To date there are no effective treatments for prion diseases, and these diseases are always fatal in both humans and animals. Additionally, the gold standard for diagnosis of these disease remains to be the analysis of biopsied brain tissue obtained post mortem. Consequently, there is a continued demand for therapeutics and ante-mortem diagnostics for prion diseases. This project addresses these demands by investigating candidate therapeutic and diagnostic ligands for prion diseases. This study investigated recombinant prion proteins (rPrPs) as inhibitors in scrapie and bovine spongiform encephalopathy (BSE) in vitro amplification by protein misfolding cyclic amplification (PMCA). Three ovine rPrPs with the polymorphisms VRQ, ARQ and ARR and hamster rPrP were tested against scrapie PMCA in dilution series to calculate IC50 values. The two most potent inhibitors, VRQ and ARQ, were then similarly tested against bovine spongiform encephalopathy (BSE) amplification. The most potent inhibitor of both disease types, the ovine rPrP VRQ, was then observed to inhibit a range of different scrapie and BSE strains at a fixed concentration. It is recommended that further investigation into rPrP inhibitors is performed. Strain characterisation of scrapie was investigated using rPrP inhibitors, following observations that the rPrP inhibitors generate a pattern of inhibition at a set concentration. Although this pattern of inhibition was repeatable in scrapie amplification by PMCA, this was limited to a single round of PMCA. Ultimately, this limited the application of this method to only amplification efficient prion strains and isolates. It is recommended that this method be investigated further in combination with the amplification of different isolates in substrates of different genotypes over multiple rounds of PMCA, as well as the analysis of glycoform ratios by western blotting. Here it was also identified that the imidazole used in the elution buffer for immobilised metal affinity chromatography (IMAC) can inhibit prion amplification in a strain dependent manner. This inhibition could be used in combination with the proposed method as a multi-faceted assay of prion strain characterisation. The use of next generation phage display (NGPD) to map the epitopes of autoantibodies in the sera of scrapie infected sheep was also investigated. This was performed to identify peptides that were immunoreactive to autoantibodies specific to the disease state. The identification of diagnostic peptides would then enable the development of an ante-mortem serological diagnostic test for scrapie. NGPD successfully selected immunoreactive peptides, of which 39 were selected for validation by peptide enzyme-linked immunosorbent assays (ELISAs). Although none of the peptides demonstrated diagnostic specificity by peptide ELISA, an optimised ELISA methodology was developed for future use in the validation of NGPD selected peptides. Further variations in the NGPD method, as well as validation by immunoassay, can be investigated to identify diagnostic peptides immunoreactive to scrapie specific autoantibodies.

The interaction between host genetics and epidemiological processes in ovine footrot was investigated using a combination of data analysis and simulation modelling. The study’s aims were to determine the potential for genetic selection to be used to reduce the prevalence of footrot in the UK and to assess different strategies for use of conventional epidemiological interventions. A stochastic simulation model was developed, incorporating host genetics for traits controlling footrot resistance, bacterial population dynamics, sheep population dynamics and epidemiological processes. Sensitivity analysis of the model showed survival time of Dichelobacter nodosus in the environment and infection rate were the key determinants of disease outcomes. Antibiotics were predicted to be the most effective conventional control method, reducing prevalence of footrot to 1-2% when administered promptly. Pasture rotation, selective culling and vaccination were all predicted to reduce prevalence but to a lower extent. Analysis of field data confirmed the likely role for some degree of host genetic control of footrot resistance, i.e. resistance appears to be lowly to moderately heritable. Using the simulation model it was then shown that genetic selection could be effective at reducing footrot prevalence. In combination with antibiotic treatment or pasture rotation elimination of footrot from an individual flock could be achieved. Genetic selection was predicted to be effective at reducing prevalence and improving resistance but the choice of selection criteria impacts the results seen. It is likely that progress would be slower in field situations because footrot traits would be diluted by simultaneous selection for other traits affecting profitability. Field studies are required to determine optimal combinations of interventions and genetic selection and to validate modelling outcomes. Combined data from longitudinal disease observations, genetic information and bacterial samples are necessary to address current knowledge gaps and to further advance understanding of host and disease processes in ovine footrot.

