Browsing by Subject "epidemiology"

Now showing 1 - 9 of 9
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    A comparison of participants and non-participants in a serum sample survey in Texas City, Texas.
    (2008-05-20) Carlos H. Martinez; Edilma Guevara, Ph.D.; Elizabeth T. Anderson
    Lack of participation and response can affect the validity and generalizability of epidemiologic surveys. Participation has decreased in recent decades, and thus there is a need to determine reasons for and implications of this change. Usually respondents have better health, habits, and socioeconomic status and are interested in their health, being described as a “worried healthy” group. It is unclear if this explanation applies to minorities. The Environmental Risk, Coping, and Hispanic Health Project of the Center for Population Health and Health Disparities of UTMB, a population-based survey conducted in Texas City, Texas, included an interview of the randomly selected participants and an invitation to donate blood for biological measures. The study represented an opportunity to compare the characteristics of participants in the initial survey who, subsequently, provided blood sample and those who declined. In this Capstone the hypothesis that disadvantaged and less healthy groups are less likely to participate in serum sample collection as part of a sero-epidemiologic study was tested. The specific aims included: to determine the percentage of respondents declining to donate blood; to compare the characteristics of those who donated blood and those who declined, for the whole sample and across ethnic groups; and to examine the association with stress. We found that participation was lower than in similar surveys, with different response rates by ethnicity. We did not find great differences between respondents and nonrespondents, other than age, smoking habit, and perceived poor health. The only factors that were maintained in a multivariate analysis were age, family income, and smoking habit. We also found interaction between age and ethnicity, with advanced age being related to less likelihood of nonresponse in all ethnicities except in Non-Hispanic Blacks, where the direction was the opposite. A comparison of respondents and nonrespondents across ethnicities showed no additional factors, with the exception of results within US-born Hispanics. In addition to age, being a smoker and reporting poor health were associated with nonresponse, while low income was associated with less likelihood of being nonrespondent. For all participants and across ethnicities perceived stress did not have an association with response
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    Comparison of the Prevalence and Genotypic Characteristics of Clostridium difficile in a Closed and Integrated Human and Swine Population in Texas
    (2011-10-21) Norman, Keri Noelle
    Clostridium difficile has been recognized as one of the leading causes of nosocomial diarrhea and pseudomembranous colitis in human hospitals and nursing homes since the 1970s; however, recent occurrences of community-acquired cases have led researchers to search for additional sources of these infections. Some of the possible sources being investigated include food animals and retail meat. The objective of this study was to compare the prevalence and genotypic characteristics of C. difficile isolated from a closed population in Texas consisting of both humans and swine. Implicit in this objective, we seek to investigate the possible food safety and occupational risks associated with swine and C. difficile. Isolation of C. difficile was performed utilizing an enrichment technique and restrictive media. Polymerase chain reaction (PCR) was used to test for the presence of the toxin A and B genes, the tcdC gene deletion, and the binary toxin gene. Genotypic characteristics were compared using PCR toxinotyping and pulsed-field gel electrophoresis (PFGE). Antimicrobial susceptibility was tested using commercially available tests (ETest?) for 11 different antibiotics. Statistical comparisons (both parametric and non-parametric, and appropriate to the data) were performed both between and among host species. We tested 2,292 aggregated human wastewater samples and 2,936 swine fecal samples from 2004 to 2006 and found 271 (11.8 percent) and 252 (8.6 percent) to be positive for C. difficile, respectively. The prevalence of C. difficile among swine production groups differed significantly (p<0.05); however, prevalence in the human occupational group cohorts (swine workers and non-workers) did not differ (p=0.81). The majority of the human and swine isolates were a PFGE NAP7 (a variant pattern with 90.5 percent similarity) toxinotype V strain. Antimicrobial resistance levels and multi-resistance patterns were generally similar between host species; however, there was decreased susceptibility (p<0.05) to ampicillin, clindamycin, and imipenem observed in swine isolates, whereas there was decreased susceptibility (p<0.05) to ciprofloxacin in the human isolates. The similarity in C. difficile prevalence between swine workers and non-workers suggests a low occupational hazard of working with swine as it relates to C. difficile source. We also found that there is a decreased prevalence of C. difficile in late production groups in swine suggesting a lowered risk of food-borne exposure. However, the majority of the isolates derived from the human wastewater and swine appeared to be of very similar strain types, suggesting that a common environmental point source predominates for both hosts.
