Effects of host heterogeneity on parasite transmission are mediated by
the dynamics of infectiousness determination
Abstract
It is well established that heterogeneities in host susceptibility and
infectiousness affect transmission, and are typically assumed to be
pre-determined traits. However, they may arise dynamically during the
transmission process. Specifically, while infectiousness may be an
inherent trait of the recipient (‘recipient-dependent’), it may instead
be determined by the donor host that infected them (‘donor-dependent’).
We investigated how the effects of heterogeneities on transmission are
affected by these contrasting scenarios by analysing two
‘Susceptible-Infected’ models for three metrics: the basic reproduction
number (R0), changes in heterogeneity, and
equilibrium host abundance. We show that the primary driver of
R0 differs between the two scenarios: covariance
between susceptibility and infectiousness for recipient-dependent,
versus maximum infectiousness for donor-dependent. Consequences for
equilibrium host abundance also differed, but changes in heterogeneity
did not. Our results show that these scenarios change epidemiological
dynamics and should be considered when exploring the consequences of
host heterogeneity on transmission.