Bir rastgele El-Ayak-Ağız Hastalığı modelinin Normal ve Laplace dağılımına sahip parametrelerle karşılaştırılması

In this study, we investigate the transmission dynamics of Hand-Foot-Mouth disease (HFMD) using a differential equation system with random parameters. We transform the parameters of the existing deterministic model into random variables with Normal and Laplace distributions. Using the results from the simulations of the random model, we analyze the changes in the compartments of the total population. The random model, unlike the deterministic system, enables the analysis of the variations in the transmission dynamics of the disease. Finally, the randomness of the system is interpreted through the comparison of the results from the deterministic and random models.Bu çalışmada, El-Ayak-Ağız Hastalığının yayılım dinamikleri bir diferansiyel denklem sistemi ve rastgele parametreler kullanarak incelenmektedir. Var olan deterministik modelin parametreleri Normal dağılım ve Laplace dağılımına sahip rastgele değişkenler haline getirilmektedir. Rastgele modelin simülasyonlarından elde edilen sonuçlarla toplam nüfusun kompartmanlarındaki değişimler analiz edilmektedir. Rastgele model, deterministik sistemin aksine, hastalığın yayılım dinamiklerindeki varyasyonların analizine imkan sağlamaktadır. Son olarak, sistemin rastgele yapısı deterministik ve rastgele sonuçların karşılaştırılması ile yorumlanmaktadı

Metal binding in sediments and cockles from tropical and temperate estuaries

Merged with duplicate record 10026.1/2277 on 27.02.2017 by CS (TIS)Merged with duplicate record 10026.1/2277 Submitted by Collection Services ([email protected]) on 2013-10-22T10:12:58Z No. of bitstreams: 1 CHUTAMAD KAVINSEKSAN.PDF: 13702377 bytes, checksum: 6f6cb1cc892cc02111a9c89243b0a740 (MD5) Approved for entry into archive by Collection Services([email protected]) on 2013-10-22T10:13:13Z (GMT) No. of bitstreams: 1 CHUTAMAD KAVINSEKSAN.PDF: 13702377 bytes, checksum: 6f6cb1cc892cc02111a9c89243b0a740 (MD5) Made available in DSpace on 2013-10-22T10:13:13Z (GMT). No. of bitstreams: 1 CHUTAMAD KAVINSEKSAN.PDF: 13702377 bytes, checksum: 6f6cb1cc892cc02111a9c89243b0a740 (MD5) Previous issue date: 2007This study concerns the partitioning of metals, primarily Cd, Cu, Fe and Zn in the tissues of the common cockle, Cerastoderma edule, from estuaries in the SW of England and the blood cockle, Anadara granosa, from estuaries of Thailand. Cockle and sediment samples were collected, at contaminated and uncontaminated sites, in the Plym, Tamar and Avon estuaries and at seven estuary mouths in the Gulf of Thailand (including the Chao Phraya). The objective was to quantify the total and available concentrations in the sediments and to measure the concentrations of the various molecular weight fractions of the metals associated with the body, gills, gut and foot of the two cockle types. In addition, the study aimed to identify and distinguish the major differences in metal handling strategies by these two organisms about which little is known. The fractions, included high molecular weight (HMW) compounds, metallothionein-like proteins (MTLP) and very low molecular weight compounds (VLMW). The MTLP concentrations were measured using polarography and the distributions of Cd, Zn, Cu and Fe among various cytosolic ligands, including MTLP, were determined by atomic absorption spectroscopy following separation by Sephadex G-75 size-exclusion chromatography. Concentrations of MTLP in body, gills, gut and foot of C edule were lower than in A. granosa and the highest MTLP level was found in the gut of A. granosa in the Chao Phraya. Generally, metal partitioning in both cockles involved the HMW pool, with the exception being for Zn binding to the VLMW pool in C. edule and Cd partitioning being mostly associated with the MTLP in A granosa. For the first time, the nature of Fe partitioning between the HMW, MTLP and VLMW pools in all organs of A granosa are reported. In most cases the concentrations of metals in the sediments were higher in the Devon estuaries as compared to those in the Gulf of Thailand. However, no significant relationships between metals in sediments and metals in cockles were observed and the induction of high MTLP concentrations in A. granosa could be due to contaminants other than the metals measured here. The results are discussed in the context of the use of MTLP and metal binding as indicators of environmental quality is discussed.The Marine Biological Association of the United Kingdo

