Thumbnail Image

Theses

Browse

1998 - 19993
Reset filters
Subject: Veterinary Pathology × Start date: 1997 × Thesis Type: Ph.D ×
Reset filters

Search Results

Now showing 1 - 3 of 3
  • Thumbnail Image
    ThesisItemOpen Access
    Prevalence and patholoygy of polioencephalomalacia in goats
    (Centre of Excellence in Pathology, College of Veterinary and Animal Sciences,Mannuthy, 1999) Divakaran Nair N; Rajan A
    Polioencephalomalacia (PEM) is a significant emerging diseases problem in goats. Although, PEM in goats was recognized and reported as early as 1956, its etiology is poorly understood and symptomatology, pathological features and therapeutic approach have not been well defined and documented. Hence an investigation was undertaken to assess the prevalence of the disease based on the data available from 76 Veterinary hospitals of the state for a period from 1991 to 1994. This data documented revealed an increasing trend in the occurance of the disease and significantly high incidence was recorded in the first five months of which the peak incidence was observed in the month of April. Spontaneous cases of the disease were studied in detail and experiments were conducted taking goat as a model using selected incriminating agents such as Amprolium (350mg/kg body weight), Amprolium and rice gruel (350 mg/kg and ad libitum rice gruel), rice gruel (ad libitum), sodium sulphate (150 mg/kg body weight followed by 500 mg/kg body weight on the 10th day) BHC (2.5 mg/kg followed by 5 mg/kg body weight on the 10th day) and Ficus tsiela Roxb. The experiment was for a period of 45 days. Symptomatology, weight of the animals at fortnightly intervals, weight of the brain, CSF protein concentration, brain autofluorescence, gross and histopathological alterations of the brain and ultrastructural pathology were the markers utilized for evaluating the disease processes. The sodium sulphate, BHC and Amprolium and rice gruel treated group showed symptoms and lesions more or less similar to the spontaneous cases. Only few animals in each group developed the disease such as two in amprolium and rice gruel treated group, four in BHC treated group and three in sodium sulphate group. This showed that individual idiosyncracy plays an important role in the manifestation of the disease. The symptoms developed at different latent periods were not progressive as compared to the spontaneous cases where the symptoms were progressive. The symptoms included lethargy, depression, knuckling at the fetlock, frequent tremors, opisthotonous and loss of eye preservation reflex. Blindness was seen in one of the natural cases. The histological lesions of the brain in all the cases were comparable in different segments of the brain. Mostly it was characterized by diffuse laminar cortical degeneration and necrosis, occasional neuronal swelling glial cell reaction and white matter vacuolation. Vascular changes predominated in the sodium sulphate group and also in the natural cases. There was glial cell response in the form of nodules in sodium sulphate group and natural cases. A predominant perivascular and neuropil accumulation of lymphocytes, gitter cells and monocytes were seen in the natural cases. These were considered as secondary deposition following a toxic degenerative neuropathy. The necrotic focicould well be delineated in few of these cases by the bluish or creamy autofluroscence of the affected brain, but was not found to be of any primary diagnostic value as all the affected brain did not show flurescence. Ultrastructural investigation revealed the basic reaction of the brain tissue to be similar in both the experimental and natural cases except for their intensity. Ultrastructural lesions were characterized by neuronal swelling, membrane lysis, segregation of the filamentous and granular component of nucleolus, cytoplasmic oganellar damage such as fragmentation of RER, partial degranulation of ribosomes, mitochondrial of RER, partial degranulation of ribosomes, mitochondrial swelling, cristolysis and complete disappearance of organelle. Neuropil spongiosis and splitting of myelin at the intraperiod line and formation of multiple vacuolations of the white matter were characteristic. From this observations it was clearly delineated that the primary insult was a biochemical one which caused much damage to the volume control mechanism of the cell and subsequent cellular damage. The CSF protein evaluation revealed high protein level in the spontaneous cases whereas in the experimental cases, the concentration remained within the normal range indicating that it has no diagnostic value. In this investigation it has not been possible to induce PEM with Amprolium even at a dose rate of 350 mg/kg bodyweight and it was proved that amprolium is not a cause for PEM. Rice gruel ad libitum was found to be tolerated by the animal except one which showed dullness and abdominal distension towards the end of the experiment. Diffuse neuronal degeneration was observed in the brain of this animal. Based on this observation it was concluded that rice gruel consumption every day as a component of the concentrate feed in goats might not cause any detrimental effects and the problem comes only when it is fed in large quantities on a single day. Ficus tsiela Roxb. Though produced vascular damage and diffuse neuronal degeneration in one of the experimental animals, goats were found to be highly resistant to ficus tsiela Roxb. Toxicity and the variation in the susceptibility of different species to this toxicity was brought to light. From this investigation it was also clarified that sodium sulphate, BHC, rice and amprolium could be initiating agents of PEM under certain circumstances and no single cause seems to be responsible for PEM.
