Genetic Characterization and Phylogenetic Analysis of Fasciola Species Isolated From Yaks on Qinghai-Tibet Plateau, China

Fasciola hepatica and Fasciola hybrid form co-existence in yak from Tibet of China: application of rDNA internal transcribed spacer

Fasciolosis is a parasitic disease affecting humans and livestock, caused by digenean trematodes of the genus Fasciola, primarily F. hepatica and F. gigantica. This study investigates the coexistence of these species and their hybrids in yaks from Tibet, China. We analyzed the nuclear rDNA internal transcribed spacer (ITS) regions, including ITS1 and ITS2, through Sanger sequencing and Next-Generation Sequencing (NGS) to assess single-nucleotide polymorphisms (SNPs). Our results reveal that one specimen (NM008B) is identical to pure F. hepatica, while another (NM008A) contains genetic information from both F. hepatica and F. gigantica, indicating potential hybridization or introgression. The morphological analysis reveals that the collected adult F. hepatica specimens exhibit distinct characteristics, while the hybrid specimens display "intermediate" features of F. hepatica and F. gigantica. This study is the first to document the coexistence of F. hepatica and hybrid Fasciola forms in a single yak. The findings underscore the complexities of hybridization dynamics and the necessity for advanced molecular techniques in accurately identifying Fasciola species. Future research should focus on mitochondrial DNA and other nuclear gene analysis to further elucidate the nature of these hybrids and their ecological implications.

Global scenario of genetic diversity in cox1 and nad1 genes of Moniezia expansa

Monieziasis is a parasite-borne production-limiting disease of livestock. Moniezia expansa is the most important species having cosmopolitan distribution. Despite of numerous prevalence reports, very little information is available about the evolutionary biology and population genetics of M. expansa. To close this research gap, this study was undertaken to recognize and inspect the genetic variation of M. expansa populations around the world using the cox1 and nad1 genes and deduce phylogenetic relationships with M. expansa populations. The cox1 and nad1 gene sequences were downloaded from the NCBI GenBank database. Followed by sequence alignment, median-joining networks were constructed using PopArt software. Diversity and neutrality indices were computed through DnaSp software while MEGA software was used to draw the maximum-likelihood phylogenetic tree. Thirty-two cox1 sequences, from five different countries, and 9 nad1 sequences from three different countries, were among the sequences used in this study. The cox1 and nad1 gene sequences had mutations in 97 and 36 different places, respectively. Twenty and 7 unique haplotypes were discovered for the cox1 and nad1 gene sequences, respectively. Comparable haplotype diversities were observed for both the genes under study (cox1 = 0.950; nad1 = 0.944). Negative Tajima's D and Fu Fs were found for the cox1 gene while these indices were positive for the nad1 gene. Phylogenetic analysis also showed the existence of unique haplotypes for both the cox1 and nad1 genes. The results of this study indicate that there is the existence of a huge genetic diversity in M. expansa isolates. For future studies, it is recommended that longer gene sequences should be used to describe genetic variation among M. expansa isolates as the length of the gene under study affects the genetic variation. Moreover, additional mitochondrial markers should also be investigated because the assertive strength of a group of gene targets is superior to defining genetic diversity.

Epidemiological Investigation of Yak (Bos grunniens) Fascioliasis in the Pastoral Area of Qinghai-Tibet Plateau, China

The objective of this investigation was to understand the epidemiology of fascioliasis in yaks in the alpine pastoral areas of the Qinghai-Tibet Plateau, China. The prevalence of Fasciola hepatica infection was estimated by examining eggs in the feces of yaks and by autopsy after the slaughter. Yaks were sampled from a total of 16 representative counties in Qinghai province, and risk factors were assessed based on regional and age characteristics. Fecal samples were obtained from 1542 yaks aged 0-1 (<1 year old), 1-2 (≥1 year old and <3 years old), and over 3 years (≥3 years old). In addition, 242 yaks over 3 years old who had not undergone fecal examinations were randomly selected for autopsy. A total of 267 fecal samples were positive for Fasciola spp. eggs. The average infection rate was 17.32% (0-60.61%), and the average infection intensity was 51.9 eggs per gram (epg) of feces, with intensities ranging from 18 to 112 epg. In Maduo, Dari, Zhiduo, Chengduo, and Datong counties, the Fasciola spp. eggs infection rate was zero. Fasciola spp. adult flukes were detected in 66 out of 242 yaks at autopsy, with a total infection rate of 27.27% and an average infection intensity of 21.2 (adult worms), with intensities ranging from 3 to 46 worms. Logistic regression model analysis showed that age was a significant risk factor for yak infection with Fasciola spp. In addition, the risk varied between regions: Haiyan, Gangcha, Duran, and Wulan were all high-risk areas for yak infection with Fasciola spp. The spatial distribution of the Fasciola spp. infection rate in each region showed a very weak negative correlation (Moran's I = -0.062), Duran formed a spatial distribution of high-low clusters with surrounding areas, and Datong formed a low-high clustering distribution characteristic with the surrounding areas. This investigation revealed that the infection rate of Fasciola spp. in yaks was higher on the Qinghai-Tibet Plateau. Increasing age was a risk factor for infection with Fasciola spp.; different regions also have a different risk of Fasciola spp. infection. Only two regions showed clustering characteristics in the spatial distribution of infection rates. These findings extend the epidemiological information on Fasciola spp. infection in yaks and provide baseline data for the execution of control measures against Fasciola spp. infection.