Data from: Infection intensity and infectivity of the tick-borne pathogen Borrelia afzelii

The ‘trade-off’ hypothesis for virulence evolution assumes that
between-host transmission rate is a positive and saturating function of
pathogen exploitation and virulence, but there are as yet few tests of
this assumption, in particular for vector-borne pathogens. Here, I show
that the infectivity (probability of transmission) of the tick-borne
bacterium Borrelia afzelii from two of its natural rodent hosts (bank vole
and yellow-necked mouse) to its main tick vector increases asymptotically
with increasing exploitation (measured as bacterial load in skin
biopsies). Hence, this result provides support for one of the basic
assumptions of the ‘trade-off hypothesis’. Moreover, there was no
difference in infectivity between bank voles and yellow-necked mice
despite bacterial loads being on average an order of magnitude higher in
bank voles, most likely because ticks took larger blood meals from mice.
This shows that interspecific variation in host resistance does not
necessarily translate into a difference in infectivity.