Echinococcus multilocularis and other zoonotic helminths in red foxes (Vulpes vulpes) from a southern German hotspot for human alveolar echinococcosis

Abstract

Background: We describe the spatial distribution of Echinococcus multilocularis in its main definitive host, the red fox, and the distribution of human cases of alveolar echinococcosis (AE) within a highly endemic focus in southern Germany (13.7-19.9/100,000 in 1992-2018). Human cases were unequally distributed within the endemicity focus. The purpose of the study was to test whether this is reflected in the small-scale distribution of E. multilocularis in foxes.

Methods: Three areas with contrasting numbers of human cases were selected within the counties of Ravensburg and Alb-Donau, Baden-Württemberg, Germany. From 2018 to 2020, a total of 240 fox carcasses were obtained from traditional hunters in these areas. Carcasses were necropsied and examined for the presence of intestinal helminths. The statistical analysis was performed with SAS version 9.4, and the geo-mapping with QGIS version 3.16.0 Hannover.

Results: The prevalence of E. multilocularis in foxes was 44/106 (41.5%) in area I (commune Leutkirch and environs), 30/59 (50.8%) in area II (commune Isny and environs), and 31/75 (41.3%) in area III (commune Ehingen and environs). From 1992 to 2018, a total of nine human cases of alveolar echinococcosis were recorded in area I, five cases were recorded in study area III, and no cases were recorded in area II. No statistically significant differences between the areas were observed (P > 0.05) for intestinal infections with E. multilocularis, and no apparent spatial correlation with the small-scale distribution of human cases was found. Concerning other zoonotic helminths, Toxocara spp. were equally common, with prevalence of 38.7%, 47.4% and 48.0%, respectively, while the frequency of Alaria alata varied among the study areas (0.0-9.4%), probably reflecting the specific habitat requirements for the establishment of its complex life cycle.

Conclusions: Echinococcus multilocularis is highly prevalent in foxes in all the studied areas. The varying number of human AE cases within these areas should therefore be caused by factors other than the intensity of parasite transmission in foxes.

Keywords: Alveolar echinococcosis; Distribution; Echinococcus multilocularis; Intestinal helminths; Vulpes vulpes.

Fig. 1

Study areas and their localization. a The study regions are located in Germany, Baden-Württemberg in the districts of b Ravensburg and Alb-Donau. c and d show the study areas Ehingen (Donau) and environs as well as Leutkirch im Allgäu and Isny im Allgäu with environs. Study area I comprises Leutkirch im Allgäu and Argenbühl. Study area II comprises Isny im Allgäu, and study area III comprises Ehingen (Donau) with Schelklingen and Oberstadion

Fig. 2

Geographical distribution of human AE cases and fox infection with E. multilocularis and other helminths. a and b Human AE cases (blue cross), foxes positive (red dot) and negative (black dot) for E. multilocularis. a Study area III; b study areas I and II, c foxes positive for E. multilocularis, d foxes negative for E. multilocularis, e human AE cases, f foxes positive for Alaria alata, g foxes positive for Toxocara/Toxascaris spp., h foxes positive for Uncinaria stenocephala, i foxes positive for Mesocestoides spp., j foxes positive for Taenia spp.