1
|
Twumasi C, Cable J, Pepelyshev A. Mathematical Modelling of Parasite Dynamics: A Stochastic Simulation-Based Approach and Parameter Estimation via Modified Sequential-Type Approximate Bayesian Computation. Bull Math Biol 2024; 86:54. [PMID: 38598133 PMCID: PMC11006762 DOI: 10.1007/s11538-024-01281-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2023] [Accepted: 03/12/2024] [Indexed: 04/11/2024]
Abstract
The development of mathematical models for studying newly emerging and re-emerging infectious diseases has gained momentum due to global events. The gyrodactylid-fish system, like many host-parasite systems, serves as a valuable resource for ecological, evolutionary, and epidemiological investigations owing to its ease of experimental manipulation and long-term monitoring. Although this system has an existing individual-based model, it falls short in capturing information about species-specific microhabitat preferences and other biological details for different Gyrodactylus strains across diverse fish populations. This current study introduces a new individual-based stochastic simulation model that uses a hybrid τ -leaping algorithm to incorporate this essential data, enhancing our understanding of the complexity of the gyrodactylid-fish system. We compare the infection dynamics of three gyrodactylid strains across three host populations. A modified sequential-type approximate Bayesian computation (ABC) method, based on sequential Monte Carlo and sequential importance sampling, is developed. Additionally, we establish two penalised local-linear regression methods (based on L1 and L2 regularisations) for ABC post-processing analysis to fit our model using existing empirical data. With the support of experimental data and the fitted mathematical model, we address open biological questions for the first time and propose directions for future studies on the gyrodactylid-fish system. The adaptability of the mathematical model extends beyond the gyrodactylid-fish system to other host-parasite systems. Furthermore, the modified ABC methodologies provide efficient calibration for other multi-parameter models characterised by a large set of correlated or independent summary statistics.
Collapse
Affiliation(s)
- Clement Twumasi
- Nuffield Department of Medicine, University of Oxford, South Parks Road, Oxford, Oxfordshire, OX1 3SY, UK.
- School of Public Health, Imperial College London, 68 Wood Lane, London, Greater London, W12 7RH, UK.
- School of Mathematics, Cardiff University, Senghennydd Road, Cardiff, South Glamorgan, CF24 4AG, UK.
- School of Biosciences, Cardiff University, Sir Martin Evans Building, Cardiff, South Glamorgan, CF10 3AX, UK.
| | - Joanne Cable
- School of Biosciences, Cardiff University, Sir Martin Evans Building, Cardiff, South Glamorgan, CF10 3AX, UK
| | - Andrey Pepelyshev
- School of Mathematics, Cardiff University, Senghennydd Road, Cardiff, South Glamorgan, CF24 4AG, UK.
| |
Collapse
|
2
|
Sodi I, Martini M, Salari F, Perrucci S. Gastrointestinal Parasite Infections and Environmental Sustainability of the Ovine Sector: Eimeria spp. Infections and Nitrogen and Phosphorus Excretions in Dairy Sheep in Italy. Pathogens 2023; 12:1459. [PMID: 38133342 PMCID: PMC10746012 DOI: 10.3390/pathogens12121459] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2023] [Revised: 12/12/2023] [Accepted: 12/14/2023] [Indexed: 12/23/2023] Open
Abstract
In sheep farming, gastrointestinal parasites can be responsible for significant reductions in animal health and production. Nitrogen (N) and phosphorus (P) fecal excretions are the main determining factors for N2O emissions from manure management and may pose other environmental problems, such as the acidification and eutrophication of natural habitats. By using the Mini-FLOTAC technique on fecal samples from sheep of different ages and physiological status from 19 dairy sheep farms in Tuscany (central Italy), gastrointestinal parasite infections were evaluated. The animal N and P fecal contents were also assessed, with the aim of evaluating possible relationships between the identified parasites and the environmental sustainability of the examined farms. The obtained results showed that Eimeria spp. (86.36%) and gastrointestinal strongyle (54.55%) infections are prevalent in the examined farms. Moreover, significantly higher (p ≤ 0.05) P and Eimeria oocyst/gram-of-feces (OPG) values were found in fecal samples from animals < 1 year of age, and a significant (p ≤ 0.05) positive correlation resulted between N content and Eimeria OPG in fecal samples from animals in the first month of lactation. The findings from this study suggest for the first time that Eimeria spp. infections may have an impact on the environmental sustainability of sheep farming.
