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Muchiut S, Fiel C, Lirón JP, Lloberas M, Ceriani C, Lorenzo R, Riva E, Bernat G, Cardozo P, Fernández S, Steffan P. Population replacement of benzimidazole-resistant Haemonchus contortus with susceptible strains: evidence of changes in the resistance status. Parasitol Res 2022; 121:2623-2632. [PMID: 35779120 DOI: 10.1007/s00436-022-07582-9] [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: 03/25/2022] [Accepted: 06/20/2022] [Indexed: 11/28/2022]
Abstract
The spread of anthelmintic resistance (AR) in nematode populations threatens the viability of sheep production systems worldwide, and warrants the adoption of sensitive, practical, and standardized tests to detect AR. The aim of this study was to characterize the replacement of an Haemonchus contortus population resistant to benzimidazoles (BZDs) by a susceptible one, by means of both phenotypic and genotypic techniques. Phenotypic methods to assess BZD resistance included in vivo tests, such as the fecal egg count reduction test (FECRT), and in vitro tests, such as the egg hatch assay (EHA). Additionally, genotypification of polymorphisms associated with BZD resistance by sequencing a fragment of the isotype 1 β-tubulin gene was carried out. The initial, BZD-resistant population (initial Balcarce population) exhibited an egg count reduction (ECR) of 59.3%. Following refugium replacement, the final population (final Balcarce population) exhibited an ECR of 95.2%. For the initial Balcarce population, the median effective dose (ED50) for the EHA was 0.607 μg thiabendazole (TBZ)/mL, with a rate of eclosion at a discriminating dose (EDD) of 0.1 μg TBZ/mL of 76.73%. For the final Balcarce population, ED50 was 0.02 μg TBZ/mL, and EDD was 1.97%. In the initial population, 93% of the analyzed individuals exhibited genotypic combinations associated with BZD resistance (53% Phe/Phe167-Tyr/Tyr200, 37% Phe/Tyr167-Phe/Tyr200, and 3% Phe/Tyr167-Glu/Leu198). Conversely, no combination associated with resistance was found in individuals from the final population. All of the tests were useful for detecting AR to BZDs. The results from the genetic and phenotypical studies were consistent, and the resulting information greatly aided in interpreting the outcomes of the population replacement and the potential impact of this strategy on management of AR.
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Affiliation(s)
- Sebastián Muchiut
- Área de Parasitología y Enfermedades Parasitarias, Facultad de Ciencias Veterinarias, Universidad Nacional del Centro de la Provincia de Buenos Aires, Pje. Arroyo Seco s/n, B7000, Tandil, Argentina. .,Centro de Investigación Veterinaria de Tandil (CIVETAN) (UNCPBA-CICPBA-CONICET), Facultad de Ciencias Veterinarias, UNCPBA, Tandil, Argentina.
| | - César Fiel
- Área de Parasitología y Enfermedades Parasitarias, Facultad de Ciencias Veterinarias, Universidad Nacional del Centro de la Provincia de Buenos Aires, Pje. Arroyo Seco s/n, B7000, Tandil, Argentina.,Centro de Investigación Veterinaria de Tandil (CIVETAN) (UNCPBA-CICPBA-CONICET), Facultad de Ciencias Veterinarias, UNCPBA, Tandil, Argentina
| | - Juan Pedro Lirón
- Centro de Investigación Veterinaria de Tandil (CIVETAN) (UNCPBA-CICPBA-CONICET), Facultad de Ciencias Veterinarias, UNCPBA, Tandil, Argentina
| | - Mercedes Lloberas
- Instituto de Innovación para la Producción Agropecuaria y el Desarrollo Sostenible (IPADS Balcarce) EEA-INTA, Balcarce, Argentina
| | - Carolina Ceriani
- Centro de Investigación Veterinaria de Tandil (CIVETAN) (UNCPBA-CICPBA-CONICET), Facultad de Ciencias Veterinarias, UNCPBA, Tandil, Argentina.,Área de Virología, Facultad de Ciencias Veterinarias, UNCPBA, Pje. Arroyo Seco s/n, B7000, Tandil, Argentina
| | - Ramiro Lorenzo
- Centro de Investigación Veterinaria de Tandil (CIVETAN) (UNCPBA-CICPBA-CONICET), Facultad de Ciencias Veterinarias, UNCPBA, Tandil, Argentina
| | - Eliana Riva
- Área de Parasitología y Enfermedades Parasitarias, Facultad de Ciencias Veterinarias, Universidad Nacional del Centro de la Provincia de Buenos Aires, Pje. Arroyo Seco s/n, B7000, Tandil, Argentina.,Centro de Investigación Veterinaria de Tandil (CIVETAN) (UNCPBA-CICPBA-CONICET), Facultad de Ciencias Veterinarias, UNCPBA, Tandil, Argentina
