The Bill and Melinda Gates Foundation, Western countries and drug companies pledged fresh support on Wednesday to wipe out diseases that blind, disable and disfigure millions of poor in tropical areas each year and urged new donors to join the fight.

Some 1.5 billion people, mainly in Asia, Africa and Latin America, are infected with one of 18 neglected tropical diseases known as NTDs, the World Health Organization (WHO) said. One billion of them are receiving treatment, half of them children.

"The best thing with these diseases is not to debate whether they are neglected or not, but to proceed to make them history," Bill Gates told a global partners' meeting held at WHO.

"We need a broader, deeper bench of investors...so that by 2030 we can achieve the goal of reaching 90% of the people who need treatment. I know this is achievable."

Gates, who has supported the initiative for over a decade with $1 billion, pledged $335 million over the next 4 years, including $42 million to continue efforts to wipe out Guinea–worm disease.

The crippling disease, transmitted by contaminated water, can lead to a 100 cm long (40–inch) worm growing in the body.

"Guinea worm is one of our great success stories, even though we're not absolutely at zero, we are down to very small numbers. Thirty years ago over 3 million people in over 20 countries were afflicted," Gates said.

Only 25 cases of Guinea–worm disease were reported in six countries last year, "putting eradication within reach", the WHO says.

The Carter Center, set up by former U.S. President Jimmy Carter, has worked for more than 20 years to wipe it out.

"We are close to finishing off this debilitating disease," Carter said, speaking by video from Atlanta, Georgia.

"We cannot be complacent, we must be creative and persistent. The Carter Center will not give up until the last Guinea worm is gone."

Dengue, onchocerciasis (river blindness) and sleeping sickness are among those carried by mosquitoes or flies that are spreading from rural areas to urban slums, the WHO warned.

"NTDs are really the diseases of neglected people, they are diseases of poverty and inequality that affect the most vulnerable among us," World Bank President Jim Kim said by video. "Now we have the largest drug donation program in history with 1.5 billion treatments in 2015 alone," he said.

GlaxoSmithKline, Novartis and Sanofi are among major donors, WHO says. Merck said on Tuesday it was developing a children's formula of its drug to treat schistosomiasis, a parasitic worm disease which kills 280,000 a year in Africa.

Britain's Minister of State for International Development, Lord Bates, said the UK government was committing an additional 250 million pounds ($321.35 million) to NTD programs.

Belgium's deputy prime minister Alexander de Croo pledged 25 million euros ($26.81 million) through 2025 to eradicate African sleeping sickness.

"Today the stars are aligned to eradicate it completely," de Croo told the talks. "The pay–off is huge."

—Stephanie Nebehay