Collapse
Affiliation(s)
- Irene Sodi
- Department of Veterinary Sciences, University of Pisa, Viale delle Piagge 2, 56124 Pisa, Italy; (I.S.); (M.M.)
| | - Mina Martini
- Department of Veterinary Sciences, University of Pisa, Viale delle Piagge 2, 56124 Pisa, Italy; (I.S.); (M.M.)
- Research Center Nutraceuticals and Food for Health, University of Pisa, Via del Borghetto 80, 56124 Pisa, Italy
| | - Federica Salari
- Department of Veterinary Sciences, University of Pisa, Viale delle Piagge 2, 56124 Pisa, Italy; (I.S.); (M.M.)
| | - Stefania Perrucci
- Department of Veterinary Sciences, University of Pisa, Viale delle Piagge 2, 56124 Pisa, Italy; (I.S.); (M.M.)
- Research Center Nutraceuticals and Food for Health, University of Pisa, Via del Borghetto 80, 56124 Pisa, Italy
| |
Collapse
|
3
|
Albuquerque ACA, Almeida FA, Bassetto CC, Amarante AFT. Influence of targeted selective anthelmintic treatment on the productive performance of wool and hair lambs naturally infected with gastrointestinal nematodes in Brazil. Vet Res Commun 2023; 47:1207-1216. [PMID: 36595201 DOI: 10.1007/s11259-022-10061-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2022] [Accepted: 12/22/2022] [Indexed: 01/04/2023]
Abstract
Targeted selective treatment (TST) is an alternative method to reduce the use of anthelmintics and delay the development of resistant nematode populations. However, there is limited information on the actual effects of this type of treatment on livestock productivity. The objective of this study was to evaluate the production performance of Santa Ines (hair) and Ile de France (wool) lambs naturally infected with gastrointestinal nematodes (GIN) under TST based on packed cell volume (PCV) versus suppressive anthelmintic treatments. Thirty-eight lambs were divided into two treatment groups: Suppressive treatment, animals were drenched with monepantel every two weeks and TST, animals were treated with the same anthelmintic when they presented PCV ≤ 20%. Feces, blood, and weight were measured weekly to determine eggs per gram of feces, PCV, total plasma protein, and weight gain. After animals were slaughtered, carcasses were weighed to determine carcass yield. In the TST group, substantial productive losses of approximately 21.3% in the wool and 25.9% in the hair lambs were observed in body weight compared to their counterparts. Significant differences in hematological variables occurred over the experimental period, especially in the wool lambs under TST. Favorable environmental conditions enabled infective larvae to survive and thrive on pasture. Haemonchus contortus and intestinal nematodes were the most common parasites found in the Ile de France lambs and the Santa Ines lambs, respectively. Although TST prevented mortality, it did not prevent production losses. Both breeds showed a significant drop in production due to GIN parasitism.
Collapse
Affiliation(s)
- Ana Cláudia A Albuquerque
- School of Veterinary Medicine and Animal Science, UNESP - São Paulo State University, Botucatu, SP, Brazil.