Epizoological Tools for Acute Hepatopancreatic Necrosis Disease (AHPND) in Thai Shrimp Farming

Acute hepatopancreatic necrosis disease (AHPND) is an emerging bacterial infection in shrimp that has been widespread across the major world shrimp producing countries since 2009. AHPND epizootics have resulted in a huge loss of global shrimp production, similar to that caused by white spot disease in the 1990’s. The epizootiological understanding of the spread of AHPND is still in its early stages, however, and most of the currently published research findings are based on experimental studies that may struggle to capture the potential for disease transmission at the country scale. The main aim of this research, therefore, is to develop epizootiological tools to study AHPND transmission between shrimp farming sites. Some tools used in this research have already been applied to shrimp epizoology, but others are used here for the first time to evaluate the spread of shrimp diseases. According to an epizootiological survey of AHPND in Thailand (Chapter 3), the first case of AHPND in the country was in eastern shrimp farms in January 2012. The disease was then transmitted to the south in December 2012. The results obtained from interviews, undertaken with 143 sample farms were stratified by three farm-scales (large, medium and small) and two locations (east and south). Both the southern location and large-scale farming were associated with a delay in AHPND onset compared with the eastern location and small- and medium-scale farming. The 24 risk factors (mostly related to farming management practices) for AHPND were investigated in a cross-sectional study (Chapter 3). This allowed the development of an AHPND decision tree for defining cases (diseased farms) and controls (non-diseased farms) because at the time of the study AHPND was a disease of unknown etiology. Results of univariate and unconditional logistic regression models indicated that two farming management practices related to the onset of AHPND. First, the absence of pond harrowing before shrimp stocking increased the risk of AHPND occurrence with an odds ratio () of 3.9 (95 % CI 1.3–12.6; P‑value = 0.01), whereas earthen ponds decreased the risk of AHPND with an of 0.25 (95 % CI 0.06–0.8; P‑value = 0.02). These findings imply that good farming management practices, such as pond-bottom harrowing, which are a common practice of shrimp farming in earthen ponds, may contribute to overcoming AHPND infection at farm level. For the purposes of disease surveillance and control, the structure of the live shrimp movement network within Thailand (LSMN) was modelled, which demonstrated the high potential for site-to-site disease spread (Chapter 4). Real network data was recorded over a 13-month period from March 2013 to March 2014 by the Thailand Department of Fisheries. After data validation, c. 74 400 repeated connections between 13 801 shrimp farming sites were retained. 77 % of the total connections were inter-province movements; the remaining connections were intra-province movements (23 %). The results demonstrated that the LSMN had properties that both aided and hindered disease spread (Chapter 4). For hindering transmission, the correlation between and degrees was weakly positive, i.e. it suggests that sites with a high risk of catching disease posed a low risk for transmitting the disease (assuming solely network spread), and the LSMN showed disassortative mixing, i.e. a low preference for connections joining sites with high degree linked to connections with high degree. However, there were low values for mean shortest path length and clustering. The latter characteristics tend to be associated with the potential for disease epidemics. Moreover, the LSMN displayed the power-law in both and degree distributions with the exponents 2.87 and 2.17, respectively. The presence of power-law distributions indicates that most sites in the LSMN have a small number of connections, while a few sites have large numbers of connections. These findings not only contribute to a better understanding of disease spread between sites, therefore, but also reveal the importance of targeted disease surveillance and control, due to the detection of scale-free properties in the LSMN. Chapter 5, therefore, examined the effectiveness of targeted disease surveillance and control in respect to reducing the potential size of epizootics in the LSMN. The study untilised network approaches to identify high-risk connections, whose removal from the network could reduce epizootics. Five disease-control algorithms were developed for the comparison: four of these algorithms were based on centrality measures to represent targeted approaches, with a non-targeted approach as a control. With the targeted approaches, technically admissible centrality measures were considered: the betweenness (the number of shortest paths that go through connections in a network), connection weight (the frequency of repeated connections between a site pair), eigenvector (considering the degree centralities of all neighbouring sites connected to a specified site), and subnet-crossing (prioritising connections that links two different subnetworks). The results showed that the estimated epizootic sizes were smaller when an optimal targeted approach was applied, compared with the random targeting of high-risk connections. This optimal targeted approach can be used to prioritise targets in the context of establishing disease surveillance and control programmes. With complex modes of disease transmission (i.e. long-distance transmission like via live shrimp movement, and local transmission), an compartmental, individual-based epizootic model was constructed for AHPND (Chapter 6). The modelling uncovered the seasonality of AHPND epizootics in Thailand, which were found likely to occur between April and August (during the hot and rainy seasons of Thailand). Based on two movement types, intra-province movements were a small proportion of connections, and they alone could cause a small AHPND epizootic. The main pathway for AHPND spread is therefore long-distance transmission and regulators need to increase the efficacy of testing for diseases in farmed shrimp before movements and improve the conduct of routine monitoring for diseases. The implementation of these biosecurity practices was modelled by changing the values of the long-distance transmission rate. The model demonstrated that high levels of biosecurity on live shrimp movements (1) led to a decrease in the potential size of epizootics in Thai shrimp farming. Moreover, the potential size of epizootics was also decreased when AHPND spread was modelled with a decreased value for the local transmission rate. Hence, not only did the model predict AHPND epizootic dynamics stochastically, but it also assessed biosecurity enhancement, allowing the design of effective prevention programmes. In brief, this thesis develops tools for the systematic epizootiological study of AHPND transmission in Thai shrimp farming and demonstrates that: (1) at farm level, current Thai shrimp farming should enhance biosecurity systems even in larger businesses, (2) at country level, targeted disease control strategies are required to establish disease surveillance and control measures. Although the epizootiological tools used here mainly evaluate the spread of AHPND in shrimp farming sites, they could be adapted to other infectious diseases or other farming sectors, such as the current spread of tilapia lake virus in Nile tilapia farms