| | - Gisele Bernat
- Área de Parasitología y Enfermedades Parasitarias, Facultad de Ciencias Veterinarias, Universidad Nacional del Centro de la Provincia de Buenos Aires, Pje. Arroyo Seco s/n, B7000, Tandil, Argentina.,Centro de Investigación Veterinaria de Tandil (CIVETAN) (UNCPBA-CICPBA-CONICET), Facultad de Ciencias Veterinarias, UNCPBA, Tandil, Argentina
| | - Patricia Cardozo
- Instituto de Innovación para la Producción Agropecuaria y el Desarrollo Sostenible (IPADS Balcarce) EEA-INTA, Balcarce, Argentina
| | - Silvina Fernández
- Área de Parasitología y Enfermedades Parasitarias, Facultad de Ciencias Veterinarias, Universidad Nacional del Centro de la Provincia de Buenos Aires, Pje. Arroyo Seco s/n, B7000, Tandil, Argentina.,Centro de Investigación Veterinaria de Tandil (CIVETAN) (UNCPBA-CICPBA-CONICET), Facultad de Ciencias Veterinarias, UNCPBA, Tandil, Argentina
| | - Pedro Steffan
- Área de Parasitología y Enfermedades Parasitarias, Facultad de Ciencias Veterinarias, Universidad Nacional del Centro de la Provincia de Buenos Aires, Pje. Arroyo Seco s/n, B7000, Tandil, Argentina.,Centro de Investigación Veterinaria de Tandil (CIVETAN) (UNCPBA-CICPBA-CONICET), Facultad de Ciencias Veterinarias, UNCPBA, Tandil, Argentina
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Sarah A, Khanal P, Holler LD, Holler SW, Hildreth MB. Extended effects of an aggressive spring-time anthelmintic treatment on Haemonchus contortus in sheep from a North America cold winter climate. Small Rumin Res 2022. [DOI: 10.1016/j.smallrumres.2021.106568] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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3
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George MM, Vatta AF, Howell SB, Storey BE, McCoy CJ, Wolstenholme AJ, Redman EM, Gilleard JS, Kaplan RM. Evaluation of changes in drug susceptibility and population genetic structure in Haemonchus contortus following worm replacement as a means to reverse the impact of multiple-anthelmintic resistance on a sheep farm. Int J Parasitol Drugs Drug Resist 2021; 15:134-143. [PMID: 33667995 PMCID: PMC7937535 DOI: 10.1016/j.ijpddr.2021.02.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2020] [Revised: 02/12/2021] [Accepted: 02/12/2021] [Indexed: 02/06/2023]
Abstract
A population of Haemonchus contortus that was highly resistant to benzimidazoles and avermectin/milbemycins with a subpopulation that was resistant to levamisole, was replaced with a susceptible laboratory isolate of H. contortus in a flock of sheep. The anthelmintic susceptibility and population genetics of the newly established population were evaluated for 3.5 years using in vivo, in vitro, and molecular methods. Successful replacement of the resistant population with a susceptible population was confirmed using phenotypic and genotypic measurements; larval development assay indicated full anthelmintic susceptibility; albendazole treatment yielded 98.7% fecal egg count reduction; pyrosequence genotyping of single nucleotide polymorphisms in positions 167 and 200 of the isotype-1 beta tubulin gene were present at 0.0 and 1.7%, respectively; microsatellite genotyping indicated the background haplotype was similar to the susceptible isolate; and haplotypes of the isotype-1 beta tubulin gene were similar to the susceptible isolate. To sustain the susceptibility of the new population, targeted selective treatment was implemented using albendazole. Surprisingly, within 1.5 years post-replacement, the population reverted to a resistant phenotype. Resistance to albendazole, ivermectin, and moxidectin was confirmed via fecal egg count reduction test, larval development assay, and pyrosequencing-based genotyping. Targeted selective treatment was then carried out using levamisole. However, within one year, resistance was detected to levamisole. Population genetics demonstrated a gradual change in the genetic structure of the population until the final population was similar to the initial resistant population. Genetic analyses showed a lack of diversity in the susceptible isolate, suggesting the susceptible isolate had reduced environmental fitness compared to the resistant population, providing a possible explanation for the rapid reversion to resistance. This work demonstrates the power of combining molecular, in vitro, and in vivo assays to study phenotypic and genotypic changes in a field population of nematodes, enabling improved insights into the epidemiology of anthelmintic resistance.
