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United States Department of Agriculture

Agricultural Research Service

Title: Oocysts of Cryptosporidium from Snakes Are Not Infectious to Ducklings But Retain Viability after Intestinal Passage Through a Refractory Host

item Graczyk, T - JOHNS HOPKINS UNIV
item Cranfield, M - THE BALTIMORE ZOO

Submitted to: Journal of Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 19, 1997
Publication Date: N/A

Interpretive Summary: Migratory waterfowl have been shown to serve as potential mechanical transmitters of Cryptosporidium parvum, the only species of Cryptosporidium infectious for humans. The present study demonstrated that ducklings could also serve as mechanical vectors for another species, one infectious for reptiles. This finding means that ducks and perhaps other migratory birds can disseminate numerous species of Cryptosporidium throughout the environment.

Technical Abstract: Six 2-wk-old Cryptosporidium-free Peking ducklings (Anas platyrhynchos) each received 2.0 x 106 viable Cryptosporidium serpentis oocysts from 6 naturally infected captive snakes. Histological sections of digestive (stomach, jejunum, ileum, cloaca, and cecum) and respiratory tract tissues (larynx, trachea, and lungs) did not contain life-cycle stages of Cryptosporidium in any of the inoculated ducklings. Because ducklings were refractory to infection, C. serpentis transmission via a diet of Peking ducklings is improbable. Viable (per in vitro excystation assay) inoculum-derived oocysts were detected in duckling feces up to 7 days post-inoculation (PI); the number of intact oocysts excreted during the first 2 days PI was significantly higher than for the remaining 5 days PI (P < 0.01). The dynamics of oocyst shedding showed that 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 circumstances such as after the ingestion of C. serpentis-infected prey, herpetivorous birds may disseminate C. serpentis oocysts in the environment.

Last Modified: 4/22/2015
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