Evaluation of a probe hybridization quantitative polymerase chain reaction assay for Cryptosporidium serpentis in eastern indigo snakes (Drymarchon couperi)

A probe-hybridization quantitative polymerase chain reaction assay specific for Cryptosporidium serpentis (qPCR) has been developed and shown to be extremely sensitive in the laboratory, but clinical sensitivity and specificity for this test are lacking. To approximate the sensitivity and specificity of the C. serpentis qPCR, the medical records from a captive snake colony were reviewed, and between November 2015 and June 2021, 63 eastern indigo snakes (Drymarchon couperi) were necropsied. Of these 63 snakes, 11 had qPCR performed on gastric biopsies collected at the time of necropsy, 8 had qPCR performed on samples collected by gastric swab within 35 days of necropsy, and 34 had qPCR performed on samples collected by cloacal swab within 84 days of necropsy. The qPCR results were then compared to the post-mortem histological findings, where all three sampling techniques had a 100% specificity. The sensitivity was highest in samples collected at necropsy (100%, CI: 63.06 – 100%) followed by the ante-mortem testing: gastric swab (87.50%, CI: 42.13 – 99.64%) and cloacal swab (66.67%, CI: 44.68 – 84.37%).