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Abstract Background Clonorchiasis, caused by Clonorchis sinensis, is one of the major parasitic zoonoses in China, particularly in China's southern Guangdong province where the prevalence of C. sinensis infection in humans is high. However, little is known of the prevalence of C. sinensis infection in its reservoir hosts dogs and cats. Hence, the prevalence of C. sinensis infection in dogs and cats was investigated in Guangdong province, China between October 2006 and March 2008. Results A total of 503 dogs and 194 cats from 13 administrative regions in Guangdong province were examined by post-mortem examination. The worms were examined, counted, and identified to species according to existing keys and descriptions. The average prevalences of C. sinensis infection in dogs and cats were 20.5% and 41.8%, respectively. The infection intensities in dogs were usually light, but in cats the infection intensities were more serious. The prevalences were higher in some of the cities located in the Pearl River Delta region which is the most important endemic area in Guangdong province, but the prevalences were relatively lower in seaside cities. Conclusions The present investigation revealed a high prevalence of C. sinensis infection in its reservoir hosts dogs and cats in China's subtropical Guangdong province, which provides relevant "base-line" data for conducting control strategies and measures against clonorchiasis in this region.

Abstract Toxoplasmosis is a zoonotic infection of humans and animals, caused by the opportunistic protozoan Toxoplasma gondii, a parasite belonging to the phylum Apicomplexa. Infection in pregnant women may lead to abortion, stillbirth or other serious consequences in newborns. Infection in immunocompromised patients can be fatal if not treated. On average, one third of people are chronically infected worldwide. Although very limited information from China has been published in the English journals, T. gondii infection is actually a significant human health problem in China. In the present article, we reviewed the clinical features, transmission, prevalence of T. gondii infection in humans in China, and summarized genetic characterizations of reported T. gondii isolates. Educating the public about the risks associated with unhealthy food and life style habits, tracking serological examinations to special populations, and measures to strengthen food and occupational safety are discussed.

Abstract Liver flukes belonging to the genus Fasciola are among the causes of foodborne diseases of parasitic etiology. These parasites cause significant public health problems and substantial economic losses to the livestock industry. Therefore, it is important to definitively characterize the Fasciola species. Current phenotypic techniques fail to reflect the full extent of the diversity of Fasciola spp. In this respect, the use of molecular techniques to identify and differentiate Fasciola spp. offer considerable advantages. The advent of a variety of molecular genetic techniques also provides a powerful method to elucidate many aspects of Fasciola biology, epidemiology, and genetics. However, the discriminatory power of these molecular methods varies, as does the speed and ease of performance and cost. There is a need for the development of new methods to identify the mechanisms underpinning the origin and maintenance of genetic variation within and among Fasciola populations. The increasing application of the current and new methods will yield a much improved understanding of Fasciola epidemiology and evolution as well as more effective means of parasite control. Herein, we provide an overview of the molecular techniques that are being used for the genetic characterization, detection and genotyping of Fasciola spp..

Abstract Background Clonorchis sinensis is a zoonotic parasite causing clonorchiasis-associated human disease such as biliary calculi, cholecystitis, liver cirrhosis, and it is currently classified as carcinogenic to humans for cholangiocarcinoma. MicroRNAs (miRNAs) are non-coding, regulating small RNA molecules which are essential for the complex life cycles of parasites and are involved in parasitic infections. To identify and characterize miRNAs expressed in adult C. sinensis residing chronically in the biliary tract, we developed an integrative approach combining deep sequencing and bioinformatic predictions with stem-loop real-time PCR analysis. Results Here we report the use of this approach to identify and clone 6 new and 62,512 conserved C. sinensis miRNAs which belonged to 284 families. There was strong bias on families, family members and sequence nucleotides in C. sinensis. Uracil was the dominant nucleotide, particularly at positions 1, 14 and 22, which were located approximately at the beginning, middle and end of conserved miRNAs. There was no significant "seed region" at the first and ninth positions which were commonly found in human, animals and plants. Categorization of conserved miRNAs indicated that miRNAs of C. sinensis were still innovated and concentrated along three branches of the phylogenetic tree leading to bilaterians, insects and coelomates. There were two miRNA strategies in C. sinensis for its parasitic life: keeping a large category of miRNA families of different animals and keeping stringent conserved seed regions with high active innovation in other places of miRNAs mainly in the middle and the end, which were perfect for the parasite to perform its complex life style and for host changes. Conclusions The present study represented the first large scale characterization of C. sinensis miRNAs, which have implications for understanding the complex biology of this zoonotic parasite, as well as miRNA studies of other related species such as Opisthorchis viverrini and Opisthorchis felineus of human and animal health significance.

