Kinetics and experimental parameters of oral Toxoplasma gondii infection in Syrian hamsters

Toxoplasma gondii is a globally prevalent intracellular parasite. Although mice are widely used as experimental models for toxoplasmosis, reliance on a single host species may limit the understanding of host-parasite interactions across different biological contexts. The Syrian hamster (Mesocricetus auratus) presents physiological and immunological characteristics that warrant evaluation as an alternative experimental model. This study aimed to characterize the kinetics of oral T. gondii infection in Syrian hamsters and to define experimental parameters, including host age and inoculum size, under controlled conditions. Hamsters aged 6-8 and 20 weeks were orally infected with sublethal doses (5, 10, or 20 cysts) of either the Brazilian atypical strain CTBr5 (ToxoDB#8) or the clonal ME49 strain (ToxoDB#1) to assess dose- and age-related susceptibility. Based on survival and parasite detectability, 6-8-week-old hamsters infected with 20 cysts were selected for kinetic analyses. Parasite dissemination was monitored in the lungs, spleen, liver, brain, and eyes at 3, 7, 15, and 30 days post-infection using quantitative PCR and histopathology. Both strains established infection without mortality under the tested conditions. CTBr5 infection was associated with prolonged parasite persistence in peripheral tissues and a delayed increase in brain parasite load, whereas ME49 showed earlier detection in neural tissue. By 30 days post-infection, brain parasite burdens were comparable between strains. Histopathological analysis confirmed cyst presence and inflammatory alterations during early chronic infection. These findings define reproducible experimental parameters and describe the temporal dynamics of oral T. gondii infection in Syrian hamsters under the tested strains and conditions, providing reference data for future studies using this species.