The role of nematode parasites in Soay sheep (<i>Ovis aries</i>L.) mortality during a population crash

Gulland, Frances M. D.

doi:10.1017/s0031182000074679

Cited by 332 publications

(330 citation statements)

References 50 publications

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“…The population exhibits a distinctive, unstable dynamic characterized by low and rising sheep numbers followed by high mortality (“crash”) winters in which more than half of the population may perish (Clutton‐Brock & Pemberton, 2004). High mortality winters are associated with strong selection on a range of phenotypic traits and are thought to result from a combination of low food availability due to competition, harsh winter climate conditions, and parasite pressure, predominantly from Strongyle gastrointestinal nematodes (GINs) (Coulson, 2001; Gulland, 1992; Gulland & Fox, 1992). Age‐related variation is well understood in this population, with differences evident between lambs, yearlings, prime age adults (2–6 years), and geriatrics (>6 years) in demographic rates and phenotypic traits both within and among the sexes (Coulson, 2001).…”

Section: Methodsmentioning

confidence: 99%

“…As previous studies have suggested that overwinter survival varies with age, sex, August weight, and FEC, we initially examined the effects of these terms in our sample (Coulson, 2001; Gulland, 1992). We found evidence for a significant age‐by‐sex interaction (χ 2 = 9.84, P = .02) with highest survival in female and adult groups, as expected.…”

Section: Methodsmentioning

confidence: 99%

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Cellular and humoral immunity in a wild mammal: Variation with age & sex and association with overwinter survival

Watson

McNeilly

Watt

et al. 2016

Ecology and Evolution

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Immune defenses are expected to be crucial for survival under the considerable parasite pressures experienced by wild animals. However, our understanding of the association between immunity and fitness in nature remains limited due to both the complexity of the vertebrate immune system and the often‐limited availability of immune reagents in nonmodel organisms. Here, we use methods and reagents developed by veterinary researchers for domestic ungulates on blood samples collected from a wild Soay sheep population, to evaluate an unusually broad panel of immune parameters. Our evaluation included different innate and acquired immune cell types as well as nematode parasite‐specific antibodies of different isotypes. We test how these markers correlate with one another, how they vary with age‐group and sex, and, crucially, whether they predict overwinter survival either within or among demographic groups. We found anticipated patterns of variation in markers with age, associated with immune development, and once these age trends were accounted for, correlations among our 11 immune markers were generally weak. We found that females had higher proportions of naïve T cells and gamma–delta T cells than males, independent of age, while our other markers did not differ between sexes. Only one of our 11 markers predicted overwinter survival: sheep with higher plasma levels of anti‐nematode IgG antibodies were significantly more likely to survive the subsequent high mortality winter, independent of age, sex, or weight. This supports a previous finding from this study system using a different set of samples and shows that circulating antibody levels against ecologically relevant parasites in natural systems represent an important parameter of immune function and may be under strong natural selection. Our data provide rare insights into patterns of variation among age‐ and sex groups in different T‐cell subsets and antibody levels in the wild, and suggest that certain types of immune response—notably those likely to be repeatable within individuals and linked to resistance to ecologically relevant parasites—may be most informative for research into the links between immunity and fitness under natural conditions.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Cellular and humoral immunity in a wild mammal: Variation with age & sex and association with overwinter survival

Watson

McNeilly

Watt

et al. 2016

Ecology and Evolution

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“…Based on these ITS data, there is no indication of a sister-group relationship between the St. Kilda and British samples. Unfortunately, definitive documentation of N. battus on St. Kilda is very recent (Gulland, 1992;Gulland and Fox, 1992), although an earlier report suggests that it may have been observed previously (Cheyne et al, 1974). Also, given the potential for more recent introductions of N. battus from the mainland via transport of other sheep breeds, it would seem unlikely that only sequences representing an early translocation and establishment would be found if additional sampling was performed on the archipelago.…”

Section: Geographic Samples Of N Battusmentioning

confidence: 99%

Relationships of Nematodirus Species and Nematodirus battus Isolates (Nematoda: Trichostrongyloidea) Based on Nuclear Ribosomal DNA Sequences

Nadler¹,

Hoberg²,

Hudspeth³

et al. 2000

The Journal of Parasitology

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“…2011; Schmid‐Hempel 2011). Gastrointestinal nematodes (GIN) are ubiquitous and have important impacts on health in naturally occurring vertebrate populations (Gulland 1992; Albon et al. 2002; Cattadori et al.…”

Section: Introductionmentioning

confidence: 99%

Fecal antibody levels as a noninvasive method for measuring immunity to gastrointestinal nematodes in ecological studies

Watt

Nussey

Maclellan

et al. 2015

Ecology and Evolution

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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.

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The role of nematode parasites in Soay sheep (Ovis ariesL.) mortality during a population crash

Cited by 332 publications

References 50 publications

Cellular and humoral immunity in a wild mammal: Variation with age & sex and association with overwinter survival

Cellular and humoral immunity in a wild mammal: Variation with age & sex and association with overwinter survival

Relationships of Nematodirus Species and Nematodirus battus Isolates (Nematoda: Trichostrongyloidea) Based on Nuclear Ribosomal DNA Sequences

Fecal antibody levels as a noninvasive method for measuring immunity to gastrointestinal nematodes in ecological studies

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