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The equine ascarids: resuscitating historic model organisms for modern purposes. Parasitol Res 2022; 121:2775-2791. [PMID: 35986167 PMCID: PMC9391215 DOI: 10.1007/s00436-022-07627-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2022] [Accepted: 08/12/2022] [Indexed: 11/23/2022]
Abstract
The equine ascarids, Parascaris spp., are important nematode parasites of juvenile horses and were historically model organisms in the field of cell biology, leading to many important discoveries, and are used for the study of chromatin diminution. In veterinary parasitology, Parascaris spp. are important not only because they can cause clinical disease in young horses but also because they are the only ascarid parasites to have developed widespread anthelmintic resistance. Despite this, much of the general biology and mechanisms of anthelmintic resistance are poorly understood. This review condenses known basic biological information and knowledge on the mechanisms of anthelmintic resistance in Parascaris spp., highlighting the importance of foundational research programs. Although two variants of this parasite were recognized based on the number of chromosomes in the 1870s and suggested to be two species in 1890, one of these, P. univalens, appears to have been largely forgotten in the veterinary scientific literature over the past 100 years. We describe how this omission has had a century-long effect on nomenclature and data analysis in the field, highlighting the importance of proper specimen identification in public repositories. A summary of important basic biology, including life cycle, in vitro maintenance, and immunology, is given, and areas of future research for the improvement of knowledge and development of new systems are given. Finally, the limited knowledge regarding anthelmintic resistance in Parascaris spp. is summarized, along with caution regarding assumptions that resistance mechanisms can be applied across clades.
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Han L, Lan T, Lu Y, Zhou M, Li H, Lu H, Wang Q, Li X, Du S, Guan C, Zhang Y, Sahu SK, Qian P, Zhang S, Zhou H, Guo W, Chai H, Wang S, Liu Q, Liu H, Hou Z. Equus roundworms (Parascaris univalens) are undergoing rapid divergence while genes involved in metabolic as well as anthelminic resistance are under positive selection. BMC Genomics 2022; 23:489. [PMID: 35787772 PMCID: PMC9252044 DOI: 10.1186/s12864-022-08702-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2021] [Accepted: 06/10/2022] [Indexed: 12/30/2022] Open
Abstract
Background The evolution of parasites is often directly affected by the host's environment. Studies on the evolution of the same parasites in different hosts are of great interest and are highly relevant to our understanding of divergence. Methods Here we performed whole-genome sequencing of Parascaris univalens from different Equus hosts (horses, zebras and donkeys). Phylogenetic and selection analyses were performed to study the divergence and adaptability of P. univalens. Results At the genetic level, multiple lines of evidence indicate that P. univalens is mainly separated into two clades (horse-derived and zebra & donkey-derived). This divergence began 300–1000 years ago, and we found that most of the key enzymes related to glycolysis were under strong positive selection in zebra & donkey-derived roundworms, whereas the lipid-related metabolic system was under positive selection in horse-derived roundworms, indicating that the adaptive evolution of metabolism has occurred over the past few centuries. In addition, we found that some drug-related genes showed a significantly higher degree of selection in diverse populations. Conclusions This work reports the adaptive evolution and divergence trend of P. univalens in different hosts for the first time. Its results indicate that the divergence of P. univalens is a continuous, dynamic process. Furthermore, the continuous monitoring of the effects of differences in nutritional and drug histories on the rapid evolution of roundworms is conducive to further understanding host-parasite interactions. Supplementary Information The online version contains supplementary material available at 10.1186/s12864-022-08702-6.
