Accumulation of Sapogenin Conjugates and Histological Changes in the Liver and Kidneys of Lambs Suffering from Alveld,a Hepatogenous Photosensitization Disease of Sheep Grazing Narthecium ossifragum

Sixteen lambs exhibiting hepatogenous photosensitization (alveld) after grazing pasture containing Narthecium ossifragum and seven nonphotosensitized lambs grazing the same pastures were studied. All the alveld-affected lambs revealed liver damage dominated by single cell necrosis, portal fibroplasia and bile duct proliferation. Crystalloid clefts were demonstrated in the bile ducts of two and in the hepatocytes and Kupffer cells of nine photosensitized lambs. Plasma bilirubin concentration was severely increased in ten of the cases of alveld whereas the activity of aspartate aminotransferase was moderately to severely increased in seven cases. The activity of glutamate dehydrogenase was moderately elevated in one of the photosensitized lambs. The main histopathological findings in the kidneys from the alveld-affected lambs were dilated tubules, often with eosinophilic material in the tubular lumina. Regenerative changes were seen in a large proportion of the renal sections. Elevated plasma concentrations of urea and creatinine, and the renal histopathological changes, suggested that the photosensitized lambs had been through a phase of renal injury. Analysis of the free and conjugated sapogenin content in liver tissue and bile was performed by gas chromatography–mass spectrometry. There were significantly higher concentrations of conjugated episapogenins in both the liver and bile in the alveld-affected lambs than in the nonphotosensitized lambs.     

Failure to induce toxicity in lambs by administering saponins from Narthecium ossifragum

It has been suggested that saponins produced by Narthecium ossifragum (Bog asphodel) may be the direct cause of the toxicity leading to the hepatogenous photosensitivity disease alveld seen in Norwegian lambs. Lambs fed large quantities of freeze-dried N. ossifragum did not develop alveld. Chemical investigations on the freeze-dried material and fresh N. ossifragum showed no difference in their saponin content. These results indicate that alveld is not caused solely by the saponins produced by N. ossifragum.     

Glycogen accumulation and histological changes in the livers of lambs with alveld and experimental sporidesmin intoxication

Alveld is a hepatogenous photosensitization disease seen in lambs grazing Narthecium ossifragum pastures in Norway. Mycotoxins, possibly sporidesmin, have been suspected to cause the liver damage in alveld as in facial eczema. The histological changes in the liver of alveld cases and in lambs photosensitized after experimental sporidesmin intoxication were compared. The liver damage characterized by necrosis in single centrilobular hepatocytes, was of the same type in both conditions. Minor to moderate portal fibroplasia and bile duct proliferation were almost always present. Accumulated glycogen was seen in hepatocytes in the centrilobular areas. This was significantly correlated to the enzymatically measured glycogen content and there was good correlation between parenchymal damage and glycogen accumulation. The glucose-6-phosphatase and glycogen phosphorylase activities were normal. These findings indicate that parenchymal damage, rather than obstruction of the bile ducts, caused the retention of phylloerythrin both in alveld cases and in experimentally sporidesmin-intoxicated lambs. The accumulation of glycogen could not be explained.Abbreviations HE haematoxylin and eoson - PAS periodic acid Schiff - EDTA ethylene diamine tetracetic acid     

Fungi onNarthecium ossifragum leaves and their possible involvement in alveld disease of Norwegian lambs

Spores ofPithomyces chartarum (Berk. & Curt.) M.B. Ellis were only rarely seen on leaves ofNarthecium ossifragum (L.) Hudson collected in summer from five areas in western Norway in which alveld, a photosensitization disease of lambs, is endemic.Cladosporium magnusianum (Jaap) M.B. Ellis was found on all 118 leaf samples collected in the summers of 1990 and 1991. The hypothesis thatP. chartarum contributes to the aetiology of alveld could not be supported, but it is possible thatC. magnusianum may have a role in the causation of the disease.     

Summer Variation in the Concentration of Steroidal Sapogenins in and the Degree of Fungal Infection on Narthecium ossifragum plants from Møre og Romsdal County,Norway

Thirty-nine leaf samples ofNarthecium ossifragum collected from eight sites in More og Romsdal County, Norway, during June–September 1997 and 41 leaf samples collected at five sites in the same county during June–August 1998 were analysed for the concentrations of steroidal sapogenins using GC-MS. The 1998 samples were also examined for fungal elements (conidia and hyphae) after incubation in a moist chamber for 10–14 days. The highest 1997 and 1998 leaf sapogenin concentrations (4881 and 7115 mg/kg dry matter, respectively) were 13–14 times greater than the lowest sapogenin concentrations found (344 and 531 mg/kg dry matter, respectively). The results did not reveal systematic differences in sapogenin concentrations between the two seasons, or between samples harvested early or late in the same seasons, or between sapogenin concentrations in plants harvested at different sites.Cladosporium magnusianum was the predominant fungus found in the samples. The degree of fungal infection on the samples was in generally low, but the number ofC. magnusianum colonies in the moist chamber preparations and fungal elements (conidia and hyphae) in leaf washings and on leaves tended to increase with time. Factor analysis and multiple regression analysis performed on the chemical and fungal results suggest that sporulation may have occurred in the fungi in response to increase in sapogenin concentrations.     

Sapogenin Levels in <Emphasis Type="Italic">Narthecium ossifragum</Emphasis> Plants and <Emphasis Type="Italic">Ovis aries</Emphasis> Lamb Faeces during Two Alveld Outbreaks in Møre og Romsdal,Norway, 2001

The proposal that saponins produced by the lily bog asphodel (Narthecium ossifragum) may be the direct cause of the hepatogenous photosensitization disease alveld seen in Norwegian lambs was investigated by comparing sapogenin levels in two control and two toxic pastures, and in faeces from lambs grazing the four pastures in the Halsa and Surnadal municipalities, Møre og Romsdal county, Norway. Generally similar levels of sapogenins, determined after hydrolysis of parent plant saponins, were found in Narthecium leaves collected in June/July 2001 from the two alveld outbreak areas and two nearby control areas. Differences in the median sapogenin levels determined for leaf samples in outbreak and control areas were not statistically significant. The total level of free and conjugated sapogenins in faeces recovered from the rectums of lambs grazing the outbreak and control pastures areas varied greatly. The results obtained do not support the hypothesis that a dose–response relationship exists between Narthecium saponin levels and the occurrence of alveld outbreaks.