Abstract:
1. The dynamics of directly transmitted pathogens in natural populations are likely to
result from the combined effects of host traits, pathogen biology, and interactions
among pathogens within a host. Discovering how these factors work in concert to
shape variation in pathogen dynamics in natural host–multi-pathogen systems is
fundamental to understanding population health.
2. Here, we describe temporal variation in incidence and then elucidate the effect of
hosts trait, season and pathogen co-occurrence on host infection risk using one
of the most comprehensive studies of co-infection in a wild population: a suite of
seven directly transmitted viral and bacterial respiratory infections from a 4-year
study of 200 free-ranging African buffalo Syncerus caffer.
3. Incidence of upper respiratory infections was common throughout the study—five
out of the seven pathogens appeared to be consistently circulating throughout
our study population. One pathogen exhibited clear outbreak dynamics in our
final study year and another was rarely detected.
4. Co-infection was also common in this system: The strongest indicator of pathogen
occurrence for respiratory viruses was in fact the presence of other viral respiratory
infections. Host traits had minimal effects on odds of pathogen occurrence
but did modify pathogen–pathogen associations. In contrast, only season predicted
bacterial pathogen occurrence.
5. Though a combination of environmental, behavioural, and physiological factors
work together to shape disease dynamics, we found pathogen associations best
determined infection risk. Our study demonstrates that, in the absence of very fine-scale data, the intricate changes among these factors are best represented
by co-infection.
