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Niciura SCM, Sanches GM. Machine learning prediction of multiple anthelmintic resistance and gastrointestinal nematode control in sheep flocks. REVISTA BRASILEIRA DE PARASITOLOGIA VETERINARIA = BRAZILIAN JOURNAL OF VETERINARY PARASITOLOGY : ORGAO OFICIAL DO COLEGIO BRASILEIRO DE PARASITOLOGIA VETERINARIA 2024; 33:e019023. [PMID: 38511818 PMCID: PMC10954252 DOI: 10.1590/s1984-29612024014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2023] [Accepted: 01/18/2024] [Indexed: 03/22/2024]
Abstract
The high prevalence of Haemonchus contortus and its anthelmintic resistance have affected sheep production worldwide. Machine learning approaches are able to investigate the complex relationships among the factors involved in resistance. Classification trees were built to predict multidrug resistance from 36 management practices in 27 sheep flocks. Resistance to five anthelmintics was assessed using a fecal egg count reduction test (FECRT), and 20 flocks with FECRT < 80% for four or five anthelmintics were considered resistant. The data were randomly split into training (75%) and test (25%) sets, resampled 1,000 times, and the classification trees were generated for the training data. Of the 1,000 trees, 24 (2.4%) showed 100% accuracy, sensitivity, and specificity in predicting a flock as resistant or susceptible for the test data. Forage species was a split common to all 24 trees, and the most frequent trees (12/24) were split by forage species, grazing pasture area, and fecal examination. The farming system, Suffolk sheep breed, and anthelmintic choice criteria were practices highlighted in the other trees. These management practices can be used to predict the anthelmintic resistance status and guide measures for gastrointestinal nematode control in sheep flocks.
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Affiliation(s)
| | - Guilherme Martineli Sanches
- Departamento de Ciência do Solo, Escola Superior de Agricultura “Luiz de Queiroz” - ESALQ, Universidade de São Paulo - USP, Piracicaba, SP, Brasil
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Höglund J, Gustafsson K. Anthelmintic Treatment of Sheep and the Role of Parasites Refugia in a Local Context. Animals (Basel) 2023; 13:1960. [PMID: 37370470 DOI: 10.3390/ani13121960] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2023] [Revised: 06/08/2023] [Accepted: 06/09/2023] [Indexed: 06/29/2023] Open
Abstract
Gastrointestinal nematodes in grazing livestock are ubiquitous and can cause severe damage, leading to substantial losses in agricultural yields. It is undeniable that the integrated use of anthelmintics is often an essential component of successful intensive livestock management. However, anthelmintic resistance has been a major challenge for several decades, especially in pasture-based lamb production. Measures are therefore needed to reduce the risk and prevent further spread. In many countries with more extensive lamb production and pronounced resistance problems than in Sweden, the importance of keeping parasites in refugia is emphasised. To ensure that treatment is necessary, the Swedish model is based on deworming certain groups of ewes based on the parasitological results of a faecal examination and then releasing them with their lambs to safe pastures. This is intended to reduce the risk of infection, which ultimately reduces the number of subsequent treatments. Whether this preventive strategy in turn means an increased risk of resistance is debatable. In this review, we explain the importance of parasites in refugia and how they can help delay the development of resistance to anthelmintics. We also discuss how likely it is that our model contributes to an increase in resistance risk and whether there is reason to question whether it is a sustainable strategy in the long term.
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Affiliation(s)
- Johan Höglund
- Department of Biomedical Sciences and Veterinary Public Health, Section for Parasitology, Swedish University of Agricultural Sciences, 750 07 Uppsala, Sweden
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Gravdal M, Robertson LJ, Tysnes KR, Höglund J, Chartier C, Stuen S. Treatment against helminths in Norwegian sheep: a questionnaire-based survey. Parasite 2021; 28:63. [PMID: 34468310 PMCID: PMC10649840 DOI: 10.1051/parasite/2021061] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2021] [Accepted: 08/19/2021] [Indexed: 02/01/2023] Open
Abstract
A questionnaire was distributed to 5487 farmers throughout Norway in order to obtain information about management practices regarding helminth infections in sheep. In addition, the farmers' perceptions of helminths and anthelmintic efficacy were investigated. Most farmers (80%) treated prophylactically against nematodes, and 24% also used prophylactic treatment against Fasciola hepatica. Overall, few farmers (11%) used parasitological analysis as a tool to assess the timing of treatment, but rather based it on other factors such as previous experience (70%). In the surveyed sheep flocks, the use of benzimidazoles was reduced from 2018 (52%) to 2019 (47%) (p < 0.01), whereas the use of macrocyclic lactones increased from 2017 (23%) to 2019 (36%) (p < 0.001). Poor anthelmintic efficacy was suspected by 10% of the farmers, and 11% reported that helminths were an increasing problem in their flocks. The majority of farmers (72%) considered their veterinarian as the most important advisor for treatment of parasites, but reported a high level of uncertainty regarding which parasites were present in their flocks, with unknown status most frequently reported for Haemonchus contortus (71.5%). This is probably related to the fact that very few farmers (15%) regularly test their animals for parasites. The present study provides up-to-date information on treatment practices for helminths in Norwegian sheep flocks.
