Pathogen transmission modes determine contact network structure, altering other pathogen characteristics

Abstract

Pathogen traits can vary greatly and heavily impact the ability of a pathogen to persist in a population. Although this variation is fundamental to disease ecology, little is known about the evolutionary pressures that drive these differences, particularly where they interact with host behaviour. We hypothesized that host behaviours relevant to different transmission routes give rise to differences in contact network structure, constraining the space over which pathogen traits can evolve to maximize fitness. Our analysis of 232 contact networks across mammals, birds, reptiles, amphibians, arthropods, fish and molluscs found that contact network topology varies by contact type, most notably in networks that are representative of fluid-exchange transmission. Using infectious disease model simulations, we showed that these differences in network structure suggest pathogens transmitted through fluid-exchange contact types will need traits associated with high transmissibility to successfully proliferate, compared to pathogens that transmit through other types of contact. These findings were supported through a review of known traits of pathogens that transmit in humans. Our work demonstrates that contact network structure may drive the evolution of compensatory pathogen traits according to transmission strategy, providing essential context for understanding pathogen evolution and ecology.

Sharing fluids shapes host social networks and pathogen traits

“…To test this hypothesis, they collated data on human pathogens, for which transmissibility data are far better and more available than for wildlife pathogens. Two characteristics of transmissibility-infectious period and infection probability-revealed that those that transmit on fluid exchange networks tend to have the longest infectious periods, and those with shorter infectious periods compensate by having moderate to high infection probability.Through this neat and logical series of steps, Collier et al [3] show that, across a wide range of taxa, the structure of animal social networks is somewhat…”

“…Through this neat and logical series of steps, Collier et al [3] show that, across a wide range of taxa, the structure of animal social networks is somewhat…”

“…predictable by the nature of the contact on which they are built, and that this structure predicts pathogen traits. Of course, being largely meta-analytical in approach, Collier et al [3] were constrained by data availability: many of these constraints represent important and exciting future research directions. Here I highlight a few outstanding examples.…”

“…While the interactions between infection and non-sexual social behaviour are already complex and require elucidation [1], sex is an important driver of animal behaviour, and the ways in which it affects pathogen transmission are underexplored. For example non-reproductive and, as Collier et al [3] point out, same-sex sexual behaviour is hugely neglected in wildlife systems, but structures human social networks in ways important for predicting disease spread [9].…”

“…Pathogen transmission on host social networks should be considered a nested process. Collier et al [3] categorize contacts between animals according to the transmission route they provide pathogens. Pathogens with airborne or respiratory droplet transmission can transmit between hosts during non-physical, close contact, such as occurs between members of a social group.…”