A Novel Retrovirus (Gunnison's Prairie Dog Retrovirus) Associated With Thymic Lymphoma in Gunnison's Prairie Dogs in Colorado, USA.

Molly D Butler,Karen Griffin,Mark D Stenglein,Sandra L Quackenbush,Marylee L Kapuscinski,Daniel W Tripp,Connie D Brewster,Karen A Fox

doi:10.3390/v12060606

Abstract

As part of research and wildlife disease surveillance efforts, we performed necropsy examinations of 125 free-ranging (n = 114) and captive (n = 11) prairie dogs in Colorado from 2009 to 2017. From these cases, we identified three cases of thymic lymphoma in free-ranging Gunnison’s prairie dogs (Cynomys gunnisoni), and we identified a novel retroviral sequence associated with these tumors. The viral sequence is 7700 nucleotides in length and exhibits a genetic organization that is consistent with the characteristics of a type D betaretrovirus. The proposed name of this virus is Gunnison’s prairie dog retrovirus (GPDRV). We screened all 125 prairie dogs for the presence of GPDRV using PCR with envelope-specific primers and DNA extracted from spleen samples. Samples were from Gunnison’s prairie dogs (n = 59), black-tailed prairie dogs (Cynomys ludovicianus) (n = 40), and white-tailed prairie dogs (Cynomys leucurus) (n = 26). We identified GPDRV in a total of 7/125 (5.6%) samples including all three of the prairie dogs with thymic lymphoma, as well as spleen from an additional four Gunnison’s prairie dogs with no tumors recognized at necropsy. None of the GPDRV-negative Gunnison’s prairie dogs had thymic lymphomas. We also identified a related, apparently endogenous retroviral sequence in all prairie dog samples. These results suggest that GPDRV infection may lead to development of thymic lymphoma in Gunnison’s prairie dogs.

Highlights

Colorado is home to three of the five free-ranging prairie dog species native to North America: the white-tailed prairie dog (Cynomys leucurus), the black-tailed prairie dog (Cynomys ludovicianus), and the Gunnison’s prairie dog (Cynomys gunnisoni)
Using PCR and generation sequencing, we identified and were able to assemble two unique retroviral sequences from lymphoid tissue of prairie dogs
One of the sequences was identified in DNA from all samples screened, which included members from each of three species of prairie dogs included in the study

Summary

Introduction

Colorado is home to three of the five free-ranging prairie dog species native to North America: the white-tailed prairie dog (Cynomys leucurus), the black-tailed prairie dog (Cynomys ludovicianus), and the Gunnison’s prairie dog (Cynomys gunnisoni). Prairie dogs are a member of the Sciuridae family, along with squirrels and other burrowing rodents. Species in that prairie dogs and their burrows provide prey and habitat for a number of wild birds and mammals, they support diverse plant and pollinator communities and the health of the local ecosystem often depends on the health of prairie dog populations [1,2]. Disease threats from plague (caused by Yersinia pestis) are well understood in prairie dogs [3,4], which are highly susceptible to Viruses 2020, 12, 606; doi:10.3390/v12060606 www.mdpi.com/journal/viruses. The roles of other infectious agents in the health of free-ranging prairie dog colonies have not been extensively considered. The most commonly reported tumors of captive prairie dogs are elodontoma and hepatocellular adenocarcinoma, of which hepatocellular carcinoma may be associated with infection by a hepadnavirus [5,6]

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