Chris Walzer

Prof. Chris Walzer

University of Veterinary Medicine Vienna, Vienna, Wien, Austria
orcid

Research Focus & Metrics

Academic Career Length

22Years (2005-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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16 May 2019 in Nature Communications
Verified
Journal Article
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NYNicholas D. Youngblut
Nicholas D. Youngblut
GRGeorg H. Reischer
Georg H. Reischer
WWWilliam Walters
William Walters
NSNathalie Schuster
Nathalie Schuster
CWChris Walzer
Chris Walzer
AFAndreas H. Farnleitner
Andreas H. Farnleitner
Multiple factors modulate microbial community assembly in the vertebrate gut, though studies disagree as to their relative contribution. One cause may be a reliance on captive animals, which can have very different gut microbiomes compared to their wild counterparts. To resolve this disagreement, we analyze a new, large, and highly diverse animal distal gut 16 S rRNA microbiome dataset, which comprises 80% wild animals and includes members of Mammalia, Aves, Reptilia, Amphibia, and Actinopterygii. We decouple the effects of host evolutionary history and diet on gut microbiome diversity and show that each factor modulates different aspects of diversity. Moreover, we resolve particular microbial taxa associated with host phylogeny or diet and show that Mammalia have a stronger signal of cophylogeny. Finally, we find that environmental filtering and microbe-microbe interactions differ among host clades. These findings provide a robust assessment of the processes driving microbial community assembly in the vertebrate intestine.

1 April 2021 in Science of The Total Environment
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Journal Article
Open access
KGKim Gruetzmacher
Kim Gruetzmacher
WKWilliam B. Karesh
William B. Karesh
JAJohn H. Amuasi
John H. Amuasi
Adnan ArshadAdnan Arshad
Adnan Arshad
AFAndrew Farlow
Andrew Farlow
CWChris Walzer
Chris Walzer
For over 15-years, proponents of the One Health approach have worked to consistently interweave components that should never have been separated and now more than ever need to be re-connected: the health of humans, non-human animals, and ecosystems. We have failed to heed the warning signs. A One Health approach is paramount in directing our future health in this acutely and irrevocably changed world. COVID-19 has shown us the exorbitant cost of inaction. The time to act is now.

25 October 2019 in Scientific Reports
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Journal Article
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Kyle JolyKyle Joly
Kyle Joly
EGEliezer Gurarie
Eliezer Gurarie
MSMathew S. Sorum
Mathew S. Sorum
PKPetra Kaczensky
Petra Kaczensky
MCMatt Cameron
Matt Cameron
MHMark Hebblewhite
Mark Hebblewhite
Long-distance terrestrial migrations are imperiled globally. We determined both round-trip migration distances (straight-line measurements between migratory end points) and total annual movement (sum of the distances between successive relocations over a year) for a suite of large mammals that had potential for long-distance movements to test which species displayed the longest of both. We found that caribou likely do exhibit the longest terrestrial migrations on the planet, but, over the course of a year, gray wolves move the most. Our results were consistent with the trophic-level based hypothesis that predators would move more than their prey. Herbivores in low productivity environments moved more than herbivores in more productive habitats. We also found that larger members of the same guild moved less than smaller members, supporting the ‘gastro-centric’ hypothesis. A better understanding of migration and movements of large mammals should aid in their conservation by helping delineate conservation area boundaries and determine priority corridors for protection to preserve connectivity. The magnitude of the migrations and movements we documented should also provide guidance on the scale of conservation efforts required and assist conservation planning across agency and even national boundaries.

