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Attwood SW, Campbell I, Upatham ES, Rollinson D. Schistosomes in the Xe Kong river of Cambodia: the detection of Schistosoma mekongi in a natural population of snails and observations on the intermediate host's distribution. Annals of Tropical Medicine & Parasitology 2013; 98:221-30. [PMID: 15119968 DOI: 10.1179/000349804225003325] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
A natural population of Neotricula aperta (Gastropoda: Pomatiopsidae) in the Xe Kong river of Cambodia was found to be infected with Schistosoma mekongi--apparently the first time this parasite has been found in snails outside the Mekong river. Only 0.14% of the N. aperta collected were found infected. Potential habitats for N. aperta were examined in selected rivers of central and southern Laos and Cambodia, so that the density of N. aperta at each site could be estimated. At survey sites where sufficient snails were collected, the population was also screened for infection with S. mekongi. The geographical distribution of N. aperta outside the Mekong river is shown to be much greater than previously documented; this is in agreement with predictions based on palaeo-geographical models and the evolutionary history and historical biogeography (phylogeography) of the species. The Xe Kong river is identified as a potential source of N. aperta colonists entering Cambodia from Laos. The findings, which indicate that there is a risk of human infection with S. mekongi in areas distant from the Mekong river, have important implications for schistosomiasis-control strategies in the region.
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Affiliation(s)
- S W Attwood
- Wolfson Wellcome Biomedical Laboratories, Department of Zoology, The Natural History Museum, Cromwell Road, London SW7 5BD, U.K
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Attwood SW, Fatih FA, Mondal MMH, Alim MA, Fadjar S, Rajapakse RPVJ, Rollinson D. A DNA sequence-based study of theSchistosoma indicum(Trematoda: Digenea) group: population phylogeny, taxonomy and historical biogeography. Parasitology 2007; 134:2009-20. [PMID: 17822572 DOI: 10.1017/s0031182007003411] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
SUMMARYPartial (DNA) sequences were collected for 2 mitochondrial loci (SrrnaandLrrna, therrnS andrrnL rRNA genes respectively) forSchistosoma indicumgroup species from 4 Southeast Asian countries. The samples included 7 populations, 4 of which were previously unstudied. In 11 cases the combination of locus and population was new. The aim of the study was to provide a phylogeny based on new independent data and multiple populations (earlier studies had mostly used a common set of field samples or laboratory lines) and to examine interrelationships and phylogeography within this species group. Paraphyly of theS. indicumgroup was confirmed, as was the basal position ofSchistosoma incognitumin theSchistosomaphylogeny. Southeast AsianSchistosoma spindaleandS. incognitumpopulations were shown to fall into their respective con-specific cohesive groupings. Estimated divergence times for these taxa were shown to be related to Pleistocene changes in sea level and the radiation of definitive host groups. A revised phylogeographical model is proposed in the light of these findings.
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Affiliation(s)
- S W Attwood
- State Key Laboratory of Biotherapy, West China Hospital, West China Medical School, Sichuan University, Chengdu 610041, PR China.
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Chen LY, Zhou BJ, Yang ZQ, Li CY, Attwood SW, Wang WL, Lei L, Sun XD, Zhang ZX. Effects of frozen storage on the structure of sarcocysts in pig muscle and implications in taxonomic studies. Exp Parasitol 2007; 115:393-8. [PMID: 17126836 DOI: 10.1016/j.exppara.2006.10.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2006] [Revised: 09/30/2006] [Accepted: 10/06/2006] [Indexed: 11/16/2022]
Abstract
UNLABELLED The morphology of the cyst wall of Sarcocystis has unique characteristics that can be used in species identification. To find a suitable way to preserve Sarcocystis cyst samples for species identification, by light microscopy and electron microscopy, we recorded the morphological changes in the cysts of Sarcocystis suihominis and Sarcocystis miescheriana from pig muscle, induced by storage at -20 degrees C. Comparisons were made between fresh cysts and those subjected to frozen storage for periods of 3 days, 20 days and 30 days. RESULTS cyst wall of the two Sarcocystis species appeared unaffected by storage. There was no obvious change in the length, nor in the width of the protrusions after storage (P>0.05), but the structure of the bradyzoite in the sarcocyst was in many cases disintegrated at -20 degrees C in 20 days for S. miescheriana and 30 days for S. suihominis. To our knowledge this is the first report that Sarcocystis cyst in muscle can be stored at -20 degrees C before and remain suitable for ultrastructural morphological study. Consequently, this paper proposes freezing as a convenient storage method for samples used in taxonomic studies of Sarcocystis.