- Institute of Biosciences, UNESP - São Paulo State University, Botucatu, SP, Brazil.
| | - Fabiana A Almeida
- Institute of Biosciences, UNESP - São Paulo State University, Botucatu, SP, Brazil
| | - Cesar C Bassetto
- Institute of Biosciences, UNESP - São Paulo State University, Botucatu, SP, Brazil
| | | |
Collapse
|
4
|
Filipe JAN, Kyriazakis I, McFarland C, Morgan ER. Novel epidemiological model of gastrointestinal nematode infection to assess grazing cattle resilience by integrating host growth, parasite, grass and environmental dynamics. Int J Parasitol 2023; 53:133-155. [PMID: 36706804 DOI: 10.1016/j.ijpara.2022.11.009] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2022] [Revised: 10/31/2022] [Accepted: 11/04/2022] [Indexed: 01/26/2023]
Abstract
Gastrointestinal nematode (GIN) infections are ubiquitous and often cause morbidity and reduced performance in livestock. Emerging anthelmintic resistance and increasing change in climate patterns require evaluation of alternatives to traditional treatment and management practices. Mathematical models of parasite transmission between hosts and the environment have contributed towards the design of appropriate control strategies in ruminants, but have yet to account for relationships between climate, infection pressure, immunity, resources, and growth. Here, we develop a new epidemiological model of GIN transmission in a herd of grazing cattle, including host tolerance (body weight and feed intake), parasite burden and acquisition of immunity, together with weather-dependent development of parasite free-living stages, and the influence of grass availability on parasite transmission. Dynamic host, parasite and environmental factors drive a variable rate of transmission. Using literature sources, the model was parametrised for Ostertagia ostertagi, the prevailing pathogenic GIN in grazing cattle populations in temperate climates. Model outputs were validated on published empirical studies from first season grazing cattle in northern Europe. These results show satisfactory qualitative and quantitative performance of the model; they also indicate the model may approximate the dynamics of grazing systems under co-infection by O. ostertagi and Cooperia oncophora, a second GIN species common in cattle. In addition, model behaviour was explored under illustrative anthelmintic treatment strategies, considering impacts on parasitological and performance variables. The model has potential for extension to explore altered infection dynamics as a result of management and climate change, and to optimise treatment strategies accordingly. As the first known mechanistic model to combine parasitic and free-living stages of GIN with host feed-intake and growth, it is well suited to predict complex system responses under non-stationary conditions. We discuss the implications, limitations and extensions of the model, and its potential to assist in the development of sustainable parasite control strategies.
Collapse
Affiliation(s)
- J A N Filipe
- Biomathematics & Statistics Scotland, Rowett Institute of Nutrition and Health, University of Aberdeen, AB25 2ZD, UK.
| | - I Kyriazakis
- Institute for Global Food Security, Queen's University Belfast, Biological Sciences, 19, Chlorine Gardens, BT9 5DL, UK
| | - C McFarland
- Institute for Global Food Security, Queen's University Belfast, Biological Sciences, 19, Chlorine Gardens, BT9 5DL, UK
| | - E R Morgan
- Institute for Global Food Security, Queen's University Belfast, Biological Sciences, 19, Chlorine Gardens, BT9 5DL, UK
| |
Collapse
|
5
|
Shanebeck KM, Lakemeyer J, Siebert U, Lehnert K. Novel infections of Corynosoma enhydri and Profilicollis sp. (Acanthocephala: Polymorphidae) identified in sea otters Enhydra lutris. Dis Aquat Organ 2020; 137:239-246. [PMID: 32132276 DOI: 10.3354/dao03442] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Infectious disease is a major cause of mortality for sea otters Enhydra lutris, a keystone species of continued concern for conservationists. Parasitic infection has long been identified as a cause of mortality in otters in both Alaska and California, USA. Corynosoma enhydri (Acanthocephala) is the only parasite that uses sea otters as its primary definitive host and is highly prevalent in otter populations; however, it is generally considered unimportant both pathologically and ecologically, although this assumption is based on limited empirical knowledge. Research has instead focused on Profilicollis infections (P. major, P. kenti, P. altmani) as a significant source of otter mortality due to associated enteritis and peritonitis, which are threats to otter health. Here we describe acanthocephalan infections in sea otters by Profilicollis spp. and C. enhydri, from a survey comparing C. enhydri infections between northern sea otters E. lutris kenyoni (n = 12) and southern sea otters E. lutris nereis (n = 19). We report a novel infection of C. enhydri in a pup approximately 1 mo of age, which shows that the early introduction to solid food at around 3 wk by their mothers may lead to subsequent infection via infected prey items. We also document the first 2 known cases of Profilicollis infection in northern sea otters, which may present an unknown threat to the Alaskan population, or may be an interesting example of accidental infection.
