PCR-RFLP assay confirms the existence of different mitochondrial lineages of Taenia hydatigena including a possible geographically restricted group

Taenia hydatigena is a widespread tapeworm of canids (primarily dogs) that causes cysticercosis in ruminants (domestic and wild) and manifests as depression and weakness secondary to various hepatic damages and sometimes mortality in young animals, although, commonly encountered cases are asymptomatic. In most taeniids, genetic polymorphism has been found to impact host preferences, distribution, disease epidemiology and management. Recently, we identified two main mitochondrial lineages of T. hydatigena in China, and here, we examined the mitochondrial nad4-nad5 genes of T. hydatigena from China, Nigeria, Pakistan and Sudan to assess the intraspecies variation of isolates from these countries and also the distribution of the distinct mitochondrial groups. In addition to China, haplogroup B variant was found in Pakistan, while haplogroup A demonstrated a widespread distribution. We then designed a PCR-restriction fragment length polymorphism (PCR-RFLP) assay using XmiI (AccI) and RsaI (AfaI) restriction enzymes to differentiate members of both haplogroups. This result provides more molecular evidence supporting the existence of distinct mitochondrial variants of T. hydatigena. The epidemiological significance of these different mitochondrial groups remains to be explored further. The current PCR-RFLP assay offers a useful molecular approach for investigating the genetic population structure of T. hydatigena in enzootic regions and in identifying/discriminating the different mitochondrial groups (haplogroups A and B).