Co-infection best predicts respiratory viral infection in a wild host

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
four‐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, behavioral, and physiological
factors work together to shape disease dynamics, we found pathogen
associations best determined infection risk. Our study demonstrates that,
in absence of very fine‐scale data, the intricate changes among these
factors are best represented by co‐infection.