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    Descriptive epidemiology and outcome of patients with intraductal papillary mucinous neoplasm (IPMN): a population-based comparison to pancreatic adenocarcinoma and review of literature.
    (2009-04-27) Advitya Malhotra; Taylor S. Riall; Karen E. Szauter; Don W. Powell
    Intraductal papillary neoplasm (IPMN) is an uncommon cancer of the pancreas, histologically characterized as a distinct entity by WHO in 1996, as noninvasive (adenoma, borderline neoplasm, carcinoma in situ) or invasive. Our understanding of this disease comes mainly from small retrospective reports and anecdotal experience. While it is clear that patients with benign IPMNs do better than patients with invasive IPMNs and adenocarcinoma, it is not clear if, once invasive, IPMNs have a more favorable prognosis than adenocarcinoma not associated with IPMNs. Our goal was to evaluate a large population-based cohort of patients with invasive IPMN and compare their demographic factors and outcomes to those of patients with pancreatic adenocarcinoma (PA). Using the Surveillance, Epidemiology, and End Results (SEER) database (1988 to 2003), we identified all patients with invasive IPMN or PA. A total of 2,166 patients with invasive IPMN and 35,515 with PA were identified. Patients with IPMN were younger than patients with PA at the time of diagnosis (67.0 vs. 70.1, P<.0001). The overall 5-year survival was 8.8% for IPMN (median, 5 months) and 3.7% for PA (median, 4 months, P < .0001). Patients with unresected IPMN had a 5-year survival rate of 4.2% compared to 2.2% in patients with unresected PA (P < .0001). Surgical resection was a significant independent predictor of improved survival, as was female gender, race other than white and black, married status and negative lymph nodes. We conclude, IPMN is a more indolent disease than PA. Patients with IPMN tend to present at a younger age, are more likely to have resectable disease, and are much more likely to undergo potentially curative resection. The long-term survival for patients with IPMN is significantly better when compared to the long-term survival of patients with PA.
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    Ecology and transmission dynamics of Everglades virus
    (2005-10-20) Lark Lee Arwen Coffey; Douglas Watts; Daniel Brooks; Billy Philips
    Everglades virus (EVEV), an alphavirus in the Venezuelan equine encephalitis (VEE) serocomplex, circulates among rodents and vector mosquitoes in Florida and occasionally infects humans, causing a febrile disease sometimes accompanied by neurological manifestations. \r\nEVEV infections of cotton rats from Florida, and from Texas, a non-endemic area were performed to validate their role in enzootic transmission and to evaluate whether the viremia induced regulates EVEV distribution. Cotton rats from both localities developed viremia levels that exceeded the threshold for infection of the vector indicating that rat susceptibility does not limit EVEV distribution. \r\nSusceptibility experiments were performed with _Aedes taeniorhynchus_ and _Culex nigripalpus_, potential EVEV vectors, to evaluate their permissiveness to EVEV infection. In contrast to the high degree of susceptibility of the established vector _Culex (Melanoconion) cedecei_, these two species were relatively refractory to oral EVEV infection, indicating that they are probably not important vectors. \r\nPet dogs were used as sentinels of EVEV activity to detect recent circulation and to delineate EVEV distribution. Four percent of Florida dog sera contained EVEV antibody and many animals lived farther north than recorded EVEV activity, indicating that EVEV is widespread in the state and may be a cause of undiagnosed febrile illness in residents.