10 August 2020 in PLOS ONE
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Journal Article
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NHNguyen Quynh Huong
Nguyen Quynh Huong
NNNguyen Thi Thanh Nga
Nguyen Thi Thanh Nga
NLNguyen Van Long
Nguyen Van Long
BLBach Duc Luu
Bach Duc Luu
ALAlice Latinne
Alice Latinne
SOSarah Olson
Sarah Olson
Outbreaks of emerging coronaviruses in the past two decades and the current pandemic of a novel coronavirus (SARS-CoV-2) that emerged in China highlight the importance of this viral family as a zoonotic public health threat. To gain a better understanding of coronavirus presence and diversity in wildlife at wildlife-human interfaces in three southern provinces in Viet Nam 2013–2014, we used consensus Polymerase Chain Reactions to detect coronavirus sequences. In comparison to previous studies, we observed high proportions of positive samples among field rats (34.0%, 239/702) destined for human consumption and insectivorous bats in guano farms (74.8%, 234/313) adjacent to human dwellings. Most notably among field rats, the odds of coronavirus RNA detection significantly increased along the supply chain from field rats sold by traders (reference group; 20.7% positivity, 39/188) by a factor of 2.2 for field rats sold in large markets (32.0%, 116/363) and 10.0 for field rats sold and served in restaurants (55.6%, 84/151). Coronaviruses were also detected in rodents on the majority of wildlife farms sampled (60.7%, 17/28). These coronaviruses were found in the Malayan porcupines (6.0%, 20/331) and bamboo rats (6.3%, 6/96) that are raised on wildlife farms for human consumption as food. We identified six known coronaviruses in bats and rodents, clustered in three Coronaviridae genera, including the Alpha-, Beta-, and Gammacoronaviruses. Our analysis also suggested either mixing of animal excreta in the environment or interspecies transmission of coronaviruses, as both bat and avian coronaviruses were detected in rodent feces on wildlife farms. The mixing of multiple coronaviruses, and their apparent amplification along the wildlife supply chain into restaurants, suggests maximal risk for end consumers and likely underpins the mechanisms of zoonotic spillover to people.

19 June 2020 in Communications Biology
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RFRobert Fitak
Robert Fitak
EMElmira Mohandesan
Elmira Mohandesan
JCJukka Corander
Jukka Corander
AYAdiya Yadamsuren
Adiya Yadamsuren
BCBattsetseg Chuluunbat
Battsetseg Chuluunbat
PBPamela Anna Burger
Pamela Anna Burger
Domestication begins with the selection of animals showing less fear of humans. In most domesticates, selection signals for tameness have been superimposed by intensive breeding for economical or other desirable traits. Old World camels, conversely, have maintained high genetic variation and lack secondary bottlenecks associated with breed development. By re-sequencing multiple genomes from dromedaries, Bactrian camels, and their endangered wild relatives, here we show that positive selection for candidate genes underlying traits collectively referred to as ‘domestication syndrome’ is consistent with neural crest deficiencies and altered thyroid hormone-based signaling. Comparing our results with other domestic species, we postulate that the core set of domestication genes is considerably smaller than the pan-domestication set – and overlapping genes are likely a result of chance and redundancy. These results, along with the extensive genomic resources provided, are an important contribution to understanding the evolutionary history of camels and the genomic features of their domestication.

26 October 2021 in Nature Microbiology
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Journal Article
Open access
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NYNicholas D. Youngblut
Nicholas D. Youngblut
GRGeorg H. Reischer
Georg H. Reischer
SDSilke Dauser
Silke Dauser
SMSophie Maisch
Sophie Maisch
CWChris Walzer
Chris Walzer
RLRuth E. Ley
Ruth E. Ley
Commonly used 16S rRNA gene primers do not detect the full range of archaeal diversity present in the vertebrate gut. As a result, several questions regarding the archaeal component of the gut microbiota remain, including which Archaea are host-associated, the specificities of such associations and the major factors influencing archaeal diversity. Using 16S rRNA gene amplicon sequencing with primers that specifically target Archaea, we obtained sufficient sequence data from 185 gastrointestinal samples collected from 110 vertebrate species that span five taxonomic classes (Mammalia, Aves, Reptilia, Amphibia and Actinopterygii), of which the majority were wild. We provide evidence for previously undescribed Archaea–host associations, including Bathyarchaeia andMethanothermobacter, the latter of which was prevalent among Aves and relatively abundant in species with higher body temperatures, although this association could not be decoupled from host phylogeny. Host phylogeny explained archaeal diversity more strongly than diet, while specific taxa were associated with both factors, and cophylogeny was significant and strongest for mammalian herbivores. Methanobacteria was the only class predicted to be present in the last common ancestors of mammals and all host species. Further analysis indicated that Archaea–Bacteria interactions have a limited effect on archaeal diversity. These findings expand our current understanding of Archaea–vertebrate associations.