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Morphology and life cycle of Schistosoma sinensium Pao, 1959, from northwest Thailand

Greer GJ, Kitikoon V, Lohachit C

J Parasitol, 1989 Feb;75(1):98-101.
PMID: 2918446

Schistosoma sinensium Pao, 1959, was first isolated from an unidentified snail in Szechuan Province, China, and was described on the basis of adult worms and eggs recovered from experimentally infected mice. We discovered snails, Tricula bollingi Davis, and rodents, Rattus rattus (L.) and Crocidura attenuata Milne-Edwards, infected with S. sinensium near Fang in northwest Thailand. Adult worms were recovered from small veins immediately adjacent to the small intestine. Eggs first appeared in the feces of experimentally infected mice at 25 days postinfection. Cercariae first emerged from experimentally infected T. bollingi at 40 days postinfection. Shortly after emerging, cercariae were found at the water surface, their bodies flat against the meniscus and tails hanging free in the water column. Our morphometric results for adults and eggs from naturally infected hosts agree well with those presented in the original description. The occurrence of a lateral spine on the egg of this Asian schistosome has created some confusion as to the affinities of S. sinensium. A comparison of 8 character states, including snail hosts, cercarial behavior, geographical distribution, and morphology of life cycle stages, indicates that S. sinensium is more closely related to S. japonicum Katsurada than it is to S. mansoni Sambon.

Matched MeSH terms: Snails/parasitology
A description of a pleurolophocercous cercaria of Procerovum sp from the Haplorchis group of heterophyid trematodes

Surin J

Southeast Asian J Trop Med Public Health, 1993 Dec;24(4):692-6.
PMID: 7939942

Freshwater snails, Stenomelania denisoniensis (Brot) from Tinaroo Dam, North Queensland, Australia were found to be infected with a heterophyid cercaria identified as Procerovum sp. The tail of the cercaria has finfolds which are bilateral anteriorly and dorso-ventral posteriorly, features which separate it from other genera in the Haplorchis-group. This group is differentiated from the cercariae of all the other heterophyid genera by the presence of the penetration glands that extend to the posterior end of the body lateral to the excretory bladder. This paper presents a full description of the cercaria, together with comparisons with other known species of Procerovum.

Matched MeSH terms: Snails/parasitology*
A survey of snail hosts and larval trematodes collected by peninsular Malaysia and Singapore from 1972 to 1977

Palmieri JR, Sullivan JT, Ow-Yang CK

Southeast Asian J Trop Med Public Health, 1977 Jun;8(2):275-7.
PMID: 918717
Matched MeSH terms: Snails/parasitology*
Preliminary report on new cercariae from Bellamya and Pila snails in Peninsular Malaysia

Lim HK, Colley FC, Ow-Yang CK

Southeast Asian J Trop Med Public Health, 1974 Sep;5(3):458-9.
PMID: 4432110
Matched MeSH terms: Snails/parasitology*
Discovery of a site of transmission and hosts of a Schistosoma japonicum-like schistosome in Peninsular Malaysia

Greer GJ, Ow-Yang CK, Singh KI, Lim HK

Trans R Soc Trop Med Hyg, 1980;74(3):425.
PMID: 7434446
Matched MeSH terms: Snails/parasitology*
Fulltext Recent range expansion of an intermediate host for animal schistosome parasites in the Indo-Australian Archipelago: phylogeography of the freshwater gastropod Indoplanorbis exustus in South and Southeast Asia

Gauffre-Autelin P, von Rintelen T, Stelbrink B, Albrecht C

Parasit Vectors, 2017 03 06;10(1):126.
PMID: 28264699 DOI: 10.1186/s13071-017-2043-6

