WASHINGTON (AP) - Africa's economy might be up to $100 billion richer today if malaria had been conquered three decades ago, but instead this devastating disease is one reason many African nations remain trapped in poverty, says a study from Harvard University.

The study, to be presented to African leaders gathering in Nigeria on Tuesday for an unprecedented summit on malaria, finds the burden of this killer parasite to be far higher than previously estimated.

"It's absolutely shocking," said study author Jