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Campos KFD, Monteiro ALG, Pontarolo DV, Molento MB. Suppressive treatment with monepantel and the fast selection for phenotypically resistant trichostrongylids of sheep. Parasitology 2022:1-5. [PMID: 35241201 DOI: 10.1017/s003118202200018x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Gastrointestinal parasite control has been a major challenge to livestock due to the failure of anthelmintic treatments. Monepantel (MNT) was introduced in 2009 as an alternative treatment option showing a new mechanism of action against nematode parasites. To study the response of MNT in a suppressive regime, 45-Suffolk and White Dorper naturally infected sheep were divided into one of three groups, G1: control – with no treatment, G2: MNT at 2.5 mg kg−1 live weight (LW) PO every 30 days, and G3: MNT at 4.0 mg kgLW−1 PO every 30 days for 6 months. Every 15 days, the animals were individually weighed (body weight, BW) and checked for Famacha (FMC) and body condition score (BCS). The efficacy of MNT was evaluated weekly by fecal egg count (FEC) every month. FEC showed >97% efficacy at the start of the experiment, revealing a significant reduction for G2 (28%) and G3 (39%) in the following months. There was no treatment, BW or BCS effect between treatments; however, there was a period (P < 0.0001) and a treatment vs period interaction (P < 0.0001) for BW. The data revealed that MNT at a therapeutic and suppressive dose had a non-linear polynomial efficacy regression (R2) of 0.988 and 0.992, respectively. This original experiment demonstrates how short-interval and suppressive MNT treatments would rapidly select Haemonchus contortus, showing a fast susceptible-resistance phenotypic population replacement. Therefore, it is suggested that MNT might be carefully used in parasite control programmes alongside other management strategies (i.e. FMC, BCS) to reduce treatment frequency and the selection process for resistance.
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Affiliation(s)
- Karla Francisca Duarte Campos
- Department of Animal Science, Sheep and Goat Production and Research Center, Federal University of Paraná, UFPR, Curitiba, PR, Brazil
| | - Alda Lúcia Gomes Monteiro
- Department of Animal Science, Sheep and Goat Production and Research Center, Federal University of Paraná, UFPR, Curitiba, PR, Brazil
| | - Desiree Vera Pontarolo
- Laboratory of Veterinary Clinical Parasitology, Department of Veterinary Medicine, Federal University of Paraná, UFPR, Curitiba, PR, Brazil
| | - Marcelo Beltrão Molento
- Laboratory of Veterinary Clinical Parasitology, Department of Veterinary Medicine, Federal University of Paraná, UFPR, Curitiba, PR, Brazil
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Ptáček M, Kyriánová IA, Nápravníková J, Ducháček J, Husák T, Chay-Canul AJ, Zaragoza-Vera C, Cruz-Bacab L, Vadlejch J. Do Live Weight, Body Condition Score, Back Muscle or Back-Fat Reserves Create the Suspicion of Goats Infected with Eimeria or Trichostrongylids? Animals (Basel) 2021; 11:3591. [PMID: 34944366 PMCID: PMC8698025 DOI: 10.3390/ani11123591] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2021] [Revised: 12/10/2021] [Accepted: 12/15/2021] [Indexed: 11/16/2022] Open
Abstract
Thirty goats of the breeds Czech Brown Shorthaired and Czech White Shorthaired and their crosses were randomly selected from a flock at a farm in the Czech Republic. All animals were monitored for one year at monthly intervals for their nutritional status (live weight, LW; body-condition score, BCS; depth of musculus longissimus thoracis et lumborum, MLTL; back-fat thickness, BT) and infection intensity with Eimeria sp. (EIM) and strongylid nematodes (STR). Regression-correlation analysis showed a possible interrelation of BCS with EIM infection. Analysis of muscle and fat reserves indicated that BT was better than MLTL in identifying EIM infection. Goat nutritional status was not significantly correlated with STR infection. A linear tendency (p = 0.092), however, was detected for the response of MLTL to STR infection. Results of this study indicated theoretical use of BCS for Eimeria identification and suggested some perspective of BCS for targeting animals infected by strongylid nematode. Validity of our results, however, was limited by number of observed animals managed under specific breeding conditions.
