Prevalence of Fox Tapeworm in Invasive Muskrats in Flanders (North Belgium)

SIMPLE SUMMARY: Fox tapeworms are pathogens that need two hosts to complete their life cycle. The reproductive part of the cycle takes place in foxes and the intermediate step usually occurs in rodents. Muskrats can also act as the intermediate host for fox tapeworms. This increases the total number of potential hosts which can also increase the number of pathogens in the environment. In Belgium, where muskrats are non-native, this is one of the ways in which an invasive alien species can have a negative effect on its new environment. From 2009 to 2017 all muskrats caught in Flanders and across the border with Wallonia and France were collected and dissected to estimate how often they were infected with fox tapeworms. Visual examination of the livers of 15,402 muskrats revealed 202 infected animals (1.31%). In Flanders, we found 82 infected animals out of 9421 (0.87%). The percentage of infected animals did not increase during the research period. All the infected animals in Flanders were found in municipalities along the Walloon border. We did not observe a northward spread of EM infection from Wallonia to Flanders. ABSTRACT: One way in which invasive alien species affect their environment is by acting as pathogen hosts. Pathogens limited by the availability of the native host species can profit from the presence of additional hosts. The muskrat (Ondatra zibethicus) is known to act as an intermediate host for the fox tapeworm (Echinococcus multilocularis). From 2009 to 2017, 15,402 muskrats caught in Flanders and across the border with Wallonia and France were collected and dissected with the aim of understanding the prevalence of this parasite in muskrats. Visual examination of the livers revealed 202 infected animals (1.31%). Out of the 9421 animals caught in Flanders, we found 82 individuals (0.87%) infected with E. multilocularis. No increase in prevalence was observed during this study. All of the infected animals in Flanders were found in municipalities along the Walloon border. We did not observe a northward spread of E. multilocularis infection from Wallonia to Flanders. We hypothesise that the low prevalence is the result of the reduced availability of intermediate hosts and the successful control programme which is keeping muskrat densities in the centre of the region at low levels and is preventing influx from other areas. Our results illustrate that muskrats are good sentinels for E. multilocularis and regular screening can gain valuable insight into the spread of this zoonosis.