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Affiliation(s)
- Maiken Gravdal
- Institute for Production Animal Clinical Science, Faculty of Veterinary Medicine, Norwegian University of Life Sciences Sandnes 4325 Norway
| | - Lucy J. Robertson
- Institute for Production Animal Clinical Science, Faculty of Veterinary Medicine, Norwegian University of Life Sciences Sandnes 4325 Norway
| | - Kristoffer R. Tysnes
- Institute for Production Animal Clinical Science, Faculty of Veterinary Medicine, Norwegian University of Life Sciences Sandnes 4325 Norway
| | - Johan Höglund
- Swedish University of Agricultural Sciences, Department of Veterinary Public Health, Section for Parasitology P.O. Box 7036 Uppsala Sweden
| | | | - Snorre Stuen
- Institute for Production Animal Clinical Science, Faculty of Veterinary Medicine, Norwegian University of Life Sciences Sandnes 4325 Norway
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Untersweg F, Ferner V, Wiedermann S, Göller M, Hörl-Rannegger M, Kaiser W, Joachim A, Rinaldi L, Krücken J, Hinney B. Multispecific resistance of sheep trichostrongylids in Austria. ACTA ACUST UNITED AC 2021; 28:50. [PMID: 34114948 PMCID: PMC8194391 DOI: 10.1051/parasite/2021048] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2020] [Accepted: 05/24/2021] [Indexed: 11/14/2022]
Abstract
Anthelmintic overuse and failure to implement methods preventing the development and spread of anthelmintic resistance (AR) have led to an alarming increase of resistant ovine trichostrongylids worldwide. The aim of the present study was to determine whether the routine anthelmintic treatment strategy was effective, to obtain insights into the frequency of AR in trichostrongylids of sheep in Austria, and to determine the presence of different trichostrongylid genera. On 30 sheep farms, the faecal egg count reduction test (FECRT) was performed with the Mini-FLOTAC technique in two consecutive studies. In study 1, only fenbendazole and moxidectin were tested, while different compounds and products were used in study 2. Overall, 33 treatment groups were formed: 11 groups were treated with benzimidazoles (fenbendazole and albendazole), 2 groups with avermectins (ivermectin, doramectin), 18 groups with moxidectin, and two groups with monepantel. Reduced efficacy was detected in 64%, 100%, 28% and 50% of these groups, respectively. The most frequently detected genus in larval cultures was Haemonchus, which had been barely detected in Austria previously, followed by Trichostrongylus. Multispecific resistance of trichostrongylids in Austria seems to be on the rise and H. contortus was detected unexpectedly frequently in comparison to previous studies. There is an urgent need to develop efficient communication strategies aimed at improving the engagement of farmers and veterinarians in sustainable parasite control.
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Affiliation(s)
- Florian Untersweg
- Institute of Parasitology, Department of Pathobiology, Vetmeduni Vienna, Veterinärplatz 1, 1210 Vienna, Austria
| | - Viktoria Ferner
- Institute of Parasitology, Department of Pathobiology, Vetmeduni Vienna, Veterinärplatz 1, 1210 Vienna, Austria
| | - Sandra Wiedermann
- Institute of Parasitology, Department of Pathobiology, Vetmeduni Vienna, Veterinärplatz 1, 1210 Vienna, Austria
| | - Marie Göller
- Institute of Parasitology, Department of Pathobiology, Vetmeduni Vienna, Veterinärplatz 1, 1210 Vienna, Austria
| | | | - Waltraud Kaiser
- Tierärztliche Praxisgemeinschaft Passail OG, 8162 Passail, Austria
| | - Anja Joachim
- Institute of Parasitology, Department of Pathobiology, Vetmeduni Vienna, Veterinärplatz 1, 1210 Vienna, Austria
| | - Laura Rinaldi
- Laboratory of Parasitology and Parasitic Diseases, Department of Veterinary Medicine and Animal Production, University of Naples Federico II, 80138 Naples, Italy
| | - Jürgen Krücken
- Institute for Parasitology and Tropical Veterinary Medicine, Freie Universität Berlin, 14163 Berlin, Germany
| | - Barbara Hinney
- Institute of Parasitology, Department of Pathobiology, Vetmeduni Vienna, Veterinärplatz 1, 1210 Vienna, Austria
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Williams EG, Brophy PM, Williams HW, Davies N, Jones RA. Gastrointestinal nematode control practices in ewes: Identification of factors associated with application of control methods known to influence anthelmintic resistance development. VETERINARY PARASITOLOGY- REGIONAL STUDIES AND REPORTS 2021; 24:100562. [PMID: 34024378 DOI: 10.1016/j.vprsr.2021.100562] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2021] [Revised: 03/17/2021] [Accepted: 03/28/2021] [Indexed: 11/25/2022]
Abstract
Gastrointestinal nematodes (GIN) negatively impact productivity and welfare in sheep globally and are estimated to cost the European sheep industry €157-477 million annually. GIN are mainly controlled by anthelmintic treatment, however, as anthelmintic resistance becomes prominent, the routine treatment of ewes against GIN has been questioned. A questionnaire survey of 383 sheep farmers in Great Britain was conducted to identify strategies currently used to control GIN infections in ewes. Ordinal and binary regression analysis were used to identify factors associated with use of practices known to influence anthelmintic resistance development, including number and timing of ewe GIN anthelmintic treatment, targeted selective treatment (TST) of ewes, drench and move of ewes and long-acting moxidectin treatment of periparturient ewes. Participating farmers treated their ewes against GIN 1.68 times per year on average, with 42.3% and 32.1% of participating farmers worming their ewes once or twice a year on average, respectively. 