickens, helminth parasites have potentially become more of a threat to commercial flocks in recent years, and routine poultry deworming is needed to improve the efficiency of chicken production. The present study deals with a field trial to study the efficacy of two generally used anthelmintics, fenbendazole and levamisole, against gastrointestinal nematodes of domestic chickens in northern Iran.MethodsOf 45 domestic chicken flocks involved in the study, 20 flocks were selected to participate in fecal egg count reduction testing based on flock size from April 2017 to September 2018. The infected chickens were randomly divided into three equal groups of 30 each. Ninety chickens in the infected groups received one of the following treatments (d 0 of treatment): Group 1: 5 mg kg−1 body weight (BW) fenbendazole for 3 consecutive days; Group 2: 16 mg kg−1 BW levamisole; Group 3 control: placebo, water + DMSO (dimethylsulfoxide). The efficacy of the treatments was evaluated by comparing fecal egg counts in the treated and control groups.ResultsExamination of three flocks of chickens from the control group showed that 95.0% of the animals were infected with gastrointestinal nematodes with an average geometric value of 361 eggs per gram of feces. Fenbendazole at a dose of 5 mg kg−1 BW for 3 days showed an efficacy of 83.7% (P ≥ 0.05), and levamisole at a dose of 16 mg kg−1 BW showed 71.8% efficacy (P ≥ 0.05) with geometric mean eggs in a gram of feces of 100 and 199.6, respectively. In general, fenbendazole and levamisole treatment led to significantly lower activity. The result of this study revealed that fenbendazole was a better and more effective dewormer than levamisole on the three Iranian domestic chicken flocks, but the difference was not significant. Capillaria spp. were the most generally resistant nematodes followed by Trichostrongylus spp. and Amidostomum anseris.ConclusionOur results indicated that fenbendazole and levamisole effectively reduced the number of nemathodes in three Iranian domestic chicken flocks. Given the results of our study, resistance can be expected in the parasitic helminths of poultry. Additional larger scale studies are required to determine the prevalence of anthelmintic resistance in the poultry industry.Graphical

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

BackgroundHelminthic 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.ResultsThis 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.ConclusionsThis 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.

Molecular and phenotypic characterisation of fenbendazole resistance in a field-derived isolate of Ostertagia ostertagi

The prevalence of anthelmintic resistance in the bovine nematode Cooperia oncophora has been well documented globally but lack of efficacy against the more pathogenic nematode species Ostertagia ostertagi is less common. The sensitivity of an O. ostertagi isolate to the benzimidazole class of anthelmintic was investigated using classical parasitological techniques following apparent clinical failure of controlled release fenbendazole capsule administration in first season grazers at pasture. A controlled efficacy test (CET) was conducted in conjunction with sequencing of the β-tubulin isotype 1 gene of larvae pre- and post-fenbendazole administration. Twelve helminth-naïve calves were infected experimentally with 20,000 third stage larvae; six received oral fenbendazole (7.5 mg/kg bodyweight) 28 days post infection. Total abomasal nematode burdens were compared between treatment and control groups to determine efficacy. Fenbendazole resistance in O. ostertagi was confirmed with a total treatment failure in reducing worm burden: efficacy of 0%. Sequence analysis of the β-tubulin isotype-1 gene from forty-five infective larvae from both control and treated groups was performed. The three commonest single nucleotide polymorphisms (SNPs) associated with benzimidazole resistance, namely F167Y, E198A and F200Y, were examined. The predominant resistance-associated SNPs were F200Y (78 % control and 79 % treated groups) and F167Y (remaining genotypes) and emphasises the importance of these SNPs in clinical disease in this isolate. The development of diagnostic molecular tools based on a characterised field-derived isolate of benzimidazole-resistant Ostertagia will enable future prevalence surveys to be undertaken to assess the possible risk posed by resistance in this economically important species.

Increasing importance of anthelmintic resistance in European livestock: creation and meta-analysis of an open database.