\r\nDespite evidence that enzootic subtype ID Venezuelan equine encephalitis viruses (VEEVs), the closest relatives of EVEV, have emerged to cause significant human and equine disease, EVEV has not caused outbreaks in Florida. Venezuelan equine encephalitis virus emergence can be mediated by adaptation to epizootic mosquito vectors via mutations in the E2 glycoprotein gene. EVEV may accrue similar E2 mutations resulting in epizootic disease in Florida. The role of the EVEV E2 gene in epizootic vector infection was evaluated with a VEEV/EVEV E2 chimera. Insertion of the EVEV E2 into the VEEV backbone reduced infection in _Ae. taeniorhynchus_ by 40%, indicating that the epizootic VEEV E2 is necessary for infection of epizootic vectors. \r\nThe intrinsic plasticity of RNA viruses can facilitate changes in host range that may cause epidemics. However, the evolutionary processes that promote cross-species virus transfers are poorly defined, especially for generalist RNA arboviruses that replicate alternately in arthropods and vertebrates and often exhibit slower evolutionary rates than other RNA viruses with similar mutation frequencies that replicate only in vertebrates. The observed genetic stability of RNA arboviruses may result from constraints imposed by alternating between disparate hosts, where optimal replication in one host involves a fitness tradeoff for the alternate host. Accordingly, freeing RNA arboviruses from the alternate replication cycle, and thereby allowing them to specialize in a single host, will facilitate faster evolution and adaptation. To test this hypothesis in vivo, VEEV was passaged serially in mosquitoes or in vertebrates to eliminate host alteration, or alternately between mosquitoes and vertebrates. Virus lineages allowed to specialize in mosquitoes exhibited increased mosquito infectivity, and vertebrate-specialized strains produced higher viremias. Alternately passaged VEEV exhibited no detectable fitness gains in either host and serial passaged VEEV exhibited fitness declines in the bypassed host. These results support the hypothesis that arbovirus adaptation and evolution is limited by obligate host alternation. \r\n\r\n
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    Effective contact of cattle and feral swine facilitating potential foot-and-mouth disease virus transmission in southern Texas, USA rangeland
    (2009-05-15) De La Garza, Guadalupe Ray, III
    For the second study, a web-based survey was developed and distributed to all members of four major health education organizations. A total of 1,925 HEs? completed the survey and 1,607 responses were utilized in the final analysis. This study indicated that participants had deficient knowledge and unfavorable attitudes toward the CDCproposed genomic competencies. In the third study, a theoretical model was developed to predict HEs? likelihood to incorporate genomic competencies into their practice. Using techniques from Structural Equation Modeling (SEM), the model was tested with the same data of the second study. Findings supported the proposed theoretical model. While genomic knowledge, attitudes, and self-efficacy were significantly associated with HEs? likelihood to incorporate genomic competencies into their practice, attitudes was the strongest predictor of likelihood. In summary, these studies indicated that participating HEs had deficient genomic knowledge, unfavorable attitudes toward a set of CDC-proposed genomic competencies, and low likelihood to adopt genomic competencies into health promotion. Relevant training should be developed and advocated. As the SEM analysis results indicated the survey findings supported the proposed theoretical model, which can be utilized to steer future training for HEs. statistics, 2) unadjusted inferential statistics, 3) stratified analysis, and 4) multivariable models. My investigation produced results in accord with generally accepted notions in addition to significant findings that interestingly counter current preconceptions. Intraspecies contact was more common than inter-species, with indirect contact occurring more frequently than direct. Direct contact between species occurred extremely rarely. The most important factors that influenced the rate of contact for both species were water, winter, and cultivated fields. Information regarding probability of infectious agent survival and transfer will be used in the future to advance current epidemiological models, including geographicautomata (Ward et al. 2007: In Press) and cellular automata models (Doran and Laffan 2005) to better understand and manage integrated domestic cattle and free-ranging wildlife populations. Such modeling provides essential and necessary knowledge for developing prevention, detection, response, and recovery strategies ? employed in advance, during, and after a disease outbreak, respectively.
