Livestock abundance predicts vampire bat demography, immune profiles and bacterial infection risk

Abstract

Human activities create novel food resources that can alter wildlife–pathogen interactions. If resources amplify or dampen, pathogen transmission probably depends on both host ecology and pathogen biology, but studies that measure responses to provisioning across both scales are rare. We tested these relationships with a 4-year study of 369 common vampire bats across 10 sites in Peru and Belize that differ in the abundance of livestock, an important anthropogenic food source. We quantified innate and adaptive immunity from bats and assessed infection with two common bacteria. We predicted that abundant livestock could reduce starvation and foraging effort, allowing for greater investments in immunity. Bats from high-livestock sites had higher microbicidal activity and proportions of neutrophils but lower immunoglobulin G and proportions of lymphocytes, suggesting more investment in innate relative to adaptive immunity and either greater chronic stress or pathogen exposure. This relationship was most pronounced in reproductive bats, which were also more common in high-livestock sites, suggesting feedbacks between demographic correlates of provisioning and immunity. Infection with both Bartonella and haemoplasmas were correlated with similar immune profiles, and both pathogens tended to be less prevalent in high-livestock sites, although effects were weaker for haemoplasmas. These differing responses to provisioning might therefore reflect distinct transmission processes. Predicting how provisioning alters host–pathogen interactions requires considering how both within-host processes and transmission modes respond to resource shifts.This article is part of the theme issue ‘Anthropogenic resource subsidies and host–parasite dynamics in wildlife’.

Macroimmunology: The drivers and consequences of spatial patterns in wildlife immune defence

“…Population density can further shape spatial patterns in immunity. High population densities could suppress immunity from overcrowding (Becker, Czirják, Volokhov, et al, ; Table ). However, high population density could instead increase parasite pressure and select for greater investment in immunity; for example, bird T‐cell‐mediated responses were highest in very dense host populations (Møller, Martín‐Vivaldi, Merino, & Soler, ).…”

“…For example, tree swallows Tachycineta bicolor in more agricultural habitats had stronger bacterial killing ability (BKA) than birds in less agricultural habitats, potentially owing to elevated parasitism (Schmitt, Garant, Bélisle, & Pelletier, ; Table ). Vampire bats Desmodus rotundus in more agricultural habitats also had stronger BKA, instead likely signalling improved defence from more food through abundant livestock prey (Becker, Czirják, Volokhov, et al, ; Table ). Given that these similar patterns can stem from distinct environmental mechanisms, data‐driven syntheses to assess how anthropogenic habitats influence immunity across spatial scales are especially needed (Messina, Edwards, Eens, & Costantini, ).…”

Habitat fragmentation is associated with dietary shifts and microbiota variability in common vampire bats

“…to infer long-term feeding patterns of each individual bat (Becker, Czirják, et al, 2018b). to infer long-term feeding patterns of each individual bat (Becker, Czirják, et al, 2018b).…”

“…Innate immune function data for this study were published previously (Becker, Czirják, et al, 2018b); briefly, we assessed a functional measure Escherichia coli ATCC 8739 (Tieleman, Williams, Ricklefs, & Klasing, 2005). In bat plasma, this pathogen is cleared mainly through complement proteins (Moore et al, 2011).…”

“…Because vampire bats with access to domestic animals feed primarily on these prey (Streicker & Allgeier, 2016), we predicted that bats residing in a more agriculturally intensified site would show evidence of a more homogenous diet and have a gut microbiota with decreased alpha diversity (Becker, Czirják, et al, 2018b;Streicker & Allgeier, 2016;Voigt & Kelm, 2006a). Lastly, we assessed whether microbiota attributes were associated with a functional measure of innate immune defense in the bats using plasma.…”