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 platyrhynchos) each received 2.0 x 10(6) 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.
Graczyk
T K
TK
Department of Molecular Microbiology and Immunology, School of Hygiene and Public Health, Johns Hopkins University, Baltimore, MD 21205, USA. tgraczyk@jhsph.edu
Cranfield
M R
MR
Fayer
R
R
D000818:Animals; D001715:Bird Diseases / Q000469:parasitology* / Q000635:transmission; D003457:Cryptosporidiosis / Q000469:parasitology* / Q000635:transmission; D003458:Cryptosporidium / Q000254:growth & development / Q000472:pathogenicity*; D004372:Ducks / Q000469:parasitology*; D005243:Feces / Q000469:parasitology; D012911:Snakes / Q000469:parasitology*