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Affiliation(s)
- Martin Ptáček
- Department of Animal Science, Faculty of Agrobiology, Food and Natural Resources, Czech University of Life Sciences Prague, 165 00 Praha-Suchdol, Czech Republic;
| | - Iveta Angela Kyriánová
- Department of Zoology and Fisheries, Faculty of Agrobiology, Food and Natural Resources, Czech University of Life Sciences Prague, 165 00 Praha-Suchdol, Czech Republic; (I.A.K.); (J.N.); (T.H.); (J.V.)
| | - Jana Nápravníková
- Department of Zoology and Fisheries, Faculty of Agrobiology, Food and Natural Resources, Czech University of Life Sciences Prague, 165 00 Praha-Suchdol, Czech Republic; (I.A.K.); (J.N.); (T.H.); (J.V.)
| | - Jaromír Ducháček
- Department of Animal Science, Faculty of Agrobiology, Food and Natural Resources, Czech University of Life Sciences Prague, 165 00 Praha-Suchdol, Czech Republic;
| | - Tomáš Husák
- Department of Zoology and Fisheries, Faculty of Agrobiology, Food and Natural Resources, Czech University of Life Sciences Prague, 165 00 Praha-Suchdol, Czech Republic; (I.A.K.); (J.N.); (T.H.); (J.V.)
| | - Alfonso J. Chay-Canul
- División Académica de Ciencias Agropecuarias, Universidad Juárez Autónoma de Tabasco, Villahermosa 86280, Tabasco, Mexico; (A.J.C.-C.); (C.Z.-V.); (L.C.-B.)
| | - Claudia Zaragoza-Vera
- División Académica de Ciencias Agropecuarias, Universidad Juárez Autónoma de Tabasco, Villahermosa 86280, Tabasco, Mexico; (A.J.C.-C.); (C.Z.-V.); (L.C.-B.)
| | - Luis Cruz-Bacab
- División Académica de Ciencias Agropecuarias, Universidad Juárez Autónoma de Tabasco, Villahermosa 86280, Tabasco, Mexico; (A.J.C.-C.); (C.Z.-V.); (L.C.-B.)
| | - Jaroslav Vadlejch
- Department of Zoology and Fisheries, Faculty of Agrobiology, Food and Natural Resources, Czech University of Life Sciences Prague, 165 00 Praha-Suchdol, Czech Republic; (I.A.K.); (J.N.); (T.H.); (J.V.)
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3
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Comparison of nonlinear mathematical models for lamb growth analysis. Trop Anim Health Prod 2021; 53:151. [PMID: 33538904 DOI: 10.1007/s11250-021-02597-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2020] [Accepted: 01/27/2021] [Indexed: 10/22/2022]
Abstract
With the objective to determine the best mathematical model that could demonstrate the relationship between body weight and age in crossbred sheep, and to evaluate its applicability in different farms, 9985 live weight records of 837 crossbred lambs of Texel, Ile de France, Suffolk, and Hampshire Down breeds were used. Brody, von Bertalanffy, Richards, Logistic, and Gompertz models were fitted to the weight data, which were compared based on adjusted R2, Syx%, chi-square, and Kolmogorov-Smirnov tests, as well as residual analysis. After selecting the model, lambs whose weights at different ages fell within, below, or above ±20% of the values predicted by the model were classified as medium, low, or high performance, respectively. To validate the model, we used a validation dataset comprising 2898 weights of lambs from 6 different farms. Based on statistical analysis and biological characteristics (sigmoid trend of weight over time, weight at birth, and standard deviation), the model that best represented the growth of the lambs was the Richards model. The percentage of lambs classified as below, within, and above the predicted values based on the model was highly similar for the original and validation data, which indicates that this model could be used in different farms. It was concluded that the Richards model best described the live weight growth of crossbred lambs and aided in classifying the lambs as high, medium, or low performance, thereby providing a complementary tool in management decision-making.