BACKGROUND: The planorbid snail Indoplanorbis exustus is the sole intermediate host for the Schistosoma indicum species group, trematode parasites responsible for cattle schistosomiasis and human cercarial dermatitis. This freshwater snail is widely distributed in Southern Asia, ranging from Iran to China eastwards including India and from the southeastern Himalayas to Southeast Asia southwards. The veterinary and medical importance of this snail explains the interest in understanding its geographical distribution patterns and evolutionary history. In this study, we used a large and comprehensive sampling throughout Indo-Malaya, including specimens from South India and Indonesia, areas that have been formerly less studied.
RESULTS: The phylogenetic inference revealed five highly divergent clades (genetic distances among clades: 4.4-13.9%) that are morphologically indistinguishable, supporting the assumption that this presumed nominal species may represent a cryptic species complex. The species group may have originated in the humid subtropical plains of Nepal or in southern adjacent regions in the Early Miocene. The major cladogenetic events leading to the fives clades occurred successively from the Early Miocene to the Early Pleistocene, coinciding with major periods of monsoonal intensification associated with major regional paleogeographic events in the Miocene and repeated climate changes due to the Plio-Pleistocene climatic oscillations. Our coverage of the Indo-Australian Archipelago (IAA) highlights the presence of a single clade there. Contrary to expectations, an AMOVA did not reveal any population genetic structure among islands or along a widely recognised zoogeographical regional barrier, suggesting a recent colonisation independent of natural biogeographical constraints. Neutrality tests and mismatch distributions suggested a sudden demographic and spatial population expansion that could have occurred naturally in the Pleistocene or may possibly result of a modern colonisation triggered by anthropogenic activities.
CONCLUSIONS: Even though Indoplanorbis is the main focus of this study, our findings may also have important implications for fully understanding its role in hosting digenetic trematodes. The existence of a cryptic species complex, the historical phylogeographical patterns and the recent range expansion in the IAA provide meaningful insights to the understanding and monitoring of the parasites potential spread. It brings a substantial contribution to veterinary and public health issues.

Matched MeSH terms: Snails/parasitology*
Susceptibility of snail vectors to Oriental anthropophilic Schistosoma

Yuan HC, Upatham ES, Kruatrachue M, Khunborivan V

Southeast Asian J Trop Med Public Health, 1984 Mar;15(1):86-94.
PMID: 6740384

Laboratory experiments were carried out to study the susceptibility of snail vectors to Oriental anthropophilic Schistosoma. Oncomelania hupensis hupensis was readily infected with the local strain of Schistosoma japonicum (Chinese strain), and also infected with S. japonicum (Philippines strain). O.h. quadrasi was only susceptible to its S. japonicum (Philippines strain). The Oncomelania races were refractory to S. mekongi, S. japonicum-like species (Malaysian strain). Tricula aperta (beta race) was readily infected with S. mekongi, S. sinensium and S. japonicum-like species from Malaysia, but not S. japonicum. T. bollingi was susceptible to S. sinensium and S. mekongi. Robertsiella kaporensis was only susceptible to the local strain, S. japonicum-like species from Malaysia. Geographical isolation may be the cause of these differences in compatibility between the snail vectors and the schistosome parasites.

Matched MeSH terms: Snails/parasitology*
Biology of Robertsiella kaporensis snails and Malaysian Schistosoma

Upatham ES, Kruatrachue M, Viyanant V, Khunborivan V, Kunatham L

Southeast Asian J Trop Med Public Health, 1985 Mar;16(1):1-9.
PMID: 4023798

Studies on the bionomics and host-parasite relationship of Robertsiella kaporensis and Malaysian Schistosoma were investigated. The study was divided into 4 parts: cultivation of snails, R. kaporensis, and maintenance of Malaysian Schistosoma life cycle, daily cercarial shedding cycle in R. kaporensis, miracidial load and cercarial shedding pattern and the infectivity of Malaysian Schistosoma cercariae. R. kaporensis were cultured in the laboratory with the use of plastic container provided with fine sand. The snails were fed with diatoms and Saraca leaves. The development period for the snail eggs was about 20-30 days, the young grew to maturity in 14-15 weeks, and the average growth rate of snails was 0.23 mm per week. The daily cercarial shedding cycle of snails had shown that the peak emergence of cercariae of Malaysian Schistosoma occurred at night, between 6-10 pm. The miracidial load which yielded the best results in terms of percentage infection rates of snails and cercarial output was the miracidial concentration of 8 miracidia per snail. The study on infectivity of Malaysian Schistosoma cercariae has shown that there was a decrease in infectivity of the cercariae to mammalian hosts as the cercariae increased in age. The percentage infection rate of mice and numbers of worms recovered were highest in mice infected with cercariae of 0-1/2 hr. old. Infection of cercariae fell rapidly after the cercariae were 16 hr. old.

Matched MeSH terms: Snails/parasitology*
Studies of Angiostrongylus malaysiensis (Nematoda, Metastrongylidae) in peninsular Malaysia: natural infection in freshwater snails and rodents in ricefields and infectivity experiments

Liat LB, Fong YL, Krishnansamy M

Southeast Asian J Trop Med Public Health, 1977 Mar;8(1):27-35.
PMID: 887993
Matched MeSH terms: Snails/parasitology*
Strigeoid trematodes of Malaysia with descriptions of a new genus and three new species

Palmieri JR, Krishnasamy M, Sullivan JT

J Helminthol, 1979 Mar;53(1):51-63.
PMID: 458132

Six species of strigeoid trematodes are reported from Malaysia. One new genus and 3 new species are described: Apatemon (Apatemon( jamesi sp. n (Strigeidae); cercaria Cotylurus sullivani sp. n. (Strigeidae); Neodiplostomum (Neodiplostomum) sp. (Diplostomatidae); Fibricola ramachandrani (Diplostomatidae); Pseudoscolopacitrema otteri gen. n. et sp. n. (Diplostomatidae); and cercaria Cyathocotyle malayi sp. n. (Cyathocotylidae). The life cycles of A. jamesi and C. malayi have also been investigated.

Matched MeSH terms: Snails/parasitology
Epidemiology and control of schistosomiasis in Southeast Asia

Harinasuta C

Southeast Asian J Trop Med Public Health, 1984 Dec;15(4):431-8.
PMID: 6535256

Schistosomiasis in Southeast Asia, caused by Schistosoma japonicum, Schistosoma mekongi and Schistosoma japonicum-like, have been reported from six different countries. The S. japonicum infections are highly prevalent in the Philippines with Oncomelania hupensis quadrasi as the vector snail, and in localized areas in Indonesia with O.h. lindoensis as the snail vector. The S. mekongi infections are recent discovery in the Lower Mekong Basin in Laos and Kampuchea, with Tricula aperta as the vector snail. The S. japonicum-like infections are found as isolated cases diagnosed by the finding of S. japonicum-like eggs in the faeces, rectal biopsy, tissue biopsy or at necropsy in Thailand and Malaysia. The control measures of schistosomiasis have been implemented in the Philippines and Indonesia, while further research studies are being conducted in Thailand and Malaysia.

Matched MeSH terms: Snails/parasitology
Angiostrongylus malaysiensis from Tuaran, Sabah, with reference to the distribution of the parasite in Malaysia

Liat LB, Wah LT, Cheah W, Cheah W, Fong YL, Fong YL

Southeast Asian J Trop Med Public Health, 1976 Sep;7(3):384-9.
PMID: 1030843

A survey of Angiostrongylus malaysiensis among wild rodent and molluscan hosts was made in the Tuaran Central Agricultural Research Station and within the vicinity of Tuaran, Sabah. Three of 19 Rattus rattus diardii, one of 2 R. exulans and one R. argentiventer were found naturally infected with the parasite. In this survey 56 of 382 molluscs comprising of Pila scutata, Achatina fulica and two species of land slugs, Laevicaulis alte and Microparmarion malayanus, were found naturally infected with the parasite. Samples of larvae from each of these molluscs were experimentally transferred to laboratory albino rats and adult worms consistent with A. malaysiensis were recovered. Comparison of the rat hosts and the molluscan intermediate hosts of the parasite in Peninsular Malaysia, Sarawak and Sabah was made, and the finding of A. malaysiensis in Tuaran is the first report of the parasite from Sabah. The distribution of the parasite throughout Malaysia is discussed. Observation on the human consumption of the freshwater snail, P. scutata, was made. Although the infection rate of this snail is low compared with other molluscan hosts examined. The importance of this mollusc as a potential source of human infection should not be overlooked. Hospital records for 1974 and 1975 were examined and clinical human angiostrongyliasis was rarely recorded in Sabah.

Matched MeSH terms: Snails/parasitology
Report of a freshwater hydrobiid snail from Pahang, Malaysia: a possible host for schistosomes infecting man

Greer GJ, Lim HK, Ow-Yang CK

Southeast Asian J Trop Med Public Health, 1980 Mar;11(1):146-7.
PMID: 7403949
Matched MeSH terms: Snails/parasitology*
Schistosoma malayensis n. sp.: a Schistosoma japonicum-complex schistosome from Peninsular Malaysia