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Affiliation(s)
- Melissa M George
- Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, 501 D.W. Brooks Drive, Athens, GA, 30602, USA.
| | - Adriano F Vatta
- Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, 501 D.W. Brooks Drive, Athens, GA, 30602, USA
| | - Sue B Howell
- Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, 501 D.W. Brooks Drive, Athens, GA, 30602, USA
| | - Bob E Storey
- Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, 501 D.W. Brooks Drive, Athens, GA, 30602, USA
| | - Ciaran J McCoy
- Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, 501 D.W. Brooks Drive, Athens, GA, 30602, USA
| | - Adrian J Wolstenholme
- Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, 501 D.W. Brooks Drive, Athens, GA, 30602, USA
| | - Elizabeth M Redman
- Department of Comparative Biology and Experimental Medicine, Faculty of Veterinary Medicine, University of Calgary, 3330, Hospital Drive, Calgary, Alberta, T2N 4N1, Canada
| | - John S Gilleard
- Department of Comparative Biology and Experimental Medicine, Faculty of Veterinary Medicine, University of Calgary, 3330, Hospital Drive, Calgary, Alberta, T2N 4N1, Canada
| | - Ray M Kaplan
- Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, 501 D.W. Brooks Drive, Athens, GA, 30602, USA
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Muchiut SM, Fernández AS, Lloberas M, Steffan PE, Luque SE, Cardozo PA, Bernat GA, Riva E, Fiel CA. Recovery of fenbendazole efficacy on resistant Haemonchus contortus by management of parasite refugia and population replacement. Vet Parasitol 2019; 271:31-37. [PMID: 31303200 DOI: 10.1016/j.vetpar.2019.06.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Revised: 06/03/2019] [Accepted: 06/05/2019] [Indexed: 12/01/2022]
Abstract
The recovery of fenbendazole efficacy against Haemonchus contortus was attempted in a sheep intensive production system, using a strategy of population replacement in which the initial absolute efficacy of fenbendazole was 0%. The strategy was based on managing the parasite populations in refugia. Firstly, the resistant parasite population was reduced by means of anthelmintic treatments with efficacious drugs (Phase I), then a new, susceptible population was introduced in summer by way of artificially infected lambs at weaning, which were left to graze on the experimental pasture for eleven months (Phase II). Lastly, the impact of the replacement strategy, in terms of benzimidazole efficacy, was measured (Phase III). Faecal egg counts from permanent lambs and worm burdens as a measure of pasture infectivity from tracer lambs were determined throughout the study. During Phase I, faecal egg counts diminished from a peak of 2968 (300-7740) epg to 0 epg at the end, while adult worm burdens of H. contortus were reduced from 2625 (800-5100) to 0, which showed that the treatment strategy used in Phase I was effective in reducing the resistant population. These parameters also showed that good levels of pasture contamination and infectivity were achieved in Phase II, as faecal egg counts of up to 7275 (3240-13080) epg and adult worm burdens of 500 (200-800) H. contortus were reached. The absolute benzimidazole efficacy on H. contortus estimated at 16 months post-population replacement (Phase III) was 97.58%. The results lead to the conclusion that the recovery of anthelmintic efficacy of fenbendazole against a resistant population of H. contortus may be achieved by means of a strategy based on management of refugia and a subsequent introduction of a susceptible population. This strategy might be translatable to other resistant nematode genera.
