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A Spatially Explicit Environmental Health Surveillance Framework for Tick-Borne DiseasesAviña, Aldo 08 1900 (has links)
In this paper, I will show how applying a spatially explicit context to an existing environmental health surveillance framework is vital for more complete surveillance of disease, and for disease prevention and intervention strategies. As a case study to test the viability of a spatial approach to this existing framework, the risk of human exposure to Lyme disease will be estimated. This spatially explicit framework divides the surveillance process into three components: hazard surveillance, exposure surveillance, and outcome surveillance. The components will be used both collectively and individually, to assess exposure risk to infected ticks. By utilizing all surveillance components, I will identify different areas of risk which would not have been identified otherwise. Hazard surveillance uses maximum entropy modeling and geographically weighted regression analysis to create spatial models that predict the geographic distribution of ticks in Texas. Exposure surveillance uses GIS methods to estimate the risk of human exposures to infected ticks, resulting in a map that predicts the likelihood of human-tick interactions across Texas, using LandScan 2008TM population data. Lastly, outcome surveillance uses kernel density estimation-based methods to describe and analyze the spatial patterns of tick-borne diseases, which results in a continuous map that reflects disease rates based on population location. Data for this study was obtained from the Texas Department of Health Services and the University of North Texas Health Science Center. The data includes disease data on Lyme disease from 2004-2008, and the tick distribution estimates are based on field collections across Texas from 2004-2008.
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Diagnostik av fästingburen encefalit med ReaScan® TBE IgM : Metodverifiering av ett snabbtest för detektion av antikroppar mot fästingburet encefalitvirus / Tick-borne encephalitis diagnostics with ReaScan® TBE IgM : Evaluation of a rapid test used for the detection of tick-borne encephalitis virus antibodiesAugustsson, Isabella January 2020 (has links)
Fästingburet encefalitvirus (TBEV) är ett RNA-virus som tillhör genuset flavivirus. Vid en TBEV-infektion är feber, trötthet, allmänpåverkan samt huvudvärk och muskelvärk vanligt förekommande symtom. Viruset överförs via saliven från fästingar under de första minuterna efter fästingbett. TBEV-IgM och ibland även TBEV-IgG återfinns i serum då symtom i centrala nervsystemet (CNS) yttrar sig i den andra fasen av sjukdomsförloppet. De senaste åren har prevalensen av fästingburen encefalit (TBE) ökat. Sedan 2017 har över 300 fall av TBE rapporterats årligen i Sverige. Laterala flödesanalyser (lateral flow assays, LFA) är billiga, enkla, snabba och baseras på portabla instrument som används bland annat inom biomedicinsk vetenskap. ReaScan® TBE IgM från det finska företaget Reagena är ett snabbtest, baserat på LFA-tekniken, för detektion av TBE-specifika IgM-antikroppar i humant serum och likvor. Syftet med studien var att undersöka om ReaScan® TBE IgM kan användas för att diagnostisera TBE på laboratoriet för Klinisk Mikrobiologi på länssjukhuset i Kalmar. Metodens prestanda undersöktes genom att analysera totalt 23 serumprover, 13 prover från TBE-patienter och 10 prover från icke-TBE-patienter. Sensitiviteten uppskattades genom att analysera 13 serumprover där förekomst av TBE-antikroppar sedan tidigare konfirmerats. Specificiteten uppskattades genom att analysera 10 serumprover från patienter utan känd TBEV-infektion. Den diagnostiska sensitiviteten respektive specificiteten beräknades till 100 %. På grund av den begränsade storleken på undersökningsmaterialet är dock den beräknade sensitiviteten och specificiteten ej helt tillförlitlig. Metodens prestanda ansågs vara tillräckligt god för att den skall kunna användas som en screening-metod för TBEV-IgM-antikroppar på laboratoriet för Klinisk Mikrobiologi på länssjukhuset i Kalmar. / Tick-borne encephalitis virus (TBEV) is an RNA virus that belongs to the genus flavivirus. Symptoms that commonly present during a TBEV infection include headaches, muscle pains, fever and malaise. The virus is transmitted with the saliva from ticks during the first minutes of their blood meal. TBEV-IgM and sometimes TBEV-IgG antibodies can be detected in the patient’s serum when central nervous system (CNS) symptoms present in the second phase of the disease. Over the last couple of years, the prevalence of tick-borne encephalitis (TBE) has increased. Since 2017 over 300 cases of TBE are reported every year in Sweden. Lateral flow assays (LFA) is the technology behind inexpensive, simple, quick and portable instruments that are used within the biomedical science field among others. ReaScan® TBE IgM developed by the Finnish company Reagena is a rapid test, based on the LFA technique, used for the detection of TBEV specific IgM antibodies in human serum and cerebrospinal fluid. The trial aimed to evaluate whether ReaScan® TBE IgM could be used to diagnose TBE at the laboratory of Clinical microbiology at the County hospital in Kalmar. The performance of the test was determined by analysing a total of 23 serum samples, 13 of which consisted of samples from patients with a previously confirmed TBE diagnosis and 10 samples from patients with no known TBEV infection. The diagnostic sensitivity and specificity were both determined to be 100 %. Due to the limited sample size, the calculated sensitivity and specificity are not particularly reliable. The performance of the test was satisfactory and it could be used as a screening method for the detection of TBEV IgM antibodies at the department of Clinical microbiology at Kalmar County Hospital.
