In just over a decade, the use of molecular approaches for the recognition of parasites has become commonplace. For trematodes, the internal transcribed spacer region of ribosomal DNA (ITS rDNA) has become the default region of choice. Here, we review the findings of 63 studies that report ITS rDNA sequence data for about 155 digenean species from 19 families, and then review the levels of variation that have been reported and how the variation has been interpreted. Overall, complete ITS sequences (or ITS1 or ITS2 regions alone) usually distinguish trematode species clearly, including combinations for which morphology gives ambiguous results. Closely related species may have few base differences and in at least one convincing case the ITS2 sequences of two "good" species are identical. In some cases, the ITS1 region gives greater resolution than the ITS2 because of the presence of variable repeat units that are generally lacking in the ITS2. Intraspecific variation is usually low and frequently apparently absent. Information on geographical variation of digeneans is limited but at least some of the reported variation probably reflects the presence of multiple species. Despite the accepted dogma that concerted evolution makes the individual representative of the entire species, a significant number of studies have reported at least some intraspecific variation. The significance of such variation is difficult to assess a posteriori, but it seems likely that identification and sequencing errors account for some of it and failure to recognise separate species may also be significant. Some reported variation clearly requires further analysis. The use of a "yardstick" to determine when separate species should be recognised is flawed. Instead, we argue that consistent genetic differences that are associated with consistent morphological or biological traits should be considered the marker for separate species. We propose a generalised approach to the use of rDNA to distinguish trematode species.

The Use and Implications of Ribosomal DNA Sequencing for the Discrimination of Digenean Species

hyperoxia greatly reduces the incidence of phenytoin-induced cleft lip and palate in A/J mice. Science 212: 671–672 10. Moerman P, Fryns J P, Goddeeris P, Lauweryns J M, van Assche A 1983 Aberrant twinning (diprosopus) associated with anencephaly. Clinical Genetics 24: 252–256 11. Ramadan R O 1996 A dicephalic goat with other defects. Zentralblatt fur Veterinarmedizin Reihe A 43: 337–343 12. Saini S S, Khehra R S, Kwatra M S 1993 A diprosopus in a domestic chicken embryo. Avian Diseases 37: 898–899 13. Tiessen R G, van Elsacker-Niele A M, Vermeij-Keers C, Oepkes D, van Roosmalen J, Gorsira M C 1994 A fetus with a parvovirus B19 infection and congenital anomalies. Prenatal Diagnosis 14: 173–176 14. Verdi G D, Hersh J H, Russell L J 1991 Partial duplication of the face: case report and review. Plastic and Reconstructive Surgery 87: 759–762 15. Wei X, Sulik K K 1993 Pathogenesis of craniofacial and body wall malformations induced by ochratoxin A in mice. American Journal of Medical Genetics 47: 862–871 16. Yoneda T, Pratt R M 1982 Vitamin B6 reduces cortisone-induced cleft palate in the mouse. Teratology 26: 255–258

http://jsava.co.za/index.php/jsava/article/download/343/330

WHO/FAO/OIE guidelines for the surveillance, prevention and control of taeniosis/cysticercosis

http://amcor.asahikawa-med.ac.jp/modules/xoonips/download.php?id=14667751

Human taeniasis and cysticercosis in Asia

The application of molecular systematics to the parasitic Platyhelminthes (Cestoda, Digenea and Monogenea) over the last decade has advanced our understanding of their interrelationships and evolution substantially. Here we review the current state of play and the early works that led to the molecular-based hypotheses that now predominate in the field; advances in their systematics, taxonomy, classification and phylogeny, as well as trends in species circumscription, molecular targets and analytical methods are discussed for each of the three major parasitic groups. A by-product of this effort has been an ever increasing number of parasitic flatworms characterized genetically, and the useful application of these data to the diagnosis of animal and human pathogens, and to the elucidation of life histories are presented. The final section considers future directions in the field, including taxon sampling, molecular targets of choice, and the current and future utility of mitochondrial and nuclear genomics in systematic study.

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Advances and trends in the molecular systematics of the parasitic Platyhelminthes.

Phylogeny of Taenia: Species definitions and origins of human parasites

Multiple analysis has characterized a recently described tapeworm of people, Taenia asiatica, in mainland China. Six adult tapeworms collected from people of the Zhuang minority residing in the southern part of China (Luzhai isolate) were comparatively analyzed with other tapeworms from people: T. asiatica (n = 2, South Korea), T. saginata (n = 1, Poland; n = 1, Korea), and T. solium (n = 1, People's Republic of China). Experimental infections with eggs from the Luzhai isolate in pigs and cattle produced cysticerci, each with a hookletless scolex and with wartlike formations on the external surface of the bladder wall. There were rostellar protrusions in the scolices of adult worms. Random amplified polymorphic DNA analysis using 3 arbitrary primers produced bands identical to those of the Korean T. asiatica. Conversely, T. saginata and T. solium exhibited different banding patterns. Phylogenetic relationships inferred from the complete nucleotide sequences of the internal transcribed spacer 2 placed the Chinese tapeworms consistently within the T. asiatica clade by 96% bootstrapping value in the maximum likelihood analysis, 96% in maximum parsimony, and 100% in neighbor joining. These collective data demonstrate that T. asiatica is sympatrically distributed with the other 2 species of Taenia in the human host in mainland China.

Identification of taenia asiatica in china: molecular, morphological, and epidemiological analysis of a luzhai isolate

A survey was performed to investigate the infection status of fishborne trematode (FBT) metacercariae in freshwater fish from Guangxi Zhuang Autonomous Region, China. A total of 307 freshwater fish of 31 species were collected from 5 administrative regions of Guangxi Zhuang Autonomous Region. They were examined by artificial digestion method from July 2003 to August 2004. No metacercariae were detected in fish from Fusui-xian. In fish from Mashan-xian and a market in Nanning, 3 species of metacercariae, Haplorchis taichui, Haplorchis pumilio, and Centrocestus formosanus, were mainly detected. Metacercariae (8 in number) of Clonorchis sinensis were found in 1 Chanodichthys dabryi purchased from a market in Nanning. In fish from Yangshuo, Metagonimus yokogawai metacercariae were detected from all 18 fish species examined. Total 13 C. sinensis metacercariae were found in 3 out of 10 Hemibarbus maculatus from Yangshuo. All 7 Zacco platypus from Yangshuo were infected with 8-112 Echinochasmus perfoliatus metacercariae. In fish from Binyang-xian, H. pumilo metacercariae were mainly detected in all 5 fish species examined, and only 1 metacercaria of C. sinensis was found in a Hemiculter leucisculus. From the above results, it was confirmed that some species of freshwater fish play a role of second intermediate hosts for FBT in Guangxi Zhuang Autonomous Region, China. In particular, 4 species of intestinal flukes, M. yokogawai, H. taichui, H. pumilio, and C. formosanus, were prevalent in fish hosts, whereas C. sinensis metacercariae were detected only in 3 fish species.

Xueming Li

Papers

Identification of taenia asiatica in china: molecular, morphological, and epidemiological analysis of a luzhai isolate

Fishborne Trematode Metacercariae in Freshwater Fish from Guangxi Zhuang Autonomous Region, China