Echinococcus multilocularis is a tapeworm transmitted between canids (foxes in particular) and various species of rodents. As a zoonotic parasite, it is capable of infecting humans and is considered a serious food-borne parasitic disease. A great deal of work has been conducted on elucidating both the infection dynamics and the epizootiology of this disease. With regard to the former aspect, there have been experimental studies of parasite growth characteristics in ecologically relevant definitive host species but in intermediate hosts the vast majority of experimental work has been conducted on inbred strains of mice. These studies are principally intended to elucidate infection mechanisms and assess treatment options in humans.

For this purpose inbred mice are appropriate organisms. However, such laboratory species are inappropriate for assessment of transmission in natural rodent populations and cannot be considered ecologically relevant. Determining such characteristics has predominantly involved mathematical modelling and trapping studies of wild ecologically relevant intermediate hosts. Whilst these studies can determine prevalence in a particular area for a given species and have enhanced our understanding of parasite epizootiology significantly, they do not provide robust data on comparative parasite development and the baseline susceptibility of individual species.

The present Ph.D. project therefore aims to experimentally evaluate differences in susceptibility and parasite developmental characteristics in a range of rodent species considered to be relevant to the parasite’s transmission in Europe. As previous epidemiological studies have indicated significant differences in relevance of various species, distinct differences were expected in the present experimental works.

Utilising oral infection (by stomach tube) of uniform doses of E. multilocularis eggs and assessment of infection over time in four species from colonies of wild rodents (Microtus agrestis, Microtus arvalis, Myodes glareolus, Mesocricetus auratus) and two strains of laboratory rodents (Mus musculus (C57Bl/6j and CD-1 International Genetic Standard)), differences in establishment and metacestode growth and fertility were assessed. Furthermore, dose response and age related susceptibility was studied. Infections were followed by measuring endocrine and immunological parameters to evaluate such factors in the context of parasite establishment growth and fertility.

The present Ph.D. project and the four resulting papers demonstrated fundamental differences in susceptibility, growth and fertility in the various wild rodent isolates (and laboratory strains) investigated and provided evidence for potential immunological reasons behind the significantly greater growth observed in ecologically relevant species as opposed to their Muridae counterparts. Evidence of an upper limit of establishment of parasite eggs was obtained regardless of egg dose for the first time in an Arvicolinae species (M. agrestis) and a window of protoscolex (the fertile stage of the metacestode) production was determined in a key intermediate host species (M. arvalis) providing useful information for subsequent work aiming to elucidate E. multilocularis epizootiology.

This thesis and the resulting publications lays a foundation by which these aspects can be investigated further in order to provide highly detailed information on a key aspect of E. multilocularis transmission, enabling better risk assessment and understanding changes in distribution.