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Safety and Stability of Samples Stored on Filter Paper for Molecular Arbovirus DiagnosisBringeland, Emelie January 2021 (has links)
Expanding urbanization, climate change, and population growth contribute to increased transmission and spread of arthropod-borne viruses (arboviruses), many of which cause severe disease in humans. Pathogenic arboviruses include dengue, Zika, tick-borne encephalitis, and sindbis viruses, which together threaten more than half the global population. Thus, there is a constant need for safe, specific, and sensitive molecular tests to identify early-stage infections for accurate diagnosis and molecular epidemiological data for disease prevention and control. The study tested the biosafety of using FTA™ cards when working with pathogenic arboviruses by conducting an infectivity assay using sindbis virus. Conditions for RNA extraction and storage of arboviruses on FTA were analyzed by measuring viral RNA (vRNA) stability using a SYBR-Green, Pan-Flavi RT-qPCR method composed of degenerate primers able to detect a variety of flaviviruses. Data from a Pan-Flavi RT-qPCR study comprising of 222 clinical blood and serum samples collected from a 2018 dengue virus outbreak in Hanoi (Vietnam) was analyzed to establish applicability of FTA for molecular epidemiology and diagnosis. Results showed that sindbis virus infectivity was inhibited by FTA-adsorption. FTA-adsorbed arboviruses were extracted with the highest yield using Trizol extraction and were preserved at storage at 4-20ºC for up to 30 days. The results showed that clinical blood samples acquired higher yields of vRNA for molecular testing than serum samples and that it may be possible to perform sequencing for genomic analysis. The study suggests that FTA cards may facilitate the storage and transportation of adsorbed arboviruses for downstream molecular epidemiological and diagnostic tests.
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Active Vibration Control of Axial Piston Machine using Higher Harmonic Least Mean Square Control of Swash PlateKim, Taeho, Ivantysynova, Monika 27 April 2016 (has links) (PDF)
Noise emission is a major drawback of the positive displacement machine. The noise source can be divided into structure borne noise source (SBNS) and fluid borne noise source (FBNS). Passive techniques such as valve plate optimization have been used for noise reduction of axial piston machines. However, passive techniques are only effective for limited operating conditions or at least need compromises in design. In this paper, active vibration control of swash plate is investigated for vibration and noise reduction over a wide range of operating conditions as an additional method to passive noise reduction techniques. A 75cc pump has been modified for implementation of active vibration control using the swash plate. One tri-axial acceleration sensor and one angle sensor are installed on the swash plate and a high speed servovalve is used for the swash plate actuation. The multi-frequency two-weight least mean square (LMS) filter synthesizes the servovalve input signal to generate a destructive interference force which minimizes the swash plate vibration. An experimental test setup has been realized using Labview field-programmable gate array (FPGA) via cRIO. Simulation and experimental studies are conducted to investigate the possibility of active vibration control.
