Foot and Mouth Disease (FMD) could have a significant impact on the U.S. agriculture industry and the welfare of U.S. producers and U.S. consumers. In order to address the potential impact from animal disease outbreaks, this project is designed to utilize a combined epidemic and economic modeling framework to evaluate animal disease management strategies which can be used to reduce the potential losses in an unusual event such as FMD outbreaks. In this study, we compare the welfare changes among three different parties with different strategies using, 1) ANOVA analysis; 2) cost benefit analysis; and 3) Risk Aversion Coefficient (RAC) analysis. Four types of index feedlots are selected in the study including, Feedlot Type 1 (> 50,000 heads of animals), Feedlot Type 4 (backgrounder feedlot), Large Beef Grazing (>100 heads of animals), and Backyard (<10 heads of animals). Results suggest that early detection of FMD events has the advantage in reducing risk as shown in the epidemiological impacts. Enhanced surveillance is found to be a preferred mitigation strategy for U.S. consumers in the scenario of smaller feedlot disease introductions (e.g. Large Beef Grazing and Backyard) and for U.S. producers in the larger feedlot disease introduction scenarios (e.g. Feedlot Type 1 and Feedlot Type 4). Adequate vaccination is not cost effective when seeking to minimize average loss but becomes a preferred strategy when the risk aversion rises. Risk modeling with stochastic programming adopted in this study also confirms the importance of incorporating risk evaluation into decision making process. It offers another option for us to evaluate the mitigation strategies. Two portfolio models are adopted in this study including, E-V model (mean variance portfolio choice model) and Unified model. The results show that the preference for control strategies depends on risk attitude. Early detection proves to be preferable for U.S. consumers and is also preferred by U.S. processors and producers as Risk Aversion Parameters (RAP) rises. Adequate vaccination strategy can benefit U.S. consumers but does not give U.S. processors a better outcome. Adequate vaccination provides a better choice for U.S. producers when the RAP rises. Enhanced surveillance is preferred for U.S. consumers. For U.S. processors, enhanced surveillance does not give a better risk/return outcome. U.S. producers are likely to switch their preferences from regular surveillance to enhanced surveillance as their RAP rises.

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The foot-and-mouth disease (FMD) virus poses a considerable threat both to farmers and to the wider economy should there be a future incursion into the UK. The most recent large-scale FMD epidemic in the UK was in 2001. Mathematical models were developed and used during this epidemic to aid decision-making about how to most effectively control and eliminate it. While the epidemic was eventually brought to a halt, it resulted in a huge loss of livestock and is estimated to have cost the UK economy around ¿6 billion. The mathematical models predicted the overall spatial spread of FMD well, but had low predictive ability for identifying precisely which farm premises became infected over the course of the epidemic. This will in part have been due to the stochastic nature of the models. However, the transmission probability between two farm premises was represented as the Euclidean distance between their point locations, which is a crude representation of FMD transmission. Additionally, the premises' point location data contain inaccuracies, sometimes identifying the farmer's residential address rather than the farm itself which may be a long way away. Local FMD transmission occurs via contaminated fomites carried by people or vehicles between premises, or by infected particles being blown by wind between proximal fields. Given that these transmission mechanisms are thought to be related to having close field boundaries, it is possible that some of the inaccuracy in model predictions is also due to imprecisely representing such transmission. In this thesis I use fine-scale geographical data of farm premises' field locations to study the contiguity of premises (where contiguous premises (CPs) are defined as having field boundaries < 15m apart). I demonstrate that the distance between two premises' point locations does not accurately represent when they are CPs. Using an area of southern Scotland containing 4767 livestock premises, I compare the predictions of model simulations using two different model formulations. The first is one of the original models based on the 2001 outbreak, and the second is a new model in which transmission probability is related to whether or not premises were contiguous. The comparison suggests that the premises that became infected during the course of the simulations were more predictable using the new model. While it cannot be concluded that this will translate into more accurate predictions until this can be validated during a future outbreak, it does suggest that the new model is more predictable in its route through the landscape, and therefore that it may better reflect local transmission routes than the original model. Networks based on contiguity of premises were constructed for the same area of southern Scotland, and showed that 90.6% (n=4318) of the premises in the area were indirectly connected to one another as part of the Giant Component (GC). The network metric of 'betweenness' was used to identify premises acting as bridges between otherwise disconnected sub-populations of premises. It was found that removing 100 premises with highest betweenness served to fragment the GC. Model simulations indicated that, even with some longer-range transmission possible, removing these premises from the network resulted in a large decrease in mean number of infected premises and outbreak duration. In real terms, premises removal from the network would mean ensuring these premises did not become infected by enhanced biosecurity and/or vaccination depending on policy. In this thesis I also considered the role of biosecurity practices in shaping FMD spread. A sample of 200 Scottish farmers were interviewed on their biosecurity practices, and their biosecurity risk quantified using a biosecurity 'risk score' developed during the 2007 FMD outbreak in Surrey. Using Moran's I and network assortativity measures it was found that there did not appear to be any clustering of biosecurity risk scores on premises. Statistical analysis found no association between biosecurity risk and the mathematical model's premises' susceptibility term (which describes the increase in a premises' susceptibility with increasing numbers of livestock). This suggests that the model's susceptibility term is not indirectly capturing a general pattern in biosecurity on different sized farm premises. Thus, this body of work shows that incorporating a more realistic representation of premises location into mathematical models, in terms of area (i.e. as fields) rather than a point, alters predictions of spatial spread. It also demonstrates that targeted control at a relatively small number of farms could effectively fragment the farming landscape, and has the potential to considerably reduce the size of an FMD outbreak. It also demonstrates that variations in premises' FMD biosecurity risks are unlikely to be indirectly affecting the spatial or demographic components of the model. This increase in understanding of how geographic, social and demographic factors relate to FMD spread through the landscape may enable more effective control of an outbreak, should there be an incursion in the UK in future.

