Small-Scale Die-Offs in Woodrats Support Long-Term Maintenance of Plague in the U.S. Southwest

Kosoy, Michael; Reynolds, Pamela J.; Bai, Ying; Sheff, Kelly; Enscore, Russell E.; Montenieri, John A.; Ettestad, Paul; Gage, Kenneth L.

doi:10.1089/vbz.2017.2142

Cited by 25 publications

(30 citation statements)

References 16 publications

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“…, Kosoy et al. ) and spillover from Columbian ground squirrels to the less abundant northern Idaho ground squirrels (also see Matchett et al. ).…”

Section: Discussionmentioning

confidence: 99%

“…In some cases, plague epizootics (outbreaks) might impact sympatric populations of these squirrels. In other cases, plague may circulate at a lower enzootic level , Kosoy et al 2017) and spillover from Columbian ground squirrels to the less abundant northern Idaho ground squirrels (also see Matchett et al 2010). In either case, populations of Columbian ground squirrels may persist, but populations of the much less abundant northern Idaho ground squirrels may dwindle and face extirpation.…”

Section: Flea Communitymentioning

confidence: 99%

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Flea sharing among sympatric rodent hosts: implications for potential plague effects on a threatened sciurid

2020

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For vector‐borne diseases, the abundance and competency of different vector species and their host preferences will impact the transfer of pathogens among hosts. Sylvatic plague is a lethal disease caused by the primarily flea‐borne bacterium Yersinia pestis. Sylvatic plague was introduced into the western United States in the early 1900s and impacts many species of rodents. Plague may be suppressing populations of the threatened northern Idaho ground squirrel (Urocitellus brunneus) if a competent flea community is allowing plague to be maintained within the few extant sites that support this rare ground squirrel. We collected fleas from four species of sympatric rodents in central Idaho: northern Idaho ground squirrels, Columbian ground squirrels (Urocitellus columbianus), yellow‐pine chipmunks (Tamias amoenus), and deer mice (Peromyscus maniculatus). We evaluated which flea species were present and whether fleas were shared among the rodent community. We documented seven species of fleas among 3356 fleas collected from the four host species of rodents, and all seven species of fleas are known vectors of plague. Three of the seven flea species were detected on all four rodent species, demonstrating potential for spillover of plague (bridge vectors) in the rodent community. We used generalized linear mixed models to evaluate which abiotic and biotic factors influence flea abundance (total number of fleas, regardless of flea species, on each individual host of the four rodent host species). Factors that impacted flea abundance varied among the four host species, but flea abundance: (1) changed over summer depending on host species, (2) was greater on males, and (3) was impacted by summer and winter precipitation depending on host species. Our results suggest this diverse flea community has the capacity to transfer Y. pestis among populations of the four rodents if Y. pestis is present. Furthermore, the disease may be more likely to persist in some locations than others, those that have higher flea abundances, more sympatric hosts, or optimal conditions for fleas, and such high‐risk sites can be identified based on their abiotic and biotic factors.

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“…, Kosoy et al. ) and spillover from Columbian ground squirrels to the less abundant northern Idaho ground squirrels (also see Matchett et al. ).…”

Section: Discussionmentioning

confidence: 99%

Section: Flea Communitymentioning

confidence: 99%

Flea sharing among sympatric rodent hosts: implications for potential plague effects on a threatened sciurid

2020

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“…Second, intraspecific and interspecific competition among both fleas and hosts could provide negative feedback that impedes the initiation of the flea-plague PFB cycle (55, 93). These phenomena could become interactively complex in systems involving multiple hosts and multiple flea species, but in situations where a single host is primarily responsible for plague circulation, host territoriality could limit transmission to enzootic rates (22). Third, disease transmission rates in general are assumed to be at least somewhat dependent on host densities (94).…”

Section: Discussionmentioning

confidence: 99%

“…Unlike vector control, plague vaccine is thought to be specific in its protective effect. In another multi-year study of woodrats ( N. albigula ) in New Mexico, Kosoy et al (22) collected nest occupancy evidence suggesting maintenance of plague by localized die-offs that shifted over space and time. Finally, either vector control or a plague vaccine improved black-footed ferret survival by > 200% despite lack of epizootic plague during the 4-year experiment in Montana (23).…”

Section: Introductionmentioning

confidence: 99%

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Prairie Dogs, Persistent Plague, Flocking Fleas, and Pernicious Positive Feedback

Biggins

Eads

2019

Front. Vet. Sci.

