Publications

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epidemiologic survey of sylvatic plague by serotesting coyote sentinels with enzyme immunoassay.the geographic distribution and areas of high sylvatic plague activity in california were verified by using coyotes (canis latrans) as sentinel animals. antibody levels against yersinia pestis were tested using the enzyme-labelled antibody (ela) test and the microtiter passive hemagglutination and hemagglutination inhibition. a survey using the ela test indicated that the overall antibody prevalence among 143 coyotes was 21%. by geographic regions, the highest antibody prevalence was 27% among c ...1979382839
plague surveillance by serological testing of coyotes (canis latrans) in los angeles county, california.sera from 19 (5.6%) of 338 coyotes (canis latrans) collected in los angeles county, california between 1986 and 1990 had antibodies against yersinia pestis using the passive hemagglutination test. coyotes were excellent sentinels of plague activity in los angeles county. enzootic plague declined dramatically in the county during the 5-yr period.19921474660
serological survey for selected diseases in the endangered san joaquin kit fox (vulpes macrotis mutica).blood from endangered san joaquin kit foxes (vulpes macrotis mutica) inhabiting the elk hills naval petroleum reserve, kern county, and the elkhorn plain, san luis obispo county, california, was collected in 1981, 1982 and 1984 and sera were tested for antibodies against 10 selected pathogens. proportions of kit fox sera containing antibodies against pathogens were: canine parvovirus, 100% in 1981-1982 and 67% in 1984; infectious canine hepatitis virus, 6% in 1981-1982 and 21% in 1984; canine di ...19882836636
serologic evidence of yersinia pestis infection in small mammals and bears from a temperate rainforest of north coastal california.from 1983 to 1985, 463 serum samples from 11 species of mammals in redwood national park (rnp) (california, usa) were evaluated for antibodies to yersinia pestis by the passive hemagglutination method. yersinia pestis antibodies occurred in serum samples from 25 (36%) of 69 black bears (ursus americanus), one (50%) of two raccoons (procyon lotor), five (3%) of 170 dusky-footed woodrats (neotoma fuscipes), and one (less than 1%) of 118 deer mice (peromyscus maniculatus). two hundred seventy-three ...19892915403
serologic and bacteriologic studies on the distribution of plague infection in a wild rodent plague pocket in the san francisco bay area of california. 19725049121
the effect of flea control on yersinia (pasteurella) pestis antibody rates in the california vole, microtus californicus, and its epizootiological implications.the effects of flea control on the prevalence of (pasteurella) pestis antibody rates in the california vole, microtus californicus, were studied in san mateo county, california, usa. in this area, which had shown antibody prevalence rates of 50% or more during epizootics in previous years, continuous flea control measures reduced the antibody rate to virtually zero and held it at that level for 12 months, although a nearby area showed an incidence of 40-80% seropositive voles for 5 months during ...19715316910
serologic survey of california wild hogs for antibodies against selected zoonotic disease agents.blood samples were collected from trapped or hunter-killed wild hogs (sus scrofa) in 4 areas of california. sera were tested for antibodies against 7 zoonotic disease agents. antibodies against brucella sp were detected in 21 (15%) of 136 samples. antibodies against coxiella burnetii were found in 50% of the collected samples (67 of 135 tested). of the 135 wild hogs screened for pseudorabies virus, 4 (3%) were seropositive. leptospira interrogans antibodies were discovered in 118 (87%) of the 13 ...19836315659
primary plague pneumonia contracted from a domestic cat at south lake tahoe, calif.primary plague pneumonia occurred in a 47-year-old south lake tahoe woman shortly after face-to-face exposure to her plague pneumonia-infected cat. both died. field investigation revealed a recent plague epizootic in squirrels and chipmunks around the patient's home. control measures included active surveillance and chemoprophylaxis of 197 contacts to the victim, a community alert on methods of self- and pet protection, and application of insecticide to reduce rodent flea populations. no seconda ...19846694294
serological surveillance of plague in dogs and cats, california, 1979-1991.following natural infection both cats and dogs develop antibodies to plague which can be measured for several months after infection. besides being helpful in the diagnosis of plague in domestic carnivores, the antibody titer has important implications in outbreak investigation and surveillance programs. we report the first serological survey for plague in domestic carnivores conducted in california between 1979 and 1991 in five different settings or programs. a total of 4115 dogs and 466 cats w ...19947924244
