White blood cell profiles in amphibians help to explain disease susceptibility following temperature shifts

Greenspan, Sasha E., Bower, Deborah S., Webb, Rebecca J., Berger, Lee, Rudd, Donna, Schwarzkopf, Lin, and Alford, Ross A. (2017) White blood cell profiles in amphibians help to explain disease susceptibility following temperature shifts. Developmental and Comparative Immunology, 77. pp. 280-286.

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Temperature variability, and in particular temperature decreases, can increase susceptibility of amphibians to infections by the fungus Batrachochytrium dendrobatidis (Bd). However, the effects of temperature shifts on the immune systems of Bd-infected amphibians are unresolved. We acclimated frogs to 16 degrees C and 26 degrees C (baseline), simultaneously transferred them to an intermediate temperature (21 degrees C) and inoculated them with Bd (treatment), and tracked their infection levels and white blood cell profiles over six weeks. Average weekly infection loads were consistently higher in 26 degrees C-history frogs, a group that experienced a 5 degrees C temperature decrease, than in 16 degrees C-history frogs, a group that experienced a 5 degrees C temperature increase, but this pattern only approached statistical significance. The 16 degrees C-acclimated frogs had high neutrophil:lymphocyte (N:L) ratios (suggestive of a hematopoietic stress response) at baseline, which were conserved post-treatment. In contrast, the 26 degrees C-acclimated frogs had low N:L ratios at baseline which reversed to high N:L ratios post-treatment (suggestive of immune system activation). Our results suggest that infections were less physiologically taxing for the 16 degrees C-history frogs than the 26 degrees C-history frogs because they had already adjusted immune parameters in response to challenging conditions (cold). Our findings provide a possible mechanistic explanation for observations that amphibians are more susceptible to Bd infection following temperature decreases compared to increases and underscore the consensus that increased temperature variability associated with climate change may increase the impact of infectious diseases. (C) 2017 Elsevier Ltd. All rights reserved.

Item ID: 51530
Item Type: Article (Research - C1)
ISSN: 1879-0089
Keywords: Batrachochytrium dendrobatidis, chytridiomycosis, immunity, leukocytes, temperature variability, thermal acclimation
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A version of this publication was included as Chapter 3 of the following PhD thesis: Greenspan, Sasha Eden (2017) Thermal thresholds in the amphibian disease chytridiomycosis. PhD thesis, James Cook University, which is available Open Access in ResearchOnline@JCU. Please see the Related URLs for access.

Funders: Australian Research Council (ARC)
Projects and Grants: ARC Discovery Grant DP130101635
Research Data: http://dx.doi.org/10.4225/28/5a0cfccef41d3, http://dx.doi.org/10.4225/28/5a0d1ac51a005
Date Deposited: 15 Nov 2017 07:38
FoR Codes: 31 BIOLOGICAL SCIENCES > 3107 Microbiology > 310702 Infectious agents @ 50%
31 BIOLOGICAL SCIENCES > 3109 Zoology > 310907 Animal physiological ecology @ 50%
SEO Codes: 96 ENVIRONMENT > 9604 Control of Pests, Diseases and Exotic Species > 960499 Control of Pests, Diseases and Exotic Species not elsewhere classified @ 50%
96 ENVIRONMENT > 9608 Flora, Fauna and Biodiversity > 960899 Flora, Fauna and Biodiversity of Environments not elsewhere classified @ 50%
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