No description available.

published_or_final_version / Zoology / Master / Master of Philosophy

No description available.

No description available.

Each of two affinity isolation methods, the first based on biotinylated porcine transferrin plus streptavidin-agarose, and the second on Sepharose-coupled porcine transferrin, followed by sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE), allowed the isolation and identification of two potential porcine-transferrin-binding polypeptides (∼64 kDa and 99 kDa) from total membranes of Actinobacillus pleuropneumoniae grown under iron-restricted conditions. Both polypeptides were iron-repressible and were identified as potential receptor candidates as they were not isolated when biotinylated human transferrin was used instead of biotinylated porcine transferrin. The 64 kDa polypeptide was the more easily removed from Sepharose-coupled porcine transferrin and only the 99 kDa polypeptide appeared to be an outer membrane protein. These results suggest that the 99 kDa polypeptide represents the porcine transferrin receptor of A. pleuropneumoniae, and that the 64 kDa polypeptide represents an associated protein serving an accessory role. Fe+3 uptake studies using plate assays and attempted isolation of a putative lactoferrin receptor using biotinylated porcine lactoferrin plus streptavidin-agarose, followed by SDS-PAGE, showed that A. pleuropneumoniae lacks a mechanism for the use of porcine lactoferrin as an iron source.

Thesis (Ph.D.)--Murdoch University, 2008. / Thesis submitted to the Faculty of Health Sciences. Includes bibliographical references (leaves 190-207)

No description available.

No description available.

Rabbit Passage of the Virus The hog cholera virus was carried through six alternate passages from pig to rabbit and then top five serial passages in rabbits. The virus could not be demonstrated in rabbit-spleen suspension prepared for the sixth serial passage in rabbits. The lack of pathogenic or antigenic properties for the pig made it impossible to detect the virus, assuming that it was present in the rabbit-spleen suspension, at the sixth serial passage. The virus did not become pathogenic for the rabbit during the alternate and serial passages, although it survived for at least 72 hours in the rabbit. No evidence or attenuation of the virus for the pig was obtained in either the alternate or serial passages. Ultraviolet Irradiation or the Virus The hog cholera virus in the form of a pig-spleen suspension was irradiated by the Westinghouse lamps CH4 and Wl793. The virus was irradiated at a distance of 15 centimeters from the lamp. The suspension was placed in an open petri dish, to a depth or l to 2 millimeters, and was constantly agitated during the irradiation. Irradiation by the CH4 lamp for 30 and 60 minutes and irradiation by the WL793 lamp for 15, 30, and 60 minutes failed to attenuate the virus for the pig. Typical hog cholera was produced in pigs injected with the irradiated virus. Nitrogen Mustard Treatment of the Virus The hog cholera virus in the form of blood virus was mixed with the nitrogen mustard, methyl-bis (β-chloroethyl)-amine, in the proportion or five milliliters of blood virus to ten milligrams of nitrogen mustard. In one lot of blood virus so treated, the virus was completely destroyed, whereas in a second lot the virus was not affected. Treatment of five milliliters of the virus, in the form of pig-spleen suspension, with ten milligrams of the nitrogen mustard completely attenuated the virus for the pig, so that, when the virus was injected into pigs, no ill effects appeared. Pigs injected with five milliliters of the mustard-treated pig-spleen virus developed a resistance to the virulent virus. The injected pigs successfully withstood the intramuscular injection or two milliliters of virulent virus, or pen exposure to cholera-infected pigs. The mustard-treated pig-spleen virus produced a satisfactory immunity in pigs injected with the treated virus 24 hours after its preparation. The mustard-treated pig-spleen virus did not spread from injected pigs to non-injected pigs kept in close contact with them. / Ph. D.

Escherichia coli diarrhoea is the most important source of mortality in piglets. The most frequently isolated strain in enterotoxigenic E. coli diarrhoea is F4ab/ac. Recent studies in South Africa reported non-fimbrial strains such as PAA and EAST-1 to be prevalent. The objective of the study was to determine whether there are breed differences among pigs with respect to E. coli adhesion phenotypes and correlate them to polymorphisms at selected candidate genes in the South African population. A total of 225 pigs aged 3-12 weeks of the imported (Large White, Landrace and Duroc), local and crossbreds, were sampled from the Eastern Cape and Limpopo provinces of South Africa and genotyped for PCR-RFLP polymorphisms at four candidate genes associated with E. coli F4ab/ac resistance/susceptibility. These genes were Mucin 4 (MUC4), Mucin 13, (MUC13), Mucin 20 (MUC20) and Transferrin Receptor (TFRC). The TFRC and MUC13 genes were less polymorphic, the C allele was close to fixation and the homozygous CC genotype was the most frequent in all three pig populations. There was a significant difference (P <0.05) in allelic and genotypic distribution amongst breeds for the TFRC locus. The g.8227G>C polymorphism in MUC4 segregated in all three breeds and the marker was moderately polymorphic. There was a significant difference (P <0.05) in genotypic distribution amongst breeds for MUC4.The g.191C>T polymorphism in MUC20 segregated in the local and crossbred pigs and was close to fixation in the imported pigs. There was a significant difference (P <0.05) in allelic and genotypic distribution amongst breeds for MUC20, which was moderately polymorphic. There was a reduction in heterozygosity in both the TFRC and MUC13 loci, although MUC4 and MUC20 genes had higher heterozygosity levels. The MUC4 gene had a negative FIS value, indicating outbreeding at this locus. The MUC20, MUC13 and TFRC genes had a positive FIS value, indicating inbreeding at these loci. Overall, the studied population was outbred. Imported pigs in TFRC and MUC20 deviated from Hardy-Weinberg equilibrium (HWE). All breeds were in HWE at the MUC4 and MUC13 genes. There was no linkage disequilibrium observed amongst the analysed loci. iv A total of 109 piglets of three breeds (Large White, indigenous and crossbred) aged 3-5 weeks, were investigated for the susceptibility to E. coli F4, PAA strains and EAST-1 toxin. Adhesion tests were conducted on pig intestinal cells, which were viewed under a phase contrast microscope. Three phenotypes were identified as, adhesive, weakly adhesive and non-adhesive. There was a significant association (P <0.05) between breed and level of adherence of the F4 and PAA strains. Highest frequencies of adhesion phenotypes were observed in the indigenous pigs for both F4 and PAA E. coli strains. Large White pigs had the lowest frequency of non-adhesion in F4 and PAA E. coli strains. The F4 strain had a higher (P <0.05) level of adherence compared to PAA and EAST-1 in Large White pigs. Age of pigs had a significant effect on the level of E. coli adherence in indigenous and crossbred pigs (P <0.05). Adhesion of F4 and EAST-1 was higher in weaned indigenous and crossbred pigs, respectively, than in suckling piglets. There was no significant difference between F4 adhesion and the genotypes at all four candidate genes genotypes. The study showed that both imported and local pig populations carry receptors and are susceptible to F4, PAA and EAST-1 E. coli infections. Indigenous pigs were less susceptible than Large White to E. coli infection. Although polymorphic and segregating in the populations, the MUC4 g.8227G>C and MUC20 g.191C>T mutations were not associated with the adhesion phenotypes and cannot be used in the selection of susceptible animals. / M.Sc.Agric. University of KwaZulu-Natal, Pietermaritzburg 2013.