Population structure and geographical segregation of Cryptosporidium parvum IId subtypes in cattle in China

Background: Cryptosporidium parvumis a zoonotic pathogen worldwide. Extensive genetic diversity and complex population structures exist inC. parvumin different geographical regions and hosts. Unlike the IIa subtype family, which is responsible for most zoonoticC. parvuminfections in industrialized countries, IId is identified as the dominant subtype family in farm animals, rodents and humans in China. Thus far, the population genetic characteristics of IId subtypes in calves in China are not clear. Methods: In the present study, 46C. parvumisolates from dairy and beef cattle in six provinces and regions in China were characterized using sequence analysis of eight genetic loci, includingmsc6-7,rpgr,msc6-5,dz-hrgp,chom3t,hsp70,mucin1andgp60. They belonged to three IId subtypes in thegp60gene, including IIdA20G1 (n= 17), IIdA19G1 (n= 24) and IIdA15G1 (n= 5). The data generated were analyzed for population genetic structures ofC. parvumusing DnaSP and LIAN and subpopulation structures using STRUCTURE, RAxML, Arlequin, GENALEX and Network. Results: Seventeen multilocus genotypes were identified. The results of linkage disequilibrium analysis indicated the presence of an epidemic genetic structure in theC. parvumIId population. When isolates of various geographical areas were treated as individual subpopulations, maximum likelihood inference of phylogeny, pairwise genetic distance analysis, substructure analysis, principal components analysis and network analysis all provided evidence for geographical segregation of subpopulations in Heilongjiang, Hebei and Xinjiang. In contrast, isolates from Guangdong, Shanghai and Jiangsu were genetically similar to each other. Conclusions: Data from the multilocus analysis have revealed a much higher genetic diversity ofC. parvumthangp60sequence analysis. Despite an epidemic population structure, there is an apparent geographical segregation inC. parvumsubpopulations within China.