OOCYSTS OF CRYPTOSPORIDIUM FROM SNAKES ARE NOT INFECTIOUS TO DUCKLINGS BUT RETAIN VIABILITY AFTER INTESTINAL PASSAGE THROUGH A REFRACTORY HOST

Six 2-week-old Cryptosporidium-free Peking ducklings (Anas platyrhynch os) each received 2.0 x 10(6) viable Cryptosporidium serpentis oocysts from 6 naturally infected captive snakes, Histological sections of di gestive (stomach, jejunum, ileum, cloaca, and cecum) and respiratory t ract tissues (larynx, trachea, and lungs) did not contain life-cycle s tages of Cryptosporidium in any of the inoculated ducklings, Because d ucklings were refractory to infection, C. serpentis transmission via a diet of Peking ducklings is improbable, Viable (per in vitro excystat ion assay) inoculum-derived oocysts were detected in duckling feces up to 7 days post-inoculation (PI): the number of intact oocysts excrete d during the first 2 days PT was significantly higher than for the rem aining 5 days PI (P < 0.01). The dynamics of oocyst shedding showed th at overall the birds released a significantly higher number of intact oocysts than oocyst shells (P < 0.01). Retention of the viability of C . serpentis oocysts following intestinal passage through a refractory avian species may have epizootiological implications, Under certain ci rcumstances such as after the ingestion of C. serpentis-infected prey, herpetivorous birds may disseminate C. serpentis oocysts in the envir onment. (C) 1998 Elsevier Science B.V.