Scientists in South Korea have found a local fish that could help control the spread of malaria.
Malaria kills hundreds of thousands each year
The fish, called the muddy loach, eats mosquito larvae and can completely remove them from rice fields.
The research was presented at the annual meeting of the American Society for Tropical Medicine and Hygiene in the US city of Philadelphia.
At the same meeting, scientists revealed how they believe farming helped spread malaria.
The concept of the muddy loach is simple: find fish which eat mosquito larvae, and put them in lakes and fields where larvae live and adult mosquitoes breed.
Researchers experimented with the fish in several locations in South Korea, in rice fields farmed both organically and conventionally.
They found that by putting enough fish in a field, all the mosquito larvae would be eaten within a day.
Muddy loaches are omnivorous and hardy, which the researchers say make them ideally suited to the job.
Revival of old technique
The idea of using fish in this way dates back a century or so, but in recent decades it has fallen out of favour as more modern techniques for combating malaria, such as chemical insecticides, drugs and bednets have taken precedence.
But the researchers say muddy loaches could make a significant impact on malaria in East Asia.
It could also help in other parts of the world, where there are other fish which could do a similar job, whether in rice fields or in lakes and ponds.
And at the end of the malaria season, farmers get to eat the fish as well, fat with all the larvae they have been consuming.
Scientists at the conference also said they believed malaria was given a boost around 10,000 years ago in Africa with the beginning of slash-and-burn agriculture.
This type of farming created small water pools where mosquitoes could breed, and a less nomadic human population to feed off.