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A biosystematic study of seven Afrotropical and two Oriental species of the Imicola species-group was undertaken; this group of Culicoides of the subgenus Avaritia includes C. imicola the most important vector of the viruses of bluetongue (BT) and African horsesickness (AHS) known in the Old World. Five African species are redescribed i.e. C. imicola, C. pseudopallidipennis, C. bolitinos, C. miombo and C. loxodontis. Two new species are described, and the extralimital C. brevitarsis and C. nudipalpis are discussed where relevant. These nine species comprise the Imicola group, one of 10 groups constituting the subgenus worldwide. Due to confusion in the literature, the Imicola group is redefined and distinguished from the Orientalis group (also redefined); 21 species of approximately 70 world species of Avaritia are reassigned to either of the two groups. A key to all nine known species of the lmicola group is given; shortcomings in the taxonomy of the Orientalis group are discussed. The adult morphology of both sexes of the nine Imicola group species was studied; this revealed deficiencies in the descriptive format currently used in taxonomic studies of world Culicoides. Accordingly, greater detail has been introduced into descriptions and includes the use of new character states. Methods for mounting Culicoides on glass slides are also improved to ensure more accurate observation and measurement of diagnostic taxonomic features; furthermore, the descriptions are based on long series of each sex. Illustrations were made from specimens mounted symmetrically, and no feature omitted from any bodypart illustrated. Certain aspects of the life-cycle of most species were investigated but especially those of C. bolitinos, C. loxodontis and C. kwagga. The immatures of these develop exclusively in the dung of the elephant, the buffalo, the blue wildebeest, both species of rhinoceros and Burchell's zebra. Two of these species, C. bolitinos and C. kwagga, have broadened their resource range as they can invade and mature in the dung of cattle and horses. This has obvious implications for the transmission of viruses, especially where indigenous herbivores are run with domesticated livestock. In an intensive two-year survey a comparison was made between the Culicoides fauna of a natural area, the Kruger National Park (KNP), and that found in areas changed by Man, namely livestock farms adjoining the KNP. This part of the eastern Transvaal lowveld is a main focus of AHS in South Africa. Light-trapping, rearing from dung, and pootering off live hosts, revealed that some species of the Imicola group are exclusively associated with certain herbivores; these include the elephant and the zebra which are suspected or proven reservoir hosts for AHS. The results thus throw further light on the epidemiology of this disease, and also show that Man plays a decisive role in determining the numbers, and distribution, of particular Imicola group species under certain conditions. In the case of C. imicola, the commonest and most widespread of all species, this range expansion, or establishment of foci, is due to man's maintenance of domesticated livestock in confined species, and especially where these are kept on irrigated pastures. However, the serendipitous discovery of a large imicola-free zone in South Africa indicates that edaphic conditions likely play an even more important role than Man and climate in determining the prevalence and abundance of C. imicola. This area is the sandy dune field west of Port Elizabeth and holds promise as a natural quarantine zone for the import and export of livestock. AFRIKAANS : 'n Biosistematiese ondersoek van sewe Afrotropiese en twee Orientale spesies van die Imicola groep is gedoen; by hierdie groep Culicoides van die subgenus Avaritia word C. imicola wat as die mees belangrikste vektor van bloutong-(BT) en perdesiekte (AHS) virus in die Ou Wereld beskou word, ingesluit. Vyf Afrika spesies, nl. C. imicola, C. pseudopallidipennis, C. bolitinos, C. miombo en C. loxodontis, is herbeskryf. Twee nuwe spesies is beskryf asook die suid-oos Asiese spesies C. brevitarsis en C. nudipalpis word bespreek waar van toepassing. Hierdie nege spesies vorm die Imicola groep, een van die 10 groepe waaruit die subgenus Avaritia wêreldwyd bestaan. As gevolg van verwarring in die literatuur is die Imicola groep hergedefinieer en geskei van die Orientalis groep ( ook hergedefinieer); 21 spesies van ongeveer 70 wereld spesies van Avaritia is heringedeel in die twee groepe. 