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Affiliation(s)
- Lei Han
- College of Wildlife and Protected Area, Northeast Forestry University, Harbin, 150040, China
| | - Tianming Lan
- BGI Life Science Joint Research Center, Northeast Forestry University, Harbin, China. .,State Key Laboratory of Agricultural Genomics, BGI-Shenzhen, Shenzhen, 518083, China.
| | - Yaxian Lu
- College of Wildlife and Protected Area, Northeast Forestry University, Harbin, 150040, China
| | - Mengchao Zhou
- College of Wildlife and Protected Area, Northeast Forestry University, Harbin, 150040, China
| | - Haimeng Li
- State Key Laboratory of Agricultural Genomics, BGI-Shenzhen, Shenzhen, 518083, China.,College of Life Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Haorong Lu
- Guangdong Provincial Key Laboratory of Genome Read and Write, BGI-Shenzhen, Shenzhen, 518120, China.,China National GeneBank, BGI-Shenzhen, Shenzhen, 518083, China
| | - Qing Wang
- State Key Laboratory of Agricultural Genomics, BGI-Shenzhen, Shenzhen, 518083, China.,College of Life Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Xiuyun Li
- Harbin Northern Forest Zoo, Harbin, 150040, China
| | - Shan Du
- Inner Mongolia Agriculture University, Hohhot, 010000, China
| | - Chunyu Guan
- Harbin Northern Forest Zoo, Harbin, 150040, China
| | - Yong Zhang
- Center for Animal Disease Control and Prevention of Ordos, Inner Mongolia Ordos, 017000, China
| | - Sunil Kumar Sahu
- State Key Laboratory of Agricultural Genomics, BGI-Shenzhen, Shenzhen, 518083, China
| | - Puyi Qian
- Guangdong Provincial Key Laboratory of Genome Read and Write, BGI-Shenzhen, Shenzhen, 518120, China.,China National GeneBank, BGI-Shenzhen, Shenzhen, 518083, China
| | - Shaofang Zhang
- Guangdong Provincial Key Laboratory of Genome Read and Write, BGI-Shenzhen, Shenzhen, 518120, China.,China National GeneBank, BGI-Shenzhen, Shenzhen, 518083, China
| | - Hongcheng Zhou
- Guangdong Provincial Key Laboratory of Genome Read and Write, BGI-Shenzhen, Shenzhen, 518120, China.,China National GeneBank, BGI-Shenzhen, Shenzhen, 518083, China
| | - Wei Guo
- State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, 150040, China
| | - Hongliang Chai
- College of Wildlife and Protected Area, Northeast Forestry University, Harbin, 150040, China.,Key Laboratory of Wildlife Conservation, China State Forestry Administration, Harbin, 150040, China
| | - Sibo Wang
- State Key Laboratory of Agricultural Genomics, BGI-Shenzhen, Shenzhen, 518083, China
| | - Quan Liu
- College of Wildlife and Protected Area, Northeast Forestry University, Harbin, 150040, China.
| | - Huan Liu
- BGI Life Science Joint Research Center, Northeast Forestry University, Harbin, China. .,State Key Laboratory of Agricultural Genomics, BGI-Shenzhen, Shenzhen, 518083, China.
| | - Zhijun Hou
- College of Wildlife and Protected Area, Northeast Forestry University, Harbin, 150040, China. .,Key Laboratory of Wildlife Conservation, China State Forestry Administration, Harbin, 150040, China.
