Successful Experimental Infant Baboon Model for Childhood Cryptosporidiosis Studies

Abstract

Background: Cryptosporidiosis causes high morbidity and mortality in children under 2 years of age globally. Thelack of an appropriate animal model that mimics the pathogenesis of disease in humans has hampered the development and testing of potential therapeutic options. This study aimed to develop and validate an infant baboon infection model of cryptosporidiosis.Methods: Eighteen immunocompetent weaned infant baboons aged 12 to 16 months were used. The animals weren=3 controls and three experimental groups of n=5 animals each inoculated with Cryptosporidium parvum oocystsas follows: group 1: 2× ­104, group 2: 2× ­105, group 3: 2× ­106 followed by daily fecal sampling for oocyst evaluation.Blood sampling for immunological assay was done on the day of infection and weekly thereafter until the end of theexperiment, followed by necropsy and histopathology. Statistical analysis was performed using R, SPSS, and GraphPadPrism software. Analysis of variance (ANOVA) and Bonferroni post hoc tests were used for comparison of the means,with p<0.05 considered as a significant difference. Correlation coefficient and probit analysis were also performed.Results: In all experimental animals but not controls, the onset of oocyst shedding occurred between days 2 and 4, with the highest oocyst shedding occurring between days 6 and 28. Histological analysis revealed parasite establishment only in infected animals. Levels of cytokines (TNF-α, IFN-γ, and IL-10) increased significantly in experimentalgroups compared to controls.Conclusion: For developing a reproducible infant baboon model, 2× ­104oocysts were an effective minimum quantifiable experimental infection dose.