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Murdoch University (2014)

Epidemiological studies on bovine fasciolosis in Botswana

Mochankana, Molefe Ernest

Titre : Epidemiological studies on bovine fasciolosis in Botswana.

Auteur : Mochankana, Molefe Ernest

Université de soutenance : Murdoch University

Grade : Doctor of Philosophy (PhD) 2014

Résumé partiel
Fasciolosis, commonly known as liver fluke disease, is a disease of the liver of domestic livestock, principally ruminants, caused by pathogenic trematodes of the genus Fasciola, which comprises two species, F. hepatica and F. gigantica. Fasciola hepatica is the more common and important of the two, with a worldwide distribution, whereas F. gigantica is more restricted, found primarily in warmer parts of the world where it causes tropical fasciolosis in cattle, sheep and goats. Fasciola gigantica infection in cattle is potentially one of the most important parasitoses affecting the productivity of herds in many developing countries by being an impediment to reproduction and growth, causing damage to livers, which can occasionally become inedible for humans and, in some cases, can result in the death of affected animals. The economic importance of fasciolosis is mainly due to direct losses from condemnation of infected livers during meat inspection at abattoirs. The disease is also a zoonosis, however, it is rarely diagnosed in humans. Prior to the study reported in this thesis, little was known on the epidemiology of this parasitic disease in Botswana. Therefore, the main aim for undertaking this study was to determine the prevalence and estimate the economic significance of fasciolosis in cattle, as well as to determine the geographical distribution of the intermediate host snail, Lymnaea natalensis. Lymnaea natalensis is an aquatic snail that has generally been accepted as the intermediate host that plays an essential role in the epidemiology of F. gigantica infection in Africa, even though a miscellany of other Lymnaeid snails can be involved in the transmission of the fluke. The present study determined the prevalence and assessed the economic importance of F. gigantica infections in cattle through retrospective and prospective studies, by acquisition of data from meat inspection records and regular visitation to inspect livers of slaughtered cattle at selected abattoirs, respectively. In addition, a cross-sectional survey of fasciolosis was carried out through a coprological examination of live animals to determine the prevalence in live cattle from six districts in Botswana. This information will be used as the basis for future epidemiological surveillance of this important parasitic disease of ruminants in Botswana. An understanding of the epidemiology of fasciolosis and distribution of the intermediate host would assist in the design of appropriate control programmes in Botswana. The results from the present study have indicated that F. gigantica infection is present in cattle in Botswana, but the prevalence is very low (0.74% ; 95% CI : 0.57, 0.94%) and not widespread as previously anticipated. The disease was present in only one (Central) of the six districts covered by this study, and was localized within the Tuli Block area, in Machaneng village, at the eastern margin of the country. Although the exact geographical origins of some of the fasciolosis-positive cattle was occasionally difficult to ascertain in abattoirs in the south of the country, it was highly likely that they originated from the northern part of the country and were already infected before being moved to the south, where they were eventually sent to the abattoirs. The prevalence reported in this study rank among the lowest, not just in Africa, but the world as a whole, in terms of prevalence, infection intensity and economic impact in cattle. The study also revealed that the only species of liver fluke found in Botswana is F. gigantica. The results of the financial losses demonstrated a low financial burden as a consequence of condemnation of Fasciola-infected livers during the twelve-year period under consideration. These findings suggest that bovine fasciolosis is neither a major cause of liver condemnations at abattoirs nor a significant cause of reduced productivity in cattle in Botswana.

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