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Greer AW, Van Wyk JA, Hamie JC, Byaruhanga C, Kenyon F. Refugia-Based Strategies for Parasite Control in Livestock. Vet Clin North Am Food Anim Pract 2020; 36:31-43. [PMID: 32029187 DOI: 10.1016/j.cvfa.2019.11.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Refugia-based strategies are intended to help slow the development of anthelmintic resistance by providing a population of parasites that are not exposed to the treatment. Evidence from field studies is lacking. There is no single way to incorporate refugia into a parasite control program. There are many options available varying greatly in complexity and practicality, and none are suitable for all situations. Incorporating refugia into production systems typically requires a change in farmer mindset and greater input of time, labor, and/or technology, but is necessary to help preserve anthelmintic efficacy and promote sustainable animal production systems.
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Affiliation(s)
- Andrew W Greer
- Faculty of Agriculture and Life Sciences, Lincoln University, PO Box 85084, Christchurch, Canterbury 7647, New Zealand.
| | - Jan A Van Wyk
- Department of Veterinary Tropical Diseases, Faculty of Veterinary Science, University of Pretoria, P/Bag X04, Onderstepoort 0110, South Africa
| | - Joseph C Hamie
- Faculty of Agriculture and Life Sciences, Lincoln University, PO Box 85084, Christchurch, Canterbury 7647, New Zealand; Department of Agricultural Research Services, Lunyangwa Agricultural Research Station, PO Box 59, Choma Road, Mzuzu, Malawi
| | - Charles Byaruhanga
- Department of Veterinary Tropical Diseases, Faculty of Veterinary Science, University of Pretoria, P/Bag X04, Onderstepoort 0110, South Africa
| | - Fiona Kenyon
- Disease Control, Moredun Research Institute, Pentlands Science Park, Bush Loan, Penicuik, Midlothian EH26 0PZ, Scotland
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Sharpton TJ, Combrink L, Arnold HK, Gaulke CA, Kent M. Harnessing the gut microbiome in the fight against anthelminthic drug resistance. Curr Opin Microbiol 2020; 53:26-34. [PMID: 32114334 DOI: 10.1016/j.mib.2020.01.017] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2019] [Revised: 01/20/2020] [Accepted: 01/24/2020] [Indexed: 01/08/2023]
Abstract
Intestinal helminth parasites present major challenges to the welfare of humans and threaten the global food supply. While the discovery of anthelminthic drugs empowered our ability to offset these harms to society, the alarming rise of anthelminthic drug resistance mitigates contemporary efforts to treat and control intestinal helminthic infections. Fortunately, emerging research points to potential opportunities to combat anthelminthic drug resistance by harnessing the gut microbiome as a resource for discovering novel therapeutics and informing responsible drug administration. In this review, we highlight research that demonstrates this potential and provide rationale to support increased investment in efforts to uncover and translationally utilize knowledge about how the gut microbiome mediates intestinal helminthic infection and its outcomes.
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Affiliation(s)
- Thomas J Sharpton
- Department of Microbiology, Oregon State University, Corvallis, OR, 97331, USA; Department of Statistics, Oregon State University, Corvallis, OR, 97331, USA.
| | - Leigh Combrink
- Department of Microbiology, Oregon State University, Corvallis, OR, 97331, USA; Department of Biomedical Sciences, Oregon State University, Corvallis, OR, 97331, USA
| | - Holly K Arnold
- Department of Microbiology, Oregon State University, Corvallis, OR, 97331, USA; Carlson College of Veterinary Medicine, Oregon State University, Corvallis, OR, 97331, USA
| | | | - Michael Kent
- Department of Microbiology, Oregon State University, Corvallis, OR, 97331, USA; Department of Biomedical Sciences, Oregon State University, Corvallis, OR, 97331, USA
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Toscano JHB, Dos Santos IB, von Haehling MB, Giraldelo LA, Lopes LG, da Silva MH, Figueiredo A, Esteves SN, Chagas ACDS. Morada Nova sheep breed: Resistant or resilient to Haemonchus contortus infection? Vet Parasitol 2019; 276S:100019. [PMID: 32904615 PMCID: PMC7458387 DOI: 10.1016/j.vpoa.2019.100019] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2019] [Revised: 09/24/2019] [Accepted: 09/28/2019] [Indexed: 02/01/2023]
Abstract
Resistance against Haemonchus contortus was assessed in a Morada Nova flock. More than 88% of the lambs had PCV ≥ 24% even with high fecal egg counts (FEC). Only susceptible lambs had decreased live weight due to parasitism. More than 98% of the ewes had FEC below 4000 EPG. PCV of the ewes was not affected by H. contortus infection.