Abstract Background Studying mitochondrial (mt) genomics has important implications for various fundamental areas, including mt biochemistry, physiology and molecular biology. In addition, mt genome sequences have provided useful markers for investigating population genetic structures, systematics and phylogenetics of organisms. Toxocara canis, Toxocara cati and Toxocara malaysiensis cause significant health problems in animals and humans. Although they are of importance in human and animal health, no information on the mt genomes for any of Toxocara species is available. Results The sizes of the entire mt genome are 14,322 bp for T. canis, 14029 bp for T. cati and 14266 bp for T. malaysiensis, respectively. These circular genomes are amongst the largest reported to date for all secernentean nematodes. Their relatively large sizes relate mainly to an increased length in the AT-rich region. The mt genomes of the three Toxocara species all encode 12 proteins, two ribosomal RNAs and 22 transfer RNA genes, but lack the ATP synthetase subunit 8 gene, which is consistent with all other species of Nematode studied to date, with the exception of Trichinella spiralis. All genes are transcribed in the same direction and have a nucleotide composition high in A and T, but low in G and C. The contents of A+T of the complete genomes are 68.57% for T. canis, 69.95% for T. cati and 68.86% for T. malaysiensis, among which the A+T for T. canis is the lowest among all nematodes studied to date. The AT bias had a significant effect on both the codon usage pattern and amino acid composition of proteins. The mt genome structures for three Toxocara species, including genes and non-coding regions, are in the same order as for Ascaris suum and Anisakis simplex, but differ from Ancylostoma duodenale, Necator americanus and Caenorhabditis elegans only in the location of the AT-rich region, whereas there are substantial differences when compared with Onchocerca volvulus,Dirofiliria immitis and Strongyloides stercoralis. Phylogenetic analyses based on concatenated amino acid sequences of 12 protein-coding genes revealed that the newly described species T. malaysiensis was more closely related to T. cati than to T. canis, consistent with results of a previous study using sequences of nuclear internal transcribed spacers as genetic markers. Conclusion The present study determined the complete mt genome sequences for three roundworms of human and animal health significance, which provides mtDNA evidence for the validity of T. malaysiensis and also provides a foundation for studying the systematics, population genetics and ecology of these and other nematodes of socio-economic importance.

To the Editor: Malaria caused by Plasmodium spp. is one of the most prevalent parasitic diseases in the world, especially in tropical countries. P. vivax represents the second most prevalent [...]

Toxocara cati(cat roundworm) is a common parasitic nematode that infects humans and other hosts, causing toxocariasis. Although its significance as a pathogen, the epidemiology, genetics and biology ofT. catiremain poorly understand in China. In the present study, genetic variation in mitochondrial (mt) cytochromecoxidase subunit 1 (cox1) gene and internal transcribed spacer (ITS) of rDNA region amongT. catiin Guangdong province, subtropical China was examined. A portion of thecox1 (pcox1) and the complete ITS (ITS1 + 5.8S rDNA + ITS2) were amplified separately from individual worms by polymerase chain reaction (PCR) and amplicons were then subjected to sequencing from both directions. The length of the sequences of pcox1, ITS-1, and ITS-2 were 308 bp, 462 bp, and 335 bp, respectively. The intra-specific sequence variations withinT. catiwere 0–3.6% for pcox1, 0–2.4% for ITS-1, and 0–2.7% for ITS-2. However, the inter-specific sequence differences were significantly higher, being 8.6%, 10.7%, and 11.3% for pcox1, ITS-1, and ITS-2, respectively. Phylogenetic analyses based on the pcox1 sequences indicated that all the isolates in Guangdong province were in genusToxocara, which confirmed that these parasites representT. cati. The molecular approach employed provides a powerful tool for elucidating the epidemiology, genetics, and biology of zoonoticT. catiin China and elsewhere. [ABSTRACT FROM PUBLISHER]

To the Editor: Sparganosis is a worldwide parasitic zoonosis caused by infection with spargana, the plerocercoid larvae of various diphyllobothroid tapeworms belonging to the genus Spirometra (1-3). Sparganosis poses a [...]

Hymenolepis nanais a common tapeworm that parasitizes in the small intestine of rodent animals and humans. The present study examined the sequence diversity of three mitochondrial (mt) genes namely NADH dehydrogenase subunits 5 (nad5), small subunit ribosomal RNA (rrnS), and ATPase subunit 6 (atp6) ofH. nanafrom mice in different geographical regions of China. A part of thenad5 (pnad5), completerrnS andatp6 genes were amplified separately from individualH. nanaisolates using polymerase chain reaction (PCR) and then sequenced. The sequences of pnad5,rrnS, andatp6 were 710 bp, 704–711 bp, and 516 bp in length, respectively. The A + T contents of the sequences were 70.1–73.5% (pnad5), 70.1–71.7% (rrnS), and 76.6–77.9% (atp6). Sequence variation withinH. nanawas 0–1.4% foratp6, 0–1.7% forrrnS, and 0–0.7% for pnad5. The inter-specific sequence differences betweenH. nanaandHymenolepis diminutawere significantly higher, which was 31.6–31.7% (pnad5), 16.1–17.6% (rrnS), and 26.5–27.1% (atp6). Phylogenetic analysis based on the combined three sequences using the maximum parsimony (MP) method supported thatH. nanais a species complex or “cryptic” species. These findings demonstrated clearly the usefulness of the three mtDNA sequences for population genetics and systematic studies ofH. nanaof human and animal health significance. [ABSTRACT FROM AUTHOR]