The UK has pledged to double the funding it gives to fighting neglected tropical diseases, in a move that will protect more than 200 million people around the world from debilitating and painful conditions. The funding programme is expected to wipe out the parasitic disease visceral leishmaniasis in Asia, eliminate Guinea worm and save hundreds of thousands of people from blindness and other disabilities.

Speaking ahead of the World Health Organisation conference on neglected tropical diseases in Geneva on Wednesday, Priti Patel, the international development secretary, said such diseases belonged to the last century. “They cause unimaginable suffering and pain to some of the world’s poorest people, forcing them into a deeper cycle of poverty with no way out. Yet they are treatable,” said Patel.

“Through our leading NGOs and pharma companies, through our world-class universities and researchers, Britain will continue to play a leading role in this fight. These diseases have been named ‘neglected’ for a reason, but I’m not prepared for them to be neglected any longer.”

Helping lead the international effort against the diseases is the Carter Center NGO, founded by former US president Jimmy Carter, who said: “We at the Carter Center applaud the UK’s exemplary commitment to addressing neglected tropical diseases, such as Guinea worm, lymphatic filariasis, and trachoma. The UK government understands that helping people help themselves is an honourable and cost-effective way to reduce poverty and increase hope.”

The UK will invest £360m in implementation programmes to treat and eliminate neglected tropical diseases between 2017-18 and 2021-22. It will also dedicate £88m to research projects developing drugs and diagnostics. The funding will provide a billion treatments for people in developing countries.

Neglected tropical diseases such as trachoma, the most common cause of infectious blindness, affect more than a billion people in developing countries. Such diseases can cause anaemia, stunt children’s growth and lead to cognitive impairments. They result in thousands of deaths each year and – by preventing people from working or going to school – cost billions in lost productivity.

It is hoped that the funding will prevent some 400,000 cases of blindness caused by trachoma, as well as tens of thousands of cases of disability caused by lymphatic filariasis, a mosquito-transmitted disease that can result in severe swelling of the legs.

Medical workers prepare treatments for visceral leishmaniasis in eastern Sudan. Photograph: Alamy

In addition, it is expected to help wipe out visceral leishmaniasis in Asia, a potentially fatal disease caused by infected sand flies that destroy internal organs. Guinea worm, a parasitic disease, will also be finally eliminated: in 2007 there were 10,000 cases of Guinea worm, compared with 25 cases in 2016.

The funding will pay for treatments such as mass drug administration programmes – where drugs are given to a particular population where a disease is endemic – and surgery. It will also pay for the training of local health staff.

Dr Caroline Harper, chief executive of Sightsavers, an international charity that fights preventable blindness, said the investment would have a dramatic impact around the world. “These diseases are really, really horrible, they make people’s lives a misery. With trachoma, imagine if all your eyelashes were running inwards and every blink you had was agony – that’s the kind of thing this can stop. This money is going to help us get much further towards actually getting rid of these diseases, and what that means is that these people are no longer debilitated and are able to contribute to their communities.”

Alan Fenwick, professor of tropical parasitology at Imperial College London, said huge progress had been made in treating and preventing such diseases. “The diseases aren’t nearly as neglected as they were when we coined the phrase in 2005, but there is still lots of work to be done. The scale of the suffering of the poorest people that will be avoided as a result of the delivery implementation treatments is immense.”

Bill Gates, co-chair of the Bill and Melinda Gates Foundation, which is a major donor to research into tropical diseases, welcomed the announcement.

“UK aid and Britain’s world-leading research institutions are playing a major role in protecting the world’s poorest people from neglected tropical diseases and enabling them to live healthier, more prosperous lives,” he said.

“With our foundation, I am proud to partner with the UK on global health and look forward to sharing more specifics about how we will further our commitment in the fight against neglected tropical diseases this week at the summit in Geneva.”