'n Sleutel vir al nege wereld spesies van die Imicola groep, asook 'n verspreidingskaart vir elke spesie, word gegee. Tekortkominge in die taksonomie van die Orientalis groep word ook bespreek. Die volwasse morfologie van beide geslagte van die nege Imicola groep spesies is bestudeer; dit het gebreke in die formaat wat tans vir die taksonomiese beskrywing van wêreld Culicoides gebruik word aan die lig gebring. Gevolglik is daar meer data in die beskrywings, wat nuwe karakterkenmerke insluit. Die metode van die montering van Culicoides op glasplaatjies is ook verbeter om meer akkurate ondersoek en meting van die diagnostiese kenmerke te verseker; verder, is beskrywings gebaseer op lang reekse van elke geslag. Illustrasies is gemaak van voorbeelde wat simmetries gemonteer is en geen kenmerk is uitgelaat van enige gelllustreerde liggaamsdeel. Aspekte van die lewensiklus van die meeste van die spesies, veral C. bolitinos, C. loxodontis en C. kwagga is ondersoek. Die onvolwassenes van hierdie spesies ontwikkel slegs in die mis van olifante, buffels, wildebeeste, renosters en zebras. Twee van die spesies, C. bolitinos en C. kwagga, het hulle broeimediums van voorkeur vergroot en kan eiers lê en tot volwassenheid ontwikkel in die mis van beeste en perde. Dit het vanselfsprekende gevolge vir virusoordrag tussen inheemse herbivore en vee, veral in gebiede waar die twee groepe saamloop. In 'n intensiewe twee-jaar studie, is 'n vergelyking gemaak tussen die Culicoides fauna soos aangetref in 'n ongerepte deel van Afrika, die Kruger Nasionale Park (KNP), en in gebiede aangrensend aan die KNP wat deur die mens in veeplase omskep is. Die deel van die Oos Transvaalse laeveld is bekend as 'n perdesiekte "hotspot" in Suid-Afrika. Ligvalvangste, uitbroei van Culicoides uit mis en versameling vanaf lewendige gash ere het aangedui dat sekere spesies van die Imicola groep eksklusief met sekere herbivore geassosieeris; hierby ingesluit is die olifant en zebra wat onderskeidelik verdagte en bevestigde gashere van AHS is. Die resultate dra by tot die verklaring van die epidemiologie van hierdie siekte en wys ook dat die mens 'n beslissende rol speel in die vasstelling van die getalle sowel as die verspreiding van spesifieke spesies van die Imicola groep. In die geval van C. imicola, die mees algemeenste en wydverspreidste spesie, is die uitbreiding, of daarstelling van fokuspunte, te wyte aan die mens se instandhouding van vaste bloedbanke op besproeide weiding. Die toevallige ontdekking van 'n groot imicola-vry sone elders in Suid-Afrika dui daarop dat grondtipe moontlik 'n bepalende rol kan speel in die aanwesigheid en volopheid van C. imicola. Hierdie "skoon" area is die sandduine-veld wes van Port Elizabeth en lyk belowend as 'n natuurlike kwarantyn gebied vir die invoer en uitvoer van lewende hawe. / Dissertation (MSc)--University of Pretoria, 2013. / Animal and Wildlife Sciences / unrestricted

African horse sickness (AHS) is a life-threatening disease of equids caused by African horse sickness virus (AHSV), a member of the genus Orbivirus in the family Reoviridae. The virus is transmitted by midges (Culicoides spp.) and the disease is most prevalent during the time of year, and in areas where vector Culicoides spp. are most abundant, namely in late summer in the summer rainfall areas of endemic regions. The disease is of importance to health and international trade in horses worldwide. Effective surveillance is critical in order to establish transparent criteria for animal trade from a country or region where AHS occurs. / The 2011 outbreak of African horse sickness in the African horse sickness controlled area in South Africa: An outbreak of AHS caused by AHSV type one (AHSV1) occurred in the surveillance zone of the AHS controlled area of the Western Cape during the summer of 2011. The epicentre of the outbreak was the town of Mamre in the magisterial district of Malmesbury, and the outbreak was confined to a defined containment zone within this area through movement control of all equids and a blanket vaccination campaign. A total of 73 confirmed cases of AHS were reported during this outbreak, which included four subclinical cases confirmed by virus isolation (VI). The estimated morbidity rate for the outbreak was 16% with an estimated mortality rate of 14% and a case fatality rate of 88% based on the figures above. Outbreak disease surveillance relied on agent identification using AHSV group specific reverse transcriptase quantitative polymerase chain reaction (GS RT-qPCR) based assays, which was novel for an AHS outbreak in South Africa. The source of this outbreak was not confirmed at the time, but was believed to be associated with an illegal 2 movement of an