Plague Among the Ground Squirrels of California

Wherry, William B.

doi:10.1093/infdis/5.5.485

Cited by 22 publications

(8 citation statements)

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“…To document whether enzootic maintenance would be predicted with realistic parameter values for Y. pestis in California rodents and fleas, the model was run with parameter values from the well-studied pla- , 1908, 1909, 1911aMcCoy and Smith, 1910;McCoy and Chapin, 1912;Eskey and Haas,1940;Holdenreid and Quan, 1956;Marchette et al, 1962a, b;Quan and Kartman, 1962;Quan et al, 1985 compv Vector of flea vector competence Tables 6, 8 Eskey and Haas, 1940;Burroughs, 1944Burroughs, , 1947Wheeler and Douglas, 1945;Holdenreid, 1952;Kartman and Prince, 1956;Kartman, et al, 1958 u Matrix of relative utilization preferences (scaled 0-1) of flea species for host species Tables 6, 8 Eskey and Haas, 1940;Burroughs, 1944Burroughs, , 1947Wheeler and Douglas, 1945;Holdenreid, 1952;Kartman and Prince, 1956;Kartman et al, 1958 c Vector of rates of recovery for each host species Tables 3, 4, 7 McCoy, 19087 McCoy, , 19097 McCoy, , 1911aMcCoy and Smith, 1910;McCoy and Chapin, 1912;Eskey and Haas, 1940;Holdenreid and Quan, 1956;Marchette et al, 1962a, b;Quan and Kartman, ...…”

Section: Parameter Estimation and Sensitivity Analysismentioning

confidence: 99%

“…Simultaneously, Y. pestis became established in native rodents in the San Francisco region (Link, 1955), and, as early as 1903, massive epizootics were reported in California ground squirrels (Spermophilus beecheyi). The agent of plague was first isolated in California ground squirrels in 1908 in the Berkeley hills in Contra Costa County (McCoy, 1908;Wherry, 1908).…”

Section: Introductionmentioning

confidence: 99%

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Modeling Plague Persistence in Host-Vector Communities in California

Foley¹,

Zipser²,

Chomel³

et al. 2007

Journal of Wildlife Diseases

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ABSTRACT:Plague is an enzootic disease in the western United States, even though long-term persistent infections do not seem to occur. Enzootic persistence may occur as a function of dynamic interactions between flea vectors and transiently infected hosts, but the specific levels of vector competence, host competence, and transmission and recovery rates that would promote persistence and emergence among wild hosts and vectors are not known. We developed a mathematical model of enzootic plague in the western United States and implemented the model with the following objectives: 1) to use matrix manipulation within a classic susceptibleRinfectiveRresistantRsusceptible (SIRS) model framework to describe transmission of the plague bacterium Yersinia pestis among rodents and fleas in California, 2) to perform sensitivity analysis with model parameters and variables to indicate which values tended to dominate model output, and 3) to determine whether enzootic maintenance would be predicted with realistic parameter values obtained from the literature for Y. pestis in California rodents and fleas. The model PlagueSIRS was implemented in discrete time as a computer simulation incorporating environmental stochasticity and seasonality, by using matrix functions in the computer language R, allowing any number of rodent and flea species to interact through parasitism and disease transmission. Sensitivity analysis indicated that the model was sensitive to flea attack rate, host recovery rate, and rodent host carrying capacity but relatively insensitive to changes in the duration of latent infection in the flea, host and vector competence, flea recovery from infection, and host mortality attributable to plague. Realistic parameters and variable values did allow for the model to predict enzootic plague in some combinations, specifically when rodent species that were susceptible to infection but resistant to morbidity were parasitized by multiple poorly competent flea species, including some that were present year-round. This model could be extended to similar vectorborne disease systems and could be used iteratively with data collection in sylvatic plague studies to better understand plague persistence and emergence in nature.

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Section: Parameter Estimation and Sensitivity Analysismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Modeling Plague Persistence in Host-Vector Communities in California

Foley¹,

Zipser²,

Chomel³

et al. 2007

Journal of Wildlife Diseases

View full text Add to dashboard Cite

show abstract

“…Throughout this study, attention was focused primarily on the California ground squirrel, Citellus beecheyi, which has long been known as a factor in the epidemiology of plague (Wherry 1908). This squirrel is one of the commonest rodents in California and is usually an important member of any natural community in which it is found; in many areas of the state it is a serious agricultural pest.…”

Section: Introductionmentioning

confidence: 99%