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Affiliation(s)
- Sebastián Manuel Muchiut
- Área de Parasitología y Enfermedades Parasitarias, Centro de Investigación Veterinaria de Tandil (CIVETAN), Facultad de Ciencias Veterinarias, Universidad Nacional del Centro de la Provincia de Buenos Aires, Pje. Arroyo Seco s/n, B7000, Tandil, Argentina.
| | - Alicia Silvina Fernández
- Área de Parasitología y Enfermedades Parasitarias, Centro de Investigación Veterinaria de Tandil (CIVETAN), Facultad de Ciencias Veterinarias, Universidad Nacional del Centro de la Provincia de Buenos Aires, Pje. Arroyo Seco s/n, B7000, Tandil, Argentina; Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Argentina
| | - Mercedes Lloberas
- Laboratorio de Parasitología, Estación Experimental Agropecuaria - Instituto Nacional de Tecnología Agropecuaria (EEA-INTA), Balcarce, Argentina
| | - Pedro Eduardo Steffan
- Área de Parasitología y Enfermedades Parasitarias, Centro de Investigación Veterinaria de Tandil (CIVETAN), Facultad de Ciencias Veterinarias, Universidad Nacional del Centro de la Provincia de Buenos Aires, Pje. Arroyo Seco s/n, B7000, Tandil, Argentina
| | | | - Patricia Alejandra Cardozo
- Laboratorio de Parasitología, Estación Experimental Agropecuaria - Instituto Nacional de Tecnología Agropecuaria (EEA-INTA), Balcarce, Argentina
| | - Gisele Anahí Bernat
- Área de Parasitología y Enfermedades Parasitarias, Centro de Investigación Veterinaria de Tandil (CIVETAN), Facultad de Ciencias Veterinarias, Universidad Nacional del Centro de la Provincia de Buenos Aires, Pje. Arroyo Seco s/n, B7000, Tandil, Argentina; Comisión de Investigaciones Científicas de la Provincia de Buenos Aires (CICPBA), Argentina
| | - Eliana Riva
- Área de Parasitología y Enfermedades Parasitarias, Centro de Investigación Veterinaria de Tandil (CIVETAN), Facultad de Ciencias Veterinarias, Universidad Nacional del Centro de la Provincia de Buenos Aires, Pje. Arroyo Seco s/n, B7000, Tandil, Argentina; Comisión de Investigaciones Científicas de la Provincia de Buenos Aires (CICPBA), Argentina
| | - César Alberto Fiel
- Área de Parasitología y Enfermedades Parasitarias, Centro de Investigación Veterinaria de Tandil (CIVETAN), Facultad de Ciencias Veterinarias, Universidad Nacional del Centro de la Provincia de Buenos Aires, Pje. Arroyo Seco s/n, B7000, Tandil, Argentina
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5
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Muchiut SM, Fernández AS, Steffan PE, Riva E, Fiel CA. Anthelmintic resistance: Management of parasite refugia for Haemonchus contortus through the replacement of resistant with susceptible populations. Vet Parasitol 2018; 254:43-48. [DOI: 10.1016/j.vetpar.2018.03.004] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2017] [Revised: 03/01/2018] [Accepted: 03/03/2018] [Indexed: 11/17/2022]
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6
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Fiel C, Steffan P, Muchiut S, Fernández A, Bernat G, Riva E, Lloberas M, Almada A, Homer D. An attempt to replace an ivermectin-resistant Cooperia spp. population by a susceptible one on grazing pastures based on epidemiological principles and refugia management. Vet Parasitol 2017; 246:53-59. [DOI: 10.1016/j.vetpar.2017.08.026] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2017] [Revised: 08/23/2017] [Accepted: 08/24/2017] [Indexed: 11/17/2022]
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7
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Reduction of benzimidazole resistance in established Haemonchus contortus populations in goats using a single infection with a benzimidazole-susceptible isolate. J Helminthol 2014; 89:641-5. [PMID: 25226395 DOI: 10.1017/s0022149x14000674] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
