HUMAN INFECTIOUS DISEASE​

Bubonic plague (Yersinia pestis)

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CONSERVATION PROBLEM

Epizootic plague kills both prairie dogs and the highly endangered black-footed ferret in western North America, presenting a major challenge for conservation.

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INTERVENTION

Vaccinating prairie dog colonies and controlling flea vectors

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TARGET

Prairie dog colonies (as well as direct vaccination of black-footed ferrets)

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MECHANISM

Both prairie dogs and ferrets are susceptible to plague; epizootics can cause colony die-offs and further impact ferret populations via loss of habitat/prey. Vaccination of prairie dog colonies (and direct vaccination of ferrets) could enhance prairie dog metapopulations and ferret conservation while also reducing spillover risk to humans by interrupting enzootic transmission.

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HUMAN INFECTIOUS DISEASE EVIDENCE

HYPOTHESIS: Reductions in plague epizootics and flea populations in prairie dog colonies suggest that human risk may be reduced, but there is no evidence for reduced spillover transmission to humans. Human plague is so rare in North America that interventions are unlikely to have any measurable human health benefit.

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CONSERVATION EVIDENCE

EXPERIMENT/BEFORE-AFTER: Vaccines have been shown to be effective in protecting ferrets, and in reducing epizootics and colony die-offs in prairie dogs. Deltamethrin treatment of prairie dog burrows for flea control has also been shown to reduce flea populations, which likely prevents epizootics.

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LOCATION AND SPATIAL SCALE

Intermountain western N. America; landscape scale interventions encompassing prairie dog metapopulations and black-footed ferret home ranges (60+ ha)

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TEMPORAL SCALE

Control requires continuous/sustained vaccination of captive-bred ferrets and bait vaccination of prairie dogs.

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HEALTH SUCCESS METRICS

Spillover of plague to U.S. human populations is exceedingly rare, so health success metrics would need to focus on proxies for human risk, like reduced enzootic transmission or rates of infection in host and vector populations. 

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CONSERVATION SUCCESS METRICS

Fewer prairie dog colony die-offs, long-term persistence of ferret populations

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HUMAN CO-BENEFITS

Ferret conservation could restore natural control (via predation) of prairie dog populations and other rodents, which are pests in western ranchlands.

 

CONSERVATION CO-BENEFITS

Prairie dogs are a keystone species because they are the primary prey for many species and many animals rely on their burrows for nesting (e.g., burrowing owls).

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COLLATERAL HUMAN IMPACTS

There could be negative impacts for cattle ranchers if vaccinated prairie dog colonies are protected.

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COLLATERAL CONSERVATION IMPACTS

Insecticides (flea control) may have collateral impacts on non-target species; no collateral impacts identified for vaccination.

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SOCIAL ACCEPTABILITY

Ranchers have historically opposed ferret conservation efforts, because it includes protections for prey of ferrets (prairie dogs), which are pests in ranchlands.

 

EQUITY CONSIDERATIONS

Outcome of intervention may not be equitable due to negative impacts on ranchers.

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PRACTICALITY/CHALLENGES

Bait vaccination may be very effective and more easily implemented than widespread insecticide use for controlling fleas, though successful control may require both. Cost and effort associated with long-term vaccination campaigns could be challenges.

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STATUS

Vaccination and flea control are already implemented as part of ferret conservation efforts, but we do not know how this is affecting human health.

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RESEARCH NEEDS

This cannot be called a win-win for conservation and people until we quantify human health outcomes. For conservation, we need large-scale studies of bait vaccine efficacy.

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REFERENCES

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BEFORE-AFTER and EXPERIMENTAL STUDIES

T. E. Rocke et al., Consumption of baits containing raccoon pox-based plague vaccines protects black-tailed prairie dogs (Cynomys ludovicianus). Vector-Borne and Zoonotic Diseases. 10, 53–58 (2010).

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T. E. Rocke et al., Sylvatic plague vaccine partially protects prairie dogs (Cynomys spp.) in field trials. EcoHealth. 14, 438–450 (2017).

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D. B. Seery et al., Treatment of black-tailed prairie dog burrows with deltamethrin to control fleas (insecta: siphonaptera) and plague. Journal of Medical Entomology. 40, 718–722 (2003).

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D. W. Tripp, T. E. Rocke, J. P. Runge, R. C. Abbott, M. W. Miller, Burrow dusting or oral vaccination prevents plague-associated prairie dog colony collapse. EcoHealth. 14, 451–462 (2017).

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OTHER SUPPORTING INFORMATION

R. C. Abbott, J. E. Osorio, C. M. Bunck, T. E. Rocke, Sylvatic plague vaccine: A new tool for conservation of threatened and endangered species? EcoHealth. 9, 243–250 (2012).

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R. J. Eisen et al., Human plague in the southwestern United States, 1957–2004: Spatial models of elevated risk of human exposure to Yersinia pestis. Journal of Medical Entomology. 44, 530–537 (2007).

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M. R. Matchett, D. E. Biggins, V. Carlson, B. Powell, T. Rocke, Enzootic plague reduces black-footed ferret (Mustela nigripes) survival in Montana. Vector-Borne and Zoonotic Diseases. 10, 27–35 (2010).

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T. E. Rocke et al., Age at vaccination may influence response to sylvatic plague vaccine (SPV) in gunnison’s prairie dogs (Cynomys gunnisoni). EcoHealth. 12, 278–287 (2015).

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P. Stapp, M. F. Antolin, M. Ball, Patterns of Extinction in Prairie Dog Metapopulations: Plague Outbreaks Follow El Niño Events. Frontiers in Ecology and the Environment. 2, 235–240 (2004).

 

G. W. Witmer, B. T. Hoffmann, The Colorado Front Range Prairie Dog Technical Workshop: an overview and summary. Proceedings of the Vertebrate Pest Conference. 20 (2002), doi:10.5070/V420110008.

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Page last updated: 3/14/2021 

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