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Development of permanently antimicrobial coatingsCloete, William Joseph 12 1900 (has links)
Thesis (MSc)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: Water-borne coatings often contain multiple additives including pigments, dispersing agents,
rheology modifiers, UV stabilizers and biocides. Due to their low molar mass and endocrinedisrupting
properties, many of these additives, upon leaching from the substrate film, with time
pollute water systems and become hazardous to the environment and to human health. In this study,
I aimed to develop a facile method for the production of a polymeric biocide to serve as alternative
to low molar mass biocides used in water-borne coatings. A secondary aim was to show that,
without additional modification, the polymeric species can be used in surfactant-free ab initio
emulsion polymerizations.
Using a two-step process, I modified a commercially available copolymer, poly(styrene-alt-maleic
anhydride) (SMA 1000), with mixed amines in order to obtain latexes with inherent antimicrobial
activity. In the first step, I reacted SMA 1000 with 3-dimethylamino-1-propylamine and aqueous
ammonia to confer antimicrobial activity and water-solubility to the SMA copolymer. In the second
step, the copolymer was incorporated into a film-forming styrene-butyl acrylate (STY/BuA) latex.
The modified SMA was incorporated into a latex in two ways: (1) post-added to the latex, and (2)
used as stabilizer in emulsion polymerization. In both cases, the latex remained stable for up to 11
months, and stability was probably due to steric stabilization of the polymer particles. Antimicrobial
activity of the latex film was achieved with both methods. When the modified SMA was post-added,
antimicrobial activity was restricted to specific areas on the eventual polymer film, and when
modified SMA was used as stabilizer, antimicrobial activity was evenly distributed throughout the
polymer film.
Fluorescence microscopy showed homogeneous distribution of antimicrobial activity upon
inoculation in Gram positive bacteria dispersions when the modified copolymer was used as
polymeric stabilizer for the synthesis of STY/BuA latexes. No antimicrobial activity against Gram
negative bacteria was achieved. The homogeneous distribution of antimicrobial activity throughout
the film was a result of adsorption of polymeric biocide/stabilizer to each individual latex particle.
With further commercial development, high molar mass copolymers modified for antimicrobial
activity may be a feasible, environmentally-friendly and healthy alternative to be used as stabilizers
in emulsion polymerizations to produce water-borne coatings. / AFRIKAANSE OPSOMMING: Waterverf bestaan gewoonlik uit ‘n verskeidenheid bestandele, onder andere: pigmente,
verspreiding middels, reologie modifiseerders, UV stabiliseerders en biologies aktiewe verbindings.
As gevolg van die lae molêre massa en die endokrien ontwrigtende vermoë van baie van die
bestandele hou hulle ‘n bedreiging in vir die omgewing in terme van waterbesoedeling en menslike
gesondheid, soos hulle die film oor tyd verlaat. In hierdie studie het ek beoog om ‘n eenvoudige
metode vir die vervaardiging van ‘n polimeries biologies aktiewe verbindings daar te stel om
sodoende as ‘n alternatief vir die lae molêre massa biologies aktiewe verbindings, wat tans in
waterverf gebruik word, te dien. ‘n Sekondêre uitkoms van die studie was om te wys dat, sonder
enige adissionele omskakelings, dieselfde polimeer gebruik kan word in seep-vrye emulsie
polimerisasie.
Deur gebruik te maak van ‘n proses, wat uit twee stappe bestaan, het ek ‘n kommersieel beskikbare
kopolimeer, poly(stireen-alt-maleinesuuranhidried) (SMA 1000), met gemengde amiene reageer om
‘n sintetiese lateks van stireen en butiel akrilaat (STY/BuA) met inherente antibakteriële aktiwiteit te
verkry. In die eerste stap is SMA 1000 met 3-dimetielamien-1-propielamien en waterige ammoniak
reageer om ‘n water oplosbare kopolimeer met inherente anti-bakteriële aktiwiteit te verkry. In die
tweede stap is hierdie kopolimeer by ‘n sintetiese lateks gevoeg op twee maniere: (1) deur dit nadat
die lateks geproduseer is by te voeg, en (2) deur die kopolimeer as stabiliseerder te gebruik in die
vervaardiging van die lateks. In albei gevalle is stabiele latekse verkry vir ‘n tydperk van tot 11
maande. Die stabilisering was van steriese geaardheid. Albei die latekse het gevolglik antibakteriële
eienskappe getoon. Daar was nie homogene verspreiding van die aktiwiteit in die geval
waar die kopolimeer na die tyd bygevoeg is nie en het veroorsaak dat daar sekere areas van die
finale film was wat geen aktiwiteit getoon het nie.
