Submitted to: Journal of Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 21, 1995
Publication Date: N/A
Interpretive Summary: Rare and expensive snakes in zoos throughout the world have been diagnosed with chronic cryptosporidiosis, a protozoan parasite known to infect humans and domestic livestock. Feeding of Cryptosporidium-infected mice to snakes has been the suspected route of transmission. However, our tests in which Cryptosporidium isolated from snakes failed to infect mice strongly suggest inability of reptilian isolates of Cryptosporidium to transmit to mammals. These findings will pose a problem for public health officials and water treatment plant operators when waterborne Cryptosporidium is detected but cannot be differentiated as mammalian or reptilian without expensive and lengthy infectivity testing.
The total number of Cryptosporidium serpentis oocysts cleaned from the feces of each of 10 captive snakes (7 species, 4 genera) with clinical cryptosporidiosis ranged from 2.0 x 10,000 to 6.5 x 1,000,000 with a mean of 1.4 x 100,000 oocysts. Oral inoculations of 9 litter-groups of 3, 5-day-old suckling BALB/c mouse pups (Mus musculus) with 6.7 x 1,000 to 1.2 x 100,000 per pup of viable, C. serpentis oocysts from 10 snakes resulted in no transmission. The mice showed normal development; the litter-group weight gain was not altered significantly (P > 0.05) relative to the total number of C. serpentis oocysts inoculated, or to the initial group weight (P > 0.05). Histological sections of stomach, duodenum, jejunum, ileum, cecum, and colon sections 4 days post-inoculation did not contain any life-cycle stages of Cryptosporidium in any inoculated mice. Because these neonatal, C. parvum-susceptible BALB/c mice were resistant to infection it is unlikely that C. serpentis transmission to the snakes "via infected prey" results when captive snakes are maintained on a diet of BALB/c mice.