Abstract:
Background: Parasite evolution is hypothesized to select for levels of parasite virulence that maximise transmission
success. When host population densities fluctuate, low levels of virulence with limited impact on the host are
expected, as this should increase the likelihood of surviving periods of low host density. We examined the effects of
Morogoro arenavirus on the survival and recapture probability of multimammate mice (Mastomys natalensis) using
a seven-year capture-mark-recapture time series. Mastomys natalensis is the natural host of Morogoro virus and is
known for its strong seasonal density fluctuations.
Results: Antibody presence was negatively correlated with survival probability (effect size: 5–8% per month depending
on season) but positively with recapture probability (effect size: 8%).
Conclusions: The small negative correlation between host survival probability and antibody presence suggests that
either the virus has a negative effect on host condition, or that hosts with lower survival probability are more likely to
obtain Morogoro virus infection, for example due to particular behavioural or immunological traits. The latter
hypothesis is supported by the positive correlation between antibody status and recapture probability which
suggests that risky behaviour might increase the probability of becoming infected.
