Parasitic caterpillar fungus in decline

Caterpillar fungus, more valuable by weight than gold and famous for its extensive medicinal use in China for thousands of years, is vanishing and may not be available in 10 years' time, according to a recent study supported by the National Geographic Society.

In a paper published online in this month's edition of , two researchers from the University of Massachusetts' biology department - Uttam Babu Shrestha and his mentor, Professor Kamaljit Bawa - wrote that the impact of trade and climate change is speeding the parasitic fungus' decline at a startling rate. The decline is so fast, they said, that more systematic conservation efforts may be needed.

Caterpillar fungus, which has been used as a tonic for pain relief and an aphrodisiac for many centuries, is used today as an immunological booster for lung and kidney illnesses, and has a cytotoxic (cell-killing) effect on cancer. It's also a dietary supplement to enhance glucose metabolism, lipid metabolism, energy metabolism, exercise physiology and sexual function.

Up to US$11 billion is spent on the fungus - commonly known as Himalayan Viagra - each year by millions of Chinese hoping to benefit from its supposed effects on male potency. According to Karl Tsim, professor of life science at Hong Kong University of Science and Technology: "No one has strong evidence that it enhances male potency so far, but this is how it is marketed. Here in Hong Kong, it is mostly prescribed to those with asthma or diseases derived from poor immune activity."

The fungus is known by various names. Its scientific name is ; it's known as in Putonghua; and in Nepali, which means "winter worm, summer grass".

The natural product of this complex system is the combination of a caterpillar larva and a fungus. The fungus attacks living ghost moth larvae in autumn, killing and mummifying the host by consuming essential nutrients. By early spring, the stalk-like fruiting body emerges from the corpse.