- Infection induces antibodies against the cercarial secretions, but not against the cercarial elastases of Schistosoma mansoni, Schistosoma haematobium, Schistosoma japonicum and Trichobilharzia ocellata. Bahgat, M., Francklow, K., Doenhoff, M.J., Li, Y.L., Ramzy, R.M., Kirsten, C., Ruppel, A. Parasite Immunol. (2001)