Fluoresensie mikroskopie het egter homegene verspreiding van die anti-bakteriële aktiwiteit reg
deur die film getoon, na inokulasie met Gram positiewe bakterië suspensies wanneer die kopolimeer
as polimerisasie stabiliseerder gebruik was. Geen aktiwiteit teen Gram negatiewe bakterië was egter
verkry nie. Die homogene verspreiding was as gevolg van die feit dat die kopolimeer sterk
adsorbeer op elke individuele lateks partikel wanneer dit as stabiliseerder gebruik word. Verdere
ontwikkeling op ‘n kommersiële basis kan daartoe lei dat polimeries biologies aktiewe verbindings
as ‘n lewensvatbare en omgewingsvriendelike alternatief vir heidige stabiliseerders in emulsies vir
waterverf gebruik kan word.
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Evolution and detection of Fusarium oxysporum f. sp. cepae in onion in South AfricaSouthwood, Michael J. 03 1900 (has links)
Thesis (PhDAgric (Plant Pathology))--Stellenbosch University, 2010. / ENGLISH ABSTRACT: In the Western Cape onion industry in South Africa, Fusarium oxysporum
Schlechtend.:Fr. f.sp. cepae (H.N. Hans.) W.C. Snyder & H.N. Hans. (Focep) has
been identified as the leading cause of harvest and storage losses. This pathogen is of
world-wide importance and causes Fusarium basal rot of onions (Allium cepa),
affecting all onion growth stages. No information is available on the evolution,
genetic diversity, molecular detection and inoculum sources of the South African
Focep population.
Similar to what is the case for South Africa, limited information is available
on Focep in other regions of the world. World-wide, four vegetative compatibility
groups (VCGs) and two single-member VCGs (SMVs) have been identified among
two Japanese and 19 Colorado (USA) isolates. This polyphyletic origin of Focep
suggested by VCG analyses was confirmed through molecular analyses of isolates
from a few countries. Only the mating type (MAT)1-1 idiomorph has been reported
for Focep isolates from Welsh onion (Allium fistulosum).
The development of sustainable management strategies of Focep is dependent
on knowledge of (i) the genetic diversity and evolution of Focep, (ii) whether high
throughput molecular methods can be developed for identifying the most virulent and
widespread Focep genotypes and (iii) the role of seedlings and seeds as primary
inoculum sources, and the Focep genotypes associated with these growth stages.
Therefore, the three main aims of the current study were to investigate the
aforementioned three aspects.
In the first aim of the study, the genetic diversity and evolution of Focep was
investigated using a collection of 79 F. oxysporum isolates from South Africa (27
Focep and 33 non-pathogenic isolates) and Colorado (19 Focep isolates). VCG
analyses revealed the presence of six VCGs, four among the Colorado Focep isolates
(VCGs 0421, 0422, 0423 and 0424) and two among the South African bulb-associated
isolates (VCGs 0425 and 0426). VCG 0421 and VCG 0425 were the two main VCGs
in Colorado and South Africa, respectively. Four SMVs and one heterokaryon selfincompatible
(HSI) isolate were also identified. The polyphyletic nature of Focep in South Africa and Colorado was shown through a combined translation elongation
factor 1α (EF-1α) and mitochondrial small-subunit (mtSSU) phylogeny. The
phylogeny divided the Focep isolates into two main clades, of which one contained
the two main VCGs (0421 and 0425), SMVs and non-pathogenic isolates. The
second, ancestral clade contained the HSI isolate, VCGs 0422, 0423 and 0424, and
non-pathogenic isolates. Unlike the clade containing the two main VCGs, which were
highly virulent toward onion bulbs, the ancestral clade contained isolates that were
mostly moderately virulent. The incongruence of the EF-1α and mtSSU datasets with
an intergenic spacer (IGS) region data set, and the presence of both MAT idiomorphs
within the same isolate for some isolates, suggested possible exchange of genetic
material between isolates.
