Deadly snake species like cobras and kraits in India can still inject venom even after the animal has died, according to a new study.
Until now the ability to posthumously inject venom was thought to be limited to a select group of snake species including American rattlesnakes, copperheads, Asian and sub-Saharan spitting cobras, and Australia’s red-bellied black snakes.
But a new study by scientists in India’s eastern state of Assam, published in the journal Frontiers in Tropical Disease, has confirmed that Indian monocled cobras and kraits can also inject venom hours after their death.
The research team, led by Susmita Thakur of Namrup College in Assam, documented three such incidents: two involving monocled cobras (Naja kaouthia) and one involving a black krait (Bungarus lividus). All cases were reported to rural health centres in Assam.
In the first case, a 45-year-old man encountered a snake attacking chickens in his house and killed it by beheading.
However, while trying to discard the body, he was bitten by the decapitated snake’s head on his right thumb. “The bite was followed by severe pain at the bite site, radiating up to his shoulder. He reported to the nearby community hospital,” the researchers wrote.
On the way to the hospital, the 45-year-old experienced repeated vomiting and “unbearable pain”, while the bite site began to blacken, the researchers noted.
A timely photograph taken of the snake helped doctors identify the bite as that of a monocled cobra.
Doctors at the hospital administered intravenous antivenom along with paracetamol for pain relief.
“The pain significantly decreased following this treatment. The patient did not develop any symptoms of neurotoxicity,” the researchers noted.
The patient was discharged after 20 days, with regular follow-ups for wound care.
In the second case, a man working in a paddy field unknowingly ran over a monocled cobra with his tractor. But when he got off the tractor after work, the snake, presumed dead, bit him on the foot.
“The patient complained of severe pain, progressive swelling, and noticeable colour change at the bite site,” scientists wrote, adding that he experienced two episodes of vomiting in the hospital, consistent with signs of envenomation.
Although the patient showed no signs of neurotoxicity, the bite resulted in an ulcer, the researchers noted.
“Despite being crushed and presumed to be dead for several hours, the snake was capable of delivering a venomous bite, requiring antivenom treatment along with extended wound care,” they wrote.
In the third reported incident, a black snake entered a house, where it was killed and its body discarded in the backyard. A neighbour who came to see the snake later picked it up by the head and was bitten on the little finger of his right hand.
Within hours, the neighbour began experiencing difficulty swallowing and developed drooping eyelids.
Doctors identified the dead snake, brought to the hospital along with the patient, as a black krait (Bungarus lividus). “The victim was envenomated by a snake that had been dead for 3 hours,” the scientists wrote.
Despite being given 20 vials of polyvalent antivenom, the patient remained unresponsive, and his condition worsened. “He gradually became quadriplegic...and unresponsive to verbal commands,” researchers wrote.
The patient’s condition improved after 43 hours of respiratory support, and he was discharged from the hospital in “good health” after six days at the hospital, the scientists wrote.
Based on these cases, researchers warned that even after sustaining fatal injuries some snakes can still inject venom, potentially leading to severe complications.
They observed that this ability persists because of the unique structural organisation of the venom apparatus in front-fanged snakes. “The venom gland consists of a large basal lumen for storage of secreted venom, which is connected to a long hollow fang,” the researchers wrote.
Envenoming may occur if the venom gland of a dead snake is accidentally pressed while handling its severed head. “In the cases highlighted here, such envenomings lead to clinical symptoms comparable to those produced by live snakes,” the scientists warned.
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