Disentangling the Effects of Season and Temperature on Hematologic Values in Prairie Rattlesnakes (Crotalus viridis)
American Association of Zoo Veterinarians Conference 2019
Matthew C. Allender1,2, DVM, MS, PhD, DACZM; Ethan Kessler2, BS; Sarah J. Baker3, PhD; Ellen Haynes1, DVM; Amy Schnelle4, DVM, MS, DACVCP
1Wildlife Epidemiology Laboratory, College of Veterinary Medicine, University of Illinois, Urbana, IL, USA; 2Illinois Natural History Survey, Prairie Research Institute, University of Illinois, Champaign, IL, USA; 3Arizona Department of Fish and Game, Phoenix, AZ, USA; 4Department of Veterinary Clinical Medicine, University of Illinois, Urbana, IL, USA


Hematologic assessment is the most common clinical tool used by practitioners and researchers to characterize both individual and population health. In reptiles, the hematologic response can be influenced by factors such as temperature and season, especially in temperate species. To improve the diagnostic utility of hematology in reptiles, it is imperative to evaluate and characterize the normal range of physiologic variation. The study objectives were to 1) determine the impact of temperature and time of year on CBC parameters; and 2) create subject-based reference intervals for 20 prairie rattlesnakes (Crotalus viridis). Animals were randomly assigned to either a control group housed at a constant temperature (75–77°F) or a treatment group housed in an environmental chamber with the temperature altered to reflect natural seasonal variation in temperature. Twice monthly for one year, blood samples were collected, and the following hematologic parameters were measured: total white blood cell count (WBC), packed cell volume (PCV), total solids (TS), and white blood cell differential counts. WBC decreased and PCV increased as the mean previous 14-day temperature increased, with no effect of season. Total solids were higher in the control group, but there was no direct effect of temperature or season. These results suggest that environmental temperature, rather than season, drives hematologic parameters, which should prove useful when interpreting hematologic assessment results of reptiles.


We thank the veterinary and graduate students in the Wildlife Epidemiology Lab that assisted with animal care or sample collection.


Speaker Information
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Matthew C. Allender, DVM, MS, PhD, DACZM
Wildlife Epidemiology Laboratory
College of Veterinary Medicine
University of Illinois
Urbana, IL, USA

Illinois Natural History Survey
Prairie Research Institute
University of Illinois
Champaign, IL, USA

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