High up in the mountains of the Tibetan plateau, nomads crawl on their hands and knees searching for a rather gruesome, but very valuable, parasitical fungus. Ophiocordyceps sinensis germinates in living moth larvae, killing and mummifying them, and then growing a stalk-like fruiting body out of its head.

Commonly known as caterpillar fungus, it is prized in traditional Chinese and Tibetan medicine. The fungus can supposedly be used to treat a wide range of ailments, including asthma, cancer and erectile dysfunction. It is considered as having a balance of yin and yang as it is apparently both animal and vegetable.

Award-winning Getty Images photojournalist Kevin Frayer travelled to the Tibetan Plateau to document the search for the caterpillar fungus.

Frayer told IBTimes UK: "I have travelled often to the Tibetan plateau but this was the first time I was able to see the cordyceps harvest. It's such a short season yet so crucial to the local economy for Tibetans. It's not a traditional way of life for them and a somewhat recent phenomenon fuelled by outrageous demand as a medicine in China. Even though the value of cordyceps is declining a bit, the local people can make enough money for the entire year."

He added: "The harvesting happens at altitudes mostly above 4,500m. The most valuable cordyceps are often in the most arduous places to reach and it's not easy." Environmentalists increasingly warn that overharvesting of caterpillar fungus carries the cost of degradation to mountain grasslands that are essential for yak and cattle grazing.

The demand has created a booming economy for what Tibetans call yartsa gunbu, or summer grass, winter worm (ie, it is a worm in winter and a grass in summer). Top quality, large caterpillar fungus can sell for around $10 (£7) each, or £35,000 per pound. Tibetans who rely primarily on farming and herding have turned to the weeks-long harvest as a means of earning income to last through the year. The annual gold rush has transformed parts of rural Tibetan areas, generating about 40% of the local economy.

Frayer told IBTimes UK: "The most worrying part of this somewhat strange industry is that many Tibetan nomads are choosing this as an alternative to the traditional life of herding yaks and other livestock, hedging everything on the fungus. In many ways it is a big gamble, and I suppose in the process traditions and self-sufficiencies can be lost."