Pregnant sows immunized with Cryptosporidium parvum significantly reduced infection in newborn piglets challenged with C. parvum but not with C. hominis.

Background: The piglet is the only model to investigate the immunogenic relationship between Cryptosporidium hominis and C. parvum, the species responsible for diarrhea in humans. Despite being indistinguishable antigenically, and high genetic homology between them, they are only moderately cross protective after an active infection.

Methodology/principal Findings: Here we examined the degree of passive protection conferred to piglets suckling sows immunized during pregnancy with C. parvum. After birth suckling piglets were challenged orally with either C. parvum or C. hominis at age 5 days. Animals challenged with C. parvum had significant reduction of infection rate, while piglets challenged with C. hominis showed no reduction despite high C. parvum serum and colostrum IgG and IgA antibody.

Conclusions/significance: We add these data to earlier studies where we described that infection derived immunity provides partial cross-protection. Together, it appears that for full protection, vaccines against human cryptosporidiosis must contain antigenic elements derived from both species.