Best practices to prevent transmission and control outbreaks of hand, foot, and mouth disease in childcare facilities: a systematic review.

INTRODUCTION: Hand, foot, and mouth disease continues to cause seasonal epidemics in the Asia-Pacific Region. Since the current Enterovirus 71 vaccines do not provide cross-protection for all Enterovirus species that cause hand, foot, and mouth disease, there is an urgent need to identify appropriate detection tools and best practice to prevent its transmission and to effectively control its outbreaks. This systematic review aimed to identify characteristics of outbreak and assess the impact and effectiveness of detection tools and public health preventive measures to interrupt transmission. The findings will be used to recommend policy on the most effective responses and interventions in Hong Kong to effectively minimise and contain the spread of the disease within childcare facilities. METHODS: We searched the following databases for primary studies written in Chinese or English: MEDLINE, EMBASE, Global Health, WHO Western Pacific Region Index Medicus database, China National Knowledge Infrastructure Databases, and Chinese Scientific Journals Database. Studies conducted during or retrospective to outbreaks of hand, foot, and mouth disease caused by Enterovirus 71 from 1980 to 2012 within childcare facilities and with a study population of 0 to 6 years old were included. RESULTS: Sixteen studies conducted on outbreaks in China showed that hand, foot, and mouth disease spread rapidly within the facility, with an outbreak length of 4 to 46 days, especially in those with delayed notification (after 24 hours) of clustered outbreak (with five or more cases discovered within the facility) to the local Center for Disease Control and Prevention and delayed implementation of a control response. The number of classes affected ranged from 1 to 13, and the attack rate for children ranged from 0.97% to 28.18%. CONCLUSIONS: Communication between key stakeholders about outbreak confirmation, risk assessment, and surveillance should be improved. Effective communication facilitates timely notification (within 24 hours) of clustered outbreaks to a local Center for Disease Control and Prevention. Timely implementation of a control response is effective in minimising incidence and length of an outbreak in childcare facilities. The government should provide incentives for childcare facilities to train infection control specialists who can serve as the first contact, knowledge, and communication points, as well as facilitate exchange of information and provision of support across stakeholders during a communicable disease epidemic

