Lisa L. Wolfe | Search USGS

USGS2017

Responses of juvenile black-tailed prairie dogs (Cynomys ludovicianus) to a commercially produced oral plague vaccine delivered at two doses

We confirmed safety and immunogenicity of mass-produced vaccine baits carrying an experimental, commercial-source plague vaccine (RCN-F1/V307) expressing Yersinia pestis V and F1 antigens. Forty-five juvenile black-tailed prairie dogs ( Cynomys ludovicianus ) were randomly divided into three treatment groups ( n =15 animals/group). Animals in the first group received one standard-dose vaccine bait (5×10 7 plaque-forming units [pfu]; STD). The second group received a lower-dose bait (1×10 7 pfu; LOW). In the third group, five animals received two standard-dose baits and 10 were left untreated but in contact. Two vaccine-treated and one untreated prairie dogs died during the study, but laboratory analyses ruled out vaccine involvement. Overall, 17 of 33 (52%; 95% confidence interval for binomial proportion [bCI] 34−69%) prairie dogs receiving vaccine-laden bait showed a positive anti-V antibody response on at least one sampling occasion after bait consumption, and eight (24%; bCI 11–42%) showed sustained antibody responses. The STD and LOW groups did not differ ( P ≥0.78) in their proportions of overall or sustained antibody responses after vaccine bait consumption. Serum from one of the nine (11%; bCI 0.3–48%) surviving untreated, in-contact prairie dogs also had detectable antibody on one sampling occasion. We did not observe any adverse effects related to oral vaccination.

Journal of Wildlife Diseases↗

USGS2011

Assessment of a recombinant F1-V fusion protein vaccine intended to protect Canada lynx (Lynx canadensis) from plague

As part of an ongoing restoration program in Colorado, USA, we evaluated adverse reactions and seroconversion in captive Canada lynx ( Lynx canadensis ) after vaccination with a recombinant F1-V fusion protein vaccine against Yersinia pestis , the bacterium that causes plague. Ten adult female lynx received the F1-V vaccine; 10 source- and age-matched lynx remained unvaccinated as controls. All of the vaccinated and control lynx remained apparently healthy throughout the confinement period. We observed no evidence of injection site or systemic reactions to the F1-V vaccine. Among vaccinated lynx, differences in log 10 reciprocal antibody titers measured in sera collected before and after vaccination (two doses) ranged from 1.2 to 5.2 for anti-F1 antibodies and from 0.6 to 5.2 for anti-V antibodies; titers in unvaccinated lynx did not change appreciably over the course of confinement prior to release, and thus differences in anti-F1 ( P =0.003) and anti-V ( P =0.0005) titers were greater among vaccinated lynx than among controls. Although our findings suggest that the F1-V fusion protein vaccine evaluated here is likely to stimulate antibody responses that may help protect Canada lynx from plague, we observed no apparent differences in survival between vaccinated and unvaccinated subject animals. Retrospectively, 22 of 50 (44%; 95% confidence interval 29–59%) unvaccinated lynx captured or recaptured in Colorado during 2000–08 had passive hemagglutination antibody titers >1:16, consistent with exposure to Y. pestis ; paired pre- and postrelease titers available for eight of these animals showed titer increases similar in magnitude to those seen in response to vaccination, suggesting at least some lynx may naturally acquire immunity to plague in Colorado habitats.

Journal of Wildlife Diseases↗