An in vivo study in goats evaluated the effect of superimposing a single artificial infection with a benzimidazole (BZ)-susceptible Haemonchus contortus isolate upon established H. contortus populations of known BZ resistance by measuring the phenotypic BZ resistance of eggs collected from faeces before and after re-infection. Two H. contortus isolates, one benzimidazole resistant (BZR) and the other susceptible (BZS), were used to infect worm-free goats. Eight goats were initially infected with 2000 third-stage larvae (L3). In each case the inoculum contained a pre-determined proportion of the two isolates: 100% BZS (one goat), 75% BZS/25% BZR (two goats), 50% BZS/50% BZR (two goats), 25%BZS/75% BZR (two goats) and, finally, 100% BZR (one goat). The phenotypic BZ susceptibility of the H. contortus population formed in each goat after the first infection was determined on days 30 and 36 post-infection using an egg-hatch assay (EHA) that estimated the concentration of thiabendazole (TBZ) required for 95% inhibition of larval hatching (EC(95)) with a 95% confidence interval (95% CI). On day 49 post-infection, goats were re-infected with 2000 L3 of the BZS isolate alone. A second set of EHA bioassays was performed 28 days and 34 days after re-infection. The first infection protocol produced three populations classified as BZS (EC(95) 0.055-0.065 μg TBZ/ml) while four were categorized as BZR (EC(95) 0.122-0.344 μg TBZ/ml). The status of one other population could not be determined. After re-infection with BZS L3, the number of susceptible populations increased to six (EC(95) 0.043-0.074 μg TBZ/ml) while the remaining two were deemed resistant (EC(95) 0.114-119 μg TBZ/ml). Re-infection with BZS L3 thereby reduced the resistance status of most H. contortus populations.
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Sakamoto CAM, Lopes WDZ, Buzzulini C, Cruz BC, Felippelli G, de Lima RCA, dos Santos TR, Santana LF, de Mendonça RP, Soares VE, Henrique CH, da Costa AJ. Anthelmintic efficacy of an oral formulation of Aurixazol against gastrointestinal nematodes of naturally and experimentally infected sheep. Vet Parasitol 2013; 198:336-44. [DOI: 10.1016/j.vetpar.2013.09.008] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2013] [Revised: 09/09/2013] [Accepted: 09/13/2013] [Indexed: 11/26/2022]
Affiliation(s)
- Claudio Alessandro M Sakamoto
- Faculdade de Ciências Agrárias e Veterinárias, UNESP/CPPAR, Via de acesso prof. Paulo Donatto Castellani, s/n CEP:14884-900, Jaboticabal, São Paulo, Brazil
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Experimental and modeling approaches to evaluate different aspects of the efficacy of Targeted Selective Treatment of anthelmintics against sheep parasite nematodes. Vet Parasitol 2010; 171:254-62. [DOI: 10.1016/j.vetpar.2010.03.040] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2009] [Revised: 03/23/2010] [Accepted: 03/26/2010] [Indexed: 11/19/2022]
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The role of targeted selective treatments in the development of refugia-based approaches to the control of gastrointestinal nematodes of small ruminants. Vet Parasitol 2009; 164:3-11. [PMID: 19450930 DOI: 10.1016/j.vetpar.2009.04.015] [Citation(s) in RCA: 171] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Anthelmintic resistance is recognised as a major problem affecting small ruminant production worldwide and now threatens the sustainability of many of these systems. One method that has been proposed to prolong the efficacy of our current anthelmintics is the maintenance of a parasite population in refugia (unexposed to a drug) which will maintain the genes for susceptibility within the parasite population. Management strategies that employ refugia-based methods include targeted or strategically timed whole flock treatments, targeted selective treatments (TST), whereby only a proportion of the flock is treated at any one time, and the dilution of resistant with susceptible parasites. The ability to effectively target anthelmintic use relies on the identification of those animals that will most benefit from treatment. This review explains the concept of refugia, describes the role of refugia-based approaches to the management of anthelmintic resistance and reviews the markers that have been studied as indicators for TSTs as well as the implementation of refugia-based strategies. Recent results suggest that targeting anthelmintic treatment on the basis of anaemia, milk production and liveweight gain may offer a means of reducing anthelmintic usage whilst still maintaining animal performance.