Quantifying the Effects of Measures to Control Highly Pathogenic Avian Influenza H5N1 in Poultry in Southeast Asia

Despite the ongoing efforts to contain its spread, H5N1 is now considered endemic within poultry in various settings worldwide, threatening both the livelihoods of those involved in poultry production in affected countries and posing a continuous public health risk. The reasons for the varying levels of success in controlling H5N1 in Southeast Asia need to be better understood. In this thesis, various different methods of quantifying the effects of individual control measures, using the types of data available in various different contexts, are discussed and applied. In the first half of this thesis a spatio-temporal survival model is fitted to H5N1 outbreak surveillance data from Vietnam and Thailand using a Bayesian framework in order to account for unobserved infection times. Following vaccination in Vietnam it was found that transmissibility had been successfully reduced but, during a wave of outbreaks in 2007, that this coincided with a reduction in the rate of at which outbreaks were reported following the introduction of infection, limiting the overall impact this reduction in transmissibility had on the total epidemic size. In Thailand, active surveillance was found to be successful in contributing to the control of infection. Furthermore, backyard producers, whilst responsible for the majority of outbreaks, were, on average, less likely to transmit infection than those involved in more intensive production. In the second half of the thesis, the use of final size methods to assess the effectiveness of vaccination from trial data is explored. This involved an investigation into the effects of different assumptions regarding the action by which vaccination confers immunity and fitting estimates of transmissibility to data collected from outbreak investigations in the context of a field trial of vaccination in Indonesia, where, making strong assumptions about the underlying infection process, a reduction in both within and between flock transmissibility was detected for outbreaks occurring in areas where vaccination was being carried out

Site selection and dynamic modelling of Manila clam, Ruditapes philippinarum, in the Tagus Estuary

This thesis assesses the viability of shellfish aquaculture in the Tagus Estuary of the species Manila clam (Ruditapes philippinarum), by means of a GIS-based site selection and the application of a dynamic modelling software at farm-scale, in order to evaluate the potential production, environmental effects, and economic feasibility. The site selection for shellfish aquaculture is based on the application of a Multi-Criteria Evaluation in a GIS software. Both are useful tools for site selection, as when combined they help decision-makers to identify the existing spatial constraints and take into consideration key variables, such as (i) the external environmental conditions that regulate shellfish growth, (ii) existing infrastructures and socioeconomic variables that are relevant for production, and (iii) contaminated areas that may reduce the shellfish quality as a food product. The dynamic modelling software used, FARM (Farm Aquaculture Resource Management), was applied in accordance with the best areas identified as being suitable for shellfish aquaculture, where the production and profit of two different locations are estimated and compared at a farm-scale level, and further extrapolated to larger areas

Aquaculture Asia, Vol. 9, No. 2, pp.1-52, April - June 2004

CONTENTS: Genetic impacts of translocations on biodiversity of aquatic species with particular reference to Asian countries, by Thuy T. T. Nguyen and Uthairat Na-Nakorn, Carp culture in Iran, by Hassan Salehi. Opportunities and challenges in Myanmar aquaculture, by U Hla Win. Impacts of mono-sex Macrobrachium culture on the future of seed availability in India, by Paramaraj Balamurugan, Pitchaimuthu Mariappan and Chellam Balasundaram. Use of new technology and skill enhancement to obtain eco-friendly production of tiger shrimp (Penaeus monodon), by Asbjørn Drengstig, Asbjørn Bergheim & Bjørn Braaten. Larval rearing and spat production of the windowpane shell Placuna placenta, by S. Dharmaraj, K. Shanmugasundaram and C.P. Suja. Trans-boundary aquatic animal diseases: Focus on Koi herpes virus (KHV), by Melba G. Bondad-Reantaso. HACCP in shrimp farming, by Siri Tookwinas and Suwimon Keerativiriyaporn. CONTENTS MARINE FINFISH MAGAZINE: First Breeding Success of Napoleon Wrasse and Coral Trout, by Sih Yang Sim (editor). Welcome to the magazine Issue 1, 2004 (April-June). Regional Developments & Update, by Sih Yang Sim. Gemma Micro – Leaving Artemia Behind, by Trine Karlsrud. Report of the Komodo fish culture project, by Trevor Meyer MSc & Peter J. Mous. Conclusion of Research on Capture and Culture of Pre-settlement Fish for the Marine Aquarium Trade in Solomon Islands, by Cathy Hair, Warwick Nash, Peter Doherty. Seed Production of Sand Bass (Psamoperca weigensis), by Le Dinh Buu. ACIAR Project “Improved hatchery and grow-out technology for marine finfish in the Asia-Pacific region”. NACA/DOF/TDH* Workshop on Seafarming and Seafood Markets

