Assessment of Echinococcus granulosus polymorphism in Qinghai province, People's Republic of China.

Cystic echinococcosis (CE) is highly endemic in the Chinese province of Qinghai, located on the Tibetan Plateau. The Echinococcus granulosus sheep strain has already been reported in this focus. To improve our understanding of the role the parasite plays in the high prevalence observed in humans, we assessed the genetic polymorphism of 55 E. granulosus samples (37 from humans) using three discriminative mitochondrial markers: coxI, nadI and atp6. We obtained a total of 13 distinct genotypes which were all related to the common sheep G1 strain. Six of these genotypes have already been reported in China and other foci around the world. The remaining seven genotypes were new variants of the strain. The parasite population which was studied in the present work did not differ substantially from those observed in other foci of CE. Environmental conditions and human behaviour could explain the high incidence of the parasitic disease, particularly in the Tibetan population in the south of Qinghai, most of whom are livestock farmers.