Molecular identification of Giardia assemblages in livestock from Jahrom, Iran

Giardia is a widespread intestinal protozoan infecting both humans and livestock, and is notable for its zoonotic transmission potential. This study aimed to assess the genetic assemblages of Giardia in cattle, sheep, and goats slaughtered in Jahrom, Iran. A total of 540 fecal samples from slaughtered 90 cattle, 247 sheep, and 203 goats were initially screened for Giardia cysts using microscopy and nested PCR targeting the glutamate dehydrogenase (gdh) gene was performed. Microscopic analysis of fecal samples revealed that 35 samples (6.5%) were positive for Giardia cysts. The overall prevalence of infection was 6.9% in sheep and goats, and 4.4% in cattle. Out of 20 isolates selected for molecular characterization, 12 were successfully sequenced, identifying assemblages AI (n = 5), AII (n = 1), and E (n = 6). All assemblage A and five assemblage E samples were associated with formed stools, while one assemblage E isolate was linked to diarrhea. Phylogenetic analysis showed that assemblage A isolates were related to human, animal, and environmental strains. Prevalence was significantly higher in younger animals and was also associated with stool consistency. The presence of assemblage A underscores a zoonotic risk, emphasizing the need for monitoring and control in livestock to reduce human infection.