Foot-and-mouth disease (FMD) is an economically devastating picornaviral disease affecting over 40 species of cloven-hoofed animals. The virus occurs as seven immunologically distinct serotypes which are characterized by high levels of intra- and intertypic variation. The three South African Territories (SAT) serotypes 1-3 are endemic to sub-Saharan Africa, a region where the epidemiology of the disease is particularly complex due to the presence of six of the seven serotypes, the role of wildlife in virus maintenance and the apparently higher levels of variation in the endemic serotypes. These factors make it imperative to establish methods suited to elucidating the regional epidemiology. One of the integral parts of this process is the genetic characterization of regionally representative viruses in order to assess the variation in the field and to clarify the role of wildlife. Nucleotide sequence data and methods suited to studying the SAT-types are however limited. A first priority was therefore to establish a PCR-based nucleotide sequencing technique targeting the highly immunogenic and phylogenetically informative 1D genome region encoding the VP1 protein. The screening of multiple serotypes and subtypes prevalent on the African continent confirmed that this method was robust and well-suited to molecular epidemiological studies in the southern Africa region. The method was first applied in the characterization of FMD virus recovered from the reproductive tract of free-living African buffalo in the Kruger National Park. Nucleotide sequencing assisted in authentication of the results and indicated that carrier status was likely, but it was not possible to unequivocally demonstrate persistent infection of FMDV. In a separate study, the role of impala antelope (Aepyceros melampus) in the epidemiology of the disease in South Africa was assessed. Genetic characterization of impala and African buffalo (Syncerus caffer) viruses collected over an eleven year period confirmed that inter-species transmission occurred on several occasions and that virus can persist in impala populations for more than 12 months. Inter-species transmission and investigation of the possible mechanisms facilitating virus transmission from persistently infected buffalo focussed on the Kruger National Park in South Africa. In order to ensure regional relevance the study was broadened to incorporate buffalo populations throughout southern Africa. Viruses of the three SAT-types recovered from diverse African buffalo populations were therefore characterized. The results reveal that independently evolving viral lineages occur in distinct geographical regions for each of the SAT-types examined and that the levels of intratypic variation are in the order of 52 - 55 % on nucleotide level across the genome region characterized. Given the strict locality-specific grouping of buffalo viruses the likely usefulness of this database for tracing the origin and course of contemporary and historical SAT-type outbreaks was investigated. Molecular epidemiological studies conclusively show that buffalo are indeed the ultimate source of infection for susceptible cloven-hoofed animals occurring in close proximity, that interspecies transmission occurs between cattle and antelope and that trans-boundary transmission of virus remains a threat to disease security in southern African countries. / Thesis (PhD (Microbiology))--University of Pretoria, 2007. / Microbiology and Plant Pathology / unrestricted

Foot-and-mouth disease virus (FMDV) is a highly infectious virus affecting cloven-hoofed animals. The most prominent of its clinical signs is the development of vesicular lesions on the feet and in or around the mouth, which are a consequence of extensive FMDV-induced epithelial cell death. Currently, there is no certain biological knowledge on why extensive epithelial cell death occurs in some FMDV-infected tissues, but not in others. Using the epithelial tissues of tongue and dorsal soft palate as examples of a tissue where lesions occur and one that does not visibly exhibit FMDV-induced cell death, this work aims to identify the potential drivers of epithelial cell death and survival. A partial differential equation (PDE) model informed by experimental data on epithelial structure, is used to test epithelium thickness and cell layer structure as potential determinants. A second PDE model investigates FMDV-interferon (IFN) dynamics and their impact on the levels of cell death and survival, while an experimental study is undertaken to provide data for model validation. The work carried out casts light on the important role of a variety of factors including FMDV replication, IFN production and release, and IFN antiviral action.