Balasubramaniam, K. N., Beisner, B. A., Vandeleest, J. J. et al. 2018. Social buffering and contact transmission: Network connections have beneficial and detrimental effects on Shigella infection risk among captive rhesus macaques. American Journal of Primatology 80(S1), 51-52 (40th Meeting of the American Society of Primatologists Scientific Program, Abstract #162).

Group living in primates may impact the risk of pathogen acquisition in two ways. First, social connectedness makes individuals more susceptible to pathogens via contact‐mediated transmission. Yet in strongly bonded societies, having close connections and strong social ties can also socially buffer individuals against susceptibility to pathogens. Using social network analyses, we assessed the potentially competing roles of contact‐mediated transmission and social buffering on the risk of infection from an enteric bacterial pathogen (Shigella flexneri) among captive rhesus macaques (Macaca mulatta). Within two groups, we found that infection risk was lowest among individuals possessing more direct (grooming out‐degree: B = −2.31, df = 195, p = 0.04) and indirect (grooming eigenvector: B = −2.76, df = 195, p = 0.02) network connections, suggesting social buffering. In a third group, we found that infection risk was highest among individuals that initiated more aggression (out‐degree: B = 5.09, p = 0.01) and less so among huddlers (betweenness: B = 3.42, df = 97, p = 0.07). Our findings reveal that social connections may, via contact transmission or social buffering, increase or decrease individuals’ susceptibility to pathogens, depending on factors such as living‐condition, pathogen‐specific transmission routes, and/or overall social context. Broadly, they extend the applicability of the social buffering hypothesis, beyond just stress‐ and immune‐function‐related benefits, to infectious disease resistance.