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No description available.

A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfillment of the requirements for the degree of Doctor of Philosophy. / The aim of this thesis was to develop DNA probes to distinguish between the protozoan parasites Theileria parva parva and T. p. lawrencei which cause East Coast fever (ECF) and Corridor disease respectively. ECF was eradicated from South Arrlca in 1954, and today Corridor disease has become the most important form of theileriosis. Although ECF has been eradicated, the vector ticks are still prevalent in South Africa and the cattle population would be highly susceptible to a recurrence of the disease, At present there is no reliable means of distinguishing between T.p. parva and T. p. lawrencei. Sequence differences between T. parva and other Theileria species have previously been found in the small subunit ribosomal RNA (rRNA) gene; probes designed to detect these sequence differences Can be used to distinguish between Theileria species. We therefore decided to search for differences in the rRNA genes of T. p. parva and T.p. lawrencei. To this end, the entire "RNA transcription unit was amplified from a cloned T. p, lawrence; parasite; the unit comprises the small subunit rRNA (SSUrRNA) gene, the internal transcribed spacer (ITS) and the large subunit rRNA (LSUrRNA) gene. The amplification products were cloned and sequenced, and the T.p, lawrencei rRNA sequence was compared to that of T. p, parva, While there was little variation in their SSUrRNA and LSUrRNA gene sequences, there was major sequence variation in the ITS The ITSs from twelve T. parva isolates were amplified, cloned and sequenced, and eleven characterisation oligonucleotide probes were identified. The T. p, parva isolates screened in this study hybridised with a limited subset of the probes, While the T. p. lawrencei isolates, hybridised with many more of the probes, indicating that the T. parva population in cattle is more homogenous than that in buffalo. There thus appears to have been a selection in cattle of a relatively homogenous subpopuiation of T. parva from a much larger, more diverse gene pool in buffalo. Although most T.p. parva isolates (93.5%) were detected by probe TPPI, and most T.p, lawrencei isolates (81.8%) were detected by / AC2017

No description available.

Thesis (PhD. (Veterinary Science))--University of Pretoria, 2008. / Includes bibliographical references. Also available in print format.

Theileriosis is a tick-transmitted protozoal disease caused by several Theileria species. The most virulent species affecting cattle are T. parva and T. annulata. Theileria parva is responsible for causing East Coast Fever (ECF), Corridor Disease and January Disease. Theileria parva is endemic in certain areas of South Africa, Zambia, Zimbabwe and elsewhere. In South Africa these areas are controlled, include mostly game reserves containing infected African buffaloes and are in declared Corridor disease infected districts. African buffaloes are natural reservoirs of the T. parva parasite and if suitable tick species (Rhipicephalus appendiculatus and R. zambeziensis) are present, cattle may become infected. Currently, T. parva is diagnosed by conducting an array of tests including Giemsa-stained blood and lymph node smears, indirect immunofluorescent antibody (IFA) test, standard PCR and PCR/DNA-probe test. Recent progress in the diagnosis of T. parva has involved the development of a Reverse-Line Blot (RLB) technique and a real-time PCR for detecting T. parva. Over the last decade, several outbreaks of T. parva have occurred in cattle in the province of KwaZulu- Natal. Between 2002 and 2004, Mr A. Green, a Red Brangus stud farmer in the Ladysmith district, lost a total of 42 cattle to T. parva infection. An investigation into the epidemiology of T. parva in KwaZulu-Natal was structured in three parts: (i) a survey of Red Brangus on Mr Green‟s farm in order to gain insight into the current prevalence of theileriosis and other tick-borne diseases in the herd; (ii) transmission experiments from T. parva-infected cattle on Mr Green‟s farm to susceptible cattle to demonstrate vector transmission as well as replicate the disease process and pathology; (iii) tick transmission experiments from persistently T. parva positive-testing buffalo and persistently T. parva negative-testing buffalo, to susceptible bovines to demonstrate suitability of tick transmission methods and compare pathology and clinical signs seen on the farm and in the tick transmission experiments. The survey demonstrated that several factors may interact in determining the number of infected animals, the period that they remain infective to ticks as well as the susceptibility of the rest of the herd to T. parva. Sampled bovines did not show clinical signs of T. parva-associated disease and with test results indicated that the number of subclinical carriers may be high. Attempts to transmit T. parva from infected cattle on Mr Green‟s farm to susceptible cattle were not successful. Transmission from an infected buffalo to a susceptible bovine was successful and transmission of T. parva from a negative-testing buffalo to a susceptible bovine could not be demonstrated. These experiments give some confidence that the tick-transmission methods and diagnostic tests used were reliable. It remains important to consider African buffalo as a possible source of T. parva infection in a cattle herd even when a direct link cannot be established. / Dissertation (MSc (Veterinary Science))--University of Pretoria, 2007. / Veterinary Tropical Diseases / MSc / unrestricted

Thesis (MSc (Veterinary Tropical Diseases)--University of Pretoria, 2009. / Includes bibliographical references. Also available in print format.

Thesis (MSc (Veterinary Science)--University of Pretoria, 2007. / Includes bibliographical references.