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C4 Intrinsic and extrinsic determinants of helminth parasite infections of female hyenas (Hofer)

Research Group: Department Evolutionary Ecology
Leibniz Institute for Zoo and Wildlife Research (IZW)
Address: Alfred-Kowalke-Str. 17, 10315 Berlin
Supervisors: Prof. Dr. Heribert Hofer
Doctoral Researcher: Miguel Veiga

Project Description

State of the art:
Little is known about positive or negative interactions within parasite communities, such as
those in the mammalian gastrointestinal tract, between parasite communities and their hosts,
or the fitness consequences of parasite infections for individual hosts, in unmanaged wildlife
populations subject to ecological and evolutionary processes. Factors likely to shape
these parasite-host interactions and their fitness consequences in wild mammals include lifehistory
stage, social environment, nutritional status, allostatic load, ecological conditions and
host immune genotype. These factors will modulate exposure to parasites, immune responses
and hence parasite load, diversity and communities present in a host and the fitness
consequences of infection to the host.

Previous own work:
During an ongoing long-term project (> 30 years) we collected data and non-invasive samples
from several hundred individually known spotted hyenas (Crocuta crocuta) in the Serengeti
National Park, Tanzania, on their life-histories, reproductive success, social processes,
allostatic load and parasite infections. We expanded our assays to measure steroid
hormone metabolites in non-invasive samples, studied the composition, species richness
and co-occurrence of gastrointestinal parasite communities, and elaborated on aspects of their
interaction with host life-history stages. We established several non-invasive methods to
measure individual genotypes and parasite-induced immune responses by the intestinal
mucosal layer obtained from exfoliated epithelial cells in feces.

Hypotheses and work plan:
1) High parasite loads of energetically costly parasites, such as the helminth Ancylostoma,
should curtail survival and reproduction. 2) Resource allocation trade-offs should result in
down-regulation of immune processes in animals with insufficient food intake to sustain key
life processes such as growth and lactation. 3) Elevated glucocorticoid levels indicate
increased allostatic load, should reduce immunocompetence and thereby increase parasite
infections. 4) Manipulation of host immune responses by helminths should elevate infection
loads. 5) Synergistic effects of co-infections should have detrimental effects on hosts during
energetically costly life stages (juvenile growth, lactation) in terms of immune responses,
parasite loads and measures of fitness. 6) Parasite species diversity and infection loads should
be affected by allele composition of host immune genes. To test these, we will continue our
multi-facetted study on host-parasite interactions and their fitness consequences on more than
200 known spotted hyenas from the Serengeti NP, for which information on their social (social
status, clan size, within-litter dominance status) and ecological environment (prey abundance,
climate), life-history stage and allostatic load will be determined. Immunological measures
developed and validated by the 1st generation will be applied, for which we will also determine
gastrointestinal parasite load and diversity at several life-history stages. Individual genotypes
will be determined for immune genes, notably Toll-like receptors (TLR) in addition to the MHC,
initially TLR-2. The results will be analyzed via multivariate statistical modelling approaches.

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