The prevalence of intestinal parasites was investigated in intensive pig farms in Guangdong Province, China between July 2000 and July 2002. Faecal samples from 3636 pigs (both sexes and five age groups) from 38 representative intensive pig farms employing different parasite control strategies were examined for the presence of helminth ova and protozoan oocysts, cysts and/or trophozoites using standard techniques. Of the 3636 pigs sampled, 209 (5.7%) were infected with Trichuris suis, 189 (5.2%) with Ascaris, 91 (2.5%) with Oesophagostomum spp., 905 (24.9%) with coccidia (Eimeria spp. and/or Isospora suis) and 1716 (47.2%) with Balantidium coli. These infected pigs were mainly from farms without a strategic anti-parasite treatment regime. Concurrent infection of multiple parasites was common, and T. suis was the most common nematode infecting breeding, young and mature pigs. The results of the present investigation provide relevant 'base-line' data for assessing the ffectiveness of control strategies against intestinal parasitism in intensively raised pigs in Guangdong Province, China.

PCR-based single strand conformation polymorphism (SSCP) analysis was used to characterize monogenean specimens of the subfamily Benedeniinae of morphologically uncertain specific status from different marine fish species, using Neobenedenia melleni, N. girellae and Entobdella corona for comparison. The first internal transcribed spacer (ITS-1) and the 50 terminal variable region (D1-D3 domains) of the large subunit ribosomal DNA (lsrDNA) were amplified separately from individual monogeneans, and the amplicons were subjected to PCR-SSCP analyses, followed by direct sequencing. Both SSCP patterns and the ITS-1 sequences data allowed specimens representing Entobdella spp. from the host Taeniura melanospilos to be unequivocally distinguished from those representing Neobenedenia spp. and those representing Benedenia spp. Neobenedenia girellae, a morphologically controversial species, had identical SSCP banding pattern and ITS-1 sequence to that of N. melleni, supporting the proposal that N. girellae is a synonym of N. melleni. Neobenedenia spp. and Benedenia spp. had identical SSCP patterns and ITS-1 sequences. These findings and the PCR-SSCP approach taken should have implications for the accurate identification and assessment of taxonomic validity of other important monogenean groups of the marine fish.

The oriental liverfluke, Clonorchis sinensis, is of major socioeconomic importance in parts of Asia, including China, Japan, Korea, Taiwan, and Vietnam. The parasite is transmitted via snails to freshwater fish, and then to human beings and other piscivorous mammals, and causes substantial clinical or subclinical disease, known as clonorchiasis. There is considerable evidence for an aetiological relation between clonorchiasis and cholangiocarcinoma in human beings. It is estimated that about 35 million people are infected globally, of whom approximately 15 million are in China. Although very little information from China has been published in the English language, recent nalyses of epidemiological data sets suggest that clonorchiasis is having an increased human-health impact due to the greater consumption of raw freshwater fish. To gain an improved insight into clonorchiasis in China, this review provides a background on the parasite and its life cycle, summarises key aspects regarding the pathogenesis, diagnosis, and treatment of clonorchiasis, describes the geographic distribution and prevalence of clonorchiasis, and makes some recommendations for future research and the control of this important disease.

Marteilia sydneyi (Paramyxea) is the causative agent of QX disease in oysters. In spite of the economic impact of this disease, its origin and the precise reason(s) for its apparent spread in Australian waters are not yet known. Given such knowledge gaps, investigating the population genetic structure(s) of M. sydneyi populations could provide insights into the epidemiolog and ecology of the parasite and could assist in its prevention and control. In this study, single strand conformation polymorphism (SSCP)-based analysis of a region (195 bp) of the first internal transcribed spacer (ITS-1) of ribosomal DNA was employed to investigate genetic variation within and among five populations of M. sydneyi from oysters from five different locations in eastern Australia. The analysis showed the existence of a genetic variant of M. sydneyi common to the Great Sandy Strait, and the Richmond and Georges Rivers, as distinct from variants at the Pimpama and Clarence Rivers. Together with historical and other information relating to the QX disease outbreaks in eastern Australia, the molecular findings support the proposal that the parasite originated in the Great Sandy Strait and/or Richmond River and then extended southward along the coast. From a technical perspective, the study emonstrated the usefulness of SSCP as a tool to study the population genetics and epidemiology of M. sydneyi.

Isolates of Fasciola (Platyhelminthes: Trematoda: Digenea) from different host species and geographical locations in Mainland China were characterised genetically. The second internal transcribed spacer (ITS-2) of nuclear ribosomalDNA(rDNA)was amplified from individual trematodes by polymerase chain reaction (PCR), and the representative amplicons were cloned and sequenced. The length of the ITS-2 sequences was 361-362 bp for all Chinese Fasciola specimens sequenced. While there was no variation in length or composition of the ITS-2 sequences among multiple specimens from France, Sichuan and Guangxi, sequence difference of 1.7% (6/362) was detected between specimens from France and Sichuan, and those from Guangxi. Based on ITS-2 sequence data, it was concluded that the Fasciola from Sichuan represented Fasciola hepatica, the one from Guangxi represented Fasciola gigantica and the one from sheep from Heilongjiang may represent an "intermediate genotype", as its ITS-2 sequences were unique in that two different ITS-2 sequences exist in the rDNA array within a single Fasciola worm. One of the sequences is identical to that of F. hepatica, and the other is almost identical to that of F. gigantica in that nucleotides at five of the six polymorphic positions represent F. gigantica. This microheterogeneity is possibly due to sequence polymorphism among copies of the ITS-2 array within the same worm. Based on the sequence differences, a PCR-linked restriction fragment length polymorphism (PCR-RFLP) assay was established for the unequivocal delineation of the Fasciola spp. from Mainland China using restriction endonuclease Hsp92II or RcaI. This assay should provide a valuable tool for the molecular identification and for studying the ecology and population genetic structures of Fasciola spp. frm Mainland China and elsewhere.