17.2% of participating farmers wormed their ewes more than twice a year, and 8.4% never worm their ewes. Participating farmers who devised GIN control strategies based on SCOPS guidelines treated their ewes significantly less per year (P < 0.001), whilst those determining treatment timing based on ewe DAG scores or the time of year treated their ewes significantly more frequently (P < 0.001). Farmers who devised GIN control strategies in conjunction with their vet had greater odds of using TST (P < 0.001), as well as farmers who determined flock treatment timing based on ewe condition (P = 0.027). The use of narrow spectrum flukicides was significantly associated with reduced number of annual ewe GIN anthelmintic treatments (P < 0.001), TST of ewes against GIN (P < 0.001) and the avoidance of moving ewes to clean pastures following GIN treatment (P < 0.001). The presence of sheep scab on a farm or in the area was significantly associated with increased annual GIN treatments for ewes (P = 0.002), not using TST strategies to control GIN in ewes (P < 0.001) and moving ewes to clean pasture after anthelmintic treatment, whilst using macrocyclic lactones treatments to prevent sheep scab was significantly associated with the treatment of periparturient ewes with long-acting moxidectin (P = 0.001). This research suggests that by encouraging the application of evidence based targeted or targeted selective treatment strategies, further interaction between farmers and veterinarians/SCOPS guidance, and the uptake of best practices for controlling liver fluke and sheep scab on farms, sustainable GIN control strategies can become the common practice in ewes.
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Affiliation(s)
- Eiry Gwenllian Williams
- Institute of Biological, Environmental and Rural Sciences (IBERS), Aberystwyth University, Penglais, Aberystwyth, Ceredigion SY23 3DA, UK
| | - Peter M Brophy
- Institute of Biological, Environmental and Rural Sciences (IBERS), Aberystwyth University, Penglais, Aberystwyth, Ceredigion SY23 3DA, UK
| | - Hefin Wyn Williams
- Institute of Biological, Environmental and Rural Sciences (IBERS), Aberystwyth University, Penglais, Aberystwyth, Ceredigion SY23 3DA, UK
| | - Nia Davies
- Hybu Cig Cymru, Tŷ Rheidol, Parc Merlin, Glanyrafon Industrial Estate, Aberystwyth, SY23 3FF., UK
| | - Rhys Aled Jones
- Institute of Biological, Environmental and Rural Sciences (IBERS), Aberystwyth University, Penglais, Aberystwyth, Ceredigion SY23 3DA, UK.
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Keegan JD, Good B, Hanrahan JP, Lynch C, de Waal T, Keane OM. Live weight as a basis for targeted selective treatment of lambs post-weaning. Vet Parasitol 2018; 258:8-13. [DOI: 10.1016/j.vetpar.2018.06.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2018] [Revised: 06/01/2018] [Accepted: 06/02/2018] [Indexed: 11/27/2022]
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Kenyon F, Hutchings F, Morgan-Davies C, van Dijk J, Bartley DJ. Worm Control in Livestock: Bringing Science to the Field. Trends Parasitol 2017. [PMID: 28647171 DOI: 10.1016/j.pt.2017.05.008] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
Parasitic roundworm infections are ubiquitous in grazing livestock. Chemical control through the frequent 'blanket' administration of anthelmintics (wormers) has been, and remains, the cornerstone in controlling these infections, but this practice is unsustainable. Alternative strategies are available but, even with the plethora of best practice advice available, have yet to be integrated into routine farming practice. This is probably due to a range of factors, including contradictory advice from different sources, changes to advice following increased scientific understanding, and top-down knowledge exchange patterns. In this article, we discuss the worm control options available, the translation of new best practice advice from science bench to field, and ideas for future work and directions.
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Which is the best phenotypic trait for use in a targeted selective treatment strategy for growing lambs in temperate climates? Vet Parasitol 2016; 226:174-88. [PMID: 27514904 DOI: 10.1016/j.vetpar.2016.07.010] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2016] [Revised: 07/02/2016] [Accepted: 07/08/2016] [Indexed: 11/22/2022]
Abstract
Targeted selective treatment (TST) requires the ability to identify the animals for which anthelmintic treatment will result in the greatest benefit to the entire flock. Various phenotypic traits have previously been suggested as determinant criteria for TST; however, the weight gain benefit and impact on anthelmintic efficacy for each determinant criterion is expected to be dependent upon the level of nematode challenge and the timing of anthelmintic treatment. A mathematical model was used to simulate a population of 10,000 parasitologically naïve Scottish Blackface lambs (with heritable variation in host-parasite interactions) grazing on medium-quality pasture (grazing density=30 lambs/ha, crude protein=140g/kg DM, metabolisable energy=10MJ/kg DM) with an initial larval contamination of 1000, 3000 or 5000 Teladorsagia circumcincta L3/kg DM. Anthelmintic drenches were administered to 0, 50 or 100% of the population on a single occasion. The day of anthelmintic treatment was independently modelled for every day within the 121day simulation. Where TST scenarios were simulated (50% treated), lambs were either chosen by random selection or according to highest faecal egg count (FEC, eggs/g DM faeces), lowest live weight (LW, kg) or lowest growth rate (kg/day). Average lamb empty body weight (kg) and the resistance (R) allele frequency amongst the parasite population on pasture were recorded at slaughter (day 121) for each scenario. Average weight gain benefit and increase in R allele frequency for each determinant criterion, level of initial larval contamination and day of anthelmintic treatment were calculated by comparison to a non-treated population. Determinant criteria were evaluated according to average weight gain benefit divided by increase in R allele frequency to determine the benefit per R. Whilst positive phenotypic correlations were predicted between worm burden and FEC; using LW as the determinant criterion provided the greatest benefit per R for all levels of initial larval contamination and day of anthelmintic treatment. Hence, LW was identified as the best determinant criterion for use in a TST regime. This study supports the use of TST strategies as benefit per R predictions for all determinant criteria were greater than those predicted for the 100% treatment group, representing an increased long-term productive benefit resulting from the maintenance of anthelmintic efficacy. Whilst not included in this study, the model could be extended to consider other parasite species and host breed parameters, variation in climatic influences on larval availability and grass growth, repeated anthelmintic treatments and variable proportional flock treatments.