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von Samson-Himmelstjerna G, Janssen IJI, Ramünke S, Goday C, Borges FDA, Koudela B, Niedźwiedź A, Tomczuk K, Studzińska MB, Kornas S, Krücken J. Very low intraspecific sequence variation in selected nuclear and mitochondrial Parascaris univalens genes. INFECTION GENETICS AND EVOLUTION 2021; 95:105035. [PMID: 34384934 DOI: 10.1016/j.meegid.2021.105035] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/18/2021] [Revised: 08/04/2021] [Accepted: 08/07/2021] [Indexed: 11/18/2022]
Abstract
Equines were over decades considered to be infected by two morphologically virtually indistinguishable ascarid species, Parascaris univalens and Parascaris equorum. Reliable species discrimination is only possible using enzyme isoelectric focussing and karyotyping with P. univalens having one and P. equorum two chromosome pairs. However, presumably the complexity of both methods prevented their routine use in nearly all previous studies about prevalence and drug resistance of Parascaris spp. These have barely been performed on the species level although most studies stated presence of one or the other species. Recently, only P. univalens has been identified by karyotyping and the last published study identifying P. equorum dates back to 1989. In order to improve species-specific detection, molecular markers are required. Here, partial 12S rRNA, cytochrome oxidase I (COI) and complete internal transcribed spacer (ITS)-1 and - 2 sequences were obtained from 24 karyotyped Parascaris specimens from Poland and 6 German specimens (not karyotyped) and used in phylogenetic analyses with orthologous sequences from GenBank. All karyotyped specimens were identified as P. univalens. In the phylogenetic analysis, they formed very homogenous clusters for all target genes and in a multi-locus analysis. Within this cluster, almost all sequences from GenBank were also included, no matter if they had been assigned to P. univalens or P. equorum. However, a small number of P. univalens ITS and COI sequences originating from donkeys from a single farm in China formed a highly supported sister cluster suggesting that they might represent another Parascaris genotype or species. Our data also strongly suggest that nearly all ITS and COI sequences previously deposited in GenBank and assigned to P. equorum actually represent P. univalens. The fact that significantly different sequences can be found in Parascaris spp. suggests that PCR-based species diagnosis will be possible once molecular markers have been identified for P. equorum from karyotyped specimens.
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Affiliation(s)
| | - I Jana I Janssen
- Institute for Parasitology and Tropical Veterinary Medicine, Freie Universität Berlin, Germany
| | - Sabrina Ramünke
- Institute for Parasitology and Tropical Veterinary Medicine, Freie Universität Berlin, Germany
| | - Clara Goday
- Departamento de Biología Celular y Molecular, Centro de Investigaciones Biológicas (CIB), Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain
| | - Fernando de A Borges
- School of Veterinary Medicine and Animal Science, Federal University of Mato Grosso do Sul, Campo Grande, Brazil
| | - Bretislav Koudela
- Central European Institute of Technology (CEITEC), University of Veterinary and Pharmaceutical Sciences, Palackého tř. 1946/1, Brno 612 42, Czech Republic; Faculty of Veterinary Medicine, University of Veterinary and Pharmaceutical Sciences, Brno, Czech Republic
| | - Artur Niedźwiedź
- Department of Internal Medicine and Clinic for Horses, Dogs and Cats, Faculty of Veterinary Medicine, Wroclaw University of Environmental and Life Sciences, Wroclaw, Poland
| | - Krzysztof Tomczuk
- Sub-Department of Parasitology and Invasive Diseases, Veterinary Faculty, University of Life Sciences, Lublin, Poland
| | - Maria Bernadeta Studzińska
- Sub-Department of Parasitology and Invasive Diseases, Veterinary Faculty, University of Life Sciences, Lublin, Poland
| | - Slawomir Kornas
- Department of Zoology and Animal Welfare, Faculty of Animal Sciences, University of Agriculture, Al. Mickiewicza 24/28, Kraków, Poland
| | - Jürgen Krücken
- Institute for Parasitology and Tropical Veterinary Medicine, Freie Universität Berlin, Germany
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Martin F, Svansson V, Eydal M, Oddsdóttir C, Ernback M, Persson I, Tydén E. First Report of Resistance to Ivermectin in Parascaris univalens in Iceland. J Parasitol 2021; 107:16-22. [PMID: 33498083 DOI: 10.1645/20-91] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Horses in Iceland have been isolated for more than 1,000 yr but still harbor a similar range of gastrointestinal parasites as do horses across the world. The long isolation of the horses and their parasites presumably means that no resistance genes have been introduced into the Parascaris spp. population. It is therefore of particular interest to investigate the efficacy of ivermectin on Parascaris spp. infecting Icelandic foals. Potential treatment failure of ivermectin in Iceland will add substantial new information on how resistance can arise independently. This study aimed to determine the efficacy of subcutaneous injection of ivermectin for the treatment of Parascaris spp. infection in foals and to identify the Parascaris species present in the west and north of Iceland. A fecal egg count reduction (FECR) test (FECRT) was performed on 50 foals from 8 farms, including an untreated control group of 6 foals, from September to November 2019. The foals were between 3 and 5 mo of age at the start of the study and had not previously been treated with anthelmintic drugs. Each foal was treated subcutaneously with off-label use of Ivomec® injection 10 mg/ml or Noromectin® 1% at a dose of 0.2 mg/kg. The FECR for each farm was calculated in 2 ways, by the eggCounts package in R and by the Presidente formula (FECRT). Both calculation methods resulted in efficacy levels between 0% and 80.78%, indicating ivermectin resistance on all farms. We also confirmed, by karyotyping, that the species of equine ascarid present in the west and north of Iceland is Parascaris univalens. This study provides evidence for treatment failure of ivermectin against P. univalens infection in foals. Since Icelandic horses have been isolated on the island for more than 1,000 yr, this implies that resistance alleles have developed independently in the Icelandic Parascaris population. The actual clinical impact of ivermectin resistance is unknown but another drug of choice should be considered to treat Parascaris infection in foals in Iceland.
