International scientists say they have sequenced the genomes of three parasites responsible for diseases that kill more than 150,000 people a year.
People living in tropical regions are at highest risk of the three diseases
Their understanding should help with treatments for Chagas disease, African sleeping sickness and leishmaniasis caused by the three pathogens.
It might even be possible to make vaccines, they told Science journal.
More than 250 scientists were involved in the project, including experts from the Wellcome Trust.
New drugs to treat these so-called "neglected diseases" are desperately needed, say scientists.
Many of the treatments used are decades old, carry side effects - some fatal - and often do not work because the parasites have developed resistance to them.
Researcher Professor Sanjeev Krishna from the University of London said: "Treating sleeping sickness is like a form of medical Russian Roulette because you don't know who will be saved or killed by the treatment available.
"It shouldn't be like that now we have completed this sequencing programme; we can concentrate on finding the 'magic bullet' medicines that will help eradicate this disease."
The three parasites - Trypanosoma brucei, Trypanosoma cruzi and Leishmania major - contain between 8,000 and 12,000 genes, but have more than 6,000 in common.
Najib El-Saued, molecular biologist at the Institute for Genomic Research, Rockville, US, said this meant it might be possible to make drugs to fight all three diseases at once.
More than 500 million people are at risk for one or more of these diseases so the potential of the scientists' findings is huge, said the Drugs for Neglected Diseases Initiative.
DNDI project manager Dr Els Thorreel said: "It's fantastic that we have all this information now available.
"This will be a big leap forward in the future. Within the next five to 10 years it should give a number of new ideas for finding better cures for these diseases."
THE PARASITE DISEASES
Sleeping sickness is spread by the tsetse fly
Chagas disease is spread by bites from beetle-like bugs
Leishmaniasis is spread through bites from sand flies.
She said it should also help scientists develop better diagnostic tests to identify and treat people early.
Dr Bernard Pecoul, executive director of the initiative, said funding was now needed to push forward this research.
Sleeping sickness disturbs a person's circadian rhythm so they stay awake at night and sleep during the day. It leaves them unable to perform simple mental tasks, such as folding a piece of paper. Fever can progress to heart, kidney and neurological problems and death.
The parasite that causes Chagas disease can lie dormant in the individual for up to 20 years before causing severe internal damage, normally to the heart.
There are three sorts of leishmaniasis, which vary in severity. The most dangerous, known as visceral leishmaniasis or black fever, is nearly always fatal if it is left untreated.
Another type, mucocutaneous leishmaniasis, produces disfiguring lesions which destroy the mucous membranes of the nose, mouth and throat.
Cutaneous leishmaniasis tends to cause multiple sores on the skin.