A leading American investigator into the illegal ivory and rhino horn trade has been found stabbed to death in his home, Kenyan police and officials have said.

Key points: Mr Bradley-Martin was at the forefront of exposing ivory traffickers in many countries

Mr Bradley-Martin was at the forefront of exposing ivory traffickers in many countries His research was instrumental in China's decision to ban its legal rhino horn trade in 1993

His research was instrumental in China's decision to ban its legal rhino horn trade in 1993 It also pressured China to end legal ivory sales, a ban that came into effect on January 1

Esmond Bradley-Martin, 75, had spent decades tracking the movement of animal products, mostly from Africa to markets in Asia.

A family member went to Mr Bradley-Martin's house on Sunday (local time) to check on him after he did not respond to phone calls, and found the body on a bed with a stab wound to the neck, said Nicolas Kamwende, head of criminal investigations in the capital, Nairobi.

Conservationist Paula Kahumbu said Mr Bradley-Martin led investigations into the illegal trade of elephant ivory and rhino horn that threatens the two species with extinction.

He was at the forefront of exposing ivory traffickers in the US, Congo, Vietnam, Nigeria, Angola, China and recently Myanmar, Ms Kahumbu said.

"It's a very big loss for conservation," she said, adding that Mr Martin had been about to publish a report exposing how the ivory trade had shifted from China to neighbouring countries.

Bradley-Martin's research pressured China to end legal ivory sales. ( ABC News: Martin Cuddihy )

Mr Bradley-Martin's research was instrumental in China's decision to ban its legal rhino horn trade in 1993.

It also pressured China to end legal ivory sales, a ban that came into force on January 1.

"His work revealed the scale of the problem and made it impossible for the Chinese Government to ignore," Ms Kahumbu said.

British High Commissioner to Kenya Nic Hailey said in a Twitter post he was "shocked and very sad to hear of the death".

"A passionate and committed man who made a big difference to our planet. May he rest in peace," he wrote.

Conservation group Save the Elephants described Mr Bradley-Martin as "a longtime ally", a passionate champion of wildlife and meticulous researcher.

The devastating effects from illegal poaching

Elephants are poached faster than they reproduce. ( Supplied: Gina Poole )

Illicit demand for elephant ivory has led to devastating losses from illegal poaching as the natural habitat available for the animals to roam has also dwindled by more than half.

As a result, the number of African elephants has shrunk from about 5 million a century ago to about 400,000. And that number continues to decline each year.

Fewer than 30,000 rhinos are estimated to remain in the wild due to poaching.

The price of rhino horn skyrocketed as demand has grown in Asian countries, mainly China and Vietnam, where consumers wrongly believe that the horn — made of the same substance as fingernails — has powerful healing properties.

Syndicates from Vietnam, China, South Korea and Thailand have been identified as being involved in the trafficking.

In an interview with National Public Radio in 2007, Mr Bradley-Martin said his greatest contribution academically to conservationism would be to show that except for one small area in India, rhino horn has never been used by Asians for sexual purposes.

Mr Bradley-Martinis the second prominent conservationist to die in East Africa in the past year.

South African Wayne Lotter, whose work targeted ivory smuggling from Africa to Asia, was shot dead in Tanzania in August.

AP/Reuters