The belief that powdered rhino horn cured cancer is being blamed for surge in demand that has wiped out three species

It may have been a consumer rumour as much as a poacher's gun that finished off the last rhino in Vietnam. An investigation into the extermination of the animal has led back to a dubious claim – one that has gone viral in Vietnam in recent years – that powdered rhino horn cures cancer.

The rumour, which has no basis in science or traditional Chinese medicine, is believed responsible for a surge in demand that is blamed for the loss of three rhino populations in the past year, a wildlife NGO claimed this week. It has prompted conservation groups to begin an urgent review of strategies to identify and affect trends in consumer behaviour.

The Javan rhino was declared extinct in Vietnam last month after the last one was found dead with a bullet in its leg and its horn sawn off. This month, it was followed by Africa's western black rhinoceros and by warnings that the Sumatran rhino is on the brink of extinction in Indonesia.

This followed years of relative stability. The illegal rhino market went quiet in the late 90s as the two main sources of demand – dagger handles in Yemen and fever suppressants in China – were choked with a mix of government crackdowns and viable alternatives. As recently as 2007, only 13 rhinos were poached in South Africa. This year, the number is already 341.

"We couldn't understand what was happening at first," said Steven Broad of Traffic, a wildlife conservation group. "Then we noticed unusual demand from Vietnam. This had not previously been a major market so at first we assumed this was a staging point for China. But now we believe, Vietnam is the final destination."

The cause appears to be a rumour, started in Vietnam five or six years ago, that rhino horn had cured cancer in a former politician. The politician was not named, nor were there any details on the cancer supposedly cured. But the rumour spread rapidly and the price of rhino horn surged, recently hitting a record high of more than $60,000 a kilogramme – a higher price than gold. This prompted poachers to dust off their rifles and take greater risks. Rangers have shot dead 16 poachers since last year. Others are using helicopters for hunts.

Killings have also increased in Kenya and Tanzania. In Britain, thieves have broken into a museum to steal rhino horn. Legal trophy hunts have suddenly been flooded with applicants from Vietnam, some of whom had clearly never handled a gun before.

Some speculate that it may come from China. Others that the rumour was deliberately started by collectors and dealers of rhino horn, whose stocks have now surged in value. Other factors may also be at play, as many rhino horn collectors in China also invest in ivory products, expecting them to rise in value as the animals become scarcer.

Many questions remain. But for now, conservationists say the case shows the need to rethink their approach. Until now this has focused on protecting animals in the wild, but there is increasing recognition that more work is needed to identify and change consumer behaviour.

"The loss of our last rhino is a sad story," said Nguyen Van Ahn, a former activist now working for Vietnam's ministry of natural resources. "We have to do more to ensure the same doesn't happen to other endangered animals. I think we have to pay more attention on the demand side. We didn't do that enough before."

The stakes are high and not just for rhino. In Vietnam alone, the Indochinese tiger, Asian elephant, saola, Tonkin snub-nosed monkey and Siamese crocodile are all on the brink of vanishing. Elsewhere in Asia, many other animals are at risk from the surge in demand.

This global trend has been accelerated by the spread of internet commerce, international travel and the rapid development of China and other Asian economies, where affluent modern lifestyles and traditional habits of wild animal consumption are proving a particularly lethal mix for pangolins, tigers, sharks, elephants and a host of other species.

The sense of crisis has been evident in three separate workshops on demand reduction organised in Asia in the past two weeksThis week in Hong Kong, WWF, Traffic, the Environment Investigation Agency, the International Fund for Animal Welfare and the World Bank joined marketing experts, media strategists and government officials in an attempt to draw up new approaches to reducing demand for tiger and rhino products in China and Vietnam.

This followed an "emergency brainstorming session" to arrest the depletion of Asia's wildlife, organised in Bangkok the previous week by the ASEAN wildlife enforcement network, the US international development agency and Freeland. Wildaid also called a gathering of interested parties on a similar subject in Beijing.

"Escalating demand in Asia and the poaching crisis in Africa and Asia perhaps are wake-up calls for many conservation groups," said Grace Ge Gabriel, the Asia regional director of the International Fund for Animal Welfare. "The fact is that putting a price tag on an endangered species is the fastest way to push it towards extinction. To reduce commercial exploitation of wildlife, we need to address every link on the trade chain, from anti-poaching to stopping smuggling to reducing market demand."

Conservationists have been trying for years to discourage purchases of ivory, whale meat, uncertified wood products and other items that up the pressure on endangered species.

While this is less glamorous, more difficult and harder to measure than the establishment of nature reserves and the fight against poachers, it is increasingly important as wild supplies decline and wealthy consumers increase. In future, more effort is likely to go into the work of surveying consumers, monitoring shopkeepers and launching marketing campaigns to shift habits, traditions and cultural norms.

The challenge and possibility were both evident around the venue for the Hong Kong meeting, which was located in the heart of the territory's massive shark fin market. It is estimated that between 25 million and 75 million sharks are killed each year to supply this billion-dollar business, which has devastated several species.

Government action to tackle this unsustainable harvest has been slow or non-existent so conservation groups have set their sights on consumers. This year, the WildAid international ambassador and basketball star Yao Ming spoke out against shark fin soup. Earlier this week, the Peninsula hotel – one of the most prestigious in Hong Kong – said it would stop serving the dish from January. It was a rare victory that campaigners hope to build on.

"Conservation groups need to help the hospitality industry develop a sustainable seafood market," said Stanley Shea of Bloom Association, a Hong Kong-based NGO that is pressing other hotels to follow suit. The demand-side strategy, he said, can help more conventional measures to protect the wild. "Now is the time for conservation groups to rethink their approach."

• This article was amended on 29 November 2011. The original said Actionaid recruited basketball star Yao Ming this year to speak out against shark fin soup. This has been corrected.