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Kearney PE, Murray PJ, Hoy JM, Hohenhaus M, Kotze A. The 'Toolbox' of strategies for managing Haemonchus contortus in goats: What's in and what's out. Vet Parasitol 2016; 220:93-107. [PMID: 26995728 DOI: 10.1016/j.vetpar.2016.02.028] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2015] [Revised: 02/19/2016] [Accepted: 02/25/2016] [Indexed: 10/22/2022]
Abstract
A dynamic and innovative approach to managing the blood-consuming nematode Haemonchus contortus in goats is critical to crack dependence on veterinary anthelmintics. H. contortus management strategies have been the subject of intense research for decades, and must be selected to create a tailored, individualized program for goat farms. Through the selection and combination of strategies from the Toolbox, an effective management program for H. contortus can be designed according to the unique conditions of each particular farm. This Toolbox investigates strategies including vaccines, bioactive forages, pasture/grazing management, behavioural management, natural immunity, FAMACHA, Refugia and strategic drenching, mineral/vitamin supplementation, copper Oxide Wire Particles (COWPs), breeding and selection/selecting resistant and resilient individuals, biological control and anthelmintic drugs. Barbervax(®), the ground-breaking Haemonchus vaccine developed and currently commercially available on a pilot scale for sheep, is prime for trialling in goats and would be an invaluable inclusion to this Toolbox. The specialised behaviours of goats, specifically their preferences to browse a variety of plants and accompanying physiological adaptations to the consumption of secondary compounds contained in browse, have long been unappreciated and thus overlooked as a valuable, sustainable strategy for Haemonchus management. These strategies are discussed in this review as to their value for inclusion into the 'Toolbox' currently, and the future implications of ongoing research for goat producers. Combining and manipulating strategies such as browsing behaviour, pasture management, bioactive forages and identifying and treating individual animals for haemonchosis, in addition to continuous evaluation of strategy effectiveness, is conducted using a model farm scenario. Selecting strategies from the Toolbox, with regard to their current availability, feasibility, economical cost and potential ease of implementation depending on the systems of production and their complementary nature, is the future of managing H. contortus in farmed goats internationally and maintaining the remaining efficacy of veterinary anthelmintics.
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Affiliation(s)
- P E Kearney
- The University of Queensland, Gatton Campus, QLD, Australia.
| | - P J Murray
- The University of Queensland, Gatton Campus, QLD, Australia
| | - J M Hoy
- The University of Queensland, Gatton Campus, QLD, Australia
| | - M Hohenhaus
- The University of Queensland, Gatton Campus, QLD, Australia
| | - A Kotze
- The University of Queensland, Gatton Campus, QLD, Australia; CSIRO, Bioscience Precinct, St Lucia, QLD, Australia
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Leathwick DM, Ganesh S, Waghorn TS. Evidence for reversion towards anthelmintic susceptibility in Teladorsagia circumcincta in response to resistance management programmes. INTERNATIONAL JOURNAL FOR PARASITOLOGY-DRUGS AND DRUG RESISTANCE 2015; 5:9-15. [PMID: 25941625 PMCID: PMC4412914 DOI: 10.1016/j.ijpddr.2015.01.001] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/13/2014] [Revised: 01/28/2015] [Accepted: 01/30/2015] [Indexed: 10/28/2022]
Abstract
Maintaining production and economic viability in the face of resistance to multiple anthelmintic actives is a challenge for farmers in many countries. In this situation, most farmers in New Zealand rely on the use of combination products, containing multiple actives with similar spectra of activity, in order to maintain control. However, there are concerns that use of combinations, once resistance has already developed to the individual actives, could rapidly lead to complete failure of all actives. This study followed seven farms, previously diagnosed with resistance to at least two classes of anthelmintic, which were implementing a tailored programme of 'best practice parasite management'. The aim was to ascertain whether the programmes, which included the almost exclusive use of combination anthelmintics, were able to prevent resistance from developing further. Strategies implemented on each farm varied, but had consistent underlying principles i.e. to avoid over-use of anthelmintics; to minimise parasite challenge to susceptible stock; to maintain refugia of susceptibility and to ensure that only effective anthelmintics were used. Annual faecal egg count reduction tests (FECRT) were undertaken in lambs on all farms to monitor anthelmintic efficacy over 5 years. The efficacy of albendazole, ivermectin and levamisole was calculated and the changes in efficacy against Teladorsagia circumcincta assessed. Overall, there was a significant improvement in the effectiveness of both levamisole and ivermectin against T. circumcincta, and a positive but non-significant trend in efficacy of albendazole, i.e. there was evidence for reversion towards susceptibility. Hence, the almost exclusive use of combination anthelmintics, integrated with other resistance management strategies, did not result in further resistance development despite all farms exhibiting resistance to multiple actives at the outset. What-is-more, the measured increases in anthelmintic efficacy suggests that adoption of best practice management strategies may extend the useful life of anthelmintics even after resistance has been diagnosed.
