Submitted to: Journal of Zoo and Wildlife Medicine
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 6, 1995
Publication Date: N/A
Interpretive Summary: Cryptosporidiosis is a chronic, life-threatening disease for rare and expensive snakes in zoological collections. Accurate and rapid diagnosis is important to prevent spread to other snakes in a collection. Of 5 tests compared to identify the oocyst stage of the parasite, a commercial antibody test proved most sensitive. Because this test is widely used to identify Cryptosporidium infectious for humans and livestock our results indicate that this test could be misleading. For example, if water tested by this method was found to contain oocysts a public health alert to stop using water could be costly and erroneous if the oocysts were of snake origin and were infectious for only reptiles.
Modified acid fast stain (Mod AFS) direct wet smear (DWS), unstained DWS (UDWS), and Sheather's sugar coverslip flotation (SSCF) techniques were compared with commercial monoclonal antibody (MAb) test MERIFLUOR Cryptosporidium/Giardia for direct fluorescence detection of C. serpentis oocysts in feces from 40 snakes without clinical signs of infection. Absolute sensitivity of MAb detection of purified C. serpentis oocysts was compared with detection of purified C. parvum oocysts. The oocysts of C. serpentis showed the same intensity of fluorescence reaction (majority, 3+ to 4+) as did C. parvum. Sensitivity of the MERIFLUOR test was 100% for SSCF-derived material, and 88% for DWS against 45% for Mod AFS DWS, 35% for SSCF, and 21% for UDWS. The threshold of MAb detection (4.7 x 1,000 oocyst/ml), the same for C. serpentis and C. parvum oocysts, was 16 times higher than the absolute sensitivity of the listed conventional techniques. Conventional techniques underestimated an average of 5.3 times the number of C. serpentis oocysts, and produced false-negative results an average of 66%; false-negatives were 100% when the concentration of oocyst was < 7.5 x 10,000/ml. The range of concentration of faecal C. serpentis oocysts (0.4 x 1,000/ml - 1.4 x 100,000/ml, mean; 5.0 x 10,000/ml) was an average of 3 times lower than those reported for C. parvum from humans and other mammals. The MAb detection proved to be more sensitive for C. serpentis oocysts than conventional techniques, and it eliminated false-negative outcomes and subjectivity associated with those methods.