Abstract
Among-individual variation in antibody-associated immunity to gastrointestinal nematode parasites (GIN) is known be associated with life-history traits and vital rates in wild vertebrate systems. To date, measurement of levels of antibodies against GIN antigens in natural populations has exclusively been based on invasive blood sampling techniques. Previous work in laboratory rodents and ruminant livestock suggests that antibody measures from feces may provide a viable noninvasive approach. We measured total and anti-GIN antibodies of different isotypes (immunoglobulin (Ig) G, IgA and IgE) from paired samples of plasma and feces from free-living Soay sheep of different ages and sexes. We tested the correlations among these measures as well as their associations with body mass and Strongyle nematode fecal egg counts (FEC). Significant positive correlations were present among plasma and fecal anti-GIN antibody levels for IgG and IgA. Generally, correlations between total antibody levels in plasma and feces were weaker and not significant. No significant relationships were found between any antibody measures and body mass; however, fecal anti-GIN antibody levels were significantly negatively correlated with FEC. Our data clearly demonstrate the feasibility of measuring anti-GIN antibodies from fecal samples collected in natural populations. Although associations of fecal antibody levels with their plasma counterparts and FEC were relatively weak, the presence of significant correlations in the predicted direction in a relatively small and heterogeneous sample suggests fecal antibody measures could be a useful, noninvasive addition to current eco-immunological studies.
Highlights
Establishing how and why immunological variation predicts parasite burden and fitness under natural conditions is a central challenge with the field of ecological immunology (Graham et al 2011; Schmid-Hempel 2011)
Ecology and Evolution published by John Wiley & Sons Ltd
We show that Gastrointestinal nematodes (GIN)-specific antibodies in feces and plasma are positively correlated, and our results suggest that fecal antibody levels represent an overlooked but potentially important tool for ecological immunologists interested in GIN parasite and host interactions and their consequences for evolutionary and population dynamics
Summary
Establishing how and why immunological variation predicts parasite burden and fitness under natural conditions is a central challenge with the field of ecological immunology (Graham et al 2011; Schmid-Hempel 2011). Variation in immunity to such parasites is a major source of these differences, with protection mediated via antibodies acting at mucosal surfaces being important in the context of GIN (Smith et al 1985; Gill et al 1993; Stear et al 1995; Miquel et al 2005; McCoy et al 2008).
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