Greer GJ, Ow-Yang CK, Yong HS

J Parasitol, 1988 Jun;74(3):471-80.
PMID: 3379527

Schistosoma malayensis n. sp., a member of the Schistosoma japonicum complex is described from Rattus muelleri in Peninsular Malaysia and 2 strains are characterized. The only morphological differences noted among adults from natural hosts were that S. malayensis are in general smaller than S. mekongi and S. japonicum. But these differences may be the result of host-induced variations and therefore are of little taxonomic value. To minimize the effects of host-induced variations, adult worms recovered from laboratory mice with similar worm burdens at 50-56 days postinfection were compared. These comparisons revealed only minor morphometric differences among these 3 species. Schistosoma malayensis eggs from naturally and experimentally infected hosts are most similar to those of S. mekongi, with eggs of both species being, in general, smaller than those of S. japonicum. The egg index for S. malayensis is usually higher than for S. japonicum and lower than for S. mekongi. Differences were noted in the developmental rates in mice for 2 isolates of S. malayensis, S. mekongi, and S. japonicum (Philippine strain), but relatively large differences observed between isolates of S. malayensis indicate that, in this case, the developmental rate is not a useful taxonomic character. Schistosoma malayensis is erected principally on the basis of differences, reported elsewhere, in the life histories and in the electrophoretic migration patterns of isoenzymes of adult worms as compared to S. mekongi and S. japonicum. These comparisons indicate that S. malayensis is more closely related to S. mekongi than to S. japonicum.

Matched MeSH terms: Snails/parasitology
Serological evidence of schistosomiasis among Orang Asli from three areas of Peninsular Malaysia

Greer GJ, Anuar H

Southeast Asian J Trop Med Public Health, 1984 Sep;15(3):303-12.
PMID: 6523170

Using ELISA and COPT diagnostic tests, serological evidence of Malaysian schistosomiasis was discovered among Orang Asli populations from three areas in Peninsular Malaysia. Serum samples collected in 1975 indicated an ELISA-positive prevalence of 25% and a COPT prevalence of 11% from Pos Iskandar, Pahang and an ELISA prevalence of 13% and a COPT of 4% from Bukit Lanjan, Selangor. Resurveys at these site in 1982-1984 showed a continued presence of serological positive individuals but prevalence rates were markedly lower: 7% and 1% for ELISA and 4% and 2% for COPT at Pos Iskandar and Bukit Lanjan respectively. Snail hosts were not found at either site. The source of infection for persons living in these lowland areas remains unknown. In a third area, Kuala Tahan, Pahang, located in the foothills of the central mountain range, foci of transmission have been found near to Orang Asli settlements. The serological prevalence rate among Negrito Orang Asli in that study area was 9% for ELISA and 4% for COPT. Thirty-three of 36 COPT-positive sera produced vacuolated bleb precipates and in 31 these were the only reactions seen. The high percentage of positives producing only these precipates suggests that among Orang Asli schistosomiasis patients such reactions are not an indication of recently acquired infection as has been reported for schistosomiasis patients in the Philippines.

Matched MeSH terms: Snails/parasitology
Schistosomiasis transmission dynamics and control in Southeast Asia

Upatham ES

Southeast Asian J Trop Med Public Health, 1984 Dec;15(4):452-61.
PMID: 6535258
Matched MeSH terms: Snails/parasitology*
Schistosomiasis malayensis-like infection among the Penan and other interior tribes (Orang Ulu) in upper Rejang River Basin Sarawak Malaysia

Sagin DD, Ismail G, Fui JN, Jok JJ

Southeast Asian J Trop Med Public Health, 2001 Mar;32(1):27-32.
PMID: 11485090

A serosurvey of various indigenous interior tribes (Orang Ulu) in upper Rejang River Basin Sarawak Malaysia, the site of a multibillion Ringgit hydroelectric power project, found 6.8% of the individual surveyed were seropositive for schistosomiasis, as determined by ELISA method using the soluble egg antigen of Schistosoma malayensis Baling strain. In all age group, the seroprevalence rate is higher (9.5%) in males than in females (4.5%) except for the 31-40 age group. Seroprevalence of schistosomiasis was found to increase with age with the above 60 age group having the highest rate followed by the 31-40 age group. Seroprevalence rate among the tribes ranges from 4.1% among the Penan to 11.6% among the Kajang. There was no seroevidence of schistosomiasis among the Ukits. A snail survey found four snail species including Brotia species, the intermediate host of the lung fluke Paragonimus westermani, however no schistosome snail host was identified. Although schistosomiasis malayensis-like infection may be endemic in the area, its public health significance remains undetermined.

Matched MeSH terms: Snails/parasitology

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