Hepatogenous photosensitivity diseases in South Africa

Various hepatogenous photosensitivity diseases of ruminants in South Africa, caused by plants, fungi and an alga, are described. Information is given on botanical, mycological, toxicological, clinical and pathological aspects of the diseases. The intoxications were grouped according to the primary site of involvement and type of lesions in the liver. The aetiology, pathogenesis, and diagnosis of these conditions received special attention and the most important features are illustrated in colour.

Suspected facial eczema in sheep in the central Orange Free State

Facial eczema is known to occur in the Humansdorp district of the Cape Province. During June 1982-January 1984, 5 outbreaks of hepatogenous photosensitivity occurred in sheep in central districts of the Orange Free State. In one of these outbreaks a diagnosis of suspected facial eczema was made histologically.

A syndrome of hepatogenous photosensitisation, resembling geeldikkop, in sheep grazing Tribulus terrestris

Two outbreaks of photosensitivity disease occurred in weaner sheep in south western New South Wales during early autumn 1982. In each instance there was a history of access to the annual herb, Tribulus terrestris and both the clinical and pathological findings were consistent with geeldikkop, a major disease in the Republic of South Africa. The prevalence rates of clinical cases were 21 and 37%, while the case fatality rates approached 70%. Clinical signs were dominated by jaundice and photosensitisation. Ochre and khaki discolouration were present in the liver and kidneys, respectively. Histopathologically, the most characteristic lesion was the presence of acicular, cholesterol-like clefts in the lumens of bile ducts and in the cytoplasm of hepatocytes and Kupffer cells. Similar structures were also evident in the lumens of nephrons in association with segmental hyperplasia of the neighbouring tubular epithelium. The possible pathogenesis of the hepatogenous photosensitisation and its resemblance to geeldikkop are discussed.

Noninfectious skin diseases of cattle

The noninfectious bovine skin disorders can best be summarized by four factors: environmental, nutritional, congenital, and neoplastic. This article has attempted to address the etiology, treatment, and prevention of most of these noninfectious diseases.

Alveld-producing saponins. II. Toxicological studies

The phototoxic lamb disease alveld, prevalent in South-Western Norway, is caused by ingestion of Narthecium ossifragum. Earlier studies have shown that peroral administration of large amounts of crude saponins from this plant elicits the disease. Such saponins have now been purified further by 2 different methods (A and B). Two A type preparations resulted in alveld when fed to 2 lambs. The most highly purified preparation (type B) did not cause alveld in the 2 lambs tested. Lambs vary, however, in their susceptibility to the disease. Both types of preparations led to increases in serum aspartate aminotransferase, bilirubin and 5′-nucleotidase in rats when injected intraperitoneally in amounts of 50 or 100 mg/kg body Weight. Cannulation of the bile duct showed that injected saponins reduced both the volume of bile and the amounts of bilirubin and bile acids excreted. Histological changes seen in the light microscope were, except for the most peripheral parts of the liver, hardly noticable. These observations support the view that saponins are the liver-toxic agents responsible for alveld. The possibility is discussed that the effect arises through a change in the lipid environment of carrier-mediated transport systems.

Kochia scoparia poisoning in cattle

Cattle consuming only high-sulfate water (2.3 g/L) and Kochia scoparia in a marginal pasture in southeastern Colorado were periodically monitored by serum chemical profiles. Serum glutamic oxaloacetic transaminase, serum sorbitol dehydrogenase, and serum bilirubin values were abnormally high over extended periods, suggesting chronic toxicosis, but the toxicosis seemed accentuated after substantial rains, when plant growth was accelerated, and flowering, pollination, and early seed development were occurring. Clinical disease was manifested primarily as photosensitization. Polioencephalomalacia was also produced. Evidence of a thiamin-destructive principle in K scoparia was obtained.

Outbreaks of photosensitisation and deaths in cattle due to Myoporum aff. Insulare R. Br. toxicity

Outbreaks of photosensitisation and deaths in cattle on 5 farms in Victoria occurred following access to Myoporum affinity insulare. Signs were observed 2 to 6 days after access to myoporum trees or pruned branches and included depression, anorexia, photosensitisation, constipation, agalactia, jaundice, and mucosal petechiation. Serum gamma glutamyl transferase and aspartate amino transferase levels were elevated in all cases. Gross findings in fatally intoxicated cows consisted of widespread haemorrhages and pale yellow mottling of the liver. Distinctive histological lesions of periportal hepatic necrosis and bile duct proliferation were seen in all cases. An 8-month-old heifer given 30 g/kg fresh minced leaves by stomach tube died approximately 70 h after initial dosing. Post-mortem findings of widespread haemorrhage and hepatic periportal necrosis and bile duct proliferation were identical to those of field cases.

