The earthworm-filled toilets take up less space than pit latrines, need to be emptied far less frequently, present less of a health risk, and can provide communities with rich compost for growing crops, according to sanitation specialists.

The tiger worm toilets were first trailed by charity Oxfam in slums in the Liberian capital of Monrovia in 2013, and have since been installed in refugee camps in Ethiopia and Myanmar.

With a record 65.3 million people uprooted by conflict or persecution worldwide in 2015, and urban populations booming across the globe, aid agencies say innovation is key to improving water and sanitation for camps and communities.

"The joy of tiger worms is that they reproduce faster with the more poo they have to feed off ... so they are self sustaining," Andy Bastable, Oxfam's head of water and sanitation, told the Thomson Reuters Foundation by phone.

While pit latrines have to be cleared out regularly, which is time-consuming and costly, the tiger worm toilets built in Monrovia four years ago have yet to need emptying, Oxfam said.

The main drawback is the initial cost of buying the two kilograms of tiger worms needed per toilet, according to the U.N. refugee agency (UNHCR), which worked with Oxfam to install the toilets in a camp for South Sudanese refugees in Ethiopia.

"Tiger worm toilets are promising but they aren't the silver bullet to change sanitation across Africa," Bastable added. "The winner will be a toilet technology that can be adapted to individual countries to meet the needs of a specific community."

While new technologies are seen as crucial, attitudes towards water and sanitation must be challenged in rural areas and countries where open defecation is rife, such as Nigeria and India, said Remi Kaupp, a technical advisor at charity WaterAid.

Aside from tiger worm toilets, other innovations being used and tested in refugee camps include harnessing solar energy to turn human waste into smokeless cooking fuel, and using urine to generate electricity and light up toilets at night.

But for ventures such as tiger worm toilets to be 'game-changing', they must go beyond being technologically impressive, said Elisa Roma, a sanitation expert at the London School of Hygiene & Tropical Medicine (LSHTM).

"There needs to be a sustained demand for such products ... (and) viable business models that allow the innovation to operate without subsidies and beyond initial aid from international funders," Roma said.