No description available.

No description available.

Digitized by Kansas Correctional Industries

Typescript, etc. / Digitized by Kansas Correctional Industries

No description available.

Jembrana disease virus (JDV) is a lentivirus causing an acute infection with a 17% case fatality rate in Bali cattle in Indonesia. Control of the disease is currently achieved by identification of infected areas and restriction of cattle movement. A detergent-inactivated whole virus tissue-derived vaccine is sometimes employed in affected areas. This thesis reports initial attempts to produce genetically engineered vaccines to replace the inactivated tissue-derived vaccine, which as it is made from homogenised spleen of infected animals, is expensive to produce and could contain adventitious agents present in the donor animals. 4 potential DNA vaccine constructs were created containing the JDV genes coding for the Tat, capsid (CA), transmembrane (TM) and surface unit (SU) proteins in a commercially available vaccine plasmid. These were assessed for functionality in a range of in vitro and in vivo assays. All proteins were expressed in vitro and administration of 2 of the constructs by a commercial ‘gene gun’ into the epidermis of mice resulted in antibody production to the appropriate protein. Due to the difficulties of licensing such a DNA vaccine in Indonesia, these vaccines were not progressed further. A mathematical model was developed to describe the progression of the acute phase of Jembrana disease following experimental infection with JDV. The model divided the disease into 6 phases based on the rates of viral replication and clearance calculated from data on sequential plasma viral RNA load detected by quantitative reverse-transcription polymerase chain reaction. This allowed statistical comparison of each phase of the disease and comparison of the severity of the disease process in groups of animals. The use of the model overcame the difficulty of comparing the disease in different animals as a consequence of the animal-to-animal variation in the disease process. The mathematical model was used to identify differences in the pathogenicity of 2 strains of JDV. One strain, JDVTAB caused a more rapid onset of disease in non-vaccinated controls, a significantly higher virus load at the onset of the febrile period and a higher peak viraemia than in animals infected with JDVPUL. This provided the first evidence of variation in pathogenicity of JDV strains. The measurement of virus load also demonstrated that some JDV infected animals developed a clinical disease that was not typical of that which had been reported previously. When infected with less than 1,000 infectious virus particles, up to 20% of infected animals failed to develop a febrile response. Infection of these animals was confirmed, however, by the detection of a high titre of circulating virus particles in plasma. These atypical infections had not been reported previously. Application of the mathematical model describing the progression of the disease in individual animals was used to examine the effect of vaccination with the inactivated tissue-derived vaccine on the progression of the disease. Several effects were noted in vaccinated animals that were subsequently infected with JDV: a reduction in the duration of the febrile response, a reduction in the severity of the febrile response in the early phases of the acute disease, and a reduction in virus load in the early and later phases of the disease process. The effect of vaccination with recombinant Tat, matrix (MA) and CA protein vaccines expressed in a bacterial expression system on subsequent JDV infection was also examined. A vaccine incorporating recombinant Tat and CA vaccine emulsified with Freund’s incomplete adjuvant decreased the febrile response particularly in the later stages of the acute disease process, decreased the severity of the leucopenia in the later phases of the acute disease, and decreased the virus load in some but not all phases of the acute disease process. Vaccines administered with Freund’s incomplete adjuvant were more efficacious than vaccines administered with QuilA, the latter actually exacerbating the disease process in vaccinated animals.

Two hereditary defects, Congenital Dropsy of cattle and Atresia of swine, are investigated. The introduction makes reference to the evolutionary significance of lethal and sub-lethal characters and compares it to the importance of such factors to the practical breeding of livestock. Some reviews published on the hereditary defects of farm animals are listed. Part one is concerned with the congenital dropsy defect which was observed and studied in the Ubyssey herd of registered Ayrshire dairy cattle owned and bred by the University of British Columbia. The history of the herd and the breeding practices employed since the herd's foundation are outlined. A single-factor recessive genetic hypothesis to account for the occurrence of the ten defective calves is formulated and tested. Genetic analyses of the pedigrees of 153 of the 501 calves born in the herd up to September 30, 1951 indicated the average theoretical probability of the defect occuring to be 0.0853. A test for the ''goodness of fit'' was applied and showed that the sample studied fits the hypothesis. The etiology and pathogenesis of the defect are investigated under a working immunogenetic hypothesis based on the two assumptions: l) that the defect, congenital dropsy, is the counterpart of the hereditary disease of new-born infants, Erythroblastosis fetalis; 2) that the Rhesus isoimmunization theory which serves to explain the familial incidence of the disease in humans may be adapted to the genetics of cattle populations. The immunogenetic studies undertaken to test this hypothesis are described and an explanation of the results, aberrant to the hypothesis, is offered. Part two deals with a more complex hereditary defect. Atresia ani of swine. The literature is reviewed. The histories and pedigrees of three abnormal litters born in a local herd of registered Yorkshire swine are presented. Two explanations of the possible mode of inheritance of the defect are put forward and tested on the sample available for study. The recommendations made to the breeder which would enable him to rid his particular herd of breeding stock of the defect are quoted. The conclusion is a brief discussion of the problems confronting the breeder of registered livestock in whose herds or flocks a hereditary defect occurs. The appendices include explanations of the methods used to calculate the coefficients of inbreeding and of probability. The chi-square test for ''goodness of fit” is outlined. The procedures for the serological reactions employed in the immunogenetic study of cattle are also presented. / Land and Food Systems, Faculty of / Graduate

No description available.

Typescript (photocopy). / Digitized by Kansas Correctional Industries

Call number: LD2668 .T4 1958 I86 / Master of Science