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Affiliation(s)
- Lian-Yong Chen
- Parasitology Department, Kunming Medical College, Kunming, Yunnan, China
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Yang ZQ, Wei CG, Zen JS, Song JL, Zuo YX, He YS, Zhang HF, Attwood SW, Chen XW, Yang GC, Zhou X, Quan X, Li CY, Han D, Liu AW, Lin P. A taxonomic re-appraisal of Sarcocystis nesbitti (Protozoa: Sarcocystidae) from the monkey Macaca fascicularis in Yunnan, PR China. Parasitol Int 2005; 54:75-81. [PMID: 15710555 DOI: 10.1016/j.parint.2004.12.004] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2004] [Accepted: 12/17/2004] [Indexed: 11/30/2022]
Abstract
The first detection of Sarcocystis nesbitti Mandour, 1969 in the Chinese mainland is reported and the morphology of the sarcocyst is described in detail. The parasite was detected in the monkey, Macaca fascicularis, maintained on a monkey farm in Yunnan Province; the infection may have occurred via faecal contamination from local rats, mice and/or birds. S. nesbitti was characterized as follows: a macroscopic sarcocyst, length of the cyst up to 2 mm; cyst wall smooth, thin and no perpendicular protrusion is seen under the light microscope; border of cyst wall wavy, primary cyst wall thin (38-65 nm) and invaginated; ground substance about 0.5-0.76 microm thick with electron-dense granules and concentric spherical bodies. The cyst wall is described as type 1 by electron microscopy. It is suspected that S. nesbitti may utilize Macaca mulatta, M. fascicularis, Cercocebus atys, and Papio papionis, as well as human as intermediate hosts. The taxonomy of S. nesbitti is re-appraised in the light of a consideration of possible experimental artefacts and examination of the past literature. Evidence is presented that S. nesbitti may be one of the species infecting humans in South Asia and that the monkey may be a potential reservoir host.
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Affiliation(s)
- Zhao-Qing Yang
- Parasitology Department, Kunming Medical College, Kunming, Yunnan 650031, China
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Lockyer AE, Olson PD, Ostergaard P, Rollinson D, Johnston DA, Attwood SW, Southgate VR, Horak P, Snyder SD, Le TH, Agatsuma T, McManus DP, Carmichael AC, Naem S, Littlewood DTJ. The phylogeny of the Schistosomatidae based on three genes with emphasis on the interrelationships of Schistosoma Weinland, 1858. Parasitology 2003; 126:203-24. [PMID: 12666879 DOI: 10.1017/s0031182002002792] [Citation(s) in RCA: 225] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Schistosomes are digenean flukes, parasitic of birds, mammals and crocodiles. The family Schistosomatidae contains species of considerable medical and veterinary importance, which cause the disease schistosomiasis. Previous studies, both morphological and molecular, which have provided a good deal of information on the phylogenetics of this group, have been limited in the number of species investigated or the type or extent of molecular data used. This paper presents the most comprehensive phylogeny to date, based on the sequences of 3 genes, complete ribosomal small subunit rRNA and large ribosomal subunit rRNA, and mitochondrial cytochrome oxidase 1, sequenced from 30 taxa including at least 1 representative from 10 of the 13 known genera of the Schistosomatidae and 17 of the 20 recognized Schistosoma species. The phylogeny is examined using morphological characters, intermediate and definitive host associations and biogeography. Theories as to the origins and spread of Schistosoma are also explored. The principal findings are that Ornithobilharzia and Austrobilharzia form a sister group to the Schistosoma; mammalian schistosomes appear paraphyletic and 2 Trichobilharzia species, T. ocellata and T. szidati, seem to be synonymous. The position of Orientobilharzia within the Schistosoma is confirmed, as is an Asian origin for the Schistosoma, followed by subsequent dispersal through India and Africa.
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Affiliation(s)
- A E Lockyer
- Department of Zoology, The Natural History Museum, Cromwell Road, London SW7 5BD, UK
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Li QQ, Yang ZQ, Zuo YX, Attwood SW, Chen XW, Zhang YP. A PCR-based RFLP analysis of Sarcocystis cruzi (Protozoa: Sarcocystidae) in Yunnan Province, PR China, reveals the water buffalo (Bubalus bubalis) as a natural intermediate host. J Parasitol 2002; 88:1259-61. [PMID: 12537125 DOI: 10.1645/0022-3395(2002)088[1259:apbrao]2.0.co;2] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
A polymerase chain reaction-based restriction fragment length polymorphism (RFLP) approach is used to examine Sarcocystis cruzi-like taxa from the atypical intermediate host, water buffalo, in Yunnan, People's Republic of China. The loci examined lie within the 18S rRNA gene. A total of 15 water buffalo isolates are compared with those of 10 S. cruzi from cattle. RFLP patterns for the S. cruzi isolates from cattle and the S. cruzi-like taxon from water buffalo are found to be identical with all the 12 restriction enzymes used. Interpopulation variation between samples from Kunming and Gengma (Yunnan) is found to be undetectable at these loci for both S. cruzi and the S. cruzi-like taxon. But RFLPs are found between the S. cruzi taxa and S. suihominis from pigs at the same study sites. These findings support the hypothesis that S. cruzi is able to use the water buffalo as an intermediate host and is not restricted to cattle as was previously supposed.
