What is the connection between the deadly 'arali' flower and horses?

The death of 24-year-old Surya Surendran from Haripad, who collapsed while completing the procedures to travel to the UK, has raised many concerns. The autopsy report revealed that Surya died after heart failure but the doctors informed that the young nurse might have died after swallowing oleander aka arali leaves or flowers. Many people are wondering whether the arali flowers are too poisonous to take the life of a person. The fact is that its leaves, flowers, stem and root have a poisonous content that is dangerous. Many people grow it in their gardens as the flowers are quite attractive. In earlier times, people knew that these flowers were lethal but nowadays many are unaware of this fact. Domestic animals such as goats and cows that inadvertently ate arali flowers used to die.

What did Sanskrit call arali?
Dr E A Siril, the head of Kerala University's Botany Department, says arali is called 'Kaajamaaraka' in Sanskrit. He explains, “It means 'poisonous enough to kill a horse.' All scientific papers on the plant says all of its parts are poisonous, especially its leaves. Especially in the present climate, its toxicity can increase manifold.” In many educational portals on equestrian science, horse owners are advised to keep their surroundings clean of oleander leaves as consuming around 30 leaves of it can kill a horse within 24 hours.
What are the complications?
The poison in arali is deadly as it can cause heart attacks. The poison will act in such a way that it will slow down the functioning of the heart leading to heart failure. The toxic substance can cause irreparable damage to the liver, lungs and heart. The lethal poison can derail the blood clotting system, and cause liver bleeding, breathing issues, bleeding in the lungs, irregular heartbeats and heart attacks. There will also be a marked dip in the platelets, which are instrumental in clotting of blood. These complications can only lead to a person’s death.

The poison in arali's leaves and flowers acts just one-third slower than the deadly cyanide. Just one gram of the poison can be fatal. As it is said that Surya unintentionally chewed arali leaves while talking on her mobile phone, the juice that she had ingested acted fast in her body. Once the poison enters the body, the person will vomit and feel dizzy. As a first aid, give buttermilk or lime juice to the patient.

Other deadly plants
Poison nut tree (Kanjiram) is as deadly as the oleander plants. Though it is said that the raw fruit of Kanjiram is the storehouse of poison, the roots and wood of the tree are also harmful. The crown flower (Erukku) used for poojas is also dangerous but not as lethal as oleander flowers.