Bidirectional interactions between host social behaviour and parasites arise through ecological and evolutionary processes

Abstract

An animal's social behaviour both influences and changes in response to its parasites. Here we consider these bidirectional links between host social behaviours and parasite infection, both those that occur from ecological vs evolutionary processes. First, we review how social behaviours of individuals and groups influence ecological patterns of parasite transmission. We then discuss how parasite infection, in turn, can alter host social interactions by changing the behaviour of both infected and uninfected individuals. Together, these ecological feedbacks between social behaviour and parasite infection can result in important epidemiological consequences. Next, we consider the ways in which host social behaviours evolve in response to parasites, highlighting constraints that arise from the need for hosts to maintain benefits of sociality while minimizing fitness costs of parasites. Finally, we consider how host social behaviours shape the population genetic structure of parasites and the evolution of key parasite traits, such as virulence. Overall, these bidirectional relationships between host social behaviours and parasites are an important yet often underappreciated component of population-level disease dynamics and host–parasite coevolution.

Social hosts evade predation but have deadlier parasites

“…The importance and implications of predation and social parasite transmission, evident from our model and data, may hold across directly transmitted parasites of group-living hosts 47 .…”

“…Predators drive defensive group-living in animals across taxa 6 , which can increase parasitism 48 , creating ecological and evolutionary feedbacks between host sociality and parasites 47 . Parasites evolve along virulence-transmission trade-offs in systems ranging from viruses of humans 16 , bacterial pathogens of birds 14 , protozoan pathogens of insects 15 , and our monogenean fish ectoparasite.…”

Delicious to the Last Piece: Why Ectoparasite Prefer Human Skin

“…Parasites vary in the number of hosts they need to survive, a phenomenon which demonstrated through the complexity of their life cycle [19]. Ecological condition combined with the host's behaviour favoured its transmission, While definite parasites need only a single host, other type of parasites use numerous hosts to veritable their complex life cycles [20].…”

The role of social structure and dynamics in the maintenance of endemic disease

“…Infection avoidance behaviour is likely to be of greater importance in driving the co-dynamics of infection and behaviour. Avoidance behaviour requires individuals to be able to perceive cues of disease, and so its role will vary among host–pathogen systems (Hawley et al 2021 ; Stockmaier et al 2021 ). There is increasing evidence of infection avoidance in a wide range of taxa (Stockmaier et al 2021 ).…”

“…For directly transmitted pathogens, host social structure does not influence the spread of pathogens that are highly transmissible in the same way that it does less transmissible pathogens. Infection avoidance behaviour also typically requires cues that an individual is diseased (Hawley et al 2021 ; Stockmaier et al 2021 ). For pathogens with pre-symptomatic transmission or that cause “hidden” pathologies, then social dynamics may not be sufficient to slow epidemic spread, and in some cases can exacerbate it when individuals change social partners before displaying symptoms (Zhou and Xia 2014 ).…”