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Plague (caused by the bacterium Yersinia pestis ) is a deadly flea-borne disease that remains a threat to public health nearly worldwide and is particularly disruptive ecologically where it has been introduced. We review hypotheses regarding maintenance and transmission of Y. pestis , emphasizing recent data from North America supporting maintenance by persistent transmission that results in sustained non-epizootic (but variable) rates of mortality in hosts. This maintenance mechanism may facilitate periodic epizootic eruptions “in place” because the need for repeated reinvasion from disjunct sources is eliminated. Resulting explosive outbreaks that spread rapidly in time and space are likely enhanced by synergistic positive feedback (PFB) cycles involving flea vectors, hosts, and the plague bacterium itself. Although PFB has been implied in plague literature for at least 50 years, we propose this mechanism, particularly with regard to flea responses, as central to epizootic plague rather than a phenomenon worthy of just peripheral mention. We also present new data on increases in flea:host ratios resulting from recreational shooting and poisoning as possible triggers for the transition from enzootic maintenance to PFB cycles and epizootic explosions. Although plague outbreaks have received much historic attention, PFB cycles that result in decimation of host populations lead to speculation that epizootic eruptions might not be part of the adaptive evolutionary strategy of Y. pestis but might instead be a tolerated intermittent cost of its modus operandi . We also speculate that there may be mammal communities where epizootics, as we define them, are rare or absent. Absence of plague epizootics might translate into reduced public health risk but does not necessarily equate to inconsequential ecologic impact.

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Enzootic plague reduces survival of Mexican woodrats (Neotoma mexicana) in Colorado

et al. 2021

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Plague is a flea‐vectored disease introduced to North America c. 1900. It is lethal to many American mammal species, causes major die‐offs (epizootics) in some populations, and may be ecologically disruptive even at lower interepizootic (enzootic) levels of transmission. We sought to determine the effects of enzootic plague on survival of Mexican woodrats (Neotoma mexicana) and to test the hypothesis that the causative bacterium Yersinia pestis can be maintained by a highly plague‐susceptible species like these woodrats. We compared apparent survival for woodrats in groups with and without plague management. Woodrat groups were (1) treated for vector control with an insecticide (deltamethrin), (2) vaccinated against plague, (3) treated with both vaccine and vector control, and (4) without plague management treatments. Flea prevalence on woodrats was reduced >90% in response to deltamethrin. Apparent survival during May–September, 2010, was 31.1% for non‐vaccinated adult woodrats living in deltamethrin‐treated nests, compared to 9.6% for woodrats in non‐treated nests. During May–September of 2010 and 2011, vaccinated juvenile woodrat survival was 16.8%, compared to 8.4% for non‐vaccinated juveniles. Peak numbers of woodrats captured were 139 for the first trapping session of 2010 and 76 for the first session of 2011, suggesting a population decline consistent with the relatively low estimated survival rates. Survival results suggest that this highly plague‐susceptible species can locally maintain enzootic plague while encountering substantial rates of mortality.

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Small-Scale Die-Offs in Woodrats Support Long-Term Maintenance of Plague in the U.S. Southwest

Cited by 25 publications

References 16 publications

Flea sharing among sympatric rodent hosts: implications for potential plague effects on a threatened sciurid

Flea sharing among sympatric rodent hosts: implications for potential plague effects on a threatened sciurid

Prairie Dogs, Persistent Plague, Flocking Fleas, and Pernicious Positive Feedback

Enzootic plague reduces survival of Mexican woodrats (Neotoma mexicana) in Colorado

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