A COMPARATIVE-STUDY ON THE BIOLOGY OF CRYPTOSPORIDIUM-SERPENTIS AND CRYPTOSPORIDIUM-PARVUM (APICOMPLEXA, CRYPTOSPORIDIIDAE)

Oocysts of Cryptosporidium serpentis (Apicomplexa: Cryptosporidiidae) were collected from a naturally infected yellow rat snake (Elaphe obsoleta quadrivittata) housed at the Houston Zoological Gardens. Oocysts of C. serpentis were 6.2 x 5.3-mu-m (range: 5.6-6.6 x 4.8-5.6-mu-m) with a shape index (length/width) of 1.16 (range 1.04-1.33); whereas those of a mammalian isolate (C. parvum) were 5.2 x 4.6-mu-m (range 4.8-5.6 x 4.2-4.8-mu-m) with a shape index of 1.15 (range: 1.04-1.22). Oral inoculation of oocysts into suckling mice (Mus musculus) resulted in successful infections of C. parvum but not C. serpentis. Purification of oocysts on cesium chloride gradients followed by I-125 surface iodination and sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed significant differences in oocyst surface proteins and electrophoretic profiles between the two species. These results suggest that food items such as laboratory mice do not appear to be capable of transmitting infections to susceptible reptilian hosts and that significant differences exist between C. serpentis and C. parvum.