C5 Ecological interdependencies and bio/pathological consequences of equine multispecies nematode infection complexes (v. Samson-Himmelstjerna)

Research Group: Institute for Parasitology and Tropical Veterinary Medicine
Address: Freie Universität Berlin, Centre for Infection Medicine,
Robert-von-Ostertag-Str. 7-13, 14163 Berlin
Supervisor: Prof. Dr. Georg v. Samson-Himmelstjerna
Doctoral Researcher: Alexander Gerhard, Irina Diekmann, Nini Militzer, Sophia Pinecki

Project Description     

State of the art:
Cyathostomins represent the by far most prevalent infectious species in equines. They consist
of in total 50 morphologically characterized species and in individual hosts often occur with
more than 10 different species simultaneously. They are currently considered to be the most
important parasites in horses due to the fact that they may cause infections associated with
severe diarrhea, weight loss and in a high proportion even death. Their relevance is further
increased by the fact that following decades of widespread anthelmintic treatments many
cyathostomin populations have developed resistance to anthelmintic treatment.
Interestingly, the latter has also recently been found to affect the intestinal microbiome in
horses. Despite their superior parasitological and clinical importance, the specific
significance of the various cyathostomin species for example concerning pathological effects
or the resistance status are largely unknown. The knowledge gaps are mainly due to the
difficult and cumbersome species identification, which only very few experts worldwide are
competent to do. To resolve this methodological bottleneck, we developed new molecular and
biochemical approaches for cyathostomin species identification within this project.

Previous own work:
To promote species-specific research in cyathostomins, a new molecular-proteomic approach
for cyathostomin species identification has been established. This approach is based on the
parallel molecular and biochemical analysis of DNA and protein extracted from individual
cyathostomin specimens. Using multi-locus, i.e. cytochrome oxidase I and ribosomal
internal transcribed spacer 2, phylogenetic as well as MALDI-TOF MS analyses, a combined
molecular/proteomic database, thus far consisting of 11 species, has been generated. To
achieve the latter, a unique analytic pipeline employing a novel protocol for concurrent DNA
and protein extraction was established. Following R-based data analysis, species
differentiation of adult worms from closely related species was achieved and 3 cryptic
cyathostomin species were identified in the Cylicostephanus minutus complex.

Hypotheses and work plan:
1) Cyathostomin species composition differs depending on the geographical and ecological
setting of wild and domestic equines. 2) Ecological and bio-pathological interdependencies
exist within and between parasitic organisms and intestinal microbiota. 3) Drug exposure is
associated with changes in parasite and microbiome species composition.
We will extend the range and spectrum of cyathostomin populations to be analyzed by the
previously established methodological approaches to wild equines. Strongylid parasite
populations in mountain zebras (Equus zebra hartmannae) in Namibia, plains zebras (Equus
quagga boehmi) in Tanzania and Przewalski’ horses (Equus ferus przewalskii) in Ukraine will
be compared with those in domestic horses (Equus ferus caballus). Libraries will be prepared
from cyathostomin stages collected from individual horses and parasite populations analyzed
regarding the effects of age, sex, clinical health, reproductive status position within the group
and fecal egg count on the species composition and richness. Further domestic populations
which are characterized by different AR phenotypes will be included. In a collaboration with
colleagues working on the analysis of the equine intestinal microbiome (LE Peachey, Bristol,
UK), we study potential interdependencies with non-parasitic intestinal organisms.

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