serologic survey and serum biochemical reference ranges of the free-ranging mountain lion (felis concolor) in california.serum samples from 58 mountain lions (felis concolor) in california (usa) were collected between april 1987 and february 1990. nineteen serum samples were used for serum biochemistry determinations; the ranges were similar to reference values in domestic cats, captive exotic felidae and free-ranging mountain lions. a serological survey was conducted to determine whether antibodies were present against selected infectious agents. fifty-four (93%) of 58 sera had antibodies against feline panleukop ...19948028105
an overview of plague in the united states and a report of investigations of two human cases in kern county, california, 1995.plague was confirmed in the united states from nine western states during 1995. evidence of yersinia pestis infection was identified in 28 species of wild or domestic mammals. thirteen of the plague positive species were wild rodents; 15 were predators/carnivores. yersinia pestis was isolated from eight species of fleas. seven confirmed cases of human plague were reported in 1995 (new mexico 3; california 2; arizona and oregon 1 each). five of the seven cases were bubonic; one was septicemic and ...19979221742
flea-borne rickettsioses: ecologic considerations.ecologic and economic factors, as well as changes in human behavior, have resulted in the emergence of new and the reemergence of existing but forgotten infectious diseases during the past 20 years. flea-borne disease organisms (e.g., yersinia pestis, rickettsia typhi, r. felis, and bartonella henselae) are widely distributed throughout the world in endemic-disease foci, where components of the enzootic cycle are present. however, flea-borne diseases could reemerge in epidemic form because of ch ...19979284376
a cryptic 19-kilobase plasmid associated with u.s. isolates of yersinia pestis: a dimer of the 9.5-kilobase plasmid.yersinia pestis, the etiologic agent of plague, carries three prototypic plasmids with sizes of 110 kb (pfra, ptox), 70 kb (plcr, pvw, pcad), and 9.5 kb (ppla, ppst). studies suggest that geographic isolates of y. pestis may be differentiated by plasmid profiles. yersinia pestis isolated from the western united states harbor an additional plasmid, estimated to be approximately 19 kb in size. this cryptic plasmid was characterized by restriction endonuclease digestion, amplification and sequencin ...19989840581
new records of sylvatic plague in kansas.sylvatic plague, or plague of wild rodents is caused by yersinia pestis and entered california (usa) from asia about 1899. extensive sampling during the 1930's and 1940's documented the spread of plague to approximately its current distribution in north america. records from the centers for disease control and prevention document plague in kansas (usa) between 1945 and 1950, but since then there has been no documentation of plague in the state. following a die-off of a black-tailed prairie dog ( ...200010813625
serologic survey for selected infectious disease agents in swift and kit foxes from the western united states.a serologic survey of swift fox (vulpes velox) and kit fox (v. macrotis) from the western usa was conducted for 12 infectious diseases. samples from swift fox were collected between 1987 and 1992 from colorado (n = 44), kansas (n = 10), and wyoming (n = 9). samples from kit fox were collected in california (n = 86), new mexico (n = 18), utah (n = 9), and arizona (n = 6). overall antibody prevalence rates were 33 of 110 (30%) for canine parvovirus (cpv), 9 of 72 (13%) for canine distemper virus ( ...200011085448
spatial analysis of yersinia pestis and bartonella vinsonii subsp. berkhoffii seroprevalence in california coyotes (canis latrans).zoonotic transmission of sylvatic plague caused by yersinia pestis occurs in california, usa. human infections with various bartonella species have been reported recently. coyotes (canis latrans) are ubiquitous throughout california and can become infected with both bacterial agents, making the species useful for surveillance purposes. this study examined the geographic distribution of 863 coyotes tested for y. pestis and bartonella vinsonii subsp. berkhoffii serologic status to gain insight int ...200312507856
serum antibody responses in a population of microtus californicus and associated rodent species during and after pasteurella pestis epizootics in the san francisco bay area. 196414270072
the detection of inapparent infections with pasteurella pestis in a microtus californicus population in the san francisco bay area. 196414270073
analysis of genetic algorithm for rule-set production (garp) modeling approach for predicting distributions of fleas implicated as vectors of plague, yersinia pestis, in california.more than 20 species of fleas in california are implicated as potential vectors of yersinia pestis. extremely limited spatial data exist for plague vectors-a key component to understanding where the greatest risks for human, domestic animal, and wildlife health exist. this study increases the spatial data available for 13 potential plague vectors by using the ecological niche modeling system genetic algorithm for rule-set production (garp) to predict their respective distributions. because the a ...200616506453