Helminth infections are ubiquitous in grazing ruminant production systems, and are responsible for significant costs and production losses. Anthelmintic Resistance (AR) in parasites is now widespread throughout Europe, although there are still gaps in our knowledge in some regions and countries. AR is a major threat to the sustainability of modern ruminant livestock production, resulting in reduced productivity, compromised animal health and welfare, and increased greenhouse gas emissions through increased parasitism and farm inputs. A better understanding of the extent of AR in Europe is needed to develop and advocate more sustainable parasite control approaches. A database of European published and unpublished AR research on gastrointestinal nematodes (GIN) and liver fluke (Fasciola hepatica) was collated by members of the European COST Action “COMBAR” (Combatting Anthelmintic Resistance in Ruminants), and combined with data from a previous systematic review of AR in GIN. A total of 197 publications on AR in GIN were available for analysis, representing 535 studies in 22 countries and spanning the period 1980–2020. Reports of AR were present throughout the European continent and some reports indicated high within-country prevalence. Heuristic sample size-weighted estimates of European AR prevalence over the whole study period, stratified by anthelmintic class, varied between 0 and 48%. Estimated regional (country) prevalence was highly heterogeneous, ranging between 0% and 100% depending on livestock sector and anthelmintic class, and generally increased with increasing research effort in a country. In the few countries with adequate longitudinal data, there was a tendency towards increasing AR over time for all anthelmintic classes in GIN: aggregated results in sheep and goats since 2010 reveal an average prevalence of resistance to benzimidazoles (BZ) of 86%, macrocyclic lactones except moxidectin (ML) 52%, levamisole (LEV) 48%, and moxidectin (MOX) 21%. All major GIN genera survived treatment in various studies. In cattle, prevalence of AR varied between anthelmintic classes from 0–100% (BZ and ML), 0–17% (LEV) and 0–73% (MOX), and both Cooperia and Ostertagia survived treatment. Suspected AR in F. hepatica was reported in 21 studies spanning 6 countries. For GIN and particularly F. hepatica, there was a bias towards preferential sampling of individual farms with suspected AR, and research effort was biased towards Western Europe and particularly the United Kingdom. Ongoing capture of future results in the live database, efforts to avoid bias in farm recruitment, more accurate tests for AR, and stronger appreciation of the importance of AR among the agricultural industry and policy makers, will support more sophisticated analyses of factors contributing to AR and effective strategies to slow its spread.

Planning anthelmintic treatments to control gastrointestinal nematode infections in sheep

A planned approach to anthelmintic treatments against gastrointestinal nematodes in sheep is vital given their clinical and economic importance, and the prevalence of anthelmintic resistance. The key nematode species in the UK are Nematodirus battus, Teladorsagia circumcincta, Trichostrongylus species and Haemonchus contortus. Knowledge of the biology of these species and the annual production cycle on UK sheep farms can guide when treatments may be necessary. The timings of these treatments can be further refined using grazing history, weather conditions and faecal egg counting. This information can then be combined with knowledge of anthelmintic resistance to make a rational treatment decision, and reduce the selection for anthelmintic resistance; for example, by using strategies that maintain populations of parasites in refugia, using multiple active treatments or improving drug bioavailability.

Anthelmintic resistance in gastrointestinal nematodes in sheep raised under mountain farming conditions in Northern Italy

Anthelmintic resistance (AR) in sheep raised under mountain farming conditions in South Tyrol (Northern Italy) was assessed on eight farms (n=99 animals). A faecal egg count reduction (FECR) test was...

Anthelmintic resistance and novel control options in equine gastrointestinal nematodes.

Control of equine nematodes has relied on benzimidazoles (BZs), tetrahydropyrimidines and macrocyclic lactones. The intensive use of anthelmintics has led to the development of anthelmintic resistance (AR) in equine cyathostomins and Parascaris equorum. Field studies indicate that BZ and pyrantel resistance is widespread in cyathostomins and there are also increasing reports of resistance to macrocyclic lactones in cyathostomins and P. equorum. The unavailability of reliable laboratory-based techniques for detecting resistance further augments the problem of nematode control in horses. The only reliable test used in horses is the fecal egg count reduction test; therefore, more focus should be given to develop and validate improved methodologies for diagnosing AR at an early stage, as well as determining the mechanisms involved in resistance development. Therefore, equine industry and researchers should devise and implement new strategies for equine worm control, such as the use of bioactive pastures or novel feed additives, and control should increasingly incorporate alternative and evidence-based parasite control strategies to limit the development of AR. This review describes the history and prevalence of AR in equine nematodes, along with recent advances in developing resistance diagnostic tests and worm control strategies in horses, as well as giving some perspective on recent research into novel control strategies.