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    Evaluation of dietary factors associated with spontaneous pancreatitis in dogs
    (2009-05-15) Lem, Kristina Yvonne
    This study estimates the association between dietary factors and spontaneous pancreatitis in dogs. A case-control study was conducted using 198 dogs with a clinical diagnosis of pancreatitis and 187 control dogs with a diagnosis of renal failure without clinical evidence of pancreatitis. Information on signalment, weight, body condition, dietary intake, medical history, diagnostic tests performed, concurrent diseases, treatment, length of hospital stay, and discharge status was extracted from medical records for dogs admitted to the Texas A&M University Small Animal Clinic (TAMU SAC) during January 2000 to December 2005. Information on dietary intake, signalment, weight, medical, surgical and environmental history was collected for the same dogs through a telephone questionnaire conducted from November 2006 through January 2007. Descriptive statistics were calculated, tabular analyses performed, and logistic regression was used to estimate odds ratios (OR) and 95% confidence intervals (CI). Based on information extracted from the medical records, ingesting unusual food (OR=4.3; CI=1.7 to 10.7), ingesting table food (OR=1.5; CI=1.0 to 2.2), or exposure to both of these dietary factors (OR=2.1; CI=1.3 to 3.2) increased the odds of pancreatitis. Collected through the telephone questionnaire, ingesting unusual food (OR=6.1; CI=2.2 to 16.5), ingesting table scraps the week before diagnosis (OR=2.2; CI=1.2 to 3.8) or regularly throughout life (OR=2.2; CI=1.2 to 4.0), and getting into the trash (OR=13.2; CI=2.1 to undefined) increased the odds of pancreatitis. Multivariable modeling estimated the associations of exposure to one or more dietary factors reported through the telephone questionnaire (OR=2.6; CI=1.4 to 5.0), overweight (OR=1.3; CI=0.7 to 2.5), year of diagnosis (OR=3.5; CI=1.9 to 6.5), neuter status (OR=3.6; CI=1.4 to 9.5), non-neuter surgery (OR=21.1; CI=3.3 to 133.9) and an interaction term between neuter status and non-neuter surgery (OR=0.1; CI=0.01 to 0.4). Dietary factors increase the odds of spontaneous pancreatitis in dogs.
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    Genetic epidemiology and familial risk factors for paratuberculosis seropositivity in beef cattle
    (2009-05-15) Osterstock, Jason Barrett
    Paratuberculosis is an intestinal infection of ruminants caused by Mycobacterium avium subsp. paratuberculosis (MAP). Genetic associations with paratuberculosis have been described in Holstein cattle. The objectives were to describe the association between paratuberculosis status of the dam and her offspring in beef cattle, develop methods to assess familial aggregation of paratuberculosis in cattle of unknown pedigree, and model the paratuberculosis status of beef cattle given familial and herdlevel covariates. Texas beef cattle were tested for paratuberculosis using serum antibody and microbiologic culture of feces. Available pedigree data were used to confirm familial relationships. The association between the paratuberculosis ELISA status of the dam and her offspring was assessed using mixed-effects models. Increased odds of being classified as a ?suspect? or greater based on ELISA results were observed if the dam was classified as a ?suspect? or greater. A positive linear association was observed between the ELISA value of the dam and her offspring. Analysis of pedigree data using conditional logistic regression identified ancestors associated with significantly increased odds of being classified as ?low positive? or greater. Microsatellite markers were used to classify cattle into genetically similar groups using allele frequency data. Nine clusters of genetically similar cattle were identified among paratuberculosis test positive cattle, herd matched controls, and pedigreed cattle. Clusters were validated using animals of known pedigree. Increased odds of paratuberculosis seropositivity were observed for some clusters compared to the cluster with the lowest seroprevalence. A predictive model was developed using a Bayesian framework to assess the association between antibody status of the dam and her offspring adjusted for herd-level risk factors. Predictors associated with highly probable increased odds of seropositivity included herd seroprevalence and herd fecal prevalence of MAP. The association between dam and offspring ELISA status was small (OR 1.35) and not highly probable. The results of this work support familial aggregation of paratuberculosis ELISA status, but herd-level risk factors appear to be more important in predicting ELISA status. A large proportion of observed serological reactions were not supported by fecal culture results; therefore, observed associations might be limited to humoral responses to Mycobacterium spp.
