Observation of Giardia duodenalis infection in Mongolian gerbils: Cysts isolated from bovine feces

Abstract

Assemblage E of Giardia duodenalis, primarily infecting ruminants, has been relatively understudied both in vivo and in vitro. Due to unsuccessful attempts at in vitro cultivation, this study focused on establishing an economical, stable, and clinically relevant experimental animal model for Assemblage E infections. Cysts were purified from bovine feces via 33 % zinc sulfate flotation, with Assemblage E identity confirmed by gdh gene sequencing. Nine five – day - old Mongolian gerbils were randomly allocated into control group (PBS), low-dose group (5 × 10⁴cysts), and high-dose group (1 × 10⁵cysts) averagely, Gerbils were received bovine-derived Assemblage E cysts via oral gavage, all infected subjects were undergone of necropsy at 8 days post-infection. Longitudinal monitoring result demonstrated that gerbils in infected groups exhibited growth retardation and excreted soft feces compared with controls. Histopathological examination result revealed that massive trophozoite were colonized on atrophied duodenal villi, meanwhile, enterocyte boundary was effacement in high-dose group. Scanning electron microscopy (SEM) detection result were showed that the trophozoite density decline along the intestinal tract: duodenum>jejunum>ileum. That could be confirmed the characteristic of trophozoite duodenal tropism. Encystation dynamics analysis was identified bile acid-mediated morphological transformation in the ileum through SEM, the process of encystation with trophozoite rounding, ventral disc degeneration and cyst wall formation. These results could recapitulate the complete life cycle of Assemblage E in experimental hosts, this study provided a validated model for investigating host-specific about giardiasis pathogenesis.