human plague--four states, 2006.plague is a zoonotic disease caused by the bacterium yersinia pestis. in 2006, a total of 13 human plague cases have been reported among residents of four states: new mexico (seven cases), colorado (three cases), california (two cases), and texas (one case). this is the largest number of cases reported in a single year in the united states since 1994. dates of illness onset ranged from february 16 to august 14; two (15%) cases were fatal. the median age of patients was 43 years (range: 13-79 yea ...200616943764
ectoparasite diversity and exposure to vector-borne disease agents in wild rodents in central coastal california.a survey of wild rodents was performed in the morro bay area of central coastal california to determine serological and polymerase chain reaction (pcr) prevalence of anaplasma phagocytophilum dumler, barbet, bekker, dasch, palmer, ray, rikihisa, and rurangirwa, borrelia burgdorferi johnson, schmidt, hyde, steigerwalt, and brenner, francisella tularensis mccoy, and yersinia pestis yersin; to describe the ectoparasitic fauna on important vector-borne disease hosts; and to determine whether pathoge ...200717427705
evidence of multiple zoonotic agents in a wild rodent community in the eastern sierra nevada.this study aimed to describe the occurrence of yersinia pestis, rickettsia rickettsii, anaplasma phagocytophilum, and ectoparasites in a wild rodent community in the eastern sierra nevada. from may to september 2006, rodents were live-trapped, examined for ectoparasites, and blood was collected. all rodents were serologically tested for antibodies to y. pestis, r. rickettsii, and a. phagocytophilum; in addition, blood samples and ectoparasites were tested by pcr to detect the presence of these z ...200818689664
plague studies in california: a review of long-term disease activity, flea-host relationships and plague ecology in the coniferous forests of the southern cascades and northern sierra nevada mountains.we review 28 years of long-term surveillance (1970-1997) for plague activity among wild rodents from ten locations within three coniferous forest habitat types in the northern sierra nevada and the southern cascade mountains of northeastern california. we identify rodent hosts and their fleas and document long-term plague activity in each habitat type. the highest seroprevalence for yersinia pestis occurred in the chipmunks, tamias senex and t. quadrimaculatus, and the pine squirrel, tamiasciuru ...201020618641
arthropod vectors and vector-borne bacterial pathogens in yosemite national park.ticks, fleas, and vector-borne pathogens were surveyed in diverse small mammals in yosemite national park, california, from 2005 to 2007. a total of 450 unique captures of small mammals was collected during a 3-yr period and yielded 16 species of fleas and 10 species of ticks, including known vectors of anaplasma phagocytophilum and borrelia burgdorferi and plague. serology was performed for a. phagocytophilum, spotted fever group rickettsia spp., b. burgdorferi, and yersinia pestis. a. phagocyt ...201121337955
demographic characteristics and infectious diseases of a population of american black bears in humboldt county, california.american black bears (ursus americanus) are common, widely distributed, and broad-ranging omnivorous mammals in northern california forests. bears may be susceptible to pathogens infecting both domestic animals and humans. monitoring bear populations, particularly in changing ecosystems, is important to understanding ecological features that could affect bear population health and influence the likelihood that bears may cause adverse impacts on humans. in all, 321 bears were captured between may ...201525700042
zoonotic vector-borne bacterial pathogens in california mountain lions (puma concolor), 1987-2010.sera collected from 442 mountain lions in 48 california counties between the years of 1987 and 2010 were tested using immunofluorescence assays and agglutination tests for the presence of antibodies reactive to yersinia pestis, francisella tularensis, bartonella henselae, borrelia burgdorferi, and anaplasma phagocytophilum antigens. data were analyzed for spatial and temporal trends in seropositivity. seroprevalences for b. burgdorferi (19.9%) and b. henselae (37.1%) were relatively high, with t ...201222925024
disease surveillance of california ground squirrels ( spermophilus beecheyi ) in a drive-through zoo in oregon, usa.rodents and other small wild mammals are often considered to be pests and vectors for disease in zoos that house small populations of valuable threatened and endangered animals. in 2005, three nonhuman primates at a drive-through zoo in oregon, us, acquired tularemia from an unknown source. due to an abundance of california ground squirrels ( spermophilus beecheyi ) on zoo grounds, we instituted serosurveillance of this species from july through september 2008 to determine the prevalence of anti ...201728418764