Phototoxic effect of Thamnosma texana (Dutchman's breeches) in sheep

Oral exposure of sheep to the airdried, aerial portions of Thamnosma texana (Dutchman's breeches) resulted in severe photosensitization. Sheep fed the plant at 9 or 12 g/kg of body weight/day and held in direct sunlight exhibited signs of phototoxicosis within 24 to 48 hours. The clinical signs manifested were increased body temperature; photophobia; edema of the muzzle, ears, and vulva; keratoconjunctivitis with edema of the cornea; and exudative dermatitis of the skin of the ears, muzzle, and vulva. Lesser dosages of the plant produced similar effects after several days, except that corneal edema and opacity were not seen. Histopathologic studies indicated no hepatic lesions, consistent with primary photosensitization. The photosensitizing effects of T texana can be attributed to the presence of photosensitizing linear furocoumarins (psoralens) in the plant.

Bog asphodel (Narthecium ossifragum) as a cause of photosensitisation in lambs in Norway

In a five year experiment, 195 lambs and their dam were kept on four plots of wet moorland rich in the plant Narthecium ossifragum. The plots were top-dressed with calcium and, or, phosphorus, or given no treatment. After three years, the plant disappeared from the plots to which phosphorus had been applied, but remained where calcium only had been used. The saponin content of the plant appeared to be uninfluenced by the type of top-dressing or time of year. Photosensitisation (alveld) occurred on all plots during the first three years. During the fourth year the disease occurred only where the plant persisted. In the fifth year the disease did not occur on any plot. Alveld was produced in two lambs by the repeated administration of large quantities of saponin preparations from N ossifragum. Lambs of haemoglobin type AA were significantly more resistant to the disease than lambs with type BB. In nearly half the cases, the bromsulphthalein liver function test indicated a susceptibility to alveld up to seven days before the appearance of clinical signs. Increased bromsulphthalein retention was more common amongst AA lambs than BB lambs, but nearly all the BB lambs developed alveld, and only a few of the AA lambs. The differences were significant.

Photosensitivity in South Africa. III. Ovine hepatogenous photosensitivity caused by the plant Athanasia trifurcata L. (Asteraceae)

Hepatogenous photosensitivity was experimentally induced in 1 out of 4 sheep dosed with milled Athanasia trifurcata. This is an unpalatable aromatic shrub commonly found along the south-western and south-eastern Cape coast on overgrazed, recently burnt or disturbed veld, up to an altitude of 1 300m. The liver lesions ranged from a few small multifocal areas of necrosis in 1 animal to various zonal patterns of necrosis (centrizonal, midzonal and peripheral) in each of the other 3. Botanical, toxicological and clinical data are given.

Photosensitivity in South Africa. IV. Pathological changes in the liver in ovine photosensitivity caused by the plant Asaemia axillaris (Thunb.) Harv. Ex Jackson

Hepatic lesions in 4 field cases of ovine hepatogenous photosensitization caused by the plant, Asaemia axillaris (Thunb.) Harv. Ex Jackson, are described. The liver was usually swollen, friable and yellowish-brown, with distinct lobulation. Microscopically, the lesions ranged from peripheral coagulative necrosis in 1 animal to others with scattered single cell or small foci of necrosis as well as hepatocellular degeneration and unrest, ductular proliferation, portal fibroplasia and cholestasis. The liver lesions are compared with those of previously reported experimental cases of A. axillaris poisoning in sheep. The significance of zonal necrosis and factors that may have a bearing on their production in different hepatotoxic plant poisoning in sheep and cattle in South Africa are discussed.

Photosensitivity in South Africa. V. A comparative study of the pathology of the ovine hepatogenous photosensitivity diseases, facial eczema and geeldikkop (Tribulosis ovis), with special reference to their pathogenesis

The subject of this study was the pathological and scanning electron microscopical changes in the biliary systems of sheep suffering from facial eczema or geeldikkop (Tribulosis ovis), or made photosensitive by ligation of the common bile duct. While an obliterative cholangitis is responsible for the retention of phylloerythrin in facial eczema, the occlusion of bile ducts with crystalloid material (microliths) appear to perform a similar function in geeldikkop. The similarities and differences between the 2 diseases are discussed in the light of their pathogenetic mechanisms.