infected animal into the Mamre area. A detailed description of the outbreak is given in Chapter 2, and the outbreak provided an opportunity to assess decision making in future AHS outbreaks in the AHS controlled area of South Africa and in countries where AHS is an exotic or emerging disease. This outbreak further highlighted deficiencies and complications of available AHSV diagnostic testing and surveillance methods, and the need for further refinement of these assays and strategies. / Development of three triplex real-time reverse transcription PCR assays for the qualitative molecular typing of the nine types of African horse sickness virus: The typing of the specific AHSV involved in the Mamre outbreak was initially done by partial, direct sequencing of the S10 gene (encoding the non-structural protein NS3) and the L2 gene (encoding the type-specific outer capsid protein VP2) which confirmed the virus to be AHSV1. This process is time consuming and it became evident that a faster alternative was needed. This led to the development of type specific RT-qPCR (TS RT-qPCR) assays to supplement the GS RT-qPCR assay that had already been developed, characterized and validated. Blood samples collected during routine diagnostic investigations from South African horses with clinical signs suggestive of AHS were subjected to analysis with the GS RT-qPCR assay and VI with subsequent serotyping by plaque inhibition (PI) assays using AHSV type-specific antisera. Blood samples that tested positive by AHSV GS RT-qPCR were then selected for analysis using AHSV TS RT-qPCR assays. The TS RT-qPCR assays were evaluated using both historic stocks of the South African reference strains of each of the 9 AHSV types, as well as recently derived stocks of these same viruses. Of the 503 horse blood samples tested, 156 were positive by both AHSV GS RT-qPCR and VI assays, whereas 135 samples that were VI negative were positive by AHSV GS RT-qPCR assay. The virus isolates made from the various blood samples included all 9 AHSV types, and there was 100% agreement between the results of conventional serotyping of individual virus isolates by PI assay and AHSV TS RT-qPCR typing results. Results of this study confirmed that the AHSV TS RT-qPCR assays for the identification of individual AHSV types are applicable and practicable and therefore are potentially highly useful and appropriate for virus typing in AHS outbreak situations in endemic or sporadic incursion areas, which can be crucial in determining appropriate and timely vaccination and control strategies. / Evaluation of the use of foals for active surveillance in an AHS containment zone during the season following an AHS outbreak: In order to further evaluate the AHS status of horses in the Mamre area after the outbreak of 2011, a targeted surveillance strategy was developed. Serial serum and whole blood samples were collected on a monthly basis from January to June, 2012 from foals (identified by microchip) that were born in the Mamre 3 district after the end of the outbreak. Sera were evaluated using traditional serological methods and the results were compared to the results obtained using the newly developed molecular assays for virus detection and identification. This study confirmed that AHSV was eradicated in the Mamre area after the outbreak and, therefore, that the control measures implemented in the area by the State Veterinary Authorities were effective. / Characterization of the dynamics of African horse sickness virus in horses by assessing the RNAaemia and serological responses following immunisation with a commercial polyvalent live attenuated vaccine: As was shown in the 2011 Mamre outbreak, detection of AHSV during outbreaks has become more rapid and efficient with the recent development of quantitative GS RT-qPCR assays to detect AHSV nucleic acid. Use of this assay together with the TS RT-qPCR assays described in Chapter 3, will not only expedite diagnosis of AHS but also facilitate further evaluation of the dynamics of AHSV infection in the equine host. A potential limitation to the application of these assays is that they detect viral nucleic acid originating from any AHSV live attenuated vaccine (AHSVLAV), which is the vaccine type routinely administered to horses in South Africa. A study was, therefore, designed to characterize the dynamics and duration of the RNAaemia as compared to the serological responses of horses following vaccination with a commercial AHSV-LAV, using GS and TS RT-qPCR assays and serum neutralisation tests. This study provided baseline data on the GS and TS nucleic acid dynamics in weanling foals vaccinated for