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The development of a new strategy for the sustainable control of bovine trypanosomosis in Southern AfricaVan den Bossche, Peter 22 September 2010 (has links)
Previously, strategy formulation for large-scale eradication of tsetse in southern Africawas dominated by straightforward technical considerations. The current shift to localised control of tsetse-transmitted bovine trypanosomosis has changed the emphasis from the vector to the disease. Nagana remains the main reason for intervening but control methods will differ according to the local situation and interventions will be restricted to those areas where the disease is present. As a result, the technical criteria to be considered will differ substantially from those considered in the planning for large-scale eradication. First, a clear picture of the extent and magnitude of the bovine trypanosomosis problem is required. Second, the selection ofthe most efficient intervention methods will vary according to the local epidemiological situation. Hence, the different epidemiological situations need to be identified and the effectiveness of available control methods needs to be evaluated in each of the situations. Finally, the long-term sustainability of an intervention will depend, to a large extent, upon the socio-economic impact of the disease and perceived benefits accruing from its control. Tsetse-transmitted bovine trypanosomosis occurs in large areas of Malawi, Zambia,Zimbabwe and Namibia. The epidemiology of the disease differs substantially between areas. On the plateau of eastern Zambia, for example, cattle are kept in a tsetse infested area. Because of the encroachment of people and cattle into the tsetse infested area and the concomitant reduction in the number of game animals, tsetse have become highly dependent on cattle as their source of food. As a result, the distribution and density of tsetse is determined largely by the distribution and changes in the distribution or grazing pattern of cattle. Trypanosoma congolense is the main.trypanosome species in tsetse and cattle. The prevalence of congolense-type trypanosomal infections in tsetse undergoes little variations between months and is affected mainly by the average age of the tsetse population. The incidence of bovine trypanosomosis is significantly correlated with the density of the tsetse population.Bovine trypanosomosis is also prevalent in areas where cattle are kept adjacent to a tsetse-infested zone or where tsetse occasionally invade a tsetse-free area. In Malawi,for example, the main foci of bovine trypanosomosis are located adjacent to tsetse infested national parks, game reserves or forest reserves. Bovine trypanosomosis also occurs far outside the known tsetse foci because of the seasonal movement of tsetse,along rivers or because of, often small, undetected tsetse foci. Such foci have been detected in Malawi and in Zimbabwe. In most of the areas, bovine trypanosomosis is caused by T congolense. However, the prevalence of T vivax infections is high in areas where tsetse take a large proportion of feeds on game animals. Please read the full abstract in the section 00 front of this document. / Thesis (PhD)--University of Pretoria, 2000. / Veterinary Tropical Diseases / unrestricted
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Bovine trypanosome prevalence at game/livestock interface of Hluhluwe-Umfolozi Game Reserve in Kwazulu-Natal Province, South AfricaNtantiso, Lundi Norman 22 November 2012 (has links)
In South Africa, trypanosomosis also known as Nagana, transmitted by Glossina brevipalpis and G. austeni, is the major cause of anaemia and chronic debilitating condition in cattle. There is a wealth of entomological information on the ecology of the two tsetse species generated following the devastating outbreak in cattle due to Nagana in 1990. However, it is unfortunate that these entomological data has not been supported by parallel studies on the epidemiology of the disease. Therefore, the present study presents the first intensive epidemiological investigations since 1990 to address the problem of animal trypanosomosis in South Africa. The relationship between trypanosomes herd average prevalence (HAP), herd average anaemia (HAA) and herd average packed cell volume (HA-PVC) were investigated in cattle in three communal diptanks located by the Hluhluwe-uMfolozi Game Reserve by regular monthly sampling for 15 months. The tsetse challenge with G. brevipalpis in two of the diptanks, Mvutshini and Ekuphindisweni, was high but low in the third (Ocilwane). In addition, G. brevipaplis and G. austeni coexist in Mvutshini diptank. This high and low tsetse challenge presented different disease scenarios. Cattle at Mvutshini and Ekuphindisweni diptanks had the highest HAP of 12.3% and 8.9%, respectively, which is significantly different (p = 0.001) from the HAP obtained from cattle at Ocilane (2.9%). Both cattle herds at Mvutshini and Ekuphindisweni diptanks also had the highest HAA, 27.7 and 33.4%, respectively, while cattle at Ocilwane had the lowest, 11.1% (statistically different; p = 0.001). Conversely, cattle at Ocilwane diptank had the highest HA-PCV, ranging between 29-32% while cattle at Mvutshini and Ekuphindisweni diptanks had the lowest HA-PCV (24-29%). The interaction between HAP and HAA is significant (p = 0.021). The overall effect of HAP on the animal health condition is clearly demonstrated when comparing the anaemia in trypanosomes infected and uninfected cattle at the 3 diptanks. Fifty percent, 63% and 100% of trypanosomes infected cattle were anaemic at Mvutshini, Ekuphindisweni and Ocilwane diptanks, respectively. In comparison, the prevalence of anaemia in uninfected cattle in the 3 diptanks was 20, 30 and 10% at Mvutshini, Ekuphindisweni and Ocilwane diptanks, respectively. By combining the data from the 3 diptanks (1,800 observations), the overall HAA in infected and uninfected cattle was 62 and 20%, respectively The results of trypanosomes seasonal surveys conducted at 7 communal diptanks in tsetse infested areas, showed that all cattle at the diptanks were infected with trypanosomes with mean HAP and HAA of 10.3 and 35.3%, respectively. The highest HAP (range 15-31%, n=4) was recorded in Ngwenyambili diptank. This high infection in the cattle herds produced high values of HAA (50%; range 40-60). The infection rate with trypanosomes in G. brevipalpis caught from the field showed immature infections in the midgut of 3.5% (16/458) while only one fly was found with mature infection in the proboscis (1/458, 0.22%). Very few G. austeni were collected (total of 9) during the same period and dissected. The infection rate with trypanosomes immature and mature infections was found to be very high; 5/9 (55.5%). Blood samples were collected from a total of 132 buffaloes randomly immobilized for tuberculosis testing by the Hluhluwe-uMfolozi Game Reserve Authority. Two buffaloes were found to have T. congolense infection by the buffy coat technique. The presence of trypanosomes infected buffaloes in this study confirms the occurrence of sylvatic cycle at the tsetse/livestock/Hluhluwe-uMfolozi Game Reserve, thus, presenting a high risk of serious disease to cattle. The objective of the study on the strategic treatment of trypanosomosis conducted on one farm in endemic area was to treat adult cows and calves at an arbitrary HAP threshold before the disease produces any clinical symptoms or production losses. The strategic use of ethidium bromide and novidium chloride produced attractive results whereby cattle were protected for an extended period of 3 to 6 months with no development of anaemia during this period. Therefore, two to four treatments per year may be sufficient to keep cattle productivity on the farm under the tsetse challenge Copyright / Dissertation (MSc)--University of Pretoria, 2012. / Veterinary Tropical Diseases / unrestricted
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