Abstract. The relationships between climatic variables and the frequency of human plague cases were modeled by Poisson regression for two adjoining regions in northeastern Arizona and northwestern New Mexico. Model outputs closely agreed with the numbers of cases actually observed, suggesting that temporal variations in plague risk can be estimated by monitoring key climatic variables, most notably maximum daily summer temperature values and time-lagged (1 and 2 year) amounts of late winter (February-March) precipitation. Significant effects also were observed for time-lagged (1 year) summer precipitation in the Arizona model. Increased precipitation during specific periods resulted in increased numbers of expected cases in both regions, as did the number of days above certain lower thresholds for maximum daily summer temperatures (80ЊF in New Mexico and 85ЊF in Arizona). The number of days above certain high-threshold temperatures exerted a strongly negative influence on the numbers of expected cases in both the Arizona and New Mexico models (95ЊF and 90ЊF, respectively). The climatic variables found to be important in our models are those that would be expected to influence strongly the population dynamics of the rodent hosts and flea vectors of plague.

Plague is a rare but highly virulent flea-borne zoonotic disease caused by the Gram-negative bacterium Yersinia pestis Yersin. Identifying areas at high risk of human exposure to the etiological agent of plague could provide a useful tool for targeting limited public health resources and reduce the likelihood of misdiagnosis by raising awareness of the disease. We created logistic regression models to identify landscape features associated with areas where humans have acquired plague from 1957 to 2004 in the four-corners region of the United States (Arizona, Colorado, New Mexico, and Utah), and we extrapolated those models within a geographical information system to predict where plague cases are likely to occur within the southwestern United States disease focus. The probability of an area being classified as high-risk plague habitat increased with elevation up to approximately 2300 m and declined as elevation increased thereafter, and declined with distance from key habitat types (e.g., southern Rocky Mountain piñon--juniper [Pinus edulis Engelm. and Juniperus spp.], Colorado plateau piñon--juniper woodland, Rocky Mountain ponderosa pine (Pinus ponderosa P.& C. Lawson var. scopulorum), and southern Rocky Mountain juniper woodland and savanna). The overall accuracy of the model was >82%. Our most conservative model predicted that 14.4% of the four-corners region represented a high risk of peridomestic exposure to Y. pestis.

Yersinia pestis, the causative agent of plague, has been detected in fleas and mammals throughout the western United States. This highly virulent infection is rare in humans, surveillance of the disease is expensive, and it often was assumed that risk of exposure to Y. pestis is high in most of the western United States. For these reasons, some local health departments in these plague-affected regions have hesitated to undertake surveillance and other prevention activities. To aid in targeting limited public health resources, we created a fine-resolution human plague risk map for New Mexico, the state reporting more than half the human cases in the United States. Our GIS-based model included three landscape features-a nonlinear relationship with elevation, distance to water, and distance to the ecotone between Rocky Mountain/Great Basin open and closed coniferous woodlands-and yielded an overall accuracy of approximately 80%. The model classified 17.25% of the state as posing significant risk of exposure to humans on privately or tribally owned land, which suggests that resource requirements for regular surveillance and control of plague could be effectively focused on < 20% of the state.

A steam pasteurization process (patent pending) has been shown to effectively reduce pathogenic bacterial populations on beef tissue and to significantly reduce naturally occurring bacterial populations on commercially slaughtered beef carcasses. The objective of this study was to determine the effectiveness of the steam pasteurization treatment for reducing bacterial populations at several anatomical locations on commerically slaughtered carcasses. Before and after pasteurization treatment (82.2 degrees C, 6.5-s exposure time), a sterile sponge was used to sample 300 cm2 at one of five locations (inside round, loin, midline, brisket, or neck). Eighty carcasses (40 before treatment and 40 after treatment) were sampled per anatomical location over 2 processing days. Before treatment, aerobic plate counts (APCs) were found to be highest (P < or = 0.01) at the midline (4.5 log10 CFU/100 cm2), intermediate at the inside round, brisket, and neck (ca. 3.8 log10 CFU/100 cm2), and lowest at the loin (3.4 log10 CFU/100 cm2). After treatment, APCs at all locations were reduced significantly (P < or = 0.01). The inside round, loin, and brisket had the lowest (P < or = 0.01) APCs (ca. 2.6 log10 CFU/100 cm2), whereas the midline and neck had APCs of 3.1 and 3.3 log10 CFU/100 cm2, respectively. The lower reduction in APCs at the neck area indicated that the treatment may not be as effective there, possibly because of the design of the pasteurization equipment. Generic Escherichia coli populations were low at all locations before treatment, with populations on 32% of all carcasses sampled being less than the detection limit of the study (5.0 CFU/100 cm2). After treatment, E. coli populations were significantly lower (P < or = 0.01) than populations before treatment and 85% of all carcasses sampled had E. coli populations below the detection limit. The maximum E. coli population detected after treatment was 25 CFU/100 cm2. For enteric bacterial populations, no differences were observed in the effectiveness of the treatment among the five carcass locations.