the first time, yearlings vaccinated for a second time and adult mares following a booster to multiple previous vaccinations. These data are fundamental to interpreting results of AHSV GS RT-qPCR testing of vaccinated horses within an area where virological surveillance is being applied. / African horse sickness caused by genome reassortment and reversion to virulence of live, attenuated vaccine viruses, South Africa, 2004 - 2014: In 2014 a further outbreak of AHS caused by AHSV1 occurred in the Porterville area of the AHS protection zone (PZ), spreading into the Wellington area in the AHS surveillance zone (SZ). Further involvement of the Robertson area (AHS PZ) subsequently also occurred. The case fatality rate was much lower than that of the Mamre outbreak. The clinical signs in infected horses were also generally milder in the 2014 outbreak, as compared to the 2011 outbreak. Whole genome sequencing of samples from the Porterville outbreak confirmed that causative virus was a recombination (reassortant) of AHSV types 1 and 4, with genes derived from the relevant vaccine strains contained in OBP comb1 of the commercial polyvalent AHSV-LAV used in South Africa. This led to further analysis of 39 AHSV strains from field cases of AHS that originated from outbreaks within the controlled area, which confirmed reversion to virulence 4 of AHSV type 1 vaccine in two outbreaks (2004 and 2011) and multiple reassortment events in two outbreaks (2004 and 2014) with genes derived from all three AHSV vaccine strains (types 1, 3 and 4). This study provided a molecular and epidemiological comparison of the five unique AHSV type 1 outbreaks in the AHS controlled area. It was shown that all the outbreaks in the AHS controlled area attributed to AHSV type 1 since the inception of the area in 1997, have been due either to reversion to virulence of the AHSV type 1 vaccine strain, or recombination of AHSV type 1 vaccine strain with one or both of the other vaccine strains in OBP comb1 of the commercial AHSV-LAV. / Thesis (PhD)--University of Pretoria, 2016. / ERC / Racing South Africa (Pty) Ltd / Equine Health Fund / Mary Slack and Daughters Foundation / THRIP / National Research Foundation / Veterinary Tropical Diseases / PhD / Unrestricted

The viral determinants of African horsesickness virus (AHSV) cytopathology are not well understood. Several AHSV proteins may play a role, including non-structural protein NS3, a cytotoxic membrane protein that localises to sites of virus release and plasma membrane disorganisation in infected cells. AHSV NS3 is highly variable and clusters into three phylogenetic groups, termed α, β and γ. In chapter 2 we examined the role of NS3 in determining the phenotypic characteristics observed during AHSV infection of cells. Three AHSV strains, AHSV-2 (γ NS3), AHSV-3 (β NS3) and AHSV-4 (α NS3), were shown to have quantitatively different phenotypes in Vero cells. To investigate the contribution of NS3 to these differences, reassortants were generated between these strains in which the S10 genome segment encoding NS3 was exchanged, alone or in combination with other segments. Exchange of NS3 resulted in changes in virus release and membrane permeability, indicating an important role for NS3 in these viral properties. The cytopathic effect and decreased viability of infected cells was not associated with NS3 alone and it is likely that a number of viral and host factors contribute to these complex phenotypes. In chapter 3 the cytolytic effect of the NS3 proteins of the orbiviruses AHSV, bluetongue virus (BTV) and equine encephalosis virus (EEV) were compared. Inducible expression in Escherichia coli (E. coli) showed differences in cytotoxicity, with EEV NS3 having a greater lytic effect than than AHSV and BTV NS3. Cytotoxicity was linked to increased membrane permeability of the cells as confirmed by an increased uptake of membrane impermeant compounds. When expressed in insect cells however all three NS3 proteins caused a marked but equivalent decrease in cell viability. Although the orbivirus NS3 proteins have similar predicted secondary structures, differences could lie in structural stability and association with membranes of specific cell types, which impacts on cytotoxicity. To determine the regions within AHSV NS3 that mediate cytotoxicity, a series of truncated mutants of NS3 where constructed and expressed in E. coli. The combined presence of both hydrophobic domains of AHSV NS3 was found to be critical for membrane permeabilisation and cytotoxicity. In chapter 4 the AHSV-2, AHSV-3 and AHSV-4 NS3 proteins (from the γ, β and α NS3 clades)were compared to examine the