  • Thumbnail Image
    ThesisItemOpen Access
    Immunopathological response of the duck (Anas platyrrhyncos domesticus) to sublethal dose of selected agro-chemicals
    (Centre of Excellence in Pathology, College of Veterinary and Animal Sciences, Mannuthy, 1998) Vijayan, N; KAU; Valsala, K V
    The study was conducted with the objective of assessing the teratologic, embryotoxic and immunopathologic effects of two agro-chemicals carbofuran and 2,4-D used in agricultural operations, on duck embryos and ducklings. The embryological studies included the observation on the embryonic defects and weight of the lymphoid organs along with the histopathologic and ultrastructural studies of the lymphoid organs like the bursa, spleen and thymus. The results showed that the contamination of the eggs with the above chemicals caused moderate deleterious effects on the lymphoid system, though no teratologic effects could be observed. The histological and ultrastructural changes also confirmed the deleterious effects at the tissue and cellular level. The immune system of the ducks exposed to the above chemicals for two different durations were assessed using a battery of tests. The humoral immune system was assessed based on the body weight, lymphoid organ weight, haematological evaluation, serum biochemical evaluation and the evaluation of HI titre against NDV. The cell-mediated immune system was assessed by the skin reactivity tests to DNCB and PHA. LMIT and GVHR were also employed to assess the cell-mediated immune system. The histological and ultrastructural studies were also conducted after six weeks and ten weeks of the experiment. The assessment of the immunological profile employing these elegant tests revealed that these agro-chemicals caused mild but significant suppression of the cell-mediated and humoral immune response. By this investigation it was clarified that these agro-chemicals have mild to moderate degree of immunotoxic effect when exposed for a short duration, but the changes were severe when exposed for longer duration. From the .studies, it was demonstrated that the immunotoxic effect of carbofuran is more compared to 2,4-D (herbicide) and the changes were dose and time dependent.
  • Thumbnail Image
    ThesisItemOpen Access
    Comparative pathology of aflatoxicosis in the duck and fish with special reference to the immune system
    (Centre of Excellence in Pathology, College of Veterinary and Animal Sciences, Mannuthy, 1998) George, K C; KAU; Rajan, A
    Pathological responses of ducklings and juvenile Indian carps Labeo rohita in experimental aflatoxicosis were studied. Both the ducklings and fishes were given sublethal toxic levels of aflatoxin B1. The ducklings and fishes were exposed to aflatoxin B1 for 2, 4, 6 and 8 weeks respectively and they were sacrificed at the end of the experiment and samples for haematological, serum protein profile, histological and ultrastructural investigations were collected. Pathological changes were studied with special reference to the humoral and cell – mediated immune responses. Among the haematological parameters, total erythrocyte count, total leucocyte count and packed cell volume were found to be reduced in fishes. The reduction was directly proportional to the duration of aflatoxin treatment. In the fishes, there was moderate fall in the total proteins and the albumin. The electrophoretic picture of the serum of the fishes also showed fall in the albumin fractions. In the ducks there was severe reduction in the albumin level and this was reflected in the electrophoretic picture as well as A: G ratio. In both the ducks and the fishes humoral immune response was suppressed due to aflatoxin treatment. Antibody titres against sheep RBC fell in the experimental groups of the ducks and the fishes. The cell - mediated immunity was assessed in the ducks and the fishes by intradermal PHA – M response, count of ANAE positive lymphocytes in the peripheral blood and leucocyte migration inhibition test. In the ducks and the fishes of the aflatoxin treated groups, there was significant fall in the skin sensitivity response and also in the number of ANAE positive lymphocyte. These findings clearly established that CMI was suppressed by aflatoxin . The histological and electron microscopic studies revealed severe degenerative and necrotic changes in the hepatocytes in the ducks and fishes. However, hepatosis was more severe in the fishes whereas in the ducks biliary proliferation was a prominent feature. The hepatic changes could be correlated with the changes in the plasma protein profile in the duck and the fish. The lymphoid organs of the duck and the fish (thymus, spleen, bursa of Fabricius and anterior kidney) showed extensive necrosis and degenerative changes. These changes clearly established the reason for the immunosuppression and low leucocytic counts observed in the aflatoxin fed ducks and fishes. The kidneys of the duck and the fish exhibited nephrotic changes. Degenerative changes were also observed in the brain and the heart of the two species. The pathologic changes due to aflatoxicosis were comparable in the ducks and fishes.