The second aim of the study was to develop molecular methods for identifying
the two main Focep VCGs (0425 and 0421), using DNA fingerprinting methods and
sequence-characterized amplified region (SCAR) markers. These techniques were
first developed using the F. oxysporum isolates from the first aim, and were then used
to investigate the prevalence of VCG 0425 among 88 uncharacterized F. oxysporum
isolates from onion bulbs in South Africa. Two random amplified polymorphic DNA
primers provided two diagnostic amplicons for VCG 0425, but attempts to develop
SCAR markers from these amplicons were unsuccessful. In contrast, an interretrotransposon
amplified polymorphism (IRAP) fingerprinting method enabled the
developed of a multiplex IR-SCAR polymerase chain reaction method that detected
the VCG 0421, 0425 and SMV 4 isolates as a group. Fingerprinting and SCAR
marker testing of the 88 uncharacterized F. oxysporum isolates from South Africa (65
Focep and 23 non-pathogenic) confirmed that VCG 0425 is the main VCG in South
Africa associated with mature onion bulbs, since 63 of the Focep isolates had the
molecular characteristics of VCG 0425.
The third aim of the study was to determine whether seed and seedling
transplants are inoculum sources of Focep, and whether the same genotype (VCG
0425) that dominated on mature bulbs could be detected from these sources. Focep
isolates were obtained from seven of the 13 investigated onion seed lots, as well as
from onion seedling transplants that were collected from all five onion nurseries in the
Western Cape. Focep seedling infection more than doubled from the 6-week growth stage to the 14-week growth stage. Seed infections by Focep were low, but the
seedborne nature of Focep was confirmed by showing that a green fluorescent protein
labelled Focep transformant could be transmitted from infected soil to onion seed via
the onion bulbs and seedstalks. It is thus clear that commercial seed and seedlings are
inoculum sources of Focep. However, the Focep genotypes on seed and seedlings are
different from those in mature bulbs and were not dominated by VCG 0425.
Furthermore, most (≤ 60%) of the seed and seedling isolates were moderately
virulent, as compared to the mostly highly virulent isolates from mature bulbs. / AFRIKAANSE OPSOMMING: In die Wes-Kaapse uiebedryf in Suid-Afrika is Fusarium oxysporum
Schlechtend.:Fr. f.sp. cepae (H.N. Hans.) W.C. Snyder & H.N. Hans. (Focep)
geïdentifiseer as die vernaamste oorsaak van oes- en opbergingsverliese. Hierdie
patogeen is van wêreldwye belang; dit veroorsaak Fusarium-bolvrot van uie (Allium
cepa) en affekteer alle plantgroeistadia. In Suid-Afrika is daar geen inligting
beskikbaar oor die evolusie, genetiese diversiteit, molekulêre opsporing en
inokulumbronne van die Focep-populasie nie.
Soortgelyk aan wat die geval in Suid-Afrika is, is daar beperkte inligting
beskikbaar oor Focep in ander wêrelddele. Wêreldwyd is daar vier vegetatiewe
versoenbaarheidsgroepe (VVGe) en twee enkellid VVGe (ELVe) geïdentifiseer onder
twee Japannese en 19 Colorado (VSA) isolate. Hierdie veelvuldige oorsprong van
Focep wat deur VVG-analise voorgestel was, is deur die molekulêre analises van
isolate uit ’n paar ander lande bevestig. Slegs die paringstipe (PT)1-1 idiomorf is vir
Focep-isolate uit Walliese-tipe uie (ook bekend as ‘lenteuie’ in Suid Africa) (Allium
fistulosum) berig.
Die ontwikkeling van volhoubare bestuurstrategieë vir Focep steun op kennis
van (i) die genetiese diversiteit en evolusie van Focep, (ii) of hoë-deurset molekulêre
metodes ontwikkel kan word vir die identifisering van die mees virulente en
wydverspreide Focep-genotipes en (iii) die rol van saailinge en saad as primêre
inokulumbronne, en die Focep-genotipes wat met hierdie groeistadia geassosieer
word. Daarom was die hoof doelstellings van hierdie studie om die bogenoemde drie
aspekte te bestudeer.
