KATHMANDU, Nepal — Every month when her period came, Tulasi Shahi was sent to stay in her uncle’s hut, the one where he keeps his cows tied up, in a village in the Dailekh district in western Nepal. This month was no different. She slept there on wooden boards laid on the ground, in keeping with a tradition known as chhaupadi that sequesters menstruating women from their families.

But while she was in the hut on Thursday night, Ms. Shahi, 18, was bitten by a poisonous snake. Her mother took her to a shaman, but he could not cure her. Then she was taken to a health clinic, but workers did not have the antivenom medicine she needed, her family said.

Ms. Shahi died early Friday morning.

“If she was given proper treatment, she would have survived,” said Kamala Shahi, a cousin of Ms. Shahi’s who works at a government health post. “She died because of superstition.”

The Supreme Court of Nepal ordered an end to chhaupadi, which is linked to Hinduism, in 2005. But it is still practiced in many of Nepal’s isolated villages, particularly in the west. A bill is pending in Parliament to formally criminalize the practice. Many people in rural villages believe that menstruating women are impure and can bring bad luck on a household. Under the chhaupadi tradition, the women are kept from taking part in normal family activities and social gatherings or from entering houses, kitchens and temples.