Day-Blooming Jessamine Poisoning (Enzootic Calcinosis) in Horses

Day-blooming jessamine is native to the West Indies and is cultivated widely throughout India and South Asia. This plant produces a substance called calcitriol. If a horse ingests a sufficient quantity of calcitriol, the normal process of calcium excretion is interrupted, leading to build up of calcium deposits in soft tissues.

Calcium is a mineral used by the body for proper muscle function. As muscles work, calcium is normally excreted into the bloodstream and replenished. If this process is interrupted, calcium builds up in the muscle tissue, causing the tissue to become hardened or mineralized. In severe cases, mineralization can disrupt or even prevent normal muscle function.

Calcification of muscle tissue is irreversible. The only way to ensure horses do not develop enzootic calcinosis is to prevent grazing on calcitriol-containing plants.

Day-blooming jessamine toxicosis is uncommon in horses. Enzootic calcinosis is a life-threatening condition that causes the calcification of the vital organs. There is no treatment for tissue mineralization, and soft-tissue calcification is not reversible.

Animals with insufficient access to alternative sources of forage are more likely to graze on calcitriol-containing plants.

Enzootic calcinosis is caused by the ingestion of calcitriol-containing plants, primarily day-blooming jessamine (Cestrum diurnum).

Calcitriol is the active form of vitamin D. Once ingested, excess calcitriol increases absorption of calcium and reduces its excretion. The calcium accumulates in the tissues, leading to soft-tissue calcification.

Early diagnosis of enzootic calcinosis can be difficult. Horses exhibiting symptoms of day-blooming jessamine toxicosis generally undergo the following diagnostics:

• Physical examination
• Blood tests
• Diagnostic imaging: x-rays and ultrasounds are used to determine the presence of calcium deposits

There is no specific treatment for enzootic calcinosis, and soft-tissue calcification is not reversible. The only treatment options are:

• Stopping use of infested pasture
• Discontinuing any ongoing vitamin D supplementation
• Pain relief medications
• IV fluids to promote calcium excretion

As there is no available treatment, enzootic calcinosis generally carries a poor prognosis.

Surviving animals are likely to suffer from chronic poor performance.

Horses removed from infested pastures before the onset of soft tissue calcification carry a good prognosis.

Day-blooming jessamine toxicosis is not contagious.

The absence of treatment for enzootic calcinosis makes prevention of the utmost importance. Prevention strategies include:

• Change of pasture to prevent access to the plant
• Eradication and destruction of calcitriol-containing plants
• Providing a sufficient amount of alternative forage such as hay or grass pasture

Day-blooming jessamine toxicosis is uncommon in horses.

• Supportive care
• Discontinuation of Vitamin D supplementation