Abstract. Within the United States, the majority of human plague cases are reported from New Mexico. We describe climatic factors involved in intra-and inter-annual plague dynamics using animal-based surveillance data from that state. Unlike the clear seasonal pattern observed at lower elevations, cases occur randomly throughout the year at higher elevations. Increasing elevation corresponded with delayed mean time in case presentation. Using local meteorological data (previous year mean annual precipitation, total degrees over 27°C 3 years before and maximum winter temperatures 4 years before) we built a time-series model predicting annual case load that explained 75% of the variance in pet cases between years. Moreover, we found a significant correlation with observed annual human cases and predicted pet cases. Because covariates were time-lagged by at least 1 year, intensity of case loads can be predicted in advance of a plague season. Understanding associations between environmental and meteorological factors can be useful for anticipating future disease trends.

No abstract

Plague is a rare but highly virulent flea-borne zoonotic disease caused by the Gram-negative bacterium Yersinia pestis Yersin. Identifying areas at high risk of human exposure to the etiological agent of plague could provide a useful tool for targeting limited public health resources and reduce the likelihood of misdiagnosis by raising awareness of the disease. We created logistic regression models to identify landscape features associated with areas where humans have acquired plague from 1957 to 2004 in the four-corners region of the United States (Arizona, Colorado, New Mexico, and Utah), and we extrapolated those models within a geographical information system to predict where plague cases are likely to occur within the southwestern United States disease focus. The probability of an area being classified as high-risk plague habitat increased with elevation up to approximately 2300 m and declined as elevation increased thereafter, and declined with distance from key habitat types (e.g., southern Rocky Mountain piñon--juniper [Pinus edulis Engelm. and Juniperus spp.], Colorado plateau piñon--juniper woodland, Rocky Mountain ponderosa pine (Pinus ponderosa P.& C. Lawson var. scopulorum), and southern Rocky Mountain juniper woodland and savanna). The overall accuracy of the model was >82%. Our most conservative model predicted that 14.4% of the four-corners region represented a high risk of peridomestic exposure to Y. pestis.

The objective of this study was to determine the prevalence of Escherichia coli O157:H7, other E. coli strains, total coliforms, and aerobic organisms on the surface of subprimal beef cuts prior to enhancement. Subprimal cuts were sampled during winter (January and February 2004) and summer (August through October 2004). During each collection period, six representative subprimal cuts (chuck tenders, 0.64-cm trimmed strips, bottom round flat, rough-trimmed brisket, cap-on top rounds, and cap-off insides) were sampled. A total of 600 samples in winter (100 samples per cut) and 599 samples in summer (100 chuck tenders, 100 0.64-cm trimmed strips, 100 bottom round flats, 100 cap-off insides, 97 rough-trimmed briskets, and 102 cap-on top rounds) were collected from five plants in the Midwest, southern Midwest, northern Midwest, and Southeast and swabbed using the sponge swab method. All sponges were analyzed for E. coli O157:H7. In addition, 400 subprimal cuts from four plants were analyzed for aerobic plate counts, total coliforms, and other E. coli strains during each collection period. E. coli O157:H7 was not detected on any of the 1,199 subprimal samples; thus, incidence of E. coli O157:H7 was < 0.083%. Seasonal differences between aerobic plate counts and total coliform counts for each of the same cuts were 1.0 log CFU per cut or less. E. coli strains were not detected in 82, 52, 69, and 82% of the chuck tenders, 0.64-cm trimmed strips, bottom round flats, and cap-off insides, respectively.