Immunity against reinfection in pigs following Taenia solium infection and a quantitative dose-response model.

Taenia solium is a zoonotic parasite causing significant health and economic burdens, with complex transmission dynamics that demand improved control strategies. This study examines how infection and reinfection affect cyst development in pigs and how acquired immunity constrains parasite burden. A total of 116 pigs were purchased from commercial farms in northern Peru and housed under controlled conditions. Of these, 110 pigs were allocated to 18 experimental groups to evaluate the impact of single and repeated infections with varying doses of T. solium eggs and to model the number of live cysts produced based on dose and age at infection. Gravid proglottids collected from human cases were used to prepare viable egg pools. Infections were administered orally via esophageal catheterization, and pigs were necropsied 10 weeks after the final infection to quantify cyst burden. A negative binomial regression model assessed the influence of infection dose, prior infection, age, and other factors. No significant differences in cyst counts were found between singly infected and reinfected pigs, regardless of initial or reinfection doses, highlighting that infection induces strong acquired immunity that prevents subsequent infections. A dose-response analysis indicated that cyst burden follows a power relationship with egg dose. Integrating data from both single and reinfected pigs into a unified model improved prediction precision. Furthermore, incorporating age at infection allowed us to model the combined effects of acquired and innate immunity, reflecting changes in susceptibility over time. These findings demonstrate that a single exposure to T. solium eggs can generate robust protective immunity in pigs. The resulting quantitative model, predicting viable cyst counts based on dose and age, offers valuable insights for integrating immunity dynamics into transmission models, supporting the development of more effective strategies for controlling T. solium.