One of the characteristic features of parasitic infections is the chronicity and persistence of the infection for long time. Their success is due to its ability to deviate the immune response of their host toward the immunoregulatory or immunosuppressive state. IL-10 is a multifunctional cytokine with both immunosuppressive and immunostimulatory effects during parasite infection, playing a crucial role in the regulation of the immunity by ameliorating the destructive immunopathology associated with excessive inflammation but often suppressing effective immune responses against pathogens and impairing parasite clearance. Several transcription factors have been characterised that act on the promoter region of human and mouse IL-10 and their role in the transcription of this cytokine has been experimentally verified. In our study, a 570 bp fragment of the 5' UTR region flanking the bovine il-10 gene was cloned and characterised by sequencing. Several SNPs relative to the reference sequence are described, the putative polymorphisms lie within the transcription factor binding sites Sp1, Cap, HSF, ADR1, MZF1, GATA1 and Hb. We have investigated the role of GATA1 in regulation of IL-10 expression from fluke naïve PBMCs in response to LFH and FhTLM and we demonstrate that both LFH and FhTLM treatment induced GATA1 expression from PBMCs. These molecules showed distinct effects on PBMC functions i.e. stimulation of IL-10 in response to FhTLM and inhibition when LFH is used. However, both factors inhibit PBMCs proliferation and IFN-γ expression. We have also found that FhTLM binds to bovine TGFβ-RIED and TGFβ-RIIED fusion proteins but with a higher avidity to TGFβ-RIIED. These results highlight the role of FhTLM as a potent immunomodulatory of the bovine immune system by binding to bovine cytokine receptors. Neospora caninum infection is the major cause of abortion in dairy cattle. Infection with this parasite leads to a polarized Th1 response with high IFN-γ and IL-12 which provide protection aginst N. caninum infection. We have determined the effects of IL-10 in the regulation of IFN-γ and its association with production parameters (milk yield, lactation numbers) by measuring the levels of these cytokines in serum of infected animals and relating these to the key production parameters. Our results have shown that 84 % of high seropositive dams gave birth to seropositive calves and IL-10 concentration was higher in seropositive animals compared to seronegative. However, no correlation was found between the IL-10 concentration of seropositive dams and their calves. Together these indicated that IL-10 is an important cytokine during neosporosis, which modulate the immune response and allow the transmission of the infection to the offspring. Finally, our results for association of the IL-10 with lifetime daily yield demonstrated that IL-10 has a negative association with milk production during infection with N. caninum. Results of our study demonstrate a key role for bovine IL-10 in the regulation of multiple facets of parasite infection and immunity.

Digital dermatitis (DD) is a superficial infectious dermatitis of the digital skin of cattle and sheep that can be very painful, causing severe lameness in affected animals. Bovine digital dermatitis (BDD) in dairy cattle has now been reported in most countries they are farmed, and DD in sheep, known as contagious ovine digital dermatitis (CODD) is rapidly emerging as a severe infectious foot disease since first reports from the UK in 1997. Spirochaetes, of the genus Treponema have frequently been found in large numbers in BDD lesions and are now considered the primary causative bacteria of BDD. Three treponeme phylogroups are consistently isolated from dairy cattle BDD in the UK and the USA, which are known as Treponema medium- like, Treponema phagedenis- like spirochaetes and Treponema pedis. Over the past 40 years research has focused on dairy cattle BDD and overlooked whether the disease exists in beef cattle herds in the UK, and whether the same aetiological agents are causal. There is also limited information on the causative bacteriological agents of CODD. Furthermore, no definitive transmission routes or infection reservoirs of DD in either cattle or sheep had thus far been delineated, with only a single study finding a potential reservoir site of DD treponemes in the dairy cattle gastrointestinal (GI) tract. Using molecular bacteriological studies it was found that CODD and beef cattle BDD, as in dairy cattle BDD, show a high association with the three DD treponeme phylogroups. All CODD and beef BDD lesions investigated had at least one of the three DD treponeme phylogroups present in the lesions and these treponemes were also isolated from a high proportion of lesions. No DD treponemes were detected in healthy sheep or beef cattle foot tissue. Upon 16S rRNA gene sequence analysis all isolates showed a high similarity, if not 100% identity, to representatives of each treponeme phylogroup isolated from dairy cattle BDD lesions, indicating a shared aetiology between DD in all three animals. Additionally, the same treponeme bacteria were detected and isolated from a new undefined foot disease in dairy goats in the UK indicating that cross-species transmission of DD may have occurred causing DD infection in a previously unaffected domestic livestock species. To understand potential transmission routes and infection reservoirs of DD, the host GI tract and hoof trimming equipment were investigated. Of the sheep gingival (n= 40) and rectal tissues (n= 40), 1/40 gingival tissues were positive for DD- associated treponemes (T. pedis), and 3/40 rectal tissues (one containing T. medium- like and two tissues containing T. pedis). No DD- associated treponeme DNA was amplified from beef cattle rectal tissues (n= 40), however 4/40 beef gingival tissues were positive for DD- associated treponemes (all containing T. phagedenis- like). A T. phagedenis- like DD treponeme was isolated from the rectal tissue of a CODD symptomatic sheep. Beef cattle (n= 41) and sheep (n= 79) faeces failed to amplify DD- associated Treponema DNA. Twenty two treponemes were isolated from sheep faeces; however, upon phylogenetic analysis these clustered with considered non-pathogenic treponemes, which interestingly exhibited farm specific diversity in their 16S rRNA gene. Trimming equipment was tested after being used to trim cattle and sheep hooves, and subsequently after disinfection of equipment. Of the blades used to trim DD symptomatic animals (n= 26, cattle and sheep combined), 25/26 were found to be positive for at least one of the DD Treponema phylotypes. This figure was reduced to 10/26 (38%) after disinfection of the blades. Following culture of a swab, an isolate belonging to the T. phagedenis- like spirochaetes was isolated from a knife sample after trimming a DD positive cow. Beef cattle sera from DD positive and negative farms were investigated to understand whether beef cattle’s perceived lower prevalence of BDD in the UK is due to a lack of exposure to treponemes, or a protective immune response. Beef cattle from DD positive farms appeared to produce a strong immunological response to treponemes, compared with DD negative farm animal sera. Therefore the perceived lower prevalence of DD in beef cattle does not appear to be due to a protective response in these animals, but more likely due to a lack of exposure to DD treponemes. In conclusion, these studies have produced vital information describing DD in beef cattle and sheep and their respective aetiological agents allowing for more appropriate treatments in the future. Additionally, given the two potential transmission routes delineated from the data, effective actions can be taken to prevent the spread of DD within current hosts and to limit emergence into yet unknown additional host species.