Collapse
Affiliation(s)
- Kyle M Shanebeck
- Institute for Terrestrial and Aquatic Wildlife Research, University of Veterinary Medicine Hannover Foundation, Werftstr. 6, 25761 Büsum, Germany
| | | | | | | |
Collapse
|
6
|
Burgunder J, Petrželková KJ, Modrý D, Kato A, Macintosh AJ. Fractal measures in activity patterns: Do gastrointestinal parasites affect the complexity of sheep behaviour? Appl Anim Behav Sci 2018; 205:44-53. [DOI: 10.1016/j.applanim.2018.05.014] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
|
7
|
Bhuiyan AA, Li J, Wu Z, Ni P, Adetula AA, Wang H, Zhang C, Tang X, Bhuyan AA, Zhao S, Du X. Exploring the Genetic Resistance to Gastrointestinal Nematodes Infection in Goat Using RNA-Sequencing. Int J Mol Sci 2017; 18:ijms18040751. [PMID: 28368324 PMCID: PMC5412336 DOI: 10.3390/ijms18040751] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2017] [Revised: 03/03/2017] [Accepted: 03/24/2017] [Indexed: 12/16/2022] Open
Abstract
Gastrointestinal nematodes (GINs) are one of the most economically important parasites of small ruminants and a major animal health concern in many regions of the world. However, the molecular mechanisms of the host response to GIN infections in goat are still little known. In this study, two genetically distinct goat populations, one relatively resistant and the other susceptible to GIN infections, were identified in Yichang goat and then four individuals in each group were chosen to compare mRNA expression profiles using RNA-seq. Field experiment showed lower worm burden, delayed and reduced egg production in the relatively resistant group than the susceptible group. The analysis of RNA-seq showed that 2369 genes, 1407 of which were up-regulated and 962 down-regulated, were significantly (p < 0.001) differentially expressed between these two groups. Functional annotation of the 298 genes more highly expressed in the resistant group yielded a total of 46 significant (p < 0.05) functional annotation clusters including 31 genes (9 in innate immunity, 13 in immunity, and 9 in innate immune response) related to immune biosynthetic process as well as transforming growth factor (TGF)-β, mitogen-activated protein kinase (MAPK), and cell adhesion molecules (CAMs) pathways. Our findings provide insights that are immediately relevant for the improvement of host resistance to GIN infections and which will make it possible to know the mechanisms underlying the resistance of goats to GIN infections.
Collapse
Affiliation(s)
- Ali Akbar Bhuiyan
- Key Laboratory of Agricultural Animal Genetics, Breeding and Reproduction, Ministry of Education, College of Animal Science and Veterinary Medicine, Huazhong Agricultural University, Wuhan 430070, China.
- Senior Scientific Officer, Bangladesh Livestock Research Institute, Savar, Dhaka-1341, Bangladesh.
| | - Jingjin Li
- Key Laboratory of Agricultural Animal Genetics, Breeding and Reproduction, Ministry of Education, College of Animal Science and Veterinary Medicine, Huazhong Agricultural University, Wuhan 430070, China.
| | - Zhenyang Wu
- Key Laboratory of Agricultural Animal Genetics, Breeding and Reproduction, Ministry of Education, College of Animal Science and Veterinary Medicine, Huazhong Agricultural University, Wuhan 430070, China.
| | - Pan Ni
- Key Laboratory of Agricultural Animal Genetics, Breeding and Reproduction, Ministry of Education, College of Animal Science and Veterinary Medicine, Huazhong Agricultural University, Wuhan 430070, China.