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Affiliation(s)
- Dave M Leathwick
- AgResearch Grasslands, private Bag 11008, Palmerston North, New Zealand
| | - Siva Ganesh
- AgResearch Grasslands, private Bag 11008, Palmerston North, New Zealand
| | - Tania S Waghorn
- AgResearch Grasslands, private Bag 11008, Palmerston North, New Zealand
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Morrison AA, Mitchell S, Mearns R, Richards I, Matthews JB, Bartley DJ. Phenotypic and genotypic analysis of benzimidazole resistance in the ovine parasite Nematodirus battus. Vet Res 2014; 45:116. [PMID: 25487605 PMCID: PMC4334412 DOI: 10.1186/s13567-014-0116-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2014] [Accepted: 10/24/2014] [Indexed: 11/29/2022] Open
Abstract
Benzimidazole resistance is common amongst many ovine trichostrongylid nematodes species globally. Although anthelmintics have been used for over half a century in some areas of the world for the control of Nematodirus battus, resistance has never been detected. Veterinary investigations conducted in 2010 demonstrated reduced efficacy in a flock that had been treated previously with fenbendazole (FBZ), suggesting probable resistance in N. battus. Infective larvae (L3; designated MNba2) were generated from the original material to conduct a controlled efficacy test (CET). Faecal egg counts showed an average of 37% reduction in the FBZ treated group 7 days post treatment compared to the untreated lambs. Average worm burden results showed no reduction after FBZ treatment compared to the untreated group (3850 and 3850 worms respectively). A molecular assay to assess the frequency of the commonly associated single nucleotide polymorphisms (SNP) in the β-tubulin isotype 1 gene, F200Y and E198A, was developed. Larval genotypes were predominantly homozygous resistant at codon 200 SNP, ranging from 56%-83% and remained stable at 70% for adult worm populations taken from treated and control lambs in the CET. Only susceptible genotypes were found at codon 198. The allele frequency for F200Y ranged between 80-83% in adult worms taken from the CET from treated and control lambs. The results confirmed initial findings and demonstrated the first report of FBZ resistance in N. battus whilst providing evidence that the P200 point mutation in the β-tubulin isotype 1 gene is a potential mechanism of resistance in the species.
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Affiliation(s)
- Alison A Morrison
- Moredun Research Institute, Pentlands Science Park, Bush Loan, Penicuik, EH26 0PZ, UK.
| | - Sian Mitchell
- Animal Health and Veterinary Laboratories Agency, Camarthen, Job's Well Road, Johnstown, Camarthen, SE31 3EZ, UK.
| | - Rebecca Mearns
- Animal Health and Veterinary Laboratories Agency, Penrith, Merrythought, Calthwaite, Penrith, Cumbria, CA11 9RR, UK.
| | - Iain Richards
- Care of Westmorland Veterinary Group, Riverside Business Park, Natland Road, Kendal, LA9 7SX, UK.
| | - Jacqui B Matthews
- Moredun Research Institute, Pentlands Science Park, Bush Loan, Penicuik, EH26 0PZ, UK.
| | - David J Bartley
- Moredun Research Institute, Pentlands Science Park, Bush Loan, Penicuik, EH26 0PZ, UK.