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Affiliation(s)
- Frida Martin
- Swedish University of Agricultural Sciences, Department of Biomedical Sciences and Veterinary Public Health, Division of Parasitology, Box 7036, 750 07 Uppsala, Sweden
| | - Vilhjálmur Svansson
- Institute for Experimental Pathology at Keldur, University of Iceland, Keldnavegur 3, 112 Reykjavik, Iceland
| | - Matthías Eydal
- Institute for Experimental Pathology at Keldur, University of Iceland, Keldnavegur 3, 112 Reykjavik, Iceland
| | - Charlotta Oddsdóttir
- Institute for Experimental Pathology at Keldur, University of Iceland, Keldnavegur 3, 112 Reykjavik, Iceland
| | - Maja Ernback
- Swedish University of Agricultural Sciences, Department of Biomedical Sciences and Veterinary Public Health, Division of Parasitology, Box 7036, 750 07 Uppsala, Sweden
| | - Isa Persson
- Swedish University of Agricultural Sciences, Department of Biomedical Sciences and Veterinary Public Health, Division of Parasitology, Box 7036, 750 07 Uppsala, Sweden
| | - Eva Tydén
- Swedish University of Agricultural Sciences, Department of Biomedical Sciences and Veterinary Public Health, Division of Parasitology, Box 7036, 750 07 Uppsala, Sweden
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Studzińska MB, Sallé G, Roczeń-Karczmarz M, Szczepaniak K, Demkowska-Kutrzepa M, Tomczuk K. A survey of ivermectin resistance in Parascaris species infected foals in south-eastern Poland. Acta Vet Scand 2020; 62:28. [PMID: 32503589 PMCID: PMC7275302 DOI: 10.1186/s13028-020-00526-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2019] [Accepted: 05/29/2020] [Indexed: 11/10/2022] Open
Abstract
Parascaris spp. are major gastro-intestinal nematodes that infect foals and can lead to respiratory symptoms, poor growth, and in some cases obstruction of the small intestine and death. Ivermectin resistance has been reported for Parascaris spp. in many countries. In Poland, the knowledge of the level of resistance against ivermectin in Parascaris spp. is limited. The aim of this study was to examine the efficacy of ivermectin against Parascaris spp. in foals from south-eastern Poland. Foals (n = 225 = reared in 7 stud farms) were treated orally with ivermectin paste. Faecal samples were collected from the rectum of each foal or from the environment straight after defaecation on 1 day prior and 2 weeks after deworming. A faecal egg count (FEC) was performed using the McMaster method with a minimum detection limit of 50 eggs/g. FEC reduction (FECR) was calculated using the Faecal Egg Count Reduction Test. The statistical analysis was limited to foals excreting more than 150 eggs/g before treatment and to stud farms with at least 6 foals excreting at or above this level. Confidence intervals were determined by 1000 bootstraps at farm level and the contribution of sex and age to FECR was quantified using a generalized equation estimation procedure. Parascaris spp. eggs were found in 40% of the foals. Following ivermectin treatment, Parascaris spp. eggs were identified in 28.4% of the foals. The mean estimated FECR ranged from 44% to 97% and average efficacy was 49.3%. FECR was more pronounced in older foals (P-values = 0. 003). The FECR was more pronounced in males than in females (P value = 0.028). This study is the first to indicate a reduced efficacy of ivermectin against Parascaris spp. in foals in Poland.