impact of sequence variation in NS3 on structure and function. The proteins were expressed in the baculovirus expression system as both wild-type proteins and C-terminal eGFP (enhanced green fluorescent protein) fusions. Exogenous addition of the baculovirus expressed proteins to Vero cells resulted in different permeabilisation levels that could be linked to that induced by the AHSV strains. Cell viability and membrane association assays in insect cells showed that all three proteins were equivalently cytotoxic and membrane associated. The subcellular localisation of the eGFP-NS3 fusion proteins was examined by confocal fluorescen imaging of live cells. NS3 localised to the plasma membrane, and as distinct punctuate foci in the perinuclear region. This suggests localisation to the internal membrane systems of cells and has important implications for the function of this membrane permeabilising protein. / Thesis (PhD)--University of Pretoria, 2011. / Genetics / unrestricted

Non-structural protein, NS1 of African horse sickness virus is a hydrophobic protein of 63 kDa that spontaneously assembles into highly distinct tubular structures when expressed in mammalian or insect cells. The spontaneous assembly of these proteins into a predictable multimeric structure, high levels of expression and ease of purification make this protein an ideal candidate for the immune display of foreign peptides. The potential of such a display system has been investigated for BTV NS1 that is able to successfully elicit both a humoral and a cellular immune response against inserted peptides. The aims of this study were to investigate both the stability of the AHSV NS1 particulate structure after insertion of peptides as well as the antigenicity and immunogenicity of the peptides presented in this system. Two overlapping regions consisting of 40 and 150 amino acids, and which correspond to a neutralising region identified within the AHSV major neutralising protein VP2, were inserted into an internal site in NS1. This site offered the best surface display of inserted peptides on the tubular structures. An enhanced green fluorescent protein, 240 amino acids long, was also inserted into the NS1 protein. Sucrose gradient analysis of the recombinant proteins indicated that the majority of the baculovirus expressed chimeric proteins formed particulate structures with a sedimentation value similar to that of the native NS1 protein. This was confirmed by transmission electron microscopic analysis, which clearly showed that all the chimeric proteins assembled into tubular structures similar to those observed for AHSV NS1 proteins. Furthermore, fluorescence analysis of sucrose gradients of NS1/eGFP also showed high levels of fluorescence that corresponded directly to particle formation. Not only do the inserts remain functional but are also presented successfully on the surface of the intact NS1 tubule structure. The potential of the NS1 vector to efficiently present peptides to the immune system was subsequently investigated. The serums generated against these chimeric proteins in guinea pigs were tested against chimeric constructs, the baculovirus expressed inserts (for eGFP) and the inserts presented on other presentation vectors. Western blot analysis showed that most of the serums generated against the chimeric proteins contained antibodies not only against the chimeric proteins but antibodies that reacted specifically with the inserted peptides on their own or on another presentation system. Preliminary immune studies seem to indicate that the humoral immune response elicited by the chimeric NS1 proteins is predominantly against the inserts. The inserts are successfully presented to the immune system on the surface of the NS1 vector and are able to elicit the production of antibodies with the potential to provide a protective immune response. / Dissertation (MSc (Genetics))--University of Pretoria, 2010. / Genetics / unrestricted