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Falzon LC, O'Neill TJ, Menzies PI, Peregrine AS, Jones-Bitton A, vanLeeuwen J, Mederos A. A systematic review and meta-analysis of factors associated with anthelmintic resistance in sheep. Prev Vet Med 2014; 117:388-402. [PMID: 25059197 DOI: 10.1016/j.prevetmed.2014.07.003] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2014] [Revised: 05/27/2014] [Accepted: 07/03/2014] [Indexed: 01/09/2023]
Abstract
BACKGROUND Anthelmintic drugs have been widely used in sheep as a cost-effective means for gastro-intestinal nematode (GIN) control. However, growing anthelmintic resistance (AHR) has created a compelling need to identify evidence-based management recommendations that reduce the risk of further development and impact of AHR. OBJECTIVE To identify, critically assess, and synthesize available data from primary research on factors associated with AHR in sheep. METHODS Publications reporting original observational or experimental research on selected factors associated with AHR in sheep GINs and published after 1974, were identified through two processes. Three electronic databases (PubMed, Agricola, CAB) and Web of Science (a collection of databases) were searched for potentially relevant publications. Additional publications were identified through consultation with experts, manual search of references of included publications and conference proceedings, and information solicited from small ruminant practitioner list-serves. Two independent investigators screened abstracts for relevance. Relevant publications were assessed for risk of systematic bias. Where sufficient data were available, random-effects Meta-Analyses (MAs) were performed to estimate the pooled Odds Ratio (OR) and 95% Confidence Intervals (CIs) of AHR for factors reported in ≥2 publications. RESULTS Of the 1712 abstracts screened for eligibility, 131 were deemed relevant for full publication review. Thirty publications describing 25 individual studies (15 observational studies, 7 challenge trials, and 3 controlled trials) were included in the qualitative synthesis and assessed for systematic bias. Unclear (i.e. not reported, or unable to assess) or high risk of selection bias and confounding bias was found in 93% (14/15) and 60% (9/15) of the observational studies, respectively, while unclear risk of selection bias was identified in all of the trials. Ten independent studies were included in the quantitative synthesis, and MAs were performed for five factors. Only high frequency of treatment was a significant risk factor (OR=4.39; 95% CI=1.59, 12.14), while the remaining 4 variables were marginally significant: mixed-species grazing (OR=1.63; 95% CI=0.66, 4.07); flock size (OR=1.02; 95% CI=0.97, 1.07); use of long-acting drug formulations (OR=2.85; 95% CI=0.79, 10.24); and drench-and-shift pasture management (OR=4.08; 95% CI=0.75, 22.16). CONCLUSIONS While there is abundant literature on the topic of AHR in sheep GINs, few studies have explicitly investigated the association between putative risk or protective factors and AHR. Consequently, several of the current recommendations on parasite management are not evidence-based. Moreover, many of the studies included in this review had a high or unclear risk of systematic bias, highlighting the need to improve study design and/or reporting of future research carried out in this field.
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Affiliation(s)
- L C Falzon
- Veterinary Public Health Institute, Vetsuisse Faculty, University of Bern, Liebefeld, Bern, Switzerland.
| | - T J O'Neill
- Dalla Lana School of Public Health, University of Toronto, Toronto, ON, Canada
| | - P I Menzies
- Department of Population Medicine, Ontario Veterinary College, University of Guelph, Guelph, ON, Canada
| | - A S Peregrine
- Department of Pathobiology, Ontario Veterinary College, University of Guelph, Guelph, ON, Canada
| | - A Jones-Bitton
- Department of Population Medicine, Ontario Veterinary College, University of Guelph, Guelph, ON, Canada
| | - J vanLeeuwen
- Centre for Veterinary Epidemiological Research, Department of Health Management, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, PE, Canada
| | - A Mederos
- National Institute of Agricultural Research of Uruguay, Montevideo, Uruguay
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Bath G. The “BIG FIVE” – A South African perspective on sustainable holistic internal parasite management in sheep and goats. Small Rumin Res 2014. [DOI: 10.1016/j.smallrumres.2013.12.017] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Leathwick DM, Besier RB. The management of anthelmintic resistance in grazing ruminants in Australasia--strategies and experiences. Vet Parasitol 2013; 204:44-54. [PMID: 24439840 DOI: 10.1016/j.vetpar.2013.12.022] [Citation(s) in RCA: 82] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2013] [Revised: 11/18/2013] [Accepted: 12/20/2013] [Indexed: 10/25/2022]
Abstract
In many countries the presence of anthelmintic resistance in nematodes of small ruminants, and in some cases also in those infecting cattle and horses, has become the status quo rather than the exception. It is clear that consideration of anthelmintic resistance, and its management, should be an integral component of anthelmintic use regardless of country or host species. Many years of research into understanding the development and management of anthelmintic resistance in nematodes of small ruminants has resulted in an array of strategies for minimising selection for resistance and for dealing with it once it has developed. Importantly, many of these strategies are now supported by empirical science and some have been assessed and evaluated on commercial farms. In sheep the cost of resistance has been measured at about 10% of the value of the lamb at sale which means that losses due to undetected resistance far outweigh the cost of testing anthelmintic efficacy. Despite this many farmers still do not test for anthelmintic resistance on their farm. Many resistance management strategies have been developed and some of these have been tailored for specific environments and/or nematode species. However, in general, most strategies can be categorised as either; identify and mitigate high risk management practices, maintain an anthelmintic-susceptible population in refugia, choose the optimal anthelmintic (combinations and formulations), or prevent the introduction of resistant nematodes. Experiences with sheep farmers in both New Zealand and Australia indicate that acceptance and implementation of resistance management practices is relatively easy as long as the need to do so is clear and the recommended practices meet the farmer's criteria for practicality. A major difference between Australasia and many other countries is the availability and widespread acceptance of combination anthelmintics as a resistance management tool. The current situation in cattle and horses in many countries indicates a failure to learn the lessons from resistance development in small ruminants. The cattle and equine industries have, until quite recently, remained generally oblivious to the issue of anthelmintic resistance and the need to take pre-emptive action. In Australasia, as in other countries, a perception was held that resistance in cattle parasites would develop very slowly, if it developed at all. Such preconceptions are clearly incorrect and the challenge ahead for the cattle and equine industries will be to maximise the advantages for resistance management from the extensive body of research and experience gained in small ruminants.