investigation of and response to 2 plague cases, yosemite national park, california, usa, 2015.in august 2015, plague was diagnosed for 2 persons who had visited yosemite national park in california, usa. one case was septicemic and the other bubonic. subsequent environmental investigation identified probable locations of exposure for each patient and evidence of epizootic plague in other areas of the park. transmission of yersinia pestis was detected by testing rodent serum, fleas, and rodent carcasses. the environmental investigation and whole-genome multilocus sequence typing of y. pes ...201627870634
spatial analysis of plague in california: niche modeling predictions of the current distribution and potential response to climate change.plague, caused by the bacterium yersinia pestis, is a public and wildlife health concern in california and the western united states. this study explores the spatial characteristics of positive plague samples in california and tests maxent, a machine-learning method that can be used to develop niche-based models from presence-only data, for mapping the potential distribution of plague foci. maxent models were constructed using geocoded seroprevalence data from surveillance of california ground s ...200919558717
use of a chitin synthesis inhibitor to control fleas on wild rodents important in the maintenance of plague, yersinia pestis, in california.a study was designed to test the insect development inhibitors fluazuron and lufenuron for the control of fleas on sylvatic rodents as an adjunct to the control of plague. historical data of flea burden from 15 prior years of study at chuchupate campground, ventura county, ca, were compared to six years of treatment period data to determine if fluazuron and lufenuron were effective in controlling flea densities. the insect development inhibitors, delivered systemically via a feed cube, reduced f ...200819263847
septicemic plague in a community hospital in california.diagnosis of a case of septicemic plague acquired in rural california was delayed because of a series of confounding events, resulting in concern about reliance on community hospitals as sentinels for detecting potential bioterrorism-related events. an epizootic study confirmed the peridomestic source of yersinia pestis infection.200818541761
multiple antimicrobial resistance in plague: an emerging public health risk.antimicrobial resistance in yersinia pestis is rare, yet constitutes a significant international public health and biodefense threat. in 1995, the first multidrug resistant (mdr) isolate of y. pestis (strain ip275) was identified, and was shown to contain a self-transmissible plasmid (pip1202) that conferred resistance to many of the antimicrobials recommended for plague treatment and prophylaxis. comparative analysis of the dna sequence of y. pestis plasmid pip1202 revealed a near identical inc ...200717375195
initiation and spread of traveling waves of plague, yersinia pestis, in the western united states.yersinia pestis invaded the continental united states in 1900 and subsequently became established in wild rodent populations in several western states, traversing 2,250 km in approximately 40 years. however, the specific path of the eastward expansion of plague into the united states is poorly understood. we directly calculated velocities of disease spread and performed trend-surface analyses on spatio-temporally unique plague cases to clarify the route and speed of the initial spread of plague ...200717297050
gray foxes (urocyon cinereoargenteus) as a potential reservoir of a bartonella clarridgeiae-like bacterium and domestic dogs as part of a sentinel system for surveillance of zoonotic arthropod-borne pathogens in northern california.two species of bartonella, a novel bartonella clarridgeiae-like bacterium and b. vinsonii subsp. berkhoffii, were isolated from rural dogs and gray foxes in northern california. a novel b. clarridgeiae-like species was isolated from 3 (1.7%) of 182 dogs and 22 (42%) of 53 gray foxes, while b. vinsonii subsp. berkhoffii was isolated from 1 dog (0.5%) and 5 gray foxes (9.4%). pcr and dna sequence analyses of the citrate synthase (glta) gene and the 16s-23s intergenic spacer region suggested that s ...200717553970
modeling plague persistence in host-vector communities in california.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 west ...200717699079
flea, rodent, and plague ecology at chuchupate campground, ventura county, california.chuchupate campground in ventura county, california, was closed to the public for 18 years (1982 to 2000) because of uncontrolled vector fleas and persistent plague antibody titers in rodents. the primary purpose of this study was to clarify the plague ecology of chuchupate campground by identifying involved rodents and their vector fleas and by determining many of their ecological parameters: abundance, flea and host preferences and diversities, and flea seasonality. rodents and fleas were iden ...200212125863
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