If space changes all - The small-scale epidemiology of the fox tapeworm

Human infections with the larval stage of Echinococcus multilocularis are considered to be the most dangerous zoonotic disease in Europe. The parasitic cycle includes foxes as the definitive hosts and small rodents as intermediate hosts. Field studies show that high prevalence in foxes does not lead to accordingly high numbers of infected intermediate hosts. Using the spatially explicit simulation model Echi, this paper describes an investigation into how low prevalence in rodents can be explained. The study demonstrates that an uneven distribution of parasite in the intermediate host populations can cause the observed prevalence ratios. This probable spatial clustering makes control measures more costly. Finally the implications for the planning of control are discussed.