Transmission dynamics of a zoonotic pathogen within and between wildlife host species

The transmission dynamics of the cowpox virus infection have been quantifie d in two mixed populations of bank voles (Clethrionomys glareolus) and wood mice (Apodemus sylvaticus), through analyses of detailed time-series of th e numbers of susceptible, infectious and newly infected individuals. The co wpox virus is a zoonosis which circulates in these rodent hosts and has bee n shown to have an adverse effect on reproductive output. The transmission dynamics within species is best described as frequency dependent rather tha n density dependent, contrary to the 'mass action' assumption of most previ ous studies, both theoretical and empirical. Estimation of a transmission c oefficient for each species in each population also allows annual and seaso nal variations in transmission dynamics to be investigated through an analy sis of regression residuals. Transmission between host species is found to be negligible despite their close cohabitation. The consequences of this fo r the combining ability of hosts as zoonotic reservoirs, and for apparent c ompetition between hosts, are discussed.