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.

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.

Worm-control practices and prevalence of anthelmintic resistance using in vivo FECRTs on smallholder sheep farms in Lithuania

Summary This study determined the prevalence of anthelmintic resistance (AR) in parasitic nematodes on smallholder sheep farms in Lithuania from April to November 2014. Faecal samples were collected from two groups of 10-15 sheep treated with fenbendazole (FBZ) or ivermectin (IVM) on 18 sheep farms. Two samples were collected from each group: on day zero (T1) and 10-14 days after treatment. Faecal egg counts (eggs per gramme, EPG) were determined using a modified McMaster technique. Animals with < 140 EPG on day zero were removed from the analysis. The prevalence of AR was estimated using the in vivo faecal egg count reduction test. AR to FBZ was detected on three of 15 farms where FBZ was used (20 %) and was suspected on one farm (6.7 %). AR to IVM was detected on two of 16 farms where IVM was used (12.5 %). The main species of resistant gastrointestinal nematodes (GINs) identified after treatment were Teladorsagia spp. and Trichostrongylus spp. A questionnaire surveying 71 sheep farmers estimated that 71.8 % of sheep farmers used anthelmintics against GINs. IVM was the most frequently (68.6 %) applied anthelmintic, and 62.7 % of the respondents reported treating their animals twice a year. This study confirmed the presence of AR to GIN infections on sheep farms in Lithuania. Future studies should assess the prevalence of AR to GIN infection using in vitro methods.

Prevalence of anthelmintic resistance on Lithuanian sheep farms assessed by in vitro methods.

BackgroundThis study examines the prevalence of drug resistance in gastrointestinal nematodes to macrocyclic lactones (ML) and benzimidazoles (BZ) in Lithuanian sheep using sensitive and precise in vitro methods. The survey was conducted from August 2013 to November 2014. Thirty-three farms with sheep previously treated with BZ and ivermectin (IVM) were included in the study. On 12 farms where only BZ were used, egg hatch discrimination dose testing (EHDDT) was conducted to detect anthelmintic resistance (AR) to BZ. On eight farms where only ML were used, micro agar larval development testing (MALDT) was conducted to detect AR to ivermectin (IVM). On the remaining 13 farms, where both classes of drugs were used, EHDDT and MALDT were both applied to detect multidrug resistance to BZ and IVM.ResultsBZ-resistant gastrointestinal nematodes were found on all 25 farms with a previous history of BZ use. High levels of resistance (>40 % of hatching) were recorded on 36 % of these farms, and low levels (<20 % of hatching) on 40 % of farms. IVM-resistant populations were found on 13 out of 21 sheep farms using this drug. Of these 13 farms with AR to IVM, low levels of resistance (<30 % development) were recorded on 84.6 % of farms and high levels (>30 % development) on 15.4 % of farms. No resistance to IVM was recorded on 38.1 % of farms. Multi-drug resistance was detected on five farms out of 13 (38.5 %) using both classes of drugs.ConclusionsThe present study demonstrates the existence of AR to BZ and ML on Lithuanian sheep farms thus confirming results in a previous in vivo study. Cases of multi-drug resistance were recorded in the present study and require further consideration. An appropriate strategy for anthelmintic treatment, measures to prevent gastrointestinal nematode infection and a better understanding of the management practices associated with resistance may slow down further development of AR.

