Data from: Density matters: How population dynamics of house mice (Mus musculus) inform the epidemiology of Leptospira

Rodents are maintenance hosts of numerous pathogens, and both their
density and the pathogen prevalence determine the risk they pose to other
animals or humans. However, density is often overlooked. We investigated a
capture-mark-recapture-sampling strategy to study introduced mice (Mus
musculus) and Leptospira as a model and demonstrate the advantages of a
combined approach. We estimated population density and Leptospira
prevalence in mice in a replicated longitudinal survey conducted between
2016 and 2018. Capture-mark-recapture sessions were undertaken at two
sites in Spring and Autumn and blood and kidney samples were collected at
the end of each session. Mouse density and areas of activity were
estimated using spatially explicit capture-recapture (SECR) models and
both were compared between Leptospira positive and negative mice.
Leptospira exposure and shedding status were estimated using Microscopic
Agglutination Test, and a combination of culture and lipL32 PCR on
kidneys. Leptospira prevalence was higher in spring (83% to 86%)
than in autumn (31% to 37%) and mouse densities simultaneously varied from
3.6 to 55.9/ha. However, despite these variations in prevalence and
density, the density of infected animals remained relatively constant over
time (3 to 8/ha). Shedding or being seropositive was also associated with
the activity of mice. Shedding or seropositive mice had a larger activity
area, and seropositive mice were trapped on average one day earlier than
seronegative mice.  Synthesis and applications. Our results show
how understanding the population dynamics of pathogen-carrying rodents is
critical in epidemiology. The wider movement patterns and easier
encounters of positive mice highlight the possibility of biases in
classical prevalence surveys and have implications for disease
transmission within and between species. Importantly, and quite
counter-intuitively, Leptospira prevalence was negatively associated with
mouse density, resulting in a constant density of shedders that
contradicts the conventional view of higher exposure risk at high rodent
density. More broadly, such hybrid sampling designs can improve animal and
disease control policies and better inform modelling studies by providing
more parameter estimates than classical prevalence surveys.