A COMPARATIVE-ASSESSMENT OF DIRECT FLUORESCENCE ANTIBODY, MODIFIED ACID-FAST STAIN, AND SUCROSE FLOTATION TECHNIQUES FOR DETECTION OF CRYPTOSPORIDIUM-SERPENTIS OOCYSTS IN SNAKE FECAL SPECIMENS

Modified acid-fast stain (Mod AFS) of a direct wet smear (DWS), unstai ned DWS (UDWS), and Sheather's sugar coverslip flotation (SSCF) techni ques were compared with the commercial monoclonal antibody (MAb) test MERIFLUOR(TM) Cryptosporidium/Giardia for direct fluorescence detectio n of C, serpentis oocysts in feces from 40 snakes without clinical sig ns of infection. MERIFLUOR(TM) test detection sensitivities for purifi ed C. serpentis and C, parvum oocysts were compared. The oocysts of C. serpentis and C. parvum showed the same intensity of fluorescence rea ction (majority, 3+ to 4+). Sensitivity of the MERIFLUOR(TM) test was 100% for SSCF-derived material and 88% for DWS versus 45% for Mod AFS DWS, 35% for SSCF, and 21% for UDWS. The threshold of MAb detection(4. 7 x 10(3) oocyst/ml), was the same for C. serpentis and C. parvum oocy sts and was 16 times higher than the absolute sensitivity of the liste d conventional techniques. Conventional techniques underestimated the number of C. serpentis oocysts by an average factor of 5.3 and produce d false-negative results an average of 66% of the time. False negative s were 100% when the concentration of oocysts was <7.5 x 10(4)/ml. The range of concentration of fecal C. serpentis oocysts (0.4 x 10(3)/ml- 1.4 x 10(5)/ml, (x) over bar = 5.0 x 10(4)/ml) was an average of three times lower than those reported for C. parvum from humans and other m ammals. The MAb detection was more sensitive for C. serpentis oocysts than were conventional techniques, and it eliminated false-negative ou tcomes and the subjectivity associated with those methods.