Studies on the pathophysiology of chronic ovine fascioliasis

Holmes, P. H (1970) Studies on the pathophysiology of chronic ovine fascioliasis. PhD thesis, University of Glasgow.

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The work described In this thesis Is concerned with the pathophysiology of chronic Fasciola hepatica infections of sheep. In this study various isotopic labelling techniques were used to investigate In particular the cause of the anaemia and hypoproteinacmia, which are invariably present in diseased animals. The cause of the blood changes has been the subject of considerable debate over a number of years, and various divergent theories have been put forward. With the advent of satisfactory isotopic methods it finally became possible to study the turnover of both red cells and plasma proteins In the parasitized Shoop, and to investigate the routes of excess less of those blood constituents. The thesis is divided into four sections. Section I. Studies on the Anaemia Produced in Sheep Chronically Infected by Fasciola Heoatica The first part of this section describes the use of 51Cr-labelled red cells in both experimentally Infected and normal sheep. It was found that the parasitized animals showed an increased rate of disappearance of red cells from the circulation, and that this less could be accounted for by an Increase in the faecal excretion of the isotope. This strongly suggested that the causation of the anaemia was a substantial loss of blood into the gut of the infected animals presumably via the bile. secondly, the ferrokinetics of infected and normal she Wore studied using 59Fe. The results Indicated that erythropolesis was greatly increased in the Infected animals as Illustrated by elevation of the 59Fe plasma disappearance rates, and red cell utilisation of 59Fe. In addition, the degree of reabsorption of haemoglobin iron was measured using red cells simultaneously labelled with 59Fe and 51Cr. It was found that only in the most severely infected sheep was significant reabsorption occurring. Section II Metabolic Studies of the Plasma Protein Changes Associated with Chronic Ovine Fascioliasis Firstly, albumin metabolism was studied using 131I-albumin In both Infected and normal sheep. It was found that the hypalbuminaemia in the diseased animals was associated with a significant hypercatabolism of albumin. From indirect evidence it was suggested that the hypoalbuminaemia was caused by on excess loss of plasma proteins into the gut, presumably associated with the red cell loss. Secondly, three separate techniques for the detection of gastrointestinal protein loss ware used in infected and control animals. All the methods, viz 131I-PVP, 95Nb-albumin and 51Crc1s, consistently showed that there was a significantly greater loss of plasma into the gastrointestinal tract in the parasitized sheep. By the use of a double labelling technique it was found that a close correlation existed between the hypoalbuminaemia, hypercatabolism, and increased plasma protein loss in the infected sheep. Lastly, the metabolism of albumin and of immunoglobulin were studied simultaneously, end it was found that the synthetic rate of immunoglobulin was increased to a greater extent than that of the albumin in the infected sheep. It was suggested that the causes of the hypergammaglobulinaemia and hypoalbumlnaemia associated with the disease are the results of the inability of albumin synthesis to be increased to the same extent as that of immunoglobulin, in the face of the substantial plasma losses occurring in the infected animals. Section III. Studies of the Onset of the Pathophysiological Changes Following Infection Red cell and albumin turnover were studied for thirteen weeks following infection of sheep with F. hepatica. The results showed that the commencement of the red cell leak and rise in albumin catabolism were associated with the arrival of the adult flukes in the bile ducts. In addition it was found that the initial anaemia and hypoproteinaemla sometimes associated with the migratory phase of the Infection were probably due to damage to hepatic cells and rupture of small blood vessels in the liver parenchyma by the migrating flukes. Section IV. Studies of the Changes in Red Cell and Albumin Turnover Following Anthelmintic Treatment of Fluke-infected and Control Sheep Following anthelmintic treatment of fluke-infected sheep it was found that there was a marked rise in both serum albumin and venous haematocrit. Those changes were as with both a dramatic fall in red cell loss into the gut, and decline in albumin catabolism once the flukes were removed. The latter effect was considered to be in part due to the cessation of the blood lost, and in part to decreased albumin synthesis presumably due to a homeostatic mechanism. The results of the work described add considerably to the information regarding the pathophysiological mechanisms occurring in fascioliasis, and are all consistent with the theory that the major factor in the aetiology of the blood changes is loss of blood into the gastrointestinal tract.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Additional Information: Adviser: W Mulligan
Keywords: Animal diseases
Date of Award: 1970
Depositing User: Enlighten Team
Unique ID: glathesis:1970-73160
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 14 Jun 2019 08:56
Last Modified: 14 Jun 2019 08:56

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