Last data update: Sep 23, 2024. (Total: 47723 publications since 2009)
Records 1-4 (of 4 Records) |
Query Trace: Schotthoefer AM [original query] |
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Changing socioeconomic indicators of human plague, New Mexico, USA
Schotthoefer AM , Eisen RJ , Kugeler KJ , Ettestad P , Reynolds PJ , Brown T , Enscore RE , Cheek J , Bueno R Jr , Targhetta J , Montenieri JA , Gage KL . Emerg Infect Dis 2012 18 (7) 1151-4 Socioeconomic indicators associated with temporal changes in the distribution of human plague cases in New Mexico were investigated for 1976-2007. In the 1980s, cases were more likely in census block groups with poor housing conditions, but by the 2000s, cases were associated with affluent areas concentrated in the Santa Fe-Albuquerque region. |
Effects of temperature on the transmission of Yersinia pestis by the flea, Xenopsylla cheopis, in the late phase period
Schotthoefer AM , Bearden SW , Holmes JL , Vetter SM , Montenieri JA , Williams SK , Graham CB , Woods ME , Eisen RJ , Gage KL . Parasit Vectors 2011 4 191 BACKGROUND: Traditionally, efficient flea-borne transmission of Yersinia pestis, the causative agent of plague, was thought to be dependent on a process referred to as blockage in which biofilm-mediated growth of the bacteria physically blocks the flea gut, leading to the regurgitation of contaminated blood into the host. This process was previously shown to be temperature-regulated, with blockage failing at temperatures approaching 30 degrees C; however, the abilities of fleas to transmit infections at different temperatures had not been adequately assessed. We infected colony-reared fleas of Xenopsylla cheopis with a wild type strain of Y. pestis and maintained them at 10, 23, 27, or 30 degrees C. Naive mice were exposed to groups of infected fleas beginning on day 7 post-infection (p.i.), and every 3-4 days thereafter until day 14 p.i. for fleas held at 10 degrees C, or 28 days p.i. for fleas held at 23-30 degrees C. Transmission was confirmed using Y. pestis-specific antigen or antibody detection assays on mouse tissues. RESULTS: Although no statistically significant differences in per flea transmission efficiencies were detected between 23 and 30 degrees C, efficiencies were highest for fleas maintained at 23 degrees C and they began to decline at 27 and 30 degrees C by day 21 p.i. These declines coincided with declining median bacterial loads in fleas at 27 and 30 degrees C. Survival and feeding rates of fleas also varied by temperature to suggest fleas at 27 and 30 degrees C would be less likely to sustain transmission than fleas maintained at 23 degrees C. Fleas held at 10 degrees C transmitted Y. pestis infections, although flea survival was significantly reduced compared to that of uninfected fleas at this temperature. Median bacterial loads were significantly higher at 10 degrees C than at the other temperatures. CONCLUSIONS: Our results suggest that temperature does not significantly effect the per flea efficiency of Y. pestis transmission by X. cheopis, but that temperature is likely to influence the dynamics of Y. pestis flea-borne transmission, perhaps by affecting persistence of the bacteria in the flea gut or by influencing flea survival. Whether Y. pestis biofilm production is important for transmission at different temperatures remains unresolved, although our results support the hypothesis that blockage is not necessary for efficient transmission. |
Effects of temperature on early-phase transmission of Yersina pestis by the flea, Xenopsylla cheopis
Schotthoefer AM , Bearden SW , Vetter SM , Holmes J , Montenieri JA , Graham CB , Woods ME , Eisen RJ , Gage KL . J Med Entomol 2011 48 (2) 411-7 Sharp declines in human and animal cases of plague, caused by the bacterium Yersinia pestis (Yersin), have been observed when outbreaks coincide with hot weather. Failure of biofilm production, or blockage, to occur in the flea, as temperatures reach 30 degrees C has been suggested as an explanation for these declines. Recent work demonstrating efficient flea transmission during the first few days after fleas have taken an infectious blood meal, in the absence of blockage (e.g., early-phase transmission), however, has called this hypothesis into question. To explore the potential effects of temperature on early-phase transmission, we infected colony-reared Xenopsylla cheopis (Rothchild) fleas with a wild-type strain of plague bacteria using an artificial feeding system, and held groups of fleas at 10, 23, 27, and 30 degrees C. Naive Swiss Webster mice were exposed to fleas from each of these temperatures on days 1-4 postinfection, and monitored for signs of infection for 21 d. Temperature did not significantly influence the rates of transmission observed for fleas held at 23, 27, and 30 degrees C. Estimated per flea transmission efficiencies for these higher temperatures ranged from 2.32 to 4.96% (95% confidence interval [CI]: 0.96-8.74). In contrast, no transmission was observed in mice challenged by fleas held at 10 degrees C (per flea transmission efficiency estimates, 0-1.68%). These results suggest that declines in human and animal cases during hot weather are not related to changes in the abilities of X. cheopis fleas to transmit Y. pestis infections during the early-phase period. By contrast, transmission may be delayed or inhibited at low temperatures, indicating that epizootic spread of Y. pestis by X. cheopis via early-phase transmission is unlikely during colder periods of the year. |
Biofilm formation is not required for early-phase transmission of Yersinia pestis
Vetter SM , Eisen RJ , Schotthoefer AM , Monteneri JA , Holmes JL , Bobrov AG , Bearden SW , Perry RD , Gage KL . Microbiology (Reading) 2010 156 2216-2225 Our study investigated whether hms-mediated biofilm formation was necessary for early-phase transmission (EPT) of Yersinia pestis. In addition to the biofilm-dependent blockage model of plague transmission from flea to mammal, an EPT model of transmission, has been described where fleas transmit Y. pestis to a host up to 4 days post infection, which is insufficient time for blockages to form in flea foreguts. An artificial feeding system was used to feed Xenopsylla cheopis and Oropsylla montana rat blood spiked with either the parental Y. pestis strain KIM5(pCD1)+, two different biofilm-mutants (DeltahmsT , DeltahmsR), or a biofilm-overproducer mutant (DeltahmsP ). Infected fleas were then allowed to feed on naive Swiss Webster mice 1-4 days after infection and the mice were monitored for signs of infection up to three weeks post-exposure. The biofilm-defective mutants were transmitted from X. cheopis and O. montana as efficiently as the parent strain, whereas the transmission efficiency of fleas fed the biofilm-overproducer was significantly less than either the parent or biofilm-deficient strains. The bacterial loads in fleas infected with a biofilm-deficient strain harbored lower bacterial loads 4 days post infection when compared to fleas infected with the parent strain. Thus defects in biofilm formation did not prevent flea-borne transmission of Y. pestis in our EPT model and biofilm over-production inhibited efficient EPT, however biofilm may play a role in infection persistence in the flea. |
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