Morada Nova is a Brazilian hair sheep breed that is well adapted to the country’s mainly tropical climate and has good potential for meat and leather production. This breed is reported to be resistant to Haemonchus contortus infection, a highly desired characteristic due to the large impact of this parasite on sheep farming. Therefore, the present study aimed to characterize 287 recently weaned Morada Nova lambs and 123 ewes in relation to their resistance against H. contortus. The animals were dewormed and 15 days later artificially infected with 4000 H. contortus L3 (D0). They were individually monitored by periodic assessment of fecal egg count (FEC), packed cell volume (PCV), and live weight (LW). On D42, the sheep were again dewormed and submitted to a new parasitic challenge, following the same scheme. The animals of each category (lambs and ewes) were ranked according to individual mean FEC values, and classified as resistant (R, 20%), intermediate (I, 60%), or susceptible (S, 20%) to H. contortus infection. At weaning, high FEC were observed in all three phenotypes (P > 0.05). After the artificial infections, there was a significant difference (P < 0.05) among the three lamb phenotypes for the mean FEC (R < I < S), PCV (R > I > S), and LW (R = I > S). The infection levels (FEC) were negatively correlated with PCV (r = -0.66; P < 0.001), and LW (r = -0.30; P < 0.001). Despite this, the lambs were resilient, since more than 88% of these animals maintained the PCV above 24%, even when heavily infected. The importance of selective parasite control before weaning to reduce the negative impact on slaughter weight was evidenced, taking into account the high positive correlation between LW at weaning and final LW (r = 0.73; P < 0.001). The ewes, in turn, were strongly resistant to the parasite. Despite highly significant differences (P < 0.001) for mean FEC between phenotypes (R < I < S), 98% of the ewes maintained FEC below 4000 EPG. Their health was not affected, since PCV and LW did not differ between phenotypes, and these parameters were not significantly correlated with FEC (P > 0.05). With the phenotypic characterization performed here, it is possible to introduce procedures for parasite control in Morada Nova flocks, facilitating the target-selective treatment approach. The results of this study can also support improvement of meat production by the Morada Nova breed.
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Affiliation(s)
- João Henrique Barbosa Toscano
- Universidade Estadual Paulista Júlio de Mesquita Filho, Via de Acesso Prof. Paulo Donato Castellane, s/n, CEP 14884-900, Jaboticabal, SP, Brazil
| | - Isabella Barbosa Dos Santos
- Universidade Estadual Paulista Júlio de Mesquita Filho, Via de Acesso Prof. Paulo Donato Castellane, s/n, CEP 14884-900, Jaboticabal, SP, Brazil
| | - Marei Borsch von Haehling
- Universidade Estadual Paulista Júlio de Mesquita Filho, Via de Acesso Prof. Paulo Donato Castellane, s/n, CEP 14884-900, Jaboticabal, SP, Brazil
| | | | - Louyse Gabrielli Lopes
- Centro Universitário Central Paulista, Rua Miguel Petroni, 5111, CEP 13563-470, São Carlos, SP, Brazil
| | - Matheus Henrique da Silva
- Centro Universitário Central Paulista, Rua Miguel Petroni, 5111, CEP 13563-470, São Carlos, SP, Brazil
| | - Amanda Figueiredo
- Universidade Estadual Paulista Júlio de Mesquita Filho, Via de Acesso Prof. Paulo Donato Castellane, s/n, CEP 14884-900, Jaboticabal, SP, Brazil
| | - Sérgio Novita Esteves
- Embrapa Pecuária Sudeste, Rodovia Washington Luiz, Km 234 s/n, Fazenda Canchim, PO Box 339, CEP 13560-970, São Carlos, SP, Brazil
| | - Ana Carolina de Souza Chagas
- Embrapa Pecuária Sudeste, Rodovia Washington Luiz, Km 234 s/n, Fazenda Canchim, PO Box 339, CEP 13560-970, São Carlos, SP, Brazil