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Malekpour SH, Rakhshandehroo E, Yektaseresht A. Molecular characterization of β-tubulin gene associated with benzimidazole resistance in larvae of field isolates of Parascaris (Nematoda: Ascarididae). J Parasit Dis 2019; 43:672-678. [PMID: 31749539 DOI: 10.1007/s12639-019-01146-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2019] [Accepted: 07/17/2019] [Indexed: 11/25/2022] Open
Abstract
Since the past 2 decades, an increasing number of resistance to the Benzimidazoles (BZs) have been reported in nematode parasites of livestock. More recently, detection of single-nucleotide polymorphisms (SNPs) at codons of 167, 198 or 200 of the β-tubulin gene has been attributed to the occurrence of resistance. In the present study, we investigated the presence of those SNPs in the β-tubulin isotype-1 gene in different isolates of Parascaris in horse. Also, the mitochondrial (mt) and ribosomal genes were sequenced for species confirmation of the isolates. The analysis of sequences inferred from COII gene confirmed that those isolates were P. equorum. The distance between mt genes obtained here and several ascarid species in equids and other hosts suggests the need for the combination of more genetic data with morphologic and other diagnostic measures. The analysis on β-tubulin isotype-1 gene revealed no resistance-related SNPs or substitutions at the expected codon positions and selection pressure with BZs has not occurred for Parascaris worms. Although the molecular data showed the susceptibility of Parascaris isolates against BZs, other mechanisms of resistance should be also investigated to confirm the validity of molecular results.
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Affiliation(s)
- Seyed Hossein Malekpour
- Department of Pathobiology, School of Veterinary Medicine, Shiraz University, P.O. Box 71441-69155 Shiraz, Iran
| | - Ehsan Rakhshandehroo
- Department of Pathobiology, School of Veterinary Medicine, Shiraz University, P.O. Box 71441-69155 Shiraz, Iran
| | - Azadeh Yektaseresht
- Department of Pathobiology, School of Veterinary Medicine, Shiraz University, P.O. Box 71441-69155 Shiraz, Iran
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Genetic characteristics and phylogenetic relationship of Parascaris spp. from Equus zebra, E. caballus, and E. asinus. Vet Parasitol 2019; 271:76-79. [DOI: 10.1016/j.vetpar.2019.06.013] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2019] [Revised: 06/18/2019] [Accepted: 06/18/2019] [Indexed: 11/18/2022]
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8
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Martin F, Höglund J, Bergström TF, Karlsson Lindsjö O, Tydén E. Resistance to pyrantel embonate and efficacy of fenbendazole in Parascaris univalens on Swedish stud farms. Vet Parasitol 2018; 264:69-73. [DOI: 10.1016/j.vetpar.2018.11.003] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2018] [Revised: 11/07/2018] [Accepted: 11/07/2018] [Indexed: 11/16/2022]
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9
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Li L, Gibson DI, Zhang LP. An annotated catalogue of the ascaridoid nematode parasites of Chinese vertebrates. Syst Parasitol 2016; 93:1-35. [PMID: 26739284 DOI: 10.1007/s11230-015-9617-5] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2015] [Accepted: 11/21/2015] [Indexed: 11/27/2022]
Abstract
A catalogue, based on both examined specimens and the published literature, of all the ascaridoid nematodes recorded in China is presented. A total of 95 recognised species, representing 26 genera in five families, are reported. Detailed information on the type-host, type-locality, original reference, synonyms, annotated subsequent references of taxonomic importance, other host records, site of infection, location of type-specimens and distribution are listed for each recognised species. Additional comments on the taxonomic status of some species are also given. Moreover, some nomenclatural changes are proposed: (i) Toxascaris selenarctis Wang, 1965 and T. ailuri Wu, He & Hu, 1987 are placed in synonymy with Baylisascaris transfuga (Rudolphi, 1819); (ii) Raphidascaris lophii Wang & Wu, 1991 is a secondary homonym of R. lophii (Wu, 1949) and a replacement name, R. wangi nom. nov., is proposed for the former species; (iii) Aliascaris aetoplatea Luo, 2001 is transferred to Terranova Leiper & Atkinson, 1914, as T. aetoplatea (Luo, 2001) n. comb., and should be considered a species inquirenda; (iv) Ophidascaris orientalis (Wang, 1965) is resurrected as a valid species; (v) Phocascaris longispiculum Wang & Wu, 1991 and Ophidascaris agkistrodontis Wang, 1979 are treated as incertae sedis; and (vi) Hysterothylacium sauridae Li, Xu & Zhang, 2008 is listed as a nomen nudum.