| | - Adeyinka Abiola Adetula
- Key Laboratory of Agricultural Animal Genetics, Breeding and Reproduction, Ministry of Education, College of Animal Science and Veterinary Medicine, Huazhong Agricultural University, Wuhan 430070, China.
| | - Haiyan Wang
- College of Informatics, Huazhong Agricultural University, Wuhan 430070, China.
| | - Cheng Zhang
- College of Informatics, Huazhong Agricultural University, Wuhan 430070, China.
| | - Xiaohui Tang
- College of Agricultural Animal Husbandry, Tibet University, Linzhi 850012, China.
| | - Anjuman Ara Bhuyan
- State Key Laboratory of Agricultural Microbiology, Ministry of Education, College of Animal Science and Veterinary Medicine, Huazhong Agricultural University, Wuhan 430070, China.
| | - Shuhong Zhao
- Key Laboratory of Agricultural Animal Genetics, Breeding and Reproduction, Ministry of Education, College of Animal Science and Veterinary Medicine, Huazhong Agricultural University, Wuhan 430070, China.
| | - Xiaoyong Du
- Key Laboratory of Agricultural Animal Genetics, Breeding and Reproduction, Ministry of Education, College of Animal Science and Veterinary Medicine, Huazhong Agricultural University, Wuhan 430070, China.
- College of Informatics, Huazhong Agricultural University, Wuhan 430070, China.
| |
Collapse
|
8
|
Verschave SH, Charlier J, Rose H, Claerebout E, Morgan ER. Cattle and Nematodes Under Global Change: Transmission Models as an Ally. Trends Parasitol 2016; 32:724-738. [DOI: 10.1016/j.pt.2016.04.018] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2016] [Revised: 04/28/2016] [Accepted: 04/29/2016] [Indexed: 12/17/2022]
|
9
|
Benavides MV, Sonstegard TS, Kemp S, Mugambi JM, Gibson JP, Baker RL, Hanotte O, Marshall K, Van Tassell C. Identification of novel loci associated with gastrointestinal parasite resistance in a Red Maasai x Dorper backcross population. PLoS One 2015; 10:e0122797. [PMID: 25867089 PMCID: PMC4395112 DOI: 10.1371/journal.pone.0122797] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2014] [Accepted: 02/21/2015] [Indexed: 12/14/2022] Open
Abstract
Gastrointestinal (GI) parasitic infection is the main health constraint for small ruminant production, causing loss of weight and/or death. Red Maasai sheep have adapted to a tropical environment where extreme parasite exposure is a constant, especially with highly pathogenic Haemonchus contortus. This breed has been reported to be resistant to gastrointestinal parasite infection, hence it is considered an invaluable resource to study associations between host genetics and resistance. The aim of this study was to identify polymorphisms strongly associated with host resistance in a double backcross population derived from Red Maasai and Dorper sheep using a SNP-based GWAS analysis. The animals that were genotyped represented the most resistant and susceptible individuals based on the tails of phenotypic distribution (10% each) for average faecal egg counts (AVFEC). AVFEC, packed cell volume (AVPCV), and live weight (AVLWT) were adjusted for fixed effects and co-variables, and an association analysis was run using EMMAX. Revised significance levels were calculated using 100,000 permutation tests. The top five significant SNP markers with - log10 p-values >3.794 were observed on five different chromosomes for AVFEC, and BLUPPf90/PostGSf90 results confirmed EMMAX significant regions for this trait. One of these regions included a cluster of significant SNP on chromosome (Chr) 6 not in linkage disequilibrium to each other. This genomic location contains annotated genes involved in cytokine signalling, haemostasis and mucus biosynthesis. Only one association detected on Chr 7 was significant for both AVPCV and AVLWT. The results generated here reveal candidate immune variants for genes involved in differential response to infection and provide additional SNP marker information that has potential to aid selection of resistance to gastrointestinal parasites in sheep of a similar genetic background to the double backcross population.