The aim of this study was to standardize and validate an immunohistochemical test for the routine diagnosis of African horsesickness in horses. Hamblin developed the primary anti- African horsesickness virus serum that I used and the avidin-biotin complex detection system was employed. During the standardization process I demonstrate that lung, heart and spleen samples are the most reliable. I also show that it is not necessary to take multiple samples per organ, because the AHSV-positive signal is generally widespread throughout the lung and heart, in particular. In order to validate the technique, samples from 118 negative and 128 positive horse cases, including all nine known serotypes, were immunostained. All of the positive cases were confirmed by means of virus isolation. Negative horse samples were obtained from countries where African horsesickness does not occur. None of the negative cases stained positive and all the positive cases were correctly identified. Therefore, there was 100 % concordance between immunohisto chemistry (when applied to formalin-fixed, paraffin-embedded heart and/or lung and/or spleen tissues from positive horse cases that had been archived for less than 10 years) and virus isolation results. Heart and lung had consistently more positive signal than spleen. The Hamblin antiserum did not cross-react with closely-related orbiviruses (specifically equine encephalosis virus and bluetongue virus) in selected horse and sheep tissues, respectively. Characteristic positive staining was observed in lung, heart and spleen samples from two dogs that died of African horsesickness. Positive signal was not affected by long-term storage in formaldehyde (up to 365 days). Also, specific positive staining could be detected in heart and/or lung and/or spleen samples in more than 95 % of positive horses where tissue blocks had been stored for between 10 and 83 years. The principal target cells in the horse and dog cases were microvascular endothelial cells, intravascular monocyte-macrophages and, to a lesser extent, interstitial macrophages in lung, spleen and liver, in particular. Positive staining is intracytoplasmic with a bead/dot and/or granular character. Beads, dots or granules may occur singly or in clusters. Occasionally, linear deposits of positive signal delineate segments of capillary vessels. The veterinary pathologist must look for characteristic positive signal in target cells, because, occasionally, certain bacteria (Rhodococcus equi and Helicobacter sp.) cross-react with the Hamblin antiserum. Clearly, the test is highly sensitive, specific and robust, sufficiently so for the routine diagnosis of African horsesickness virus. / Dissertation (MSc)--University of Pretoria, 2008. / Paraclinical Sciences / unrestricted

The purpose of this research is to explore the operational characteristics of a Maglev-based Automated Highway System and how it would interact with freeway operations. The extension of traditional traffic flow phenomenon, including weaving, merging, and stopping distance, into the automated system is looked at. These are also extended into platoon operations and their effect on such properties as gap control and ultimately the capacity of such a system. The ability to incorporate an AHS system into the existing Interstate Highway System is investigated. This includes placing the magways in the right-of-way of the highway system and interfacing the AHS with the existing freeways. A model is developed and run to simulate the assignment of traffic between the freeway and the guideway links. Both operational concepts of user equilibrium and system optimal conditions are explored, and equations are found to estimate the amount of traffic which can be found on the links based on the total traffic volume. / Master of Science

There have been numerous reports of vaccinated horses that contract fatal African horse sickness due to African horse sickness virus (AHSV) serotypes that are included in the current commercial vaccine used in southern Africa, which emphasizes the importance of thorough characterization of the equine immune response to AHSV. In particular, there are concerns about possible interference between vaccine strains in the polyvalent vaccine which led us to hypothesise that the administration of individual AHSV serotypes could induce a better immunity to individual serotypes than that achieved with the current polyvalent vaccines. There is also little published information describing the half-life of maternally derived neutralising antibody in foals to the nine AHSV serotypes. This is important for revising and developing vaccination protocols for foals of vaccinated mares. Given the lethality of both natural and experimental AHSV infections in horses, several aspects of immunity induced by different types of AHSV vaccines were evaluated. The neutralising antibody response of horses (foals) immunized with a commercial modified live virus (MLV) AHSV vaccine was evaluated and compared to the immune response elicited to monovalent MLV AHSV serotypes. Foals were immunized with either the polyvalent AHSV vaccine, or one of four monovalent vaccines containing individual AHSV serotypes 1, 4, 7 and 8. There were marked differences in the immunogenicity of individual virus serotypes contained in the vaccine. Foals more