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Affiliation(s)
- Liang Li
- Key Laboratory of Animal Physiology, Biochemistry and Molecular Biology of Hebei Province, College of Life Science, Hebei Normal University, Shijiazhuang, 050024, Hebei Province, People's Republic of China.
| | - David I Gibson
- Department of Life Sciences, Natural History Museum, Cromwell Road, London, SW7 5BD, UK
| | - Lu-Ping Zhang
- Key Laboratory of Animal Physiology, Biochemistry and Molecular Biology of Hebei Province, College of Life Science, Hebei Normal University, Shijiazhuang, 050024, Hebei Province, People's Republic of China
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Tydén E, Skarin M, Andersson-Franko M, Sjöblom M, Höglund J. Differential expression of β-tubulin isotypes in different life stages of Parascaris spp after exposure to thiabendazole. Mol Biochem Parasitol 2016; 205:22-8. [DOI: 10.1016/j.molbiopara.2016.02.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2015] [Revised: 02/10/2016] [Accepted: 02/11/2016] [Indexed: 11/25/2022]
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Nielsen MK. Evidence-based considerations for control ofParascarisspp. infections in horses. EQUINE VET EDUC 2015. [DOI: 10.1111/eve.12536] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Affiliation(s)
- M. K. Nielsen
- Department of Veterinary Science; M.H. Gluck Equine Research Center; University of Kentucky; Lexington USA
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Absence of genetic structure in Baylisascaris schroederi populations, a giant panda parasite, determined by mitochondrial sequencing. Parasit Vectors 2014; 7:606. [PMID: 25532965 PMCID: PMC4292857 DOI: 10.1186/s13071-014-0606-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2014] [Accepted: 12/16/2014] [Indexed: 11/25/2022] Open
Abstract
Background Infection with the parasitic nematode, Baylisascaris schroederi (Ascaridida: Nematoda), is one of the most important causes of death in giant pandas, and was responsible for half of deaths between 2001 and 2005. Mitochondrial (mt) DNA sequences of parasites can unveil their genetic diversity and depict their likely dynamic evolution and therefore may provide insights into parasite survival and responses to host changes, as well as parasite control. Methods Based on previous studies, the present study further annotated the genetic variability and structure of B. schroederi populations by combining two different mtDNA markers, ATPase subunit 6 (atp6) and cytochrome c oxidase subunit I (cox1). Both sequences were completely amplified and genetically analyzed among 57 B. schroederi isolates, which were individually collected from ten geographical regions located in three important giant panda habitats in China (Minshan, Qionglai and Qinling mountain ranges). Results For the DNA dataset, we identified 20 haplotypes of atp6, 24 haplotypes of cox1, and 39 haplotypes of atp6 + cox1. Further haplotype network and phylogenetic analyses demonstrated that B. schroederi populations were predominantly driven by three common haplotypes, atp6 A1, cox1 C10, and atp6 + cox1 H11. However, due to low rates of gene differentiation between the three populations, both the atp6 and cox1 genes appeared not to be significantly associated with geographical divisions. In addition, high gene flow was detected among the B. schroederi populations, consistent with previous studies, suggesting that this parasite may be essentially homogenous across endemic areas. Finally, neutrality tests and mismatch analysis indicated that B. schroederi had undergone earlier demographic expansion. Conclusions These results confirmed that B. schroederi populations do not follow a pattern of isolation by distance, further revealing the possible existence of physical connections before geographic separation. This study should also contribute to an improved understanding of the population genetics and evolutionary biology of B. schroederi and assist in the control of baylisascariasis in giant pandas. Electronic supplementary material The online version of this article (doi:10.1186/s13071-014-0606-3) contains supplementary material, which is available to authorized users.