Collapse
Affiliation(s)
| | - Tad S. Sonstegard
- Animal Genomics & Improvement Laboratory, USDA/ARS/Beltsville Agricultural Research Center, Beltsville, MD, United States of America
| | - Stephen Kemp
- Animal Biosciences, The International Livestock Research Institute (ILRI), Nairobi, Kenya
| | - John M. Mugambi
- National Veterinary Research Centre, Kenya Agricultural Research Institute (KARI), Muguga, Kenya
| | - John P. Gibson
- Centre for Genetic Analysis and Applications, University of New England, Armidale, NSW, Australia
| | | | - Olivier Hanotte
- Medicine & Health Sciences, The University of Nottingham, Nottingham, United Kingdom
| | - Karen Marshall
- Animal Biosciences, The International Livestock Research Institute (ILRI), Nairobi, Kenya
| | - Curtis Van Tassell
- Animal Genomics & Improvement Laboratory, USDA/ARS/Beltsville Agricultural Research Center, Beltsville, MD, United States of America
| |
Collapse
|
10
|
Sweeny JP, Robertson ID, Ryan UM, Jacobson C, Woodgate RG. Impacts of naturally acquired protozoa and strongylid nematode infections on growth and faecal attributes in lambs. Vet Parasitol 2012; 184:298-308. [DOI: 10.1016/j.vetpar.2011.08.016] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2011] [Revised: 07/26/2011] [Accepted: 08/08/2011] [Indexed: 11/24/2022]
|
11
|
Chaparro M, Canziani G, Saumell C, Fiel C. Estimation of pasture infectivity according to weather conditions through a fuzzy parametrized model for the free-living stage of Ostertagia ostertagi. Ecol Modell 2011. [DOI: 10.1016/j.ecolmodel.2011.03.019] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
|
12
|
Singleton DR, Stear MJ, Matthews L. A mechanistic model of developing immunity to Teladorsagia circumcincta infection in lambs. Parasitology 2011; 138:322-32. [PMID: 20946694 DOI: 10.1017/S0031182010001289] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Acquired immunity influences the severity of parasitic disease, but modelling the effects of acquired immunity in helminth infections has proved challenging. This may be due to a lack of suitable immunological data, or to the perceived complexity of modelling the immune response. We have developed a model of T. circumcincta infection in domestic sheep that incorporates the effects of acquired immunity on parasite establishment and fecundity. A large data set from commercially managed populations of Scottish Blackface sheep was used, which included relationships between IgA activity and worm length, and between worm length and fecundity. Use was also made of a recently published meta-analysis of parasite establishment rates. This realistic but simple model of nematode infection emulates observed patterns of faecal egg counts. The end-of-season faecal egg counts are remarkably robust to perturbations in the majority of the parameters, possibly because of priming of the immune system early in the season, reducing parasite establishment and growth and, therefore, faecal egg counts. Lowering the amount of early infection leads to higher end-of-season egg counts. The periparturient rise in egg counts in ewes appears to have an important role in supplying infection for the priming of the immune response. This feedback in the immune priming suggests that nematode infections may be difficult to eliminate.
Collapse
|
13
|
van Dijk J, Sargison N, Kenyon F, Skuce P. Climate change and infectious disease: helminthological challenges to farmed ruminants in temperate regions. Animal 2010; 4:377-92. [DOI: 10.1017/s1751731109990991] [Citation(s) in RCA: 162] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
|
14
|
Celi P, Eppleston J, Armstrong A, Watt B. Selenium supplementation increases wool growth and reduces faecal egg counts of Merino weaners in a selenium-deficient area. Anim Prod Sci 2010. [DOI: 10.1071/an09168] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
This paper reports on the effects of selenium supplementation on liveweight (LW), greasy fleece weight (GFW), fibre diameter (FD), impact of parasite infection and plasma glutathione peroxidase (GSH-Px) activity in weaned Merino sheep reared in a selenium-deficient area (blood GSH-Px <40 U/g Hb). At weaning, 208 Merino wethers were assigned to two groups: control (CTRL) and treatment (SEL). The SEL group was injected with 0.5 mL of Deposel, a slow release selenium injection. LW, blood and faecal samples were taken at 6-week intervals over a 24-week period. At the end of the trial the animals were shorn and GFW and FD measurements were taken. The SEL group had significantly higher (P < 0.01) LW compared with the CTRL group at Weeks 6, 12, 18 and 24. There was a significant difference (P < 0.05) in GFW between the SEL and CTRL group, 2.93 and 2.75 kg, respectively. There was no difference in FD between the two groups. A trend (P < 0.06) towards lower faecal egg counts in the SEL group was seen but the difference between the two groups was not significant. As expected, the SEL group had significantly (P < 0.001) higher plasma GSH-Px activity compared with the CTRL group. In conclusion, selenium supplementation in weaned Merino sheep reared in a selenium-deficient area could increase the LW and GFW of the young sheep while perhaps reducing the level of parasitic infection.