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Affiliation(s)
- Qing-Qing Li
- Parasitology Department, Kunming Medical College, Kunming, Yunnan, People's Republic of China 650031
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Li QQ, Yang ZQ, Zuo YX, Attwood SW, Chen XW, Zhang YP. A PCR-Based RFLP Analysis of Sarcocystis cruzi (Protozoa: Sarcocystidae) in Yunnan Province, PR China, Reveals the Water Buffalo (Bubalus bubalis) as a Natural Intermediate Host. J Parasitol 2002. [DOI: 10.2307/3285506] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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Yang ZQ, Li QQ, Zuo YX, Chen XW, Chen YJ, Nie L, Wei CG, Zen JS, Attwood SW, Zhang XZ, Zhang YP. Characterization of Sarcocystis species in domestic animals using a PCR-RFLP analysis of variation in the 18S rRNA gene: a cost-effective and simple technique for routine species identification. Exp Parasitol 2002; 102:212-7. [PMID: 12856319 DOI: 10.1016/s0014-4894(03)00033-x] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Thirteen restriction endonucleases were used to investigate nuclotide sequence variation in the 18S rRNA DNA of 88 individuals from ten Sarcocystis taxa collected as cysts from their intermediate hosts, swine, cattle and water buffalo. A DNA sequence of approximately 900 bp was used. A total of 26 electromorphs were detected. The electromorphs were sorted into seven different haplotypes that coincided with the six named species and an unidentified species from cattle. These findings support those of our morphological examinations, which suggested that the taxa resembling Sarcocystis hirsuta, S. hominis, both found in water buffalo, and S. sinensis found in cattle, are not new species but are in fact S. hirsuta and S. hominis as found in cattle, and S. sinensis as found in water buffalo; this finding supports the idea that these species can utilize both cattle and water buffalo as intermediate hosts and are not restricted to one or the other host group as previously thought. PCR-RFLP resolved by agarose gel electrophoresis is shown to be an easy and rapid method of discriminating between these species.
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Affiliation(s)
- Zhao-Qing Yang
- Laboratory of Cellular and Molecular Evolution, Kunming Institute of Zoology, Chinese Academy of Sciences, Parasitology Department, Kunming Medical College, Biology Department, Yunnan University, Kunming, Yunnan, China
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Abstract
Partial (DNA) sequences are presented for 2 nuclear (18S and 28S rRNA genes) and 2 mitochondrial (12S rRNA and ND1 genes) loci for 5 species belonging to the Schistosoma japonicum, S. sinensium and S. indicum groups of Asian Schistosoma. Fresh field isolates were collected and cultured for the following taxa: S. incognitum (S. indicum group, central Thailand), S. mekongi (S. japonicum group, southern Laos), S. ovuncatum (S. sinensium group, northern Thailand), S. spindale (S. indicum group, northeast Thailand and central Thailand isolates) and S. sinensium (S. sinensium group, Sichuan Province, China). This represents the first published DNA sequence data for S. ovuncatum and for S. sinensium s.s. from the type locality in China. The paper also presents the first sequence data at the above loci for S. incognitum (except for the 28S sequences) and S. sinensium. Congruence was observed between the phylogenies estimated for each locus, although the relationships of S. incognitum were not so well resolved. Fitch-Margoliash, maximum likelihood (M/L) and maximum parsimony methods were used to estimate the phylogenies and the agreement between them was similar to that observed between loci. The ML tree was considered to best represent the data and additional 28S sequences (taken from the GenBank), for S. haematobium, S. japonicum, S. mansoni and Orientobilharzia turkestanicum, were used to construct an overall phylogeny. The S. indicum group taxa showed considerable divergence from the other Asian species and closest affinity with the African group. S. ovuncatum and S. sinensium appeared as sister taxa but their status as sibling species remained supported. The findings are discussed in the context of phylogeographical hypotheses for the origin of Schistosoma. An Asian origin for Schistosoma is also considered.
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Affiliation(s)
- S W Attwood
- Department of Zoology, The Natural History Museum, London, UK.
