Validation of various parasite detection tests for use in the Australian marsupials quenda (Isoodon obesulus) and brushtail possums (Trichosurus vulpecula)

Abstract

We aimed to validate the use of 1) the modified agglutination test and a polymerase chain reaction (PCR) protocol in detecting Toxoplasma gondii infection in quenda ( Isoodon obesulus) and brushtail possums ( Trichosurus vulpecula); 2) immunofluorescence microscopy of feces and a PCR and sequencing protocol in detecting Giardia spp. infection in quenda; and 3) a fecal flotation protocol in detecting gastrointestinal helminth infections of quenda. Quenda and brushtail possum carcasses, and samples from trapped quenda, were tested with 2 parasite detection tests per parasite, and results were modeled using Bayesian latent class analysis to estimate test sensitivity and specificity. The modified agglutination test and the PCR protocol were highly specific at detecting T. gondii infections in quenda and brushtail possums (≥93%); however, data were insufficient to assess sensitivity with adequate precision. Immunofluorescence microscopy and the PCR and sequencing protocol were both highly specific at detecting Giardia spp. in quenda (≥96%), but the PCR and sequencing protocol was relatively insensitive (69%, 95% credible interval [CrI]: 60–77%) compared to the highly sensitive immunofluorescence microscopy (98%, 95% CrI: 93–99%). The fecal flotation protocol was generally highly specific in the detection of gastrointestinal helminth infections (≥94%, with the exception of Trichuris spp. (88%, 95% CrI: 71–99%). The fecal flotation protocol was moderately to highly sensitive (≥74%) in the detection of strongyles, Labiobulura spp., Linstowinema spp., and Trichuris spp. Sensitivity was poor for detection of the cestode genus Potorolepis (36%, 95% CrI: 14–67%).