Distribution of alveolar echinococcosis according to environmental and geographical factors in Germany, 1992-2018.

Alveolar echinococcosis (AE) is a rare zoonotic disease caused by the larval stage of Echinococcus multilocularis. Despite its low world-wide prevalence, this disease shows differences in the regional distribution of cases. In the present cohort study, we analyse the distribution of AE according to environmental and geographical factors in Germany. We identified the place of residence of 591 cases of AE from the national database for AE, and georeferenced these localities in the Universal Transverse Mercator coordinate system. Data on elevation, air temperature, precipitation height and land cover were mapped out and correlated with the distribution of cases of disease during the period 1992-2018. Moran's I statistic was used for spatial autocorrelation. Differences in frequency distribution between elevation, air temperature, precipitation height and landscape feature classes were analysed with the Kruskal-Wallis test. With the multiple linear regression analysis, we determined the influences and interactions of geographical and climatic factors on the number of AE cases. The results showed a heterogeneous distribution of AE cases with a higher concentration in southern Germany than in the rest of Germany (I = 0.225517, Z = 35.8182 and p < 0.001). There was a statistically significant difference in frequency distribution between precipitation height, air temperature, elevation and landscape feature classes and AE cases in Germany (p < 0.0001). In regions with higher elevations (505-672 m), moderate average air temperatures (6.0-7.9°C) and higher precipitation rates (701-1000 mm) most AE cases were recorded. It seems, that regions with higher precipitation rates, higher elevations and moderate average air temperatures have a higher infection burden and infection conditions. It is therefore extremely important to generate greater awareness of the disease in these regions, with the aim of recognising potential cases of AE as early as possible and introducing the appropriate therapeutic measures.
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