English

The prevalence of anthelmintic resistance and the consumer demand for alternative farming systems that limit the use of chemical anthelmintics has made the search for alternative gastrointestinal nematode parasites control methods crucial. Traditional medicinal/herbal plants can offer an alternative to the reliance on chemical anthelmintic drugs. This study evaluates the efficacy of crude aqueous extracts of Tephrosia vogelii Hook., Tephrosia villosa Pers., and Carica papaya Linn. leaves and Carica papaya Linn. seeds against gastrointestinal nematodes using in vitro egg hatch and larval development inhibition assays. Rectal faecal samples from sheep were subjected to parasitological examination for faecal egg counts (FEC) using the McMaster counting technique. 100 g of dried and poultice aqueous leaf extract of T. vogelii, T. villosa, C. papaya leaves and seeds was blended into liquefaction in 200 ml of distilled water then boiled at 90-100°C for 1 h and cooled. Levamisol and distilled water were used as positive and negative control in the bioassay. Egg hatch assay revealed more than 95.8% reduction in egg hatch at concentration of 500 mg/ml for dried and poultice paste of T. vogelii leaves and C. papaya seeds. Larval development inhibition assay results showed that both dried and poultice paste of T. vogelii leaves and C. papaya seeds extract yielded more than 98% inhibition at a concentration of 500 mg/ml. Based on the LD50 dried extract of C. papaya seeds was most potent extracts for the inhibition of both egg hatching (49.94 mg/ml) and larval development (49.32 mg/ml). Both poultice and dried extract for all the plants showed significant and dose dependent egg and larval development inhibition. These findings indicate that the evaluated plants have potential anthelmintic effect and could provide viable alternatives for the control of gastrointestinal helminthes in ruminants. Key words: Aqueous extracts, Anthelmintic activity, Medicinal plants, Tephrosia vogelii, Tephrosia villosa, Carica papaya.

Prevalence and severity of anthelmintic resistance in ovine gastrointestinal nematodes in Australia (2009-2012).

This study aimed to provide an indication of the prevalence and severity of anthelmintic resistance (AR) in the Australian sheep industry by compiling the results of faecal worm egg count reduction tests (FECRTs). Government and private parasitology laboratories, pharmaceutical companies and veterinarians known to have conducted FECRTs were asked to provide results that conformed to Australian and New Zealand standard diagnostic procedures. Data were available from a total of 390 tests, with larval differentiation conducted in 222 cases. Pooled results from all states for the macrocyclic lactone (ML) class showed a lower prevalence of AR against combined species for moxidectin (54%) compared with abamectin (77%) and ivermectin (87%). Analysis by state revealed higher levels of ML-resistant Teladorsagia sp. in Tasmania and Western Australia than in other states and ML-resistant Haemonchus sp. was more frequently detected in New South Wales. This compilation of results of FECRTs conducted by Australian parasitology laboratories in 2009-12 showed widespread AR of the common sheep nematodes (Teladorsagia, Trichostrongylus and Haemonchus) to all broad-spectrum anthelmintics, with the exception of monepantel, whether used singly or in combination.

Anthelmintic resistance in Northern Ireland (I): Prevalence of resistance in ovine gastrointestinal nematodes, as determined through faecal egg count reduction testing

The prevalence of anthelmintic resistance in Northern Ireland sheep flocks was evaluated between July and October 2011. Sampling kits were sent to 172 flock owners and returns were received from 91. Within this survey population, 27 flock owners used benzimidazole products, 10 used levamisole products, 15 used avermectin products, 26 used milbemycin products and 4 flock owners used the amino acetonitrile derivative, Monepantel. The remaining 9 flock owners used combination drenches (broad spectrum wormer plus fasciolicide). However, 15 sets of samples were ineligible for faecal egg count reduction testing due to either too low an egg count or insufficient faecal volume.Treatment efficacy below 95%, indicating significant resistance, was detected in 81% (n=24) of flocks tested for benzimidazole resistance; in 14% (n=1) of flocks tested for levamisole resistance; and in 50% (n=7) and 62% (n=13) of flocks tested for avermectin and milbemycin resistance, respectively. Monepantel resistance was absent in all (n=3) flocks tested.Combination products (broad spectrum nematocide plus flukicide) containing levamisole were entirely effective, while treatment efficacy below 95% was detected in 60% (n=3) of flocks where the nematocide in the combination product was a benzimidazole. Where parasite identification based on coproculture was completed, Trichostrongylus was the dominant genus detected in all cases post-treatment, indicating the occurrence of anthelmintic-resistant Trichostrongylus spp. populations. Benzimidazole efficacy was highest in treating Trichostrongylus spp. (51%) and lowest when treating Teladorsagia spp. Levamisole was 100% effective in treating Cooperia, but ineffective (0%) in treating Trichostrongylus spp. Avermectin efficacy was highest when treating Haemonchus contortus (100%) and Teladorsagia spp. (73%), with a marginally lower efficacy against Trichostrongylus spp. (71%). Moxidectin efficacy was 33% against Trichostrongylus spp., 68% against Teladorsagia spp., 97% against Cooperia spp. and 100% against Haemonchus contortus infections.

