Sylvatic Plague Vaccine Partially Protects Prairie Dogs (Cynomys spp.) in Field Trials

Abstract

Sylvatic plague, caused by Yersinia pestis, frequently afflicts prairie dogs (Cynomys spp.), causing population declines and local extirpations. We tested the effectiveness of bait-delivered sylvatic plague vaccine (SPV) in prairie dog colonies on 29 paired placebo and treatment plots (1–59 ha in size; average 16.9 ha) in 7 western states from 2013 to 2015. We compared relative abundance (using catch per unit effort (CPUE) as an index) and apparent survival of prairie dogs on 26 of the 29 paired plots, 12 with confirmed or suspected plague (Y. pestis positive carcasses or fleas). Even though plague mortality occurred in prairie dogs on vaccine plots, SPV treatment had an overall positive effect on CPUE in all three years, regardless of plague status. Odds of capturing a unique animal were 1.10 (95% confidence interval [C.I.] 1.02–1.19) times higher per trap day on vaccine-treated plots than placebo plots in 2013, 1.47 (95% C.I. 1.41–1.52) times higher in 2014 and 1.19 (95% C.I. 1.13–1.25) times higher in 2015. On pairs where plague occurred, odds of apparent survival were 1.76 (95% Bayesian credible interval [B.C.I.] 1.28–2.43) times higher on vaccine plots than placebo plots for adults and 2.41 (95% B.C.I. 1.72–3.38) times higher for juveniles. Our results provide evidence that consumption of vaccine-laden baits can protect prairie dogs against plague; however, further evaluation and refinement are needed to optimize SPV use as a management tool.Electronic supplementary materialThe online version of this article (doi:10.1007/s10393-017-1253-x) contains supplementary material, which is available to authorized users.

Reintroducing a keystone burrowing rodent to restore an arid North American grassland: challenges and successes

“…Previous efforts to establish prairie dog colonies on the SNWR had limited success despite multiple release efforts, and the chances for success in this system may become increasingly difficult with the climate becoming more arid and drought‐prone (Davidson et al ). While restoration goals may be more easily obtained in the mesic parts of their range, those populations are often exposed to more frequent sylvatic epizootics, and so require intensive management efforts via regular dusting with insecticide or distribution of the sylvatic plague vaccine to facilitate their persistence (Biggins et al ; Rocke et al ; Tripp et al ). With such uncertainty regarding reintroduction success for prairie dogs, and for wildlife reintroductions in general, we underscore the importance of setting well‐defined, quantifiable success criteria with associated time frames for assessment, prior to implementing a reintroduction project and embarking upon long‐term monitoring (Seddon et al ; IUCN/SSC ).…”

Local factors associated with on‐host flea distributions on prairie dog colonies

“…We analyzed flea abundance and prevalence on prairie dogs from 23 paired plots that had been included in a large‐scale sylvatic plague vaccine (SPV) trial (see further details in Rocke et al., ). A pair consisted of one plot treated with SPV‐laden baits and one plot that received placebo baits.…”

“…To determine plague status of our study plots, spleen and liver tissues from prairie dog carcasses, as well as flea pools collected from live and dead animals, were tested for the presence of Y. pestis using real‐time PCR (see Rocke et al., for details). In brief, tissue DNA was extracted using the Wizard SV Genomic DNA Purification System (Promega; Madison, WI), and PCR was performed for the caf1 gene sequence located on the Y. pestis pG8786 plasmid (Genbank accession ) and the pla gene located on the Y. pestis pPCP1 plasmid (Genbank accession ).…”

“…We evaluated factors associated with prevalence of fleas and overall flea abundance, including variables related to climate and seasonal weather patterns (NDVI [normalized difference vegetation index—a measure of vegetation greenness, see Table ], number of days with a temperature over 85°F [Collinge et al., ], amount of precipitation during the prior year's growing season, winter precipitation amount, and day of sampling), plot‐level variables (catch per unit effort as an index of relative abundance of prairie dogs [see Rocke et al., for details], treatment [placebo vs. vaccine], plague status [plague detected vs. not detected], and elevation), and individual covariates (age, sex, body condition [=weight/foot length]) (Table ). To incorporate effects of plot, we used a random effect for BTPD ( n = 22 plots), UPD ( n = 14), and WTPD ( n = 8).…”

Mucosal vaccines and technology

“…Use of gel-beads to deliver Eimeria spp. in the United States [29,30]. oocysts, and significantly higher weight gain post-challenge infection [26].…”