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    Investigations on the diagnosis, colonization, and epidemiology of grapevines with Pierce's disease
    (Texas A&M University, 2005-02-17) Vest, Mandi Ann
    Pierce?s disease (PD) of grapevines, caused by Xylella fastidiosa, is devastating Texas vineyards. Two rapid diagnostic techniques, real-time polymerase chain reaction (PCR) and enzyme-linked immunosorbent assay (ELISA), were compared on the basis of cost, reliability, and their ability to quantify X. fastidiosa in diseased tissues. A high correlation was found between the two techniques for measuring bacterial titer in vitro. A similar relationship was not detected when applying the methods to diseased tissue. There was a 75% similarity between the techniques when used to diagnose PD in artificially infected grapevines. Where the two methods differed, real-time PCR was more successful in identifying plants known to be infected with the bacterium. In uninoculated grapevines, the two techniques were similar, where the positive rates were 7% and 4% for ELISA and real-time PCR respectively. In a second study, 3 grape cultivars, ?Cynthiana?, ?Cabernet Sauvignon?, and ?Chardonnay?, were inoculated with 2 isolates of X. fastidiosa to measure disease development and colonization by the pathogen. The bacteria colonized similar distances from the inoculation point over a 25 week period in all three cultivars. Real-time PCR and ELISA absorbance values suggest that the concentrations of bacteria ranged between 104 and 106 cells/ml in a 1.27 cm section of grapevine cane. Concentrations of bacteria didn?t vary based on distance from the inoculation point. Marginal leaf-scorch symptoms were seen on ?Cabernet Sauvignon? and ?Chardonnay? grapevines 9 weeks post-inoculation. Leaf-scorch symptoms were not observed on ?Cynthiana?. The vigor of all inoculated grapevines was reduced compared to negative control grapevines the season after initial infection. In a third study, a Texas vineyard planted in Viognier grapevines was surveyed for PD symptoms on 3 separate dates. In October 2003, 45/50 rows had significant aggregation of symptomatic grapevines according to Ordinary Runs Analysis. Aggregation of symptomatic grapevines was found down the row more often than across the row. The rapid rate of disease progress and mortality rate of vines in this vineyard suggest that vine-to-vine spread is occurring and that Viognier vines are highly susceptibly to PD.
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    Patterns of antimicrobial resistance among enteric bacteria found in multi-site group-level cohorts of humans and swine
    (Texas A&M University, 2006-04-12) Campbell, Linda Diane
    The prevalence of antimicrobial resistance (AMR) phenotypes and genotypic characteristics (Class 1 integron and AMR gene cassettes) in commensal Escherichia coli (EC) and vancomycin resistant Enterococcus faecium (EF) isolated from humans and swine in a semi-closed, integrated farrow-to-fork population were evaluated in a crosssectional study. Our objective was to establish baseline antimicrobial resistance patterns and to evaluate the stability of isolate recovery phenotype within multiple grab samples per collection day and over multiple biweekly samples collected during a period of several months. This data will serve as a baseline for continuing longitudinal studies within the population. These continuing studies should produce the first comprehensive epidemiological data to document the transmission dynamics of antimicrobial resistance in the farrow-to-fork continuum. Outcome variables assessed included: phenotypic resistance in EC, pan-susceptibility, multi-resistance and genotypic resistance. Potential predictor variables included: 1) host species, 2) unit, 3) unit type, 4) housing cohort by species, and 5) time of day. There were significant differences (p<0.05) between host species with swine at higher odds for both single and multiple resistance. There were also differences in resistance based on unit location, unit-type, and housing cohort within both humans and swine. Our study found no significant differences (p>0.05) in resistance between swine workers and non-swine workers with the sole exception of resistance to cephalothin, with non-swine workers at 1.89 higher odds for resistance (p=0.02). A total of 17 VRE were isolated from human wastewater samples, and to the author??s knowledge these represent the first environmentally isolated VRE in the U.S. Several unique multi-resistance phenotypes were observed and future evaluation of AMR phenotype in continuing longitudinal studies provides a unique opportunity to study phenotypic patterns and dissemination through the study population.