Om die eerste doel van die studie te bereik is die genetiese diversiteit en
evolusie van Focep bestudeer deur gebruik te maak van ‘n versameling van 79 F.
oxysporum-isolate uit Suid-Afrika (27 Focep en 33 nie-patogeniese isolate) en uit
Colorado (19 Focep-isolate). VVG-analises het die teenwoordigheid van ses VVGe
aangetoon – vier onder die Colorado Focep-isolate (VVGe 0421, 0422, 0423 en 0424)
en twee onder die Suid-Afrikaanse bol-geassosieerde isolate (VVGe 0425 en 0426).
VVG 0421 en VVG 0425 was die twee hoof VVGe in onderskeidelik Colorado en Suid-Afrika. Vier ELVe en een meerkernige self-onversoenbare (MSO) isolaat is ook
geïdentifiseer. Die veelvuldige oorsprong van Focep in Suid-Afrika en Colorado is
ook aangetoon deur ‘n gekombineerde translasie verlengings faktor 1α (VF-1α) en
mitokondriale klein-subeenheid (mtKSE) filogenie. Dié filogenie het die Focepisolate
in twee groepe verdeel, waarvan die een groep die twee hoof VVGe (0421 en
0425), ELVe en nie-patogeniese isolate bevat het. Die tweede, basal groepering het
die MSO-isolaat, VVGe 0422, 0423 en 0424, en nie-patogeniese isolate bevat. In
teenstelling met die eersgenoemde groepering wat hoogs virulente isolate van uiebolle
bevat het, het die basale groepering isolate bevat wat meestal matig virulent was. Die
inkongruensie van die VF-1α en mtKSE-datastelle met ‘n intergeen-gespasieerde
(IGS) area datastel – asook die teenwoordigheid van beide PT-idiomorwe binne
dieselfde isolaat by sommige isolate – het op ’n moontlike uitruiling van genetiese
materiaal tussen isolate gedui.
Die tweede doel van die studie was om molekulêre metodes te ontwikkel vir
die identifisering van die twee hoof Focep VVGe (0425 en 0421) deur gebruik te
maak van DNA-vingerafdrukke en nukleotied-gekarakteriseerde geamplifiseerde area
(NKAA) merkers. Hierdie tegnieke is ontwikkel deur van die F. oxysporum-isolate
van die eerste doelstelling gebruik te maak en is daarna gebruik om die frekwensie
van VVG 0425 onder 88 ongekarakteriseerde F. oxysporum-isolate van uiebolle in
Suid-Afrika te ondersoek. Twee gerandomiseerde geamplifiseerde polimorfiese DNS
(RAPD) merkers het twee diagnostiese nukleotiedbasis-areas vir VVG 0425 gelewer,
maar pogings om NKAA-merkers uit hierdie geamplifiseerde nukleotiedbasis-areas te
onwikkel was onsuksesvol. In teenstelling hiermee het ‘n inter-retrotransposon
geamplifiseerde polimorfisme (IRAP) vingerafdrukmetode die ontwikkeling van ‘n
multipleks IR-NKAA polimerase kettingreaksiemetode moontlik gemaak wat die
VVG 0421-, VVG 0425- en ELV 4-isolate as ’n groep aangedui het.
Vingerafdruktoetsing en NKAA-merkertoetsing van die 88 ongekaraktariseerde F.
oxysporum isolate van Suid-Afrika (65 Focep en 23 nie-patogenies) het bevestig dat
VVG 0425 die hoof VVG in Suid-Afrika is wat met volwasse bolle geassosieer word,
aangesien 63 van die Focep-isolate die molekulêre eienskappe van VVG 0425 gehad
het. Die derde doel van die studie was om vas te stel of saad en saailinge
inokulumbronne van Focep is, en of dieselfde genotipe (VVG 0425) wat op volwasse
bolle dominant is, waargeneem kon word op hierdie bronne. Focep-isolate is verkry
van sewe van die 13 uiesaadlotte asook van uiesaailinge wat in al vyf
uiesaailingkwekerye in die Wes-Kaap versamel is. Focep-saailinginfeksie was meer
as dubbel in die 14-week groeistadium as wat dit in die 6-week stadium was.
