A model for the transmission of Echinococcus multilocularis in Hokkaido, Japan

Abstract

A mathematical model for Echinococcus multilocularis transmission would be useful to estimate its prevalence and manage control strategies. We propose a mathematical model which quantitatively describes the transmission of E. multilocularis multilocularis.

Dynamics of the Force of Infection: Insights from Echinococcus multilocularis Infection in Foxes

“…A decreased cost of baiting foxes increases the cost benefit as a similar reduction in the numbers of human AE cases would be expected to be achieved as earlier suggested [15] based on epidemiological data [23], [24]. Theoretical models [40], [41], have also suggested seasonal transmission of E. multilocularis in Japan. However, our model is also challenged with field data, where as the conclusions of previous models are based on simulations.…”

Synthesising 30 Years of Mathematical Modelling of Echinococcus Transmission

“…However, this is dependent on the level of endemicity as classic age-prevalence curves of E. granulosus indicate that very young dogs may not survive long enough to become infectious [35]. The inclusion of an age structure in the definitive (fox) host when modelling E. multilocularis occurred as a result of field data showing higher worm burdens in juvenile foxes compared with adult foxes in Hokkaido, Japan [27] and is also thought to allow the model to more realistically reflect population dynamics by assigning different death rates to hosts of varying age [17], [27].…”

“…Two E. multilocularis models from Japan therefore accounted for seasonally dynamic host populations because the primary definitive host, the red fox ( Vulpes vulpes ), and intermediate host, the grey-sided vole ( Clethrionomys rufocanus ), showed marked seasonal variations in population size [17], [27]. However, it is argued by others that introducing seasonally dynamic host populations would add unnecessary complexity and provide results that are unlikely to be quantitatively influenced [13], particularly if the overall annual growth rate of host populations is negligible.…”

“…Other influences on host dynamics that have been identified as potentially important for inclusion in E. multilocularis models are contexts where there are 1) higher rates of death of juvenile foxes; 2) definitive host migration (such as in the arctic fox of the tundra zone of Eurasia and North America); and 3) large scale small mammal population variations due to changes in habitat composition (e.g. resulting from anthropogenic environmental influences such as deforestation and overgrazing) [17], [27], [43].…”

“…Although humans rarely contribute to transmission [5] they are indeed a host and valuable insight into the impact of interventions targeting both definitive and intermediate hosts can be gained by their inclusion into Echinococcus transmission models. While the risk of echinococcosis in humans and the impact of control interventions (targeting definitive hosts) on this risk have indeed been discussed in a number of papers detailing animal models of E. multilocularis – it is noteworthy that this has not been done for E. granulosus – this risk is based on the assumption that the number of human cases is proportional to the quantity of parasite eggs deposited in the environment [17]–[19]. The assumption that human risk increases linearly with increased prevalence of infected foxes is acknowledged to be an over simplification [18], although this is still an important indicator of risk.…”