Toxoplasmosis is caused by the intracellular protozoan Toxoplasma gondii. It is anopportunistic zoonosis in warm-blooded animals and humans, with a worldwide distribution. Toxoplasma gondii dense granule protein 16 (TgGRA16) can modulate some functions in host cells and is considered a significant virulent factor of the parasite. The present study reports sequence variation in TgGRA16 gene among T. gondii strains from different hosts and geographical locations, and the construction of phylogenetic relationships of these T. gondii strains based on sequences of TgGRA16, and analysis of B cell epitopes in TgGRA16. Our results showed that all TgGRA16 gene sequences were 1518 bp and the C+G contents ranged from 52.17% to 52.59%. Sequence variation in the TgGRA16 gene was 0-1.51%. Phylogenetic analysis revealed that TgGRA16 gene sequence could not be used to differentiate the different T. gondii genotypes. Six B cell epitopes were predicted in TgGRA16. These results indicated that TgGRA16 gene is not an ideal marker for studying genetic relationships of T. gondii isolates, but may represent a good vaccine candidate against toxoplasmosis.

Ascaris is a helminthic parasite, which infects a wide range of host species causing ascariasis, a predominant disease worldwide. This parasite causes significant economic losses to the pig industry. The current study was designed to determine the Ascaris nematode by the genetic characterization of three mitochondrial (mt) genes namely NADH dehydrogenase subunit 1 (nad1), cytochrome oxidase subunit 1 (cox1) and cytochrome oxidase subunit 2 (cox2). A high infection rate of Ascaris nematode has been found in Tibetan pigs at the slaughter houses in Tibet Autonomous Region of China. The nad1, cox1 and cox2 genes sequences collected from adult Ascaris individuals were amplified by polymerase chain reaction. The cloned-amplicons and the positive products were sequenced and phylogenetic analysis was performed. The results indicated that the Ascaris infecting the Tibetan pigs were Ascaris suum (A. suum). This is the first report on the isolation, identification and genetic characterization of three mitochondrial genomes (nad1, cox1, and cox2) of A. suum originated from Tibetan pigs at high altitudes in Tibet.