Collapse
|
15
|
Stafford K, Morgan E, Coles G. Weight-based targeted selective treatment of gastrointestinal nematodes in a commercial sheep flock. Vet Parasitol 2009; 164:59-65. [DOI: 10.1016/j.vetpar.2009.04.009] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
|
16
|
Abstract
Global climate change predictions suggest that far-ranging effects might occur in the population dynamics and distributions of livestock parasites, provoking fears of widespread increases in disease incidence and production loss. However, several biological mechanisms (including increased parasite mortality and more rapid acquisition of immunity), in tandem with changes in husbandry practices (including reproduction, housing, nutrition, breed selection, grazing patterns and other management interventions), might act to mitigate increased parasite development rates, preventing dramatic rises in overall levels of disease. Such changes might, therefore, counteract predicted climate-driven increases in parasite challenge. Optimum mitigation strategies will be highly system specific and depend on detailed understanding of interactions between climate, parasite abundance, host availability and the cues for and economics of farmer intervention.
Collapse
Affiliation(s)
- Eric R Morgan
- Veterinary Parasitology & Ecology Group, School of Biological Sciences, University of Bristol, Bristol, BS8 1UG, UK.
| | | |
Collapse
|
17
|
van Oosterhout C, Potter R, Wright H, Cable J. Gyro-scope: an individual-based computer model to forecast gyrodactylid infections on fish hosts. Int J Parasitol 2007; 38:541-8. [PMID: 18022176 DOI: 10.1016/j.ijpara.2007.09.016] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2007] [Revised: 09/13/2007] [Accepted: 09/18/2007] [Indexed: 11/28/2022]
Abstract
Individual-based computer models (IBM) feature prominently in current theoretical ecology but have only been applied in a small number of parasitological studies. Here we designed an IBM to simulate the infection dynamics of gyrodactylid parasites and immune defence of naïve hosts (i.e. fish previously not exposed to these parasites). We compared the results of the model with empirical data from guppies (Poecilia reticulata) infected with Gyrodactylus parasites. The laboratory experiments on guppies showed that larger fish acquired a heavier parasite load at the peak of the infection. The survival probability declined with increased body size and no fish survived a parasite load of 80 or more worms in this experiment (i.e. lethal load). The model was a good predictor of the Gyrodactylus infection dynamics of guppies and the model output was congruent with previously published data on Gyrodactylus salaris infections of salmon (Salmo salar). Computer simulations indicated that the infections persisted longer on larger hosts and that the parasite load increased exponentially with the body size of the host. Simulations furthermore predicted that the parasite load of fish with a standard length in excess of 17mm (i.e. the size of adult guppies) reached a lethal load. This suggests that in the conditions of the experiment, the immune defence of naïve guppies can offer moderate protection against gyrodactylid infections to juveniles, but not to naïve adult guppies. The model is a useful tool to forecast the development of gyrodactylid infections on single hosts and make predictions about optimal life history strategies of parasites.
Collapse
Affiliation(s)
- C van Oosterhout
- Molecular Ecology and Fisheries Genetics Laboratory, University of Hull, Hull HU6 7RX, UK.
| | | | | | | |
Collapse
|