consistently seroconverted to AHSV 1 and responses to other serotypes were highly variable, and often weak or not detected. The serotype-specific responses of foals given the monovalent MLV vaccines were similar to those of foals given the polyvalent preparation suggesting that there is no apparent enhanced immune response through the administration of a monovalent vaccine as opposed to the polyvalent vaccine. Furthermore, the immunogenicity of individual AHSV serotypes contained in the commercial MLV vaccine varies remarkably. Neutralising antibody titres to the 9 known serotypes of AHSV were determined in a cohort of brood mares that were regularly vaccinated with the MLV AHSV vaccine, and the passive transfer and rate of decay of maternal antibody to the individual virus serotypes in their foals were measured. Similar to the data obtained from immunized foals, there was marked variation in the neutralising antibody response of the mares to individual AHSV serotypes even after repeated vaccination. This was mirrored in the duration of maternally-derived antibodies in their respective foals. In an effort to further characterize cellular immune (CMI) responses to AHSV, the immunity in horses induced by an experimental canarypox virus vectored recombinant (ALVAC®-AHSV4) vaccine was characterised. The detection of VP2/VP5 specific IFN-γ responses was assessed by enzyme-linked immune spot (ELISpot) assay and clearly demonstrated that all ALVAC®-AHSV4 vaccinated horses developed significant IFN-γ production compared to unvaccinated horses. Flow cytometry demonstrated that this vaccine induced mainly CD8+ T-cells, able to recognize multiple T-cell epitopes throughout all of VP2 and only the N-terminus portion of VP5. In summary, the antibody and cellular response of horses to different AHSV vaccines was evaluated and compared. The results are relevant to the design of more efficacious AHSV vaccines and to identification of protective immunity in horses to this virus. / Thesis (PhD)--University of Pretoria, 2013. / gm2014 / Veterinary Tropical Diseases / unrestricted

One of today's most serious social, economical and environmental problems is traffic congestion. In addition to the financial cost of the problem, the number of traffic related injuries and casualties is very high. A recently considered approach to increase safety while reducing congestion and improving driving conditions is Automated Highway Systems (AHS). The AHS will evolve from the present highway system to an intelligent vehicle/highway system that will incorporate communication, vehicle control and traffic management techniques to provide safe, fast and more efficient surface transportation. A key factor in AHS deployment is intelligent vehicle control. While the technology to safely maneuver the vehicles exists, the problem of making intelligent decisions to improve a single vehicle's travel time and safety while optimizing the overall traffic flow is still a stumbling block. We propose an artificial intelligence technique called stochastic learning automata to design an intelligent vehicle path controller. Using the information obtained by on-board sensors and local communication modules, two automata are capable of learning the best possible (lateral and longitudinal) actions to avoid collisions. This learning method is capable of adapting to the automata environment resulting from unmodeled physical environment. Simulations for simultaneous lateral and longitudinal control of an autonomous vehicle provide encouraging results. Although the learning approach taken is capable of providing a safe decision, optimization of the overall traffic flow is also possible by studying the interaction of the vehicles. The design of the adaptive vehicle path planner based on local information is then carried onto the interaction of multiple intelligent vehicles. By analyzing the situations consisting of conflicting desired vehicle paths, we extend our design by additional decision structures. The analysis of the situations and the design of the additional structures are made possible by the study of the interacting reward-penalty mechanisms in individual vehicles. The definition of the physical environment of a vehicle as a series of discrete state transitions associated with a "stationary automata environment" is the key to this analysis and to the design of the intelligent vehicle path controller. This work was supported in part by the Center for Transportation Research and Virginia DOT under Smart Road project, by General Motors ITS Fellowship program, and by Naval Research Laboratory under grant no. N000114-93-1-G022. / Ph. D.

