Comparison of sampling techniques and diagnostic tests for Cryptosporidium serpentis in eastern indigo snakes (Drymarchon couperi).

Abstract

The purpose of this study was to compare various sampling techniques and commercially available diagnostic tests for Cryptosporidium serpentis. A colony of 80 eastern indigo snakes (Drymarchon couperi) in human care was screened for the presence of C serpentis using endoscopic gastric mucosal biopsies for histologic and molecular analyses. At the time of endoscopic examination and biopsy, a cloacal swab, gastric swab, and gastric lavage sample were also collected. A C serpentis-specific probe hybridization quantitative PCR (qPCR) was performed on each sample. The gastric lavage sample was divided equally for direct microscopy, acid-fast stain, rapid qualitative immunochromatographic assay, direct fluorescent antibody, and 5 different PCR analyses. If a fecal sample was available at the time of endoscopic evaluation, it was also evaluated for Cryptosporidium oocysts by direct microscopy and acid-fast staining. When comparing test results to histologic analyses, the sensitivity of the probe hybridization qPCR of gastric biopsy, gastric lavage, and gastric swab was 100% while the cloacal swab was 72%. When gastric lavage tests were compared, qPCRs outperformed the other tests. Endoscopic biopsy for histologic and qPCR analyses is recommended for disease diagnosis, while gastric lavage or gastric swab samples for qPCR analysis are as sensitive as endoscopic biopsy for screening for the pathogen but cannot diagnose disease. The results from this study allow the veterinary practitioner to select the most appropriate sample and testing methodology when evaluating an ophidian patient for gastric cryptosporidiosis.