Progress has been made in tackling diseases that blind, disable and disfigure millions of poor in tropical areas each year, but drug companies need to step up donations of medicines, the World Health Organization (WHO) said on Wednesday.

One billion people, mainly in Asia, Africa and Latin America, are still treated each year for at least one of 18 neglected tropical diseases known as NTDs, it said.

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.

"There is no group of diseases that is so intimately linked to poverty," Dr. Dirk Engels, director of WHO's department of control of neglected tropic diseases, told a news briefing.

"A number of companies have accompanied us in the scaling up by making more medicines available. Is that enough? No, there are still diseases that are neglected and we still have problems with access to basic medicines," he said.

GlaxoSmithKline, Novartis and Sanofi are among major donors, WHO says. Merck said earlier 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.

New products need an access plan for patients "because just counting on the commercial mechanisms won’t work", Enders said.

The Bill and Melinda Gates Foundation is backing research and development into NTDs. Bill Gates met with CEOs of major pharmaceutical companies in Geneva on Tuesday.

"Good progress, some of these diseases are on track to be done (eliminated) by 2020, some by 2025. Some will take longer than that," Gates told a news conference, noting that there were only 3,000 cases of sleeping sickness last year.

EXPENSIVE MEDICINES

Needs remain huge despite the fight over the past decade and a 2012 London meeting to galvanize attention and set targets, WHO said.

"Cutaneous leishmaniasis, for instance. It doesn’t kill so it attracts less attention, but it is really disfiguring and it causes a lot of stigma and a lot of mental problems," Engels said of the disease spread by female sandflies.

"The medicines exist...They are too expensive and (neither) people nor countries have the ability to pay."

Drugs companies currently have 109 research and development projects for medicines or vaccines for NTDs, which typically take 10-15 years to develop, the International Federation of Pharmaceutical Manufacturers & Associations (IFPMA) said.

"There are quite a number of new medicines and diagnostics in the pipeline, which may actually further change the perspective for these neglected tropical diseases and hopefully allow us to go further towards eliminating or near eliminating these diseases by 2030," Enders said.

Only 25 human cases of Guinea worm disease were reported last year, "putting eradication within reach", he added.

"We have just acknowledged the first African country that has eliminated lymphatic filariasis as a public health problem – Togo – so that may be a start of a number of them," Enders said.

The mosquito-borne infection, also known as elephantiasis, causes enlargement of limbs and genitals from adult worms in the lymphatic system.