Saadinfeksies deur Focep was laag, maar die saadgedraagde aard van Focep is
bevestig deur aan te toon dat ’n Focep-transformant wat met ‘n groen fluoreserende
proteïen geëtiketeer is, van geïnfekteerde grond na uiesaad oorgedra kon word via die
uiebolle en -saadstele. Dit is dus duidelik dat kommersiële saad en saailinge as
inokulumbronne van Focep dien. Die Focep-genotipes op saad en saailinge verskil
egter van dié in volwasse bolle en is nie deur VVG 0425 gedomineer nie. Verder was
die meeste (≤ 60%) saad- en saailingisolate matig virulent, in teenstelling met die
meestal hoogs virulente isolate uit volwasse bolle.
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Implementation of hazard analysis and critical control point (HACCP) system in a food service unit serving immuno-suppressed patient diets / E.E. VermeulenVermeulen, Emma Emmerenza January 2006 (has links)
Main aim: To supply recommendations to implement a Hazard Analysis of
Critical Control Points (HACCP) system in a hospital food service unit serving
low bacterial diets in order to prevent or decrease the infection rates in
Hematopoietic Stem Cell Transplant (HSCT) patients.
Objectives: Firstly, to investigate the current food safety and hygiene
status in a hospital food service unit, serving low bacterial diets, by means of
a questionnaire and bacterial swabs taken from the food service unit.
Secondly, to utilize the gathered information in a structured action plan to
implement HACCP standards successfully in the appointed food service unit.
The implementation of HACCP will not be done by the author.
Design: The primary research was done in a food service unit of a 350
bed private hospital. One unsuspected audit with a pre-designed audit form
was done. The audit consisted out of ten categories. A percentage was
allocated to each category. Four swabs, as well as four food samples, were
taken during the audit. The swabs and samples were tested to assess the
microbiological safety of the foods prepared in the appointed hospital food
service unit. The results of the audit, swabs and food samples were used to
evaluate the current Food and Safety System of the hospital food service unit
according to internationally approved HACCP standards.
Setting: The study was conducted in the metropolitan area of Gauteng,
South Africa.
Results: None of the ten areas audited was of an acceptable standard
and an average of 37% was scored. Category 5, the service and distribution
area, scored the highest (69%) and category 10, the quality procedures and
records division, scored the lowest (6%). According to United States Food
and Drug Administration Baseline Report five forbidden policies could lead to
increased risk of food borne illnesses. All five forbidden policies were
detected in the food service unit during the audit. The microbiological tests
showed relatively high microbial counts.
Conclusion: The results of the study confirmed that instead of focusing
mainly on the selection of food items allowed, and the cooking methods used
in HSCT diets, the type of food service, together with the food and safety
protocol that the food service follows, could play an important role in providing
food that is safe for HSCT patient use. / Thesis (M.Sc. (Dietetics))--North-West University, Potchefstroom Campus, 2007.
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The impacts of weather and climate change on the spread of bluetongue into the United KingdomBurgin, Laura Elizabeth January 2011 (has links)
A large epizootic of the vector-borne disease bluetongue occurred in northern Europe from 2006-2009, costing the economies of the infected countries several hundreds of millions of euros. During this time, the United Kingdom (UK) was exposed to the risk of bluetongue by windborne incursions of infected Culicoides biting midges from the northern coast of mainland Europe. The first outbreaks which occurred in the UK in 2007 were attributed to this cause. Although bluetongue virus (BTV) no longer appears to be circulating in northern Europe, it is widely suggested that it and other midge-borne diseases may emerge again in the future, particularly under a changing climate. Spread of BTV is strongly influenced by the weather and climate however limited use has been made of meteorologically based models to generate predictions of its spread to the UK. The extent to which windborne BTV spread can be modelled at timescales from days to decades ahead, to inform tactical and strategic decisions taken to limit its transmission, is therefore examined here. An early warning system has been developed to predict possible incursion events on a daily timescale, based on an atmospheric dispersion model adapted to incorporate flight characteristics of the Culicoides vectors. The system’s warning of the first UK outbreak in September 2007 was found to be greatly beneficial to the UK livestock industry. The dispersion model is also shown to be a useful post-outbreak epidemiological analysis tool. A novel approach has been developed to predict BTV spread into the UK on climate-change timescales as dispersion modelling is not practical over extended periods of time. Using a combination of principal component and cluster analyses the synoptic scale atmospheric circulations which control when local weather conditions are suitable for midge incursions were determined. Changes in the frequency and timing of these large scale circulations over the period 2000 to 2050 were then examined using an ensemble of regional climate model simulations. The results suggest areas of UK under the influence of easterly winds may face a slight increase in risk and the length of the season where temperatures are suitable for BTV replication is likely to increase by around 20 days by 2050. However a high level of uncertainty is associated with these predictions so a flexible decision making approach should be adopted to accommodate better information as it becomes available in the future.