H5N1/highly pathogenic avian influenza in Cambodia : evaluating poultry movement and the extent of interaction between poultry and humans

Since 2003, highly pathogenic avian influenza (HPAI), subtype H5N1, has spread across the Asian, African and European continents at an exceptional rate. To date, H5N1 remains primarily a pandemic within poultry populations with limited onward transmission to humans. Since there have been a limited number of human cases throughout the world, epidemiologic uncertainties exist regarding the extent of contact necessary to result in successful transmission between infected poultry and humans. In this thesis I undertook two large-scale surveys to evaluate poultry movement and the extent of interaction between humans and poultry to better define the risks of sustained transmission of H5N1 in poultry and onward transmission to humans. The thesis begins with a review of current knowledge on the epidemiology of HPAI, specifically subtype H5N1, and current options for its control worldwide and specifically within Cambodia. The first half of the thesis presents the methodology and results from a large-scale cross sectional survey of 3,600 rural subjects from 115 villages in six provinces throughout Cambodia. The results from this survey are used to explore animal ownership and husbandry, poultry mortality experienced and poultry mortality reporting, and the extent and frequency of poultry handling behaviours of subjects and how they differ by age and gender. The second half of the thesis presents results from a second cross-sectional survey of 715 rural villagers, 123 rural, peri-urban and urban market sellers and 139 middlemen from six Provinces and Phnom Penh, which was conducted to evaluate poultry movement and trading practices. The results from this survey are used to construct poultry movement networks using social network analysis techniques, to identify critical points for surveillance and to understand the potential transmission and control of HPAI over this network and to identify a spatial model to predict poultry movements. Finally in the last chapter the key findings are presented and discussed in the context of HPAI transmission in the region

The impact of surveillance and control on highly pathogenic avian influenza outbreaks in poultry in Dhaka division, Bangladesh

In Bangladesh, the poultry industry is an economically and socially important sector, but it is persistently threatened by the effects of H5N1 highly pathogenic avian influenza. Thus, identifying the optimal control policy in response to an emerging disease outbreak is a key challenge for policy-makers. To inform this aim, a common approach is to carry out simulation studies comparing plausible strategies, while accounting for known capacity restrictions. In this study we perform simulations of a previously developed H5N1 influenza transmission model framework, fitted to two separate historical outbreaks, to assess specific control objectives related to the burden or duration of H5N1 outbreaks among poultry farms in the Dhaka division of Bangladesh. In particular, we explore the optimal implementation of ring culling, ring vaccination and active surveillance measures when presuming disease transmission predominately occurs from premises-to-premises, versus a setting requiring the inclusion of external factors. Additionally, we determine the sensitivity of the management actions under consideration to differing levels of capacity constraints and outbreaks with disparate transmission dynamics. While we find that reactive culling and vaccination policies should pay close attention to these factors to ensure intervention targeting is optimised, across multiple settings the top performing control action amongst those under consideration were targeted proactive surveillance schemes. Our findings may advise the type of control measure, plus its intensity, that could potentially be applied in the event of a developing outbreak of H5N1 amongst originally H5N1 virus-free commercially-reared poultry in the Dhaka division of Bangladesh