The present status of anthelmintic resistance in gastrointestinal nematode infections of sheep in the northwest of Spain by in vivo and in vitro techniques

The aim of this study was to update the anthelmintic resistance (AR) status in sheep flocks infected by gastrointestinal nematodes (GIN) by means of in vivo and in vitro methods in the northwest of Spain. With this objective, we studied the efficacy of benzimidazoles (BZs), imidazothiazoles (IMs) and macrocyclic lactones (MLs), between 2006 and 2011. The sampling area was the Autonomous Community of Castilla y León but the majority of the flocks were located in the province of León. When the mean of GIN eggs per gram (epg) in faeces in a flock was higher than 150, the in vivo Faecal Egg Count Reduction Test (FECRT) was carried out. According to this test, AR was present in 63.6% of flocks, independently of the anthelmintic used. Flocks were mainly resistant to levamisole (LEV) (59.0%), followed by ivermectin (IVM) (27.3%) and albendazole (13.6%). Multidrug-resistance was also observed in 27.2% of the flocks, one of them being resistant to all anthelmintic families, including long-acting moxidectin. Comparing the evolution of AR in the last decade, between 1999 and 2011, the level of resistance to BZs and MLs was fairly constant throughout the time by means of the FECRT. However, the resistance to LEV increased significantly in only one decade since during the period 1999–2003 the percentage was 38.5%. The AR status was also measured by in vitro techniques in those flocks with an egg output lower than 150 epg. The prevalence of AR to BZs reached the 35.3% by Egg Hatch Assay. However, the level of resistance reported for LEV and IVM was 61.5% and 23.5%, respectively, by using the Larval Feeding Inhibition Assay, percentages very similar to those reported with the FECRT.

Research and implementation of novel approaches for the control of nematode parasites in Latin America and the Caribbean: Is there sufficient incentive for a greater extension effort?

The widespread presence of anthelmintic resistant gastrointestinal parasitic nematodes in outdoor ruminant production systems has driven the need to identify and develop novel approaches for the control of helminths with the intention to reduce the dependence on commercial anthelmintic drugs. This paper identifies what has been done in Latin America (LA) in terms of estimating the prevalence of anthelmintic resistance (AR) in ruminant production systems and the application of different novel approaches for the control of helminths in those systems, including research and extension activities. Firstly, the paucity of knowledge of AR is discussed in the context of different countries, as well as, the available economic resources for research, the technical infrastructure available and the practical difficulties of the production systems. It is then proposed that the search for novel approaches is not only driven by AR but also by the need for techniques that are feasible for application by resource-poor farmers in non-commercial subsistence farming systems. However, the commercial benefits of these approaches are often limited and so are funding inputs in most countries. The workers participating in the research into different novel approaches are identified as well as the different methods being studied in the different areas of LA according to their published results. In addition, the difficulties experienced during extension efforts to reach farmers and help them to adopt novel approaches for the control of parasitic nematodes in LA are discussed. The role of regulatory authorities in these countries is discussed as some methods of control might need an official confirmation of their efficacy as well as authorization prior to application as they may affect animal products (i.e. residues) and/or impose a hazard for animal welfare. The role of the pharmaceutical companies is also discussed.

Assessment of ivermectin efficacy against gastrointestinal nematodes in cattle on four Scottish farms

CURRENT control strategies targeted against gastrointestinal nematode infections in cattle rely heavily on the use of anthelmintics. Three drug classes are licensed for this purpose in the UK: benzimidazoles, imidazothiazoles...