Solanum malacoxylon is a plant species belonging to the Solanaceae, or nightshade, family. Native to South America, this plant is notable for its toxic effects on grazing animals, particularly cattle. Its impact on livestock has made it a subject of veterinary and scientific interest in regions where it grows. The plant’s toxicity stems from a potent compound that disrupts normal physiological processes in animals that consume it.
Plant Identification and Habitat
Solanum malacoxylon is a perennial shrub that grows with woody stems and possesses lance-shaped leaves that often have a waxy texture. The plant produces flowers that are purplish or white, which eventually develop into small berries. This plant is native to the marshy habitats and loamy soils of South America, with a strong presence in countries like Argentina, Brazil, and Paraguay. It thrives in grasslands, plains, and disturbed areas where it can establish itself among native forage species. The highest incidence of poisoning occurs during the dry season, as animals are more likely to ingest dried leaves when other food sources become scarce.
Livestock Poisoning and Symptoms
The ingestion of Solanum malacoxylon by livestock leads to a debilitating condition known by regional names such as “enteque seco” or “espichamento”. This illness primarily affects cattle, but cases have also been reported in sheep, horses, and buffalo. The condition is a form of enzootic calcinosis, a disease characterized by the abnormal deposition of calcium in the body’s soft tissues.
The symptoms of poisoning are marked and severe. Affected livestock exhibit progressive and often rapid weight loss, which has led to the name “Manchester wasting disease” in some descriptions. A defining feature is stiffness in the joints and limbs, which causes difficulty moving and a visibly pained gait. Animals often show reluctance to stand or walk, preferring to lie down for extended periods. The severity of these signs is directly related to the amount of the plant consumed and the duration of exposure.
The Mechanism of Vitamin D Toxicity
The toxicity of Solanum malacoxylon is caused by a specific chemical compound within the plant. It contains a potent glycoside of 1,25-dihydroxycholecalciferol, which is the active form of vitamin D3, also known as calcitriol. When an animal eats the plant, this compound is absorbed directly through the intestine. The ingestion of this plant-based analog bypasses all natural control mechanisms for vitamin D production.
This uncontrolled influx of active vitamin D3 leads to a state of severe vitamin D toxicity. The primary consequence is a profound disruption of the body’s calcium and phosphorus metabolism. It triggers excessive calcium absorption from the gut, resulting in hypercalcemia, or abnormally high levels of calcium in the blood. Soft tissues throughout the body, including major arteries, the heart, the lungs, and the kidneys, begin to harden as calcium phosphate is deposited, leading to organ damage.
Human Relevance and Potential Uses
While Solanum malacoxylon is highly toxic to grazing animals, direct poisoning in humans is not a common concern. The plant’s primary risk is to livestock that consume it in pastures. However, because it belongs to the Solanaceae family, which contains many poisonous species, and because it contains such a powerful bioactive compound, human exposure and ingestion should be avoided.
The same compound that makes the plant toxic also gives it potential for scientific and medical exploration. Because it contains a naturally occurring and highly active form of vitamin D, researchers have studied its properties. There is interest in its potential as a source for developing treatments for certain human and animal health issues related to calcium metabolism. For instance, extracts could theoretically be used in carefully controlled veterinary applications or serve as a basis for creating pharmaceuticals for disorders where calcium regulation is a problem.