Abstract:

Giardia duodenalis is one of the significant zoonotic enteric protozoan parasites instigating symptoms like abdominal pain, diarrhea, nausea, vomiting, and delayed development in the susceptible hosts. The Mongolian gerbil has long been employed as a stable and reliable animal model to establish infection and subsequently study pathogenic dynamics of various intestinal parasites. Although previous reports have established an infection model of G. duodenalis in Mongolian gerbils, a systematic assessment of its pathogenicity was lacking. With an aim to investigate the pathogenicity of G. duodenalis in Mongolian gerbils, this study meticulously used 30 three-week-old gerbils which were randomly divided into control and treatment (infected group). An oral dose of 5×10⁶ G. duodenalis trophozoites were administered to each gerbil to establish intestinal infection. Three gerbils from each group were randomly euthanized at the 3rd, 7th, 14th, 21st and 28th day post-infection to evaluate changes in their body weight, overall pathogenicity of G. duodenalis including its infection burden, gross pathological and ultrastructural alterations in the intestine, and fluctuation in cytokine levels. Morphological changes during the encystation process of G. duodenalis were also observed both internally and externally. The results revealed that artificially infected gerbils by G. duodenalis manifested retarded development and slow weight gain. After counting trophozoite burden and scanning electron microscopy of pathological sections of intestine it was evident that myriad of trophozoites were attached to the intestine. Following infection significant villous atrophy was witnessed with blunting morphology accompanied by deepening crypts resulting in decreased villous: crypt ratio. Serum levels of pro-inflammatory cytokines IL-1β, IL-6, IL-17, and TNF-α were elevated following G. duodenalis infection while IL-10 decreased. Encystation results showed that pH and bile content influence the morphological changes like rounding off of trophozoites coupled with flagellar and adhesive disc degeneration ultimately leading to cyst formation. This study successfully established Mongolian gerbil as a suitable animal infection model for G. duodenalis, and systematic evaluation of its pathogenicity laid a foundation for further research pertaining to G. duodenalis pathogenicity, host's immune responses and development of potential drug.

Key words: Giardia duodenalis, infection model, pathogenicity