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Abstract
An account is given of progress made over the last 20 years in the study of Mekong schistosomiasis, causative agent Schistosoma mekongi (Trematoda: Digenea). Emphasis is given to the discussion of work concerning the origin and subsequent dispersal of S. mekongi and related taxa, including relevant snails. The role of such phylogeographical data in schistosomiasis control and the prediction of areas at risk is examined. New palaeogeographical models are reviewed in relation to traditional explanations for the biogeographic deployment of Southeast Asian Schistosoma and their intermediate hosts. The demographics and molecular ecology of Neotricula aperta (Gastropoda: Pomatiopsidae), the snail host of S. mekongi, are reviewed with particular reference to new models for the life cycle of this species and their importance in snail control. The use of population genetic data in the limitation of N. aperta populations is evaluated and strategies suggested for schistosomiasis control efforts directed against the intermediate host. Developments in the taxonomy of N. aperta, and related taxa, and changes in nomenclature are covered. The direction of future investigations into the problem of Mekong schistosomiasis is also discussed.
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Affiliation(s)
- S W Attwood
- Wolfson Wellcome Biomedical Laboratories, Department of Zoology, Natural History Museum, London, SW7 5BD, UK
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Attwood SW, Panasoponkul C, Upatham ES, Meng XH, Southgate VR. Schistosoma ovuncatum n. sp. (Digenea: Schistosomatidae) from northwest Thailand and the historical biogeography of Southeast Asian Schistosoma Weinland, 1858. Syst Parasitol 2002; 51:1-19. [PMID: 11721191 DOI: 10.1023/a:1012988516995] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Schistosoma sinensium Bao, 1958 was first isolated from an unidentified snail in Sichuan Province, PR China. This species was apparently rediscovered in Chiang Mai Province, northwest Thailand (Baidikul et al., 1984); the definitive host was the rat Rattus rattus and the intermediate host was the snail Tricula bollingi. In this paper S. sinensium is rediscovered in Sichuan Province and compared with worms recovered from experimentally infected mice, which had been exposed to cercariae shed by T. bollingi from Chiang Mai. Evidence is presented suggesting that the schistosome collected by Baidikul was not S. sinensium and that a new species is involved. The new species, named Schistosoma ovuncatum (etymology: ovum (egg) + uncatus (hooked)), is described and compared with related taxa. All previous papers on the Thai schistosome have used worms recovered from field-collected rodents only; this is the first account in which the life-cycle has been completed in the laboratory, using cercariae shed by T. bollingi, and the resulting worms described. S. ovuncatum differs from S. sinensium in terms of size and shape of body and egg, number of testes, size of ovary, length of vitellarium, intermediate host and biogeographical distribution. The relationships of the two taxa and their position with respect to the Schistosoma indicum- and S. japonicum-groups are discussed. The implications of the findings for the evolution of human schistosomiasis in the region are also commented upon.
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Affiliation(s)
- S W Attwood
- Department of Zoology, The Natural History Museum, Cromwell Road, London SW7 5BD, UK
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Attwood SW, Kitikoon V, Southgate VR. Neotricula aperta (Gastropoda: Pomatiopsidae), the intermediate host of Schistosoma mekongi: allozyme variation and relationships between Khmer, Lao, and Thai populations. J Zool (1987) 1998. [DOI: 10.1111/j.1469-7998.1998.tb00161.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Abstract
All three strains of Neotricula aperta (Gastropoda: Pomatiopsidae) sampled from populations in northeast Thailand were found to be compatible with a Schistosoma mekongi isolate from Kratie District, eastern Cambodia. The infection rates were: 3.0%, alpha-strain; 6.0%, beta-strain, and 20.5%, gamma-strain. The greater infectivity to the gamma-strain, over both the alpha- and beta-strains, was statistically significant. Comparisons of infectivity patterns for the Kratie isolate, with those described in earlier studies using S. mekongi isolates from southern Laos, revealed differences among the strains. The gamma-strain of N. aperta is responsible for endemic transmission of human schistosomiasis in southern Laos and at Kratie. Consequently, the findings of this study are of use in the prediction of changes in the distribution of Mekong schistosomiasis, particularly its introduction to northeast Thailand from the neighbouring countries, Cambodia and Laos.
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Affiliation(s)
- S W Attwood
- Department of Social and Environmental Medicine, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
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Attwood SW. Changes in Neotricula beta-aperta population density following construction of the Pak Mun Dam in northeast Thailand, with implications for the transmission of schistosomiasis. Southeast Asian J Trop Med Public Health 1996; 27:24-8. [PMID: 9031395] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Affiliation(s)
- S W Attwood
- Science Department: Zoology, Natural History Museum, London, UK
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