Update on the genetic diversity and population structure of Echinococcus granulosus in Gansu Province, Tibet Autonomous Region, and Xinjiang Uygur Autonomous Region, Western China, inferred from mitochondrial cox1, nad1, and nad5 sequences.

The identification of additional Echinococcus granulosus sensu lato (s.l.) complex species/genotypes in recent years raises the possibility that there might be more variation among this species in China than is currently understood. The aim of this study was to explore intra- and inter-species variation and population structure of Echinococcus species isolated from sheep in three areas of Western China. Of the isolates, 317, 322, and 326 were successfully amplified and sequenced for cox1, nad1, and nad5 genes, respectively. BLAST analysis revealed that the majority of the isolates were E. granulosus s.s., and using the cox1, nad1, and nad5 genes, respectively, 17, 14, and 11 isolates corresponded to Elodea canadensis (genotype G6/G7). In the three study areas, G1 genotypes were the most prevalent. There were 233 mutation sites along with 129 parsimony informative sites. A transition/transversion ratio of 7.5, 8, and 3.25, respectively, for cox1, nad1, and nad5 genes was obtained. Every mitochondrial gene had intraspecific variations, which were represented in a star-like network with a major haplotype with observable mutations from other distant and minor haplotypes. The Tajima's D value was significantly negative in all populations, indicating a substantial divergence from neutrality and supporting the demographic expansion of E. granulosus s.s. in the study areas. The phylogeny inferred by the maximum likelihood (ML) method using nucleotide sequences of cox1-nad1-nad5 further confirmed their identity. The nodes assigned to the G1, G3, and G6 clades as well as the reference sequences utilized had maximal posterior probability values (1.00). In conclusion, our study confirms the existence of a significant major haplotype of E. granulosus s.s. where G1 is the predominant genotype causing of CE in both livestock and humans in China.

Comparison of mitochondrial genetic variation of Taenia hydatigena cysticerci from China and Mongolia.

Parasitic infection is one of the many challenges facing livestock production globally. Cysticercosis tenuicollis is a common parasitic disease in domestic and wild ruminants (intermediate host) caused by the larval stage of Taenia hydatigena that primarily infects dogs (definitive host). Although genetic studies on this parasite exist, only a few describe the genetic variation of this parasite in Mongolia. Our aim was thus, to identify the mitochondrial differences in ovine isolates of Cysticercus tenuicollis entering China from Mongolia and comparison with existing Chinese isolates from sheep and goats based on the recently described PCR-RFLP method and mitochondrial genes of NADH dehydrogenase subunit 4 (nad4) and the NADH dehydrogenase subunit 5 (nad5). Sixty-nine isolates were collected during routine veterinary meat inspections from sheep that originated from Mongolia, at the modern slaughterhouses in Erenhot City, Inner Mongolia. Additional 114 cysticerci were also retrieved from sheep and goats from northern (Inner Mongolia Autonomous Region, Ningxia Hui Autonomous Region, and Gansu Province), western (Tibet Autonomous Region), and southern (Jiangxi Province and Guangxi Province) China. The PCR-RFLP approach of the nad5 showed nine mitochondrial subclusters A1, A2, A3, A5, A8, A9, A10, A11, and B of T. hydatigena isolates from sheep and goats from Mongolia and China. Meanwhile, haplogroup A1 RFLP profile was more widespread than other variants. These data supplements existing information on the molecular epidemiology of T. hydatigena in China and Mongolia and demonstrate the occurrence of similar genetic population structures in both countries.

Echinococcus granulosus sensu lato in animal intermediate hosts: What is with the organ location?

Organ or tissue tropism/preference in many parasites is essential for their establishment, survival and pathogenesis. In protozoan parasites e.g. Trypanosoma and Plasmodium, tissue tropism is associated with many important aspects such as transmission, treatment, and pathogenesis. In these parasites, tissue tropism is achieved by mechanisms such as sequestration, extravasation, transcellular migration, and vascular permeability. In contrast, little is known about the mechanism behind organ tropism/preference and the potential implication in parasitic metazoans like Echinococcus. Since intraspecies/genetic variation was described for Echinococcus, the organ preference of currently known species and subspecies among animal intermediate hosts remains unclear or perhaps poorly investigated. Here, analysis of 89,359 Echinococcus cysts from different animal intermediate hosts across 47 countries suggests a potential organ distribution pattern in different animal intermediate hosts. For example, E. granulosus s.s. (G1, G3) and E. canadensis (G7) were found more in the liver of sheep and pigs, respectively than in other organs, whereas E. ortleppi and E. canadensis G6 were significantly higher in the lung of cattle and camels, respectively. While the mechanism of organ tropism in Echinococcus and whether it is species/genotype-dependent, host-dependent, or a combination of both is still a subject of future investigations, further and detailed investigation could provide significant information that may be applicable in the diagnosis and treatment of organ-specific cystic echinococcosis or designing host or genotype-specific interventions.