A highly endemic area of Echinococcus multilocula is identified through a comparative re-assessment of prevalence in red fox (Vulpes vulpes), Alto Adige (Italy: 2019-2020)

Background: Surveillance of E. multilocularis at the edge of its range is hindered by fragmented distributional patterns and low prevalence and burden in definitive hosts. Thus, tests with adequate levels of sensitivity are especially important for discriminating between infected and non-infected areas. Aim: We reassessed the prevalence of E. multilocularis at the southern border of its distribution in Alto Adige (Italy), to improve surveillance in wildlife and provide more accurate estimates of exposure risk. Methods: We compared results from the diagnostic test currently implemented for surveillance (based on Coproscopy+Multiplex PCR - CMPCR), against a real-time quantitative PCR (qPCR) for 235 fox faeces collected in 2019-2020. The performances of the two tests were estimated using a scraping technique (SFCT) as the gold standard applied to the small intestines of a subsample (n=123) of the same hosts. True prevalence was calculated and sample size required by each faecal test for the detection of the parasite was then estimated. Results: True prevalence of E. multilocularis in foxes (14.3%) was definitely higher than reported in the last decade (never >5% from 2012 to 2018). The qPCR also had a higher sensitivity (83%) compared to CMPCR (21%). Agreement with the gold standard was far higher for qPCR (0.816) than CMPCR (0.298) as well, determining a smaller sample size required to detect the disease. Conclusions: Alto Adige should be considered a highly endemic area. Surveillance at the edges of E. multilocularis distribution should adopt qPCR diagnostics on definitive hosts on a small geographic scale.