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Nielsen MK, Wang J, Davis R, Bellaw JL, Lyons ET, Lear TL, Goday C. Parascaris univalens—a victim of large-scale misidentification? Parasitol Res 2014; 113:4485-90. [DOI: 10.1007/s00436-014-4135-y] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2014] [Accepted: 09/08/2014] [Indexed: 10/24/2022]
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Tydén E, Dahlberg J, Karlberg O, Höglund J. Deep amplicon sequencing of preselected isolates of Parascaris equorum in β-tubulin codons associated with benzimidazole resistance in other nematodes. Parasit Vectors 2014; 7:410. [PMID: 25175357 PMCID: PMC4156605 DOI: 10.1186/1756-3305-7-410] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2014] [Accepted: 08/18/2014] [Indexed: 11/30/2022] Open
Abstract
Background The development of anthelmintic resistance (AR) to macrocyclic lactones in the equine roundworm Parascaris equorum has resulted in benzimidazoles now being the most widely used substance to control Parascaris infections. However, over-reliance on one drug class is a risk factor for the development of AR. Consequently, benzimidazole resistance is widespread in several veterinary parasites, where it is associated with single nucleotide polymorphisms (SNPs) in drug targets encoded by the β-tubulin genes. The importance of these SNPs varies between different parasitic nematodes, but it has been hypothesised that they occur, at low allele frequencies, even in unselected populations. This study investigated whether these SNPs exist in the P. equorum population and tested the hypothesis that BZ resistance can develop from pre-existing SNPs in codons 167, 198 and 200 of the β-tubulin isotype 1 and 2 genes, reported to be associated with AR in strongylids. The efficacy of the oral paste formula fenbendazole on 11 farms in Sweden was also assessed. Methods Two isotype-specific primer pairs were designed, one on either side of the codon 167 and one on either side of codons 198 and 200. A pool of 100 000 larvae was sequenced using deep amplicon sequencing by Illumina HiSeq. Faecal egg count reduction test was used to assess the efficacy of fenbendazole. Results No SNPs were observed in codons 167, 198 or 200 of the β-tubulin isotype 1 or 2 genes of P. equorum, even though 100 000 larvae were sequenced. Faecal egg count reduction testing of fenbendazole showed that this anthelmintic was still 100% effective, meaning that the likelihood of finding high allele frequency of SNPs associated with benzimidazoles resistance in P. equorum was low. Unexpectedly, the allele frequencies observed in single worms were comparable to those in pooled samples. Conclusions We concluded that fenbendazole does not exert selection pressure on the β-tubulin genes of isotypes 1 and 2 in P. equorum. The fact that no pre-existing SNPs were found in codons 167, 198 and 200 in P. equorum also illustrates the difficulties in generalising about AR mechanisms between different taxonomic groups of nematodes. Electronic supplementary material The online version of this article (doi:10.1186/1756-3305-7-410) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Eva Tydén
- Department of Biomedical Sciences and Veterinary Public Health, Division of Parasitology, Swedish University of Agricultural Sciences, Uppsala S-750 07, Sweden.
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