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No measurable adverse effects of Lassa, Morogoro and Gairo arenaviruses on their rodent reservoir host in natural conditionsMarien, Joachim, Borremans, Benny, Gryseels, Sophie, Soropogui, Barre, De Bruyn, Luc, Bongo, Gedeon Ngiala, Becker-Ziaja, Beate, de Bellocq, Joelle Gouy, Guenther, Stephan, Magassouba, N'Faly, Leirs, Herwig, Fichet-Calvet, Elisabeth 27 April 2017 (has links)
Background: In order to optimize net transmission success, parasites are hypothesized to evolve towards causing minimal damage to their reservoir host while obtaining high shedding rates. For many parasite species however this paradigm has not been tested, and conflicting results have been found regarding the effect of arenaviruses on their rodent host species. The rodent Mastomys natalensis is the natural reservoir host of several arenaviruses, including Lassa virus that is known to cause Lassa haemorrhagic fever in humans. Here, we examined the effect of three arenaviruses (Gairo, Morogoro and Lassa virus) on four parameters of wild-caught Mastomys natalensis: body mass, head-body length, sexual maturity and fertility. After correcting for the effect of age, we compared these parameters between arenavirus-positive (arenavirus RNA or antibody) and negative animals using data from different field studies in Guinea (Lassa virus) and Tanzania (Morogoro and Gairo viruses). Results: Although the sample sizes of our studies (1297, 749 and 259 animals respectively) were large enough to statistically detect small differences in body conditions, we did not observe any adverse effects of these viruses on Mastomys natalensis. We did find that sexual maturity was significantly positively related with Lassa virus antibody presence until a certain age, and with Gairo virus antibody presence in general. Gairo virus antibody-positive animals were also significantly heavier and larger than antibody-free animals. Conclusion: Together, these results suggest that the pathogenicity of arenaviruses is not severe in M. natalensis, which is likely to be an adaptation of these viruses to optimize transmission success. They also suggest that sexual behaviour might increase the probability of M. natalensis to become infected with arenaviruses.
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Selective inhibition of acetylcholinesterase 1 from disease-transmitting mosquitoes : design and development of new insecticides for vector controlEngdahl, Cecilia January 2017 (has links)
Acetylcholinesterase (AChE) is an essential enzyme with an evolutionary conserved function: to terminate nerve signaling by rapid hydrolysis of the neurotransmitter acetylcholine. AChE is an important target for insecticides. Vector control by the use of insecticide-based interventions is today the main strategy for controlling mosquito-borne diseases that affect millions of people each year. However, the efficiency of many insecticides is challenged by resistant mosquito populations, lack of selectivity and off-target toxicity of currently used compounds. New selective and resistance-breaking insecticides are needed for an efficient vector control also in the future. In the work presented in this thesis, we have combined structural biology, biochemistry and medicinal chemistry to characterize mosquito AChEs and to develop selective and resistance-breaking inhibitors of this essential enzyme from two disease-transmitting mosquitoes.We have identified small but important structural and functional differences between AChE from mosquitoes and AChE from vertebrates. The significance of these differences was emphasized by a high throughput screening campaign, which made it evident that the evolutionary distant AChEs display significant differences in their molecular recognition. These findings were exploited in the design of new inhibitors. Rationally designed and developed thiourea- and phenoxyacetamide-based non-covalent inhibitors displayed high potency on both wild type and insecticide insensitive AChE from mosquitoes. The best inhibitors showed over 100-fold stronger inhibition of mosquito than human AChE, and proved insecticide potential as they killed both adult and larvae mosquitoes.We show that mosquito and human AChE have different molecular recognition and that non-covalent selective inhibition of AChE from mosquitoes is possible. We also demonstrate that inhibitors can combine selectivity with sub-micromolar potency for insecticide resistant AChE.
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