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Niewiadomska AM, Jayabalasingham B, Seidman JC, Willem L, Grenfell B, Spiro D, Viboud C. Population-level mathematical modeling of antimicrobial resistance: a systematic review. BMC Med 2019; 17:81. [PMID: 31014341 PMCID: PMC6480522 DOI: 10.1186/s12916-019-1314-9] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/17/2018] [Accepted: 03/25/2019] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND Mathematical transmission models are increasingly used to guide public health interventions for infectious diseases, particularly in the context of emerging pathogens; however, the contribution of modeling to the growing issue of antimicrobial resistance (AMR) remains unclear. Here, we systematically evaluate publications on population-level transmission models of AMR over a recent period (2006-2016) to gauge the state of research and identify gaps warranting further work. METHODS We performed a systematic literature search of relevant databases to identify transmission studies of AMR in viral, bacterial, and parasitic disease systems. We analyzed the temporal, geographic, and subject matter trends, described the predominant medical and behavioral interventions studied, and identified central findings relating to key pathogens. RESULTS We identified 273 modeling studies; the majority of which (> 70%) focused on 5 infectious diseases (human immunodeficiency virus (HIV), influenza virus, Plasmodium falciparum (malaria), Mycobacterium tuberculosis (TB), and methicillin-resistant Staphylococcus aureus (MRSA)). AMR studies of influenza and nosocomial pathogens were mainly set in industrialized nations, while HIV, TB, and malaria studies were heavily skewed towards developing countries. The majority of articles focused on AMR exclusively in humans (89%), either in community (58%) or healthcare (27%) settings. Model systems were largely compartmental (76%) and deterministic (66%). Only 43% of models were calibrated against epidemiological data, and few were validated against out-of-sample datasets (14%). The interventions considered were primarily the impact of different drug regimens, hygiene and infection control measures, screening, and diagnostics, while few studies addressed de novo resistance, vaccination strategies, economic, or behavioral changes to reduce antibiotic use in humans and animals. CONCLUSIONS The AMR modeling literature concentrates on disease systems where resistance has been long-established, while few studies pro-actively address recent rise in resistance in new pathogens or explore upstream strategies to reduce overall antibiotic consumption. Notable gaps include research on emerging resistance in Enterobacteriaceae and Neisseria gonorrhoeae; AMR transmission at the animal-human interface, particularly in agricultural and veterinary settings; transmission between hospitals and the community; the role of environmental factors in AMR transmission; and the potential of vaccines to combat AMR.
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Affiliation(s)
- Anna Maria Niewiadomska
- Division of International Epidemiology and Population Studies, Fogarty International Center, National Institutes of Health, Bethesda, USA
| | - Bamini Jayabalasingham
- Division of International Epidemiology and Population Studies, Fogarty International Center, National Institutes of Health, Bethesda, USA.,Present Address: Elsevier Inc., 230 Park Ave, Suite B00, New York, NY, 10169, USA
| | - Jessica C Seidman
- Division of International Epidemiology and Population Studies, Fogarty International Center, National Institutes of Health, Bethesda, USA
| | | | - Bryan Grenfell
- Division of International Epidemiology and Population Studies, Fogarty International Center, National Institutes of Health, Bethesda, USA.,Princeton University, Princeton, NJ, USA
| | - David Spiro
- Division of International Epidemiology and Population Studies, Fogarty International Center, National Institutes of Health, Bethesda, USA
| | - Cecile Viboud
- Division of International Epidemiology and Population Studies, Fogarty International Center, National Institutes of Health, Bethesda, USA.