Historically African Horsesickness (AHS) outbreaks are rare occurrences in the Western Cape Province. The 2004 outbreak was particularly troubling since it followed only five years after the previous outbreak and even before any cases were reported further inland, which is traditionally the source of infection for the southern (non-endemic) parts of the country. Following confirmation of the diagnosis, control measures were immediately instituted and an epidemiological investigation was initiated. The investigation revealed, inter alia, that serological profiles of case horses were inconsistent. A case was subsequently defined as a horse showing typical symptoms of AHS and from which virus could be isolated. The disease pattern for both the 2004 and 1999 outbreaks can be classified as sporadic epidemics. This type of epidemic pattern is to be expected in a vector borne disease and it is typical in a disease situation where some of the animals are immune. The temporal pattern revealed that the level of immunity in the equine population of the affected area was higher during the 2004 outbreak than during the 1999 outbreak. In addition, it showed a clustering of cases during the initial stages of both the 2004 and 1999 outbreaks. This illustrated the efficacy of the control measures (including movement and vector control), which was instituted immediately after the diagnosis of the first case. The analysis of the spatial pattern during both the 2004 and 1999 outbreaks identified the Eerste-river-valley as a high-risk area for the outbreak of AHS in the surveillance zone. The population pattern during the 2004 outbreak illustrated that the risk of dying of AHS was higher in horses of 5 years and younger (p<0.10). It was shown that vaccination and stabling offers the best protection against the risk of dying as a result of AHS infection in an exposed population (p<0.05). A questionnaire survey was conducted as part of the epidemiological investigation and it revealed that only 12.4% of equine holdings in the affected area practiced vector control, while a high percentage of horses (69.6%) were protected by means of vaccination, which impacts negatively on the purpose of a surveillance zone. The number of Culicoides imicola midges in the area where the outbreak was detected was extremely high, constituting 94.6% of the Culicoides midge population. This is comparable with the 1999 outbreak when 96.0% of the midges collected were identified as C. imicola. However, during a similar survey in 1996, C. imicola comprised only 11.3% of the population (Neville et al. 1988, Venter, G., personal communication 2004). Furthermore, the outbreak was detected even before significant rainfall was recorded in the region and transmission occurred at average minimum temperatures below 15 °C. The virus responsible for the 2004 outbreak was typed as AHS serotype 1, while AHS serotype 7 was identified as the cause of the 1999 outbreak. The source of the infection in the 1999 outbreak was the illegal movement of two horses from the Free State Province in the infected zone into the surveillance zone. Although no absolute proof could be obtained, there is strong evidence that the source of the 2004 outbreak was again the movement of horses, this time from Namibia, accentuating that horse movements constitutes the highest risk to the integrity of the free zone. Since the ability to control an outbreak successfully is directly dependant on rapid detection and given the large number of vaccinated horses as a result of the outbreaks and the AHS movement control policy, amendments to the export policy and legislation are recommended. AHS outbreaks in the control area of South Africa cause substantial financial loss to the horse industry and the controlling authorities. / Dissertation (MSc (Veterinary Science))--University of Pretoria, 2006. / Production Animal Studies / unrestricted