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Affiliation(s)
- D M Leathwick
- AgResearch, Grasslands Research Centre, Private Bag 11008, Palmerston North 4442, New Zealand.
| | - R B Besier
- Department of Agriculture and Food Western Australia, 444 Albany Highway, Albany, WA 6330, Australia
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Animal health aspects of adaptation to climate change: beating the heat and parasites in a warming Europe. Animal 2013; 7 Suppl 2:333-45. [PMID: 23739475 DOI: 10.1017/s175173111300075x] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Weather patterns in northern European regions have changed noticeably over the past several decades, featuring warmer, wetter weather with more extreme events. The climate is projected to continue on this trajectory for the foreseeable future, even under the most modest warming scenarios. Such changes will have a significant impact on livestock farming, both directly through effects on the animals themselves, and indirectly through changing exposure to pests and pathogens. Adaptation options aimed at taking advantage of new opportunities and/or minimising the risks of negative impacts will, in themselves, have implications for animal health and welfare. In this review, we consider the potential consequences of future intensification of animal production, challenges associated with indoor and outdoor rearing of animals and aspects of animal transportation as key examples. We investigate the direct and indirect effects of climate change on the epidemiology of important livestock pathogens, with a particular focus on parasitic infections, and the likely animal health consequences associated with selected adaptation options. Finally, we attempt to identify key gaps in our knowledge and suggest future research priorities.
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A comparative study of the effects of four treatment regimes on ivermectin efficacy, body weight and pasture contamination in lambs naturally infected with gastrointestinal nematodes in Scotland. INTERNATIONAL JOURNAL FOR PARASITOLOGY-DRUGS AND DRUG RESISTANCE 2013; 3:77-84. [PMID: 24533296 DOI: 10.1016/j.ijpddr.2013.02.001] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2012] [Revised: 02/14/2013] [Accepted: 02/18/2013] [Indexed: 11/22/2022]
Abstract
Refugia-based drenching regimes have been widely recommended to slow development of anthelmintic resistance but there are few comparisons between different treatment approaches in the UK. The impact of four ivermectin treatment regimes on drug efficacy, lamb body weight and nematode contamination during a 154 day grazing season were evaluated in a consecutive five year field study. Regimes were whole-flock treatment every 4 weeks (NST), targeted selective treatment (TST) based on individual performance, strategic whole-flock treatments at pre-determined times (SPT) or whole-flock treatment when clinical signs were apparent (MT). Mean numbers of ivermectin drenches administered per season were 4.0, 1.8, 2.0 and 1.4 for NST, TST, SPT and MT groups, respectively. The mean anthelmintic efficacy (AE) for each treatment group was based on faecal egg count reduction post-treatment employing a bootstrap sampling based algorithm. Mean AE was 95-98% for all groups in 2006 and mean AE (95% confidence limits) for NST declined to 62% (55%, 68%) in 2010. In comparison, AE for TST, SPT and MT in 2010 were 86% (81%, 92%), 86% (83%, 90%) and 83% (78%, 88%), respectively. Body weight in TST and SPT was similar to NST in all years (p > 0.05), however MT lambs were lighter than NST in 2006-2008 (p ⩽ 0.04). Tracer lamb worm burdens was lowest in NST but was not significantly different between other groups. Overall, both the TST and SPT regimes appeared to maintain animal performance and conserve anthelmintic efficacy compared with a neo-suppressive anthelmintic treatment regime.
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Anthelmintic resistance in Northern Ireland (III): Uptake of ‘SCOPS’ (Sustainable Control of Parasites in Sheep) recommendations by sheep farmers. Vet Parasitol 2013; 193:179-84. [DOI: 10.1016/j.vetpar.2012.11.032] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2012] [Revised: 11/22/2012] [Accepted: 11/27/2012] [Indexed: 11/17/2022]
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Niciura SCM, Veríssimo CJ, Gromboni JGG, Rocha MIP, de Mello SS, Barbosa CMP, Chiebao DP, Cardoso D, Silva GS, Otsuk IP, Pereira JR, Ambrosio LA, Nardon RF, Ueno TEH, Molento MB. F200Y polymorphism in the β-tubulin gene in field isolates of Haemonchus contortus and risk factors of sheep flock management practices related to anthelmintic resistance. Vet Parasitol 2012; 190:608-12. [DOI: 10.1016/j.vetpar.2012.07.016] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2012] [Revised: 07/11/2012] [Accepted: 07/12/2012] [Indexed: 11/24/2022]
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Laurenson YCSM, Kyriazakis I, Forbes AB, Bishop SC. Exploration of the epidemiological consequences of resistance to gastro-intestinal parasitism and grazing management of sheep through a mathematical model. Vet Parasitol 2012; 189:238-49. [DOI: 10.1016/j.vetpar.2012.05.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2012] [Revised: 05/09/2012] [Accepted: 05/10/2012] [Indexed: 10/28/2022]
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Morgan E, van Dijk J. Climate and the epidemiology of gastrointestinal nematode infections of sheep in Europe. Vet Parasitol 2012; 189:8-14. [DOI: 10.1016/j.vetpar.2012.03.028] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Learmount J, Taylor M, Bartram D. A computer simulation study to evaluate resistance development with a derquantel–abamectin combination on UK sheep farms. Vet Parasitol 2012; 187:244-53. [DOI: 10.1016/j.vetpar.2011.12.033] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2011] [Revised: 12/20/2011] [Accepted: 12/29/2011] [Indexed: 10/14/2022]
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The role of combination anthelmintic formulations in the sustainable control of sheep nematodes. Vet Parasitol 2012; 186:151-8. [DOI: 10.1016/j.vetpar.2011.11.030] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2011] [Revised: 11/03/2011] [Accepted: 11/07/2011] [Indexed: 11/22/2022]
