Photosensitisation and crystal-associated cholangiohepatopathy in sheep grazing Brachiaria decumbens

Two outbreaks of photosensitivity and jaundice in sheep grazing the grass, Brachiaria decumbens. In West Java in 1983 and 1983 and 1990 are described. Aggregates of acicular clefts and crystals were present in bile canaliculi, bile ducts, Kupffer cells, hepatocytes and in kidney tubules. The number of crystals increased with the length of exposure to the plant and sheep that died had the largest accumulations. These crystalline structures have been reported before in this syndrome, but are similar to those seen in Tribulus terrestris and Panicum spp toxicities.

Photosensitivity in South Africa. VI. The experimental induction of geeldikkop in sheep with crude steroidal saponins from Tribulus terrestris

Geeldikkop was induced in sheep by the oral administration of crude steroidal saponins from Tribulus terrestris. Two of the sheep developed typical lesions of geeldikkop, including birefringent crystalloid material in bile ducts and concentric periductal lamellar fibrosis. The clinical pathological changes in these sheep were also consistent with those of geeldikkop: aspartate transaminase and gamma-glutamyl transferase activities in the sera of both were elevated, and one had bilirubinaemia. A third sheep became photosensitive without typical lesions of geeldikkop in the liver or changes in the activities of liver enzymes before euthanasia. The findings of these trials are consistent with reports from abroad that ovine hepatogenous photosensitization, caused by Agave lechuguilla and Narthecium ossifragum, can be induced with crude saponins from the respective plants.

Microsomal enzymes in lambs and adult sheep, and their possible relationship to alveld

The difference in susceptibility to alveld between lambs and adult sheep may be caused by differences in the microsomal enzyme activities in their livers. There was no difference in NADPH-cytochrome c reductase or 7-ethoxyresorufin-O-deethylase (EROD) activity between ewes, control lambs and phenobarbitone-dosed lambs 3 weeks after dosing ceased. However, aldrin epoxidase activity was at that time significantly highest in the phenobarbitone-dosed lambs and significantly lowest in the ewes. The liver cytosolic glutathione transferase activity was significantly highest in the ewes and significantly lowest in the control lambs at the same time.

[Cobalt deficiency and photosensitivity in a flock of Texel lambs]

In a flock of thirty lambs ten animals showed symptoms of photosensitisation within a short period of time. Soon after treatment with vitamin B12 the symptoms disappeared. Clinical examination, differential diagnosis, treatment and course of the disease are discussed. It is assumed that the lambs suffered from 'white liver disease'.

Photosensitization problems in livestock

Photosensitization is a sunburn-like condition caused by the presence of certain photoactive compounds in the skin when it is exposed to the appropriate wavelength of light. Most photoactive compounds (phototoxic agents) that cause PS in livestock are of plant origin, others are drugs, chemicals, or endogenous porphyrins. Photosensitization is a disease caused by phototoxic xenobiotics, or by acquired or hereditary dysfunction of (1) heme synthesis or (2) PE excretion by the liver. Hepatotoxins, especially those of plant origin, most frequently are the cause of the condition. Photosensitization primarily is a disorder of sheep and cattle, but all classes of livestock are susceptible. Clinical recognition of the syndrome usually presents no difficulty because of the restriction of lesions to areas of skin unprotected from sunlight. Prognosis generally depends on the extent of hepatic injury. The most important elements of treatment are termination of exposure to the photo- or hepatotoxin, protection from light, treatment and prevention of infection and fly strike, and provision of nutritious feed.

Photosensitization of cattle in Montana: is Descurainia pinnata the culprit?

Recurrent photosensitization of cattle in Montana has been blamed on Descurainia pinnata, tansy mustard. Two feeding trials were conducted to determine if tansy mustard was phototoxic. Pen-fed cattle consumed 2.4 and 4.1 kg/hd/day of tansy mustard in the 2 trials, and no photosensitization was detected. Liver clearance of BSP was within normal limits, as were blood chemistry values for AST, CK and GGT. Field cases have confirmed that tansy mustard was present and grazed in pastures where affected animals have grazed. We suspect that other factors may be necessary to predispose cattle to photosensitization by tansy mustard, and future work will attempt to determine the cause of the photosensitization.

