This is the VOA SpecialEnglish Development Report.
Researchers in the United States have discovered that theorganism that causes the disease malaria is genetically moredeveloped, and much older, than earlier thought. Because of this,they say it will be harder to develop medicines to prevent and treatthe deadly disease.
Plasmodium falciparum(plas-MO-dee-um fall-SIP-ah-rum) is the parasite that causes themost deadly kind of malaria. Each year, the disease kills more thantwo-million people and infects more than two-hundred-million people.In the past, doctors used the drug chloroquine (KLOR-oh-kwine) totreat malaria. However, over the past few decades the falciparumparasite has developed resistance to the medicine.
This resistance to chloroquine was first discovered in parts ofSouth America and Southeast Asia in the nineteen-fifties. Healthexperts believed resistance to the drug then spread to other partsof the world. However, a new study by scientists at the NationalInstitutes of Health near Washington, D-C, disputes this idea.
The researchers studied the genetic structures of eighty-sevenfalciparum parasites collected from around the world. They learnedthat the parasites had been developing resistance to chloroquineindependently in two areas in South America, one area in Papua NewGuinea and one area in Southeast Asia.
In a second study, the scientists examined more than two-hundredgenes from five falciparum parasites. The parasites were collectedin South Asia, Africa, South America, Central America and Papua NewGuinea. The researchers discovered several genetic differences amongthe parasites. They also learned that the parasites have beendeveloping separately for at least one-hundred-thousand years.
For several years, scientists have debated when malaria firstdeveloped. A few years ago, a genetic study of falciparum parasitesfound the disease to be between three-thousand and five-thousandyears old. The study also found the parasites to be geneticallysimilar. This latest research disputes those results.
Xin-zhuan Su (sin-schwan soo) led the two studies published lastmonth in the publication Nature. He says that new treatments tofight malaria may be possible as scientists learn more about thehistory of the falciparum parasite.
This VOA Special English Development Report was written by JillMoss.