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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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Jackson A, Ellis KA, McGoldrick J, Jonsson NN, Stear MJ, Forbes AB. Targeted anthelmintic treatment of parasitic gastroenteritis in first grazing season dairy calves using daily live weight gain as an indicator. Vet Parasitol 2017; 244:85-90. [PMID: 28917324 DOI: 10.1016/j.vetpar.2017.07.023] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2017] [Revised: 07/16/2017] [Accepted: 07/22/2017] [Indexed: 12/26/2022]
Abstract
Control of parasitic gastroenteritis in cattle is typically based on group treatments with anthelmintics, complemented by grazing management, where feasible. However, the almost inevitable evolution of resistance in parasitic nematodes to anthelmintics over time necessitates a reappraisal of their use in order to reduce selection pressure. One such approach is targeted selective treatment (TST), in which only individual animals that will most benefit are treated, rather than whole groups of at-risk cattle. This study was designed to assess the feasibility of implementing TST on three commercial farms, two of which were organic. A total of 104 first-grazing season (FGS), weaned dairy calves were enrolled in the study; each was weighed at monthly intervals from the start of the grazing season using scales or weigh-bands. At the same time dung and blood samples were collected in order to measure faecal egg counts (FEC) and plasma pepsinogen, respectively. A pre-determined threshhold weight gain of 0.75kg/day was used to determine those animals that would be treated; the anthelmintic used was eprinomectin. No individual animal received more than one treatment during the grazing season and all treatments were given in July or August; five animals were not treated at all because their growth rates consistently exceeded the threshold. Mean daily live weight gain over the entire grazing season ranged between 0.69 and 0.82kg/day on the three farms. Neither FEC nor pepsinogen values were significantly associated with live weight gain. Implementation of TST at farm level requires regular (monthly) handling of the animals and the use of weigh scales or tape, but can be integrated into farm management practices. This study has shown that acceptable growth rates can be achieved in FGS cattle with modest levels of treatment and correspondingly less exposure of their nematode populations to anthelmintics, which should mitigate selection pressure for resistance by increasing the size of the refugia in both hosts and pasture.
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Affiliation(s)
- A Jackson
- Scottish Centre for Production Animal Health and Food Safety, School of Veterinary Medicine, College of Veterinary and Life Sciences; University of Glasgow, Bearsden, Glasgow, G61 1Q, United Kingdom
| | - K A Ellis
- Scottish Centre for Production Animal Health and Food Safety, School of Veterinary Medicine, College of Veterinary and Life Sciences; University of Glasgow, Bearsden, Glasgow, G61 1Q, United Kingdom
| | - J McGoldrick
- Scottish Centre for Production Animal Health and Food Safety, School of Veterinary Medicine, College of Veterinary and Life Sciences; University of Glasgow, Bearsden, Glasgow, G61 1Q, United Kingdom
| | - N N Jonsson
- Institute of Biodiversity, Animal Health and Comparative Medicine, College of Veterinary and Life Sciences; University of Glasgow, Bearsden, Glasgow, G61 1Q, United Kingdom
| | - M J Stear
- La Trobe University, Animal, Plant and Soil Sciences, Melbourne, Australia
| | - A B Forbes
- Scottish Centre for Production Animal Health and Food Safety, School of Veterinary Medicine, College of Veterinary and Life Sciences; University of Glasgow, Bearsden, Glasgow, G61 1Q, United Kingdom.
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Berk Z, Laurenson YCSM, Forbes AB, Kyriazakis I. Modelling the impacts of pasture contamination and stocking rate for the development of targeted selective treatment strategies for Ostertagia ostertagi infection in calves. Vet Parasitol 2017; 238:82-86. [PMID: 28408216 PMCID: PMC5441451 DOI: 10.1016/j.vetpar.2017.03.025] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2017] [Revised: 03/23/2017] [Accepted: 03/27/2017] [Indexed: 02/01/2023]
Abstract
Stocking rate effect on design of targeted selective treatments (TST) was evaluated. Initial pasture contamination effect on the design of TST was evaluated. Different phenotypic traits and methods of selection for treatment were addressed. Benefit was assessed as weight gain/frequency of resistant alleles in helminths. Treatment according to threshold triggers of average daily gain was most beneficial.