Neurological disorders in sheep during signal grass (Brachiaria decumbens) toxicity

Severe neurological dysfunction was observed in sheep 4 weeks after grazing on Signal grass (Brachiaria decumbens). These neurological disorders included the stamping of forelegs, star-gazing, incoordination, head-pressing against the fence and circling movements. Histologically, numerous vacuolations of various sizes were observed in the white matter of the brain giving rise to a spongy appearance.

Clinical biochemistry of sporidesmin natural intoxication (facial eczema) of sheep

The effects of facial eczema, i.e. intoxication by the mycotoxin sporidesmin, were investigated by extensive biochemical screening of serum in 100 controls (A), 31 clinically ill (B) and 219 apparently healthy (C) Manech ewes under field conditions. Dramatic increases of gamma-glutamyltransferase1), alkaline phosphatases, bilirubin, cholesterol, aspartate and alanine aminotransferases, and lactate dehydrogenase confirmed the severity of liver damage in group B, but they were also observed in slightly more than 50% of group C animals. This demonstrated the true extent of the disease, which could be best assessed by the measurement of serum gamma-glutamyltransferase; but since this enzyme was still elevated one year later, it cannot be used as a reliable prognostic parameter.

Experimentally induced photosensitization in cattle with Cooperia pedunculata

Photosensitization was induced in 2 Charolais heifers following administration of a mixture of air-dried, ground, green (75%) and dead (25%) leaves of the south Texas forb, Cooperia pedunculata, and subsequent exposure to sunlight. Plant material used in this study was collected from a pasture where natural cases of primary bovine photosensitization were occurring. Signs of photosensitization were observed in one heifer after 2 doses of plant material--10 g/kg on day 1 and 5 g/kg on day 2. Continued administration of plant material at 5 g/kg/d on days 3, 4, 7, 8, and 9 resulted in severe signs and lesions of photosensitization and death on day 23. A second heifer developed signs of mild photosensitization following administration of plant material at 1.7 g/kg/d for 4 days. This heifer recovered by day 18. Clinical and pathologic findings of this trial were consistent with the primary form of photosensitization observed in natural cases seen in cattle of south Texas exposed to this plant.

Photosensitization of cattle in southeast Texas: identification of phototoxic activity associated with Cooperia pedunculata

A microbiological assay (Candida albicans) was used to screen plants in southeast Texas where bovine photosensitization (PS) of unknown cause was a recurring problem. Phototoxic activity was identified associated with dead leaf tips of Cooperia pedunculata, a native, perennial forb of the Amaryllis family (Amaryllidaceae) from central, southeast, and south Texas and parts of Mexico. A syndrome compatible with naturally occurring PS in cattle was induced in laboratory mice after oral administration of dead leaf material from C pedunculata. Availability and phototoxic activity of dead leaf material of C pedunculata corresponded with occurrence of PS in cattle. Seemingly, C pedunculata was involved in recurring PS.

Kleingrass (Panicum coloratum L.) poisoning in sheep

Twenty-four lambs grazing pastures of Panicum coloratum developed photosensitization secondary to hepatic dysfunction. Lesions were necrosis of scattered hepatocytes, obstruction of small bile ducts and bile canaliculi by small aggregates of birefringent crystals, and accumulation of birefringent crystals in phagocytes within sinusoids. The number of crystals in livers of affected sheep varied, depending on the amount of time of exposure to toxic plants and severity of hepatic abnormalities. Crystals in the liver were soluble in acidified ethyl alcohol, acetic acid, pyridine, chloral hydrate, and methanol, but not in xylene, petroleum ether, diethyl ether, acetone, water, or cold ethyl alcohol. Crystals were not stained by oil red O. There was necrosis of epithelial cells in renal distal convoluted tubules, papillary muscles of the heart, and the adrenal cortex. Lesions of Panicum coloratum-associated disease are similar to those associated with photosensitization induced by Tribulus terrestris, Agave lecheguilla, and Nolina texana.

