Some aspects of the pathophysiology of parasitic infections with particular reference to ovine haemonchosis
Başlık:
Some aspects of the pathophysiology of parasitic infections with particular reference to ovine haemonchosis
Yazar:
Karugah, Ariel Kabaara, author.
ISBN:
9780438053380
Yazar Ek Girişi:
Fiziksel Tanımlama:
1 electronic resource (234 pages)
Genel Not:
Source: Dissertation Abstracts International, Volume: 76-08C.
Advisors: Peter Holmes.
Özet:
This thesis consists of six reviews and a dissertation. Factors involved in the epidemiology and pathogenesis of haemonchosis are reviewed in Chapter 1. The epidemiology is essentially governed by prevailing climatic conditions and the marked egg-laying capacity of H. contortus. Host responses to infection vary considerably depending on breed and age as well as immunological status. In susceptible animals the principal pathogenic effects are closely attributable to the blood-sucking activities of developing and adult stages leading to anaemia and hypoproteinaemia. Anaemia is singled out as the most important factor affecting the pathogenesis of trypanosomiasis (Chapter 2) and most authors describe it as normocytic normochromic with a tendency to be macrocytic normochromic. Though its aetiology is not resolved. the possible mechanisms involved are described. The possible role played by immunosuppression is also discussed. The merits and limitations of radioisotopes used to study parasitic anaemias; procedures such as labelling with radioisotopes post-injection treatment of samples, calculations and inteirpretation of results are discussed in Chapter 3. Anaemia of fascioliasis, haemonchosis, trypanosomiasis, schistosomiasis and ancylostomiasis are discussed to illustrate how, by using radioisotopes, the aetiology and salient features of parasitic anaemia have been studied. Red cell destruction, dyshaemopoiesis, haemodilution and possibly nutritional status are the main causes implicated. A similar protocol is followed in the case of parasitic hypoproteinaemias (Chapter 4). Hypercatabolism of plasma proteins and plasma leak as illustrated by fascioliasis, ostertagiasis, haemonchosis and schistosomiasis are the salient features. Opinion on the role of nutritional status regarding establishment of parasitic infections is divided (Chapter 5) but there is general agreement that poorly fed animals tend to be more susceptible to the effects of an established infection. Further, whether or not infection depresses feed digestibility is not resolved but feed utilisation for growth is thought to be depressed - perhaps reflecting disturbances in post-absorptive nitrogen metabolism. Development of a vaccine against haemonchosis and trypano-somiasis is described as a distant possibility (Chapter 6). In the case of haemonchosis this is due mainly to the poor immune response, especially in laubs under 6 months of age, and the possibility that, under grazing conditions, a state of acquired immunologic immaturity develops. Whilst in trypanosomiasis the fundamental problem is antigenic variation. This is further complicated by the poorly understood immunosuppression which is closely associated with trypanosomiasis. The objective of the study in Chapter 7 was to compare and relate to certain epidemiological observations the production performance of naturally grazing Red Kasai and Merino sheep in Kenya, sub-divided into drenched (rotating) and non-drenched (permanent) flocks. The superiority of Red Kasai over Merino was (a) confirmed regarding the ability to maintain lover faecal egg counts; and (b) suggested regarding the ability to gain weight both under good and poor pasture conditions, and a slightly higher twinning rate. The benefits of drenching were generally apparent, e.g. slightly higher litter size and generally better weight gains in drenched sheep. Nutritional status wasthought to have played a bigger role than the level of infection.
Notlar:
School code: 0547
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Yer Numarası | Demirbaş Numarası | Shelf Location | Lokasyon / Statüsü / İade Tarihi |
---|---|---|---|
XX(684458.1) | 684458-1001 | Proquest E-Tez Koleksiyonu | Arıyor... |
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