Day-Blooming or Wild Jessamine
Introduced from the West Indies as an ornamental tree, day-blooming jessamine or wild jasmin (Cestrum diurnum) has become widely distributed in Florida, Texas, and California. It is a shrub or small tree that grows up to 16 ft. (5 m) high, with alternate elliptic leaves that have a dark green, glossy upper surface. Its fragrant white tubular flowers are born in small clusters on axillary peduncles. Multiple green berries that turn black when ripe are produced after flowering.
|
|
The toxin in day-blooming jessamine is similar to the active metabolite of vitamin D. Consequently, horses eating it absorb excessive amounts of calcium, resulting in a high calcium concentration in the blood and tissue calcinosis. Prolonged ingestion of the plant results in the calcification of the elastic tissues of the arteries, tendons, and ligaments. The high blood calcium concentration results in inhibition of normal bone resorption, resulting in excessive bone formation.
Other members of this genus-night-blooming jessamine (Cestrum nocturnum) and green cestrum or willowleafed jessamine (C. parqui)-are also poisonous, but not due to a vitamin D-like toxin causing calcinosis. Their toxicity is instead due to the action of atropine-like toxins that are common in the family Solanaceae.
Characteristic clinical signs of plant-induced calcinosis in horses are a chronic weight loss despite normal appetite, and a generalized stiffness leading to severe lameness and prolonged periods of lying down. Lameness is due to pain in the calcified ligaments and tendons of the legs. Radiographs show increased bone density, decreased size of the medullary cavity and increased calcification of cartilage and bone growth plates.
Recovery from plant-induced calcinosis rarely occurs. Recovery is likely in less severely affected horses if they are denied further access to the toxic plants and are given a good diet. Care should be taken to ensure that horses are not placed in pastures or pens that contain Cestrum species or other calcinosis-inducing plants.
|
