Mathematical modelling of Echinococcus multilocularis abundance in foxes in Zurich, Switzerland

Abstract

BackgroundIn Europe, the red fox (Vulpes vulpes) is the main definitive host of Echinococcus multilocularis, the aetiological agent of a severe disease in humans called alveolar echinococcosis. The distribution of this zoonotic parasite among the fox population is remarkably aggregated with few heavily infected animals harbouring much of the parasite burdens and being responsible for most of the environmental parasitic egg contamination. Important research questions explored were: (i) spatial differences in parasite infection pressure related to the level of urbanization; (ii) temporal differences in parasite infection pressure in relation to time of the year; (iii) is herd immunity or an age-dependent infection pressure responsible for the observed parasite abundance; (iv) assuming E. multilocularis infection is a clumped process, how many parasites results from a regular infection insult.MethodsBy developing and comparing different transmission models we characterised the spatio-temporal variation of the infection pressure, in terms of numbers of parasites that foxes acquired after exposure per unit time, in foxes in Zurich (Switzerland). These included the variations in infection pressure with age of fox and season and the possible regulating effect of herd immunity on parasite abundance.ResultsThe model fitting best to the observed data supported the existence of spatial and seasonal differences in infection pressure and the absence of parasite-induced host immunity. The periodic infection pressure had different amplitudes across urbanization zones with higher peaks during autumn and winter. In addition, the model indicated the existence of variations in infection pressure among age groups in foxes from the periurban zone.ConclusionsThese heterogeneities in infection exposure have strong implications for the implementation of targeted control interventions to lower the intensity of environmental contamination with parasite eggs and, ultimately, the infection risk to humans.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-016-1951-1) contains supplementary material, which is available to authorized users.

Urban colonization through multiple genetic lenses: The city‐fox phenomenon revisited

“…For example, Zurich foxes may have different selection pressures associated with anthropogenic food availability (Contesse, Hegglin, Gloor, Bontadina, & Deplazes, 2004), which could influence selection on metabolic pathways (Harris & Munshi-South, 2017). City foxes may also experience different disease pressures than rural foxes, as seen with the zoonotic cestode Echinococcus multilocularis transmission cycle within Zurich city foxes (Hofer et al, 2000;Otero-Abad, Rüegg, Hegglin, Deplazes, & Torgerson, 2017). These variable selection pressures, combined with shifts in behavior to avoid human interactions (Gloor et al, 2001;Sih et al, 2011;Soulsbury, Baker, Iossa, & Harris, 2010), could facilitate strong pressures on city foxes not present in rural conspecifics and shape genetic differentiation between the subpopulations.…”

Global dynamics for mathematical model of Echinococcus multilocularis in rodents and red foxes

“…Echinococcus multilocularis is a zoonotic disease caused by a tiny tapeworm of the genus Echinococcus . The parasite is responsible for Echinococcosis, an etiological agent of human alveolar echinococcosis that has high fatality rate if left untreated …”

“…The parasite is responsible for Echinococcosis, an etiological agent of human alveolar echinococcosis that has high fatality rate if left untreated and low prevalence in rodents (0.4%‐30%) . However, the geographical distribution of EM seems to be expanding to many countries, and it is termed as an emerging and reemerging pathogen in some parts of the globe …”

“…E multilocularis is geographically confined in the Northern Hemisphere with high prevalence in red foxes population (1%‐76.7%) and low prevalence in rodents (0.4%‐30%) . However, the geographical distribution of EM seems to be expanding to many countries, and it is termed as an emerging and reemerging pathogen in some parts of the globe .…”

Regulation of Hepatic MicroRNAs in Response to Early Stage Echinococcus multilocularis Egg Infection in C57BL/6 mice

“…Human alveolar echinococcosis (AE) is a parasitic disease caused by infection with the larval stage (metacestode) of the cyclophyllid tapeworm Echinococcus multilocularis ( E. multilocularis ; Cestoda, Taeniidae) [1]. In Europe, E. multilocularis undergoes a sylvatic life cycle that predominantly includes the red fox ( Vulpes vulpes ) as major definitive host (HD) and rodents (family Arvicolidae) acting as intermediate hosts (IHs) [2]. For humans, accidental infection with E. multilocularis eggs through the oral route can lead to the development of AE, affecting primarily the liver in 98% of cases [1].…”