It is found as a weed, widely distributed in disturbed places, old lands, overgrazed areas and along stream banks especially in dry, hot regions.
General: A perennial, flat-growing, creeper with an underground root system from which a number of branches develop annually, spreading around to cover the soil.
Leaves: The leaves are compound with 5 - 8 pairs of leaflets. These are even woolly when young.
Flowers: The small yellow flowers are borne in the axils of the leaves.
Fruit: Woody fruit with strong, sharp, conical, spiny growths.
• Plants rarely toxic - often regarded as good food in the Karoo.
• During outbreaks certain camps are toxic.
• Latent period 2-5 days. (Latent period for facial eczema is 10-14 days)
Toxic principle: Steroidal saponins.
MECHANISM OF ACTION:
• Hydrolysis of a steroidal saponin to diosgenin with subsequent hydrogenation,
reduction and epimerisation which occurs in the rumen.
• Epismilagenin and episarsasapogenin, amongst others, are formed, absorbed
and conjugated with glucuronic acid in the liver to be excreted via the bile.
• However, the epismilagenin and episarsasapogenin glucuronides bind to Ca2+
to form an insoluble salt which precipitates to form biliary crystals which obstruct the bile ducts.
Obstruction of biliary system.
• Signs are typical of secondary photosensitivity
- swollen head,
- sloughing of skin and
• Severe icterus.
• Problem of no shade in the Karoo.
• Sheep stand in the shade of fence poles and bushes, or even other sheep’s shadow.
• Wilted dubbeltjies
• Signs in large numbers for definitive diagnosis
• Histopathology of especially liver and kidney.
• Icterus and photodermatitis.
• Liver: Slight hepatomegally and discoloured, khaki to yellow - brown.
• Chalky white sediment in bile ducts and gall bladder.
• Liver morphology never distorted as in F.E. (facial eczema).
• Kidneys: Swollen and light in colour, with small green foci distributed through cortex.
• Accumulation of crystalloid sediment in bile ducts leading to partial or complete
occlusion and concentric, lammellar periductal fibrosis.
• The crystalloid material washes out and clefts remain.
• Plate-like structures seen on scanning EM.
1. Keep in shade
2. Diet low in chlorophyll
3. Valuable animals - barrier creams and tattoo ink will protect from sunburn.
4. Antihistamines, corticosteroids, cholagogues, liver supportive treatment.
• extensive nature of farming,
• Karoo sun.
Colour photos. Final web-ready size: JPEG, 72 ppi. Photo 1: 26.4 kb; Photo 2: 30.9 kb; Photo 3: 19.6 kb, Photo 4: 44.5 kb. Original TIFF file housed at the Dept. of Paraclinical Sciences, Section Pharmacology and Toxicology, University of Pretoria.