Takeshi Yasumoto and colleagues explain that 20,000-60,000 people every year come down with ciguatera poisoning from eating fish tainted with a ciguatoxin - the most common source of food poisoning from a natural toxin.

Fish, such as red snapper and sea bass, get the toxin by eating smaller fish that feast on marine algae that produce the toxin in tropical and subtropical areas, such as the Gulf Coast of the U.S.

There's no warning that a fish has the toxin - it smells, looks and tastes fine. But within hours of ingesting the toxin, people with ciguatera have symptoms that often include vomiting, diarrhea, numbness or tingling in the arms and legs and muscle and joint aches.

Debilitating symptoms may last for months. The current test for the toxin involved giving it to laboratory mice and watching them for symptoms.

It is time-consuming, may miss the small amounts present in fish, and can't tell the difference between certain forms of the disease. That's why Yasumoto's group developed a faster, more sensitive test.

They describe development of a new test, using standard laboratory instruments, that avoids those draw backs. Yasumoto's team proved its effectiveness by identifying 16 different forms of the toxin in fish from the Pacific Ocean.

Clear regional differences emerged - for example, snappers and groupers off Okinawa shores had one type, whereas spotted knifejaw captured several miles north of Okinawa had another type.

They also identified 12 types of toxin in a marine alga in French Polynesia, which could be the primary toxin source.

The researchers say that the method outperforms current detection methods and in addition to helping diagnose patients, it will also help scientists study how the toxins move through the food chain from one animal to another.