Prophylaxis of trichostrongylid infection afforded by low-dose phenothiazine given in two successive years to first-season calves on a common area of pasture

Reduced trichostrongylid infection on herbage and in calves was obtained when first-season calves, grazing a common area of pasture, received low-dosage phenothiazine (PTZ) in two successive years. The average daily dose of PTZ was 7.0 or 10.3 mg kg-1 in the first year and, in the second, between 5.0 and 7.0 mg kg-1. The effect on herbage infection was attributed mainly to ovicidal action. Treatment increased weight gain by 22 and 50 to 60 per cent in the respective seasons. The results suggested a cumulative effect produced by treating calves of successive years. Two calves developed PTZ-induced photosensitivity (corneal opacity) in the first season, and two calves in the second season but in the latter, severe bronchopneumonia was believed to be a predisposing factor. To avoid photosensitivity and still maintain adequate drug activity, the daily intake of PTZ should probably be restricted to around 6 mg kg-1.

Crystal-associated cholangiohepatopathy and photosensitisation in lambs

Four outbreaks of hepatogenous photosensitisation occurred in weaned lambs in north eastern Victoria during the summers of 1985 and 1986. Attack rates varied between 7% and 43% and case fatality rates between 60% and 71%. Clinical signs included photosensitisation and jaundice. Serum biochemistry suggested hepatobiliary and hepatoparenchymal damage with impaired renal function. At necropsy livers were an ochre colour and kidneys a mottled brown to khaki. Histopathologically, needle-shaped to lenticular clefts were observed in and around bile ducts and in hepatocytes, hepatic sinusoidal macrophages and renal tubules. Optically active rhomboidal crystals were present in bile sediments. Panicum schinzii was identified as a possible cause in 2 of the 4 outbreaks. The clinical disease was reproduced in 2 of 6 lambs grazed on a toxic paddock. The disease was indistinguishable from geeldikkop except for the fact that Tribulus terrestris was not present on any of the 4 farms.

Ovine hepatogenous photosensitivity caused by the plant Nidorella foetida (Thunb.) DC. (Asteraceae)

Following a field outbreak of hepatogenous photosensitivity in sheep, an identical condition was reproduced experimentally by dosing 2 sheep with green, homogenized, Nidorella foetida material, collected from the camp where the outbreak occurred. This is a rare, unpalatable, aromatic shrub found in swampy places in the south-western Cape Province. The main lesion was a hepatosis, characterized by peripheral coagulative necrosis and midzonal degeneration in the 2 acute cases and mild bile duct proliferation and hepatic regeneration in the more chronic field case. Botanical, toxicological, clinical and pathological data are given.

Hepatic enzyme changes in bovine hepatogenous photosensitivity caused by water-damaged alfalfa hay

In the winter of 1983, practitioners reported extensive photosensitization in 7 herds of cattle. All herds had a history of having been fed water-damaged alfalfa hay. A cow from one herd was referred to the veterinary teaching hospital at Oklahoma State University. In this herd of approximately 40 adult Polled Herefords, all cattle had had some degree of clinical involvement over the past 4 to 6 weeks. Clinical signs included scaling and erythema of sparsely haired skin, muzzle, and teats, as well as icterus, anorexia, and weight loss. One cow died, and the remaining cattle recovered over an 8- to 10-week period after removal of the hay from the ration. In the referred cow, values for total and conjugated bilirubin, BUN, creatinine, sorbitol dehydrogenase, serum alkaline phosphatase, serum aspartate transaminase, and serum gamma-glutamyl transferase were higher than normal. In the herd of origin, extremely high serum gamma-glutamyl transferase values (180 to 1,400 IU/L) persisted (normal, 2 to 35 IU/L). Feeding the same alfalfa hay to 2 clinically normal cows reproduced the syndrome. The characteristic hepatic lesion was bile duct necrosis, with secondary bile duct hyperplasia.