Evaluation of the performance of five diagnostic tests for Fasciola hepatica infection in naturally infected cattle using a Bayesian no gold standard approach

The clinical and economic importance of fasciolosis has been recognised for centuries, yet diagnostic tests available for cattle are far from perfect. Test evaluation has mainly been carried out using gold standard approaches or under experimental settings, the limitations of which are well known. In this study, a Bayesian no gold standard approach was used to estimate the diagnostic sensitivity and specificity of five tests for fasciolosis in cattle. These included detailed liver necropsy including gall bladder egg count, faecal egg counting, a commercially available copro-antigen ELISA, an in-house serum excretory/secretory antibody ELISA and routine abattoir liver inspection. In total 619 cattle slaughtered at one of Scotland’s biggest abattoirs were sampled, during three sampling periods spanning summer 2013, winter 2014 and autumn 2014. Test sensitivities and specificities were estimated using an extension of the Hui Walter no gold standard model, where estimates were allowed to vary between seasons if tests were a priori believed to perform differently for any reason. The results of this analysis provide novel information on the performance of these tests in a naturally infected cattle population and at different times of the year where different levels of acute or chronic infection are expected. Accurate estimates of sensitivity and specificity will allow for routine abattoir liver inspection to be used as a tool for monitoring the epidemiology of F. hepatica as well as evaluating herd health planning. Furthermore, the results provide evidence to suggest that the copro-antigen ELISA does not cross-react with Calicophoron daubneyi rumen fluke parasites, while the serum antibody ELISA does

MONITORING THE DIVERSITY OF RHIZOBIUM-MELILOTI FIELD AND MICROCOSM ISOLATES WITH A NOVEL RAPID GENOTYPING METHOD USING INSERTION ELEMENTS

KOSIER B, Pühler A, SIMON R. MONITORING THE DIVERSITY OF RHIZOBIUM-MELILOTI FIELD AND MICROCOSM ISOLATES WITH A NOVEL RAPID GENOTYPING METHOD USING INSERTION ELEMENTS. MOLECULAR ECOLOGY. 1993;2(1):35-46.Rhizobium meliloti strains isolated from alfalfa plants grown in a mining recultivation field, in a model ecosystem (microcosm) and in soil core containers were characterized by two new taxonomic methods, fingerprinting and handprinting, using insertion sequence elements (IS) as hybridization probes. The diversity of strains within the field population could first be detected with IS-fingerprinting, whereby nearly three times more groups of Rhizobium meliloti strains could be identified in comparison to the groups according to plasmid profiles. This complexity and diversity of the rhizobial population was also detected in microcosm studies. Strains identified among the field population were also detected in the microcosm studies. The persistence of rhizobia in soil was demonstrated in soil core samples held in a cold room for 2 years. A decrease in the genomic diversity of the R. meliloti population upon soil storage was observed. A novel monitoring method, IS-handprinting, in which the presence of certain endogenous insertion elements within a strain is registered, was successfully employed to characterize genetically the field R. meliloti strains with simplicity and speed. In contrast to IS-fingerprinting, IS-handprinting is based on a simple plus-or-minus detection, which is sufficient for a taxonomic characterization. Both methods, using a non-radioactive detection system, are sensitive enough to detect one copy of an insertion element in a strain's genome. IS-fingerprinting, with its fine resolution, would be suitable for ecological studies of individual strains in any complex ecosystem, whereas IS-handprinting would be suitable for monitoring strains and characterizing large numbers of strains