A simulation study was carried out to assess whether variation in pasture contamination or stocking rate impact upon the optimal design of targeted selective treatment (TST) strategies. Two methods of TST implementation were considered: 1) treatment of a fixed percentage of a herd according to a given phenotypic trait, or 2) treatment of individuals that exceeded a threshold value for a given phenotypic trait. Four phenotypic traits, on which to base treatment were considered: 1) average daily bodyweight gain, 2) faecal egg count, 3) plasma pepsinogen, or 4) random selection. Each implementation method (fixed percentage or threshold treatment) and determinant criteria (phenotypic trait) was assessed in terms of benefit per R (BPR), the ratio of average benefit in weight gain to change in frequency of resistance alleles R (relative to an untreated population). The impact of pasture contamination on optimal TST strategy design was investigated by setting the initial pasture contamination to 100, 200 or 500 O. ostertagi L3/kg DM herbage; stocking rate was investigated at a low (3calves/ha), conventional (5 calves/ha) or high (7 calves/ha) stocking rates. When treating a fixed percentage of the herd, treatments according to plasma pepsinogen or random selection were identified as the most beneficial (i.e. resulted in the greatest BPR) for all levels of initial pasture contamination and all stocking rates. Conversely when treatments were administered according to threshold values ADG was most beneficial, and was identified as the best TST strategy (i.e. resulted in the greatest overall BPR) for all levels of initial pasture contamination and all stocking rates.
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Affiliation(s)
- Zoe Berk
- School of Agriculture Food and Rural Development, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK.
| | - Yan C S M Laurenson
- Animal Science, School of Environmental and Rural Science, University of New England, Armidale, New South Wales 2351, Australia
| | - Andrew B Forbes
- Scottish Centre for Production Animal Health and Food Safety, School of Veterinary Medicine, University of Glasgow, G61 1QH, Scotland, UK
| | - Ilias Kyriazakis
- School of Agriculture Food and Rural Development, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK
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11
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Modelling the consequences of targeted selective treatment strategies on performance and emergence of anthelmintic resistance amongst grazing calves. INTERNATIONAL JOURNAL FOR PARASITOLOGY-DRUGS AND DRUG RESISTANCE 2016; 6:258-271. [PMID: 27915061 PMCID: PMC5137182 DOI: 10.1016/j.ijpddr.2016.11.002] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/03/2016] [Revised: 11/03/2016] [Accepted: 11/07/2016] [Indexed: 11/20/2022]
Abstract
The development of anthelmintic resistance by helminths can be slowed by maintaining refugia on pasture or in untreated hosts. Targeted selective treatments (TST) may achieve this through the treatment only of individuals that would benefit most from anthelmintic, according to certain criteria. However TST consequences on cattle are uncertain, mainly due to difficulties of comparison between alternative strategies. We developed a mathematical model to compare: 1) the most 'beneficial' indicator for treatment selection and 2) the method of selection of calves exposed to Ostertagia ostertagi, i.e. treating a fixed percentage of the population with the lowest (or highest) indicator values versus treating individuals who exceed (or are below) a given indicator threshold. The indicators evaluated were average daily gain (ADG), faecal egg counts (FEC), plasma pepsinogen, combined FEC and plasma pepsinogen, versus random selection of individuals. Treatment success was assessed in terms of benefit per R (BPR), the ratio of average benefit in weight gain to change in frequency of resistance alleles R (relative to an untreated population). The optimal indicator in terms of BPR for fixed percentages of calves treated was plasma pepsinogen and the worst ADG; in the latter case treatment was applied to some individuals who were not in need of treatment. The reverse was found when calves were treated according to threshold criteria, with ADG being the best target indicator for treatment. This was also the most beneficial strategy overall, with a significantly higher BPR value than any other strategy, but its degree of success depended on the chosen threshold of the indicator. The study shows strong support for TST, with all strategies showing improvements on calves treated selectively, compared with whole-herd treatment at 3, 8, 13 weeks post-turnout. The developed model appeared capable of assessing the consequences of other TST strategies on calf populations.
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