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Refugia-based strategies for sustainable worm control: factors affecting the acceptability to sheep and goat owners. Vet Parasitol 2011; 186:2-9. [PMID: 22197747 DOI: 10.1016/j.vetpar.2011.11.057] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Sustainable nematode management programs aim to minimise animal production loss and prevent parasitic disease, without increasing the level of anthelmintic resistance. Resistance management strategies are now largely based on the "refugia" concept, by which populations of nematodes not recently exposed to treatment are deliberately allowed to survive. Progeny from the unselected parasites provide a source of less-resistant worms which can dilute resistant worms surviving anthelmintics, and hence reduce the rate of resistance development. This can be achieved by either modifying strategic treatment regimens to ensure the survival of infective worm larvae on pasture, or by avoiding treatments to individual animals identified as best able to cope with parasites. These strategies include "targeted treatment" (based on estimates of worm-burdens) and "targeted selective treatment" (based on indications of parasitic effects). However, the departure from conventional anthelmintic approaches represents a major conceptual challenge to many livestock owners. Factors that may affect the wide adoption of refugia strategies include the increased risk of parasitism and production loss, the effectiveness of reducing the development of resistance, the practicality of implementation, and the direct effects on costs and labour efficiency. The acceptance of particular strategies is likely to vary considerably according to environmental effects, nematode species, animal production aims and resource availability. However, recent indications that comparatively small changes to present practices can provide substantial refugia benefits suggest that appropriate resistance management approaches can be developed for different situations.
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Domke AVM, Chartier C, Gjerde B, Leine N, Vatn S, Osterås O, Stuen S. Worm control practice against gastro-intestinal parasites in Norwegian sheep and goat flocks. Acta Vet Scand 2011; 53:29. [PMID: 21569497 PMCID: PMC3118134 DOI: 10.1186/1751-0147-53-29] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2011] [Accepted: 05/13/2011] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Anthelmintic treatment is the most common way of controlling nematode infections in ruminants. However, several countries have reported anthelmintic resistance (AR), representing a limitation for sustainable small ruminant production. The knowledge regarding worm control management represents a baseline to develop a guideline for preventing AR. The aim of the present study was therefore to improve our knowledge about the worm control practices in small ruminant flocks in Norway. METHODS A questionnaire survey regarding worm control practices was performed in small ruminant flocks in Norway. Flocks were selected from the three main areas of small ruminant farming, i.e. the coastal, inland and northern areas. A total of 825 questionnaires, comprising 587 sheep flocks (return rate of 51.3%) and 238 goat flocks (52.6%) were included. RESULTS The results indicated that visual appraisal of individual weight was the most common means of estimating the anthelmintic dose used in sheep (78.6%) and goat (85.1%) flocks. The mean yearly drenching rate in lambs and ewes were 2.5 ± 1.7 and 1.9 ± 1.1, respectively, whereas it was 1.0 (once a year) in goats. However, these figures were higher in sheep in the coastal area with a rate of 3.4 and 2.2 in lambs and ewes, respectively. Benzimidazoles were the predominant anthelmintic class used in sheep flocks (64.9% in 2007), whereas benzimidazoles and macrocyclic lactones were both equally used in dairy goat flocks. In the period of 2005-2007, 46.3% of the sheep flocks never changed the anthelmintic class. The dose and move strategy was practiced in 33.2% of the sheep flocks. CONCLUSIONS The present study showed that inaccurate weight calculation gives a risk of under-dosing in over 90% of the sheep and goat flocks in Norway. Taken together with a high treatment frequency in lambs, a lack of anthelmintic class rotation and the common use of a dose-and-move strategy, a real danger for development of anthelmintic resistance (AR) seems to exist in Norwegian sheep and goat flocks. This risk seems particularly high in coastal areas where high treatment frequencies in lambs were recorded.
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Affiliation(s)
- Atle V M Domke
- Norwegian School of Veterinary Science, Sandnes, Norway.
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Reynecke D, Van Wyk J, Gummow B, Dorny P, Boomker J. A stochastic model accommodating the FAMACHA© system for estimating worm burdens and associated risk factors in sheep naturally infected with Haemonchus contortus. Vet Parasitol 2011; 177:231-41. [DOI: 10.1016/j.vetpar.2011.01.042] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2009] [Revised: 01/14/2011] [Accepted: 01/18/2011] [Indexed: 10/18/2022]
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Woodgate RG, Besier RB. Sustainable use of anthelmintics in an Integrated Parasite Management Program for sheep nematodes. ANIMAL PRODUCTION SCIENCE 2010. [DOI: 10.1071/an10022] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Anthelmintic resistance is a major problem affecting sheep nematode control; however, chemical treatments will always be a likely routine part of any parasite control program. The present paper, with the aim of minimising the selection pressure for worsening anthelmintic resistance, outlines important practical and strategic aspects of planning the anthelmintic component of an integrated approach to sheep worm management.
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Leathwick DM, Hosking BC, Bisset SA, McKay CH. Managing anthelmintic resistance: Is it feasible in New Zealand to delay the emergence of resistance to a new anthelmintic class? N Z Vet J 2009; 57:181-92. [DOI: 10.1080/00480169.2009.36900] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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