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Webster LMI, Johnson PCD, Adam A, Mable BK, Keller LF. Absence of three known benzimidazole resistance mutations in Trichostrongylus tenuis, a nematode parasite of avian hosts. Vet Parasitol 2008; 158:302-10. [PMID: 19027239 DOI: 10.1016/j.vetpar.2008.09.029] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2008] [Revised: 08/22/2008] [Accepted: 09/15/2008] [Indexed: 11/16/2022]
Abstract
Benzimidazole (BZ) resistance is widespread in nematode parasites of livestock, but very little is known about the levels of BZ resistance in parasites with avian hosts. We investigated BZ resistance in Trichostrongylus tenuis, a nematode parasite of red grouse, Lagopus lagopus scotica. BZ anthelmintics had been in use in this system for up to 15 years, yet existing phenotypic evidence for resistance was inconclusive. We screened 1530 individuals from 14 populations at the principal beta-tubulin locus for BZ resistance (isotype 1, residue 200) and 940 of these at two further resistance sites (isotype 1, residue 167; isotype 2, residue 200). No BZ resistant genotypes were found. Alternative mechanisms may be responsible for BZ resistance in this system, or the method and timing of treatments may reduce selection pressure for BZ resistance by creating substantial refugia for susceptible genotypes.
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Affiliation(s)
- Lucy M I Webster
- Division of Environmental and Evolutionary Biology, Institute of Biological and Life Sciences, Graham Kerr Building, University of Glasgow, Glasgow G128QQ, UK.
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Kumsa B, Abebe G. Multiple anthelmintic resistance on a goat farm in Hawassa (southern Ethiopia). Trop Anim Health Prod 2008; 41:655-62. [PMID: 18791803 DOI: 10.1007/s11250-008-9237-z] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2008] [Accepted: 08/28/2008] [Indexed: 10/21/2022]
Abstract
A study was conducted to determine the presence of anthelmintic resistance on Hawassa University goat farm in southern Ethiopia. The 180 goats were stratified by age and sex and randomly assigned to treatment groups (albendazole, tetramisole and ivermectin and untreated control). Each treatment group included 15 goats and treatments were administered according to weight of each goat with 7.5 mg/kg bw albendazole, 22.5 mg/kg bw tetramisole and 0.2 mg/kg bw ivermectin dose rates recommended by scientists. Faecal samples were collected on day 0 before treatment, and again on day 12 post treatment. Efficacy of all the drugs was assessed on day 12 post treatment by faecal egg count reduction test (FECRT). Multiple anthelmintic resistance in Haemonchus spp. against albendazole, tetramisole and ivermectin was recorded in all age categories of the goats. Likewise, Trichostrongylus/Teladorsagia spp. showed resistance against ivermectin. Coprocultures from all pre- and post-treatments revealed the predominance of Haemonchus spp. Resistance against anthelmintics is attributed to the high frequency of treatment and low dosage of treatment practices on the farm. Large scale studies, however, are needed to assess the current status of anthelmintic resistance against the most commonly used anthelmintics in different agroecology, species of animals and management systems in Ethiopia.
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Affiliation(s)
- Bersissa Kumsa
- Department of Parasitology, Faculty of Veterinary Medicine, Addis Ababa University, Debre Zeit, Ethiopia.
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