Data from: Contact and contagion: bighorn sheep demographic states vary in probability of transmission given contact

1. Understanding both contact and probability of transmission given
contact are key to managing wildlife disease. However, wildlife disease
research tends to focus on contact heterogeneity, in part because
probability of transmission given contact is notoriously difficult to
measure. Here we present a first step toward empirically investigating
probability of transmission given contact in free-ranging wildlife. 2. We
used measured contact networks to test whether bighorn sheep demographic
states vary systematically in infectiousness or susceptibility to
Mycoplasma ovipneumoniae, an agent responsible for bighorn sheep
pneumonia. 3. We built covariates using contact network metrics,
demographic information, and infection status, and used logistic
regression to relate those covariates to lamb survival. The covariate set
contained degree, a classic network metric describing node centrality, but
we also built covariates that broke the network metrics into particular
categories that differentiated between contacts with yearlings, ewes with
lambs, and ewes without lambs, and animals with and without active
infections. 4. Yearlings, ewes with lambs, and ewes without lambs showed
similar group membership patterns, but direct interactions involving touch
occurred at a rate two orders of magnitude higher between lambs and
reproductive ewes than between any classes of adults or yearlings, and one
order of magnitude higher than direct interactions between lambs. 5.
Although yearlings and non-reproductive bighorn ewes regularly carried
Mycoplasma ovipneumoniae, our models suggest that a contact with an
infected reproductive ewe had approximately five times the odds of
producing a lamb mortality event of an identical contact with an infected
dry ewe or yearling. Consequently, management actions targeting infected
animals might lead to unnecessary removal of young animals who carry
pathogens but rarely transmit. 6. This analysis demonstrates a simple
logistic regression approach for testing a priori hypotheses about
variation in odds of transmission given contact for free-ranging hosts,
and may be broadly applicable for investigations in wildlife disease
ecology.