Comparison of agglutinatio test, microscopy and nPCR for diagnosis of Toxoplasma gondii isolated from sheep and goat of Central Ethiopia

Abstract

Toxoplasmosis is one of the most globally widespread zoonoses with considerable health and economic impacts. Toxoplasmosis is conventionally diagnosed by serology. Bioassay is used for isolating strains of T. gondii, for assessing their pathogenicity in mice or for further molecular detection and genotyping. The aim of the present study was to compare the performance of microscopic cyst detection (MCD) and Direct Agglutination Test (DAT) with nested Polymerase Chain Reaction (nPCR) for the detection of T. gondii infection in mice (n=399) inoculated with heart tissue homogenates from seropositive sheep (n=4 7) and goats (n=44) in Central Ethiopia. Comparison of the diagnosis of T. gondii infection using DAT, MCD and nPCR revealed positive results on 30.58%, 28.82% and 53.13% of mice examined, respectively. There was a substantial agreement between DAT and MCD (Kappa = 0.69) for evidence of T. gondii infection in mice. Moderate agreement was observed between nPCR and MCD (Kappa = 0.43) and nPCR and DAT (Kappa= 0.47). Nested-PCR is more sensitive to diagnose T. gondii infection in mice compared to DAT (Sensitivity= 53.3%; specificity= 95.2%) and MCD (Sensitivity = 49.5%; specificity = 94. 7%), however, the joint use of the three techniques increased the sensitivity of detection. This is the first report on nPCR based detection of T. gondii DNA in mice infected with tissue homogenates of sheep and goats of Ethiopia.

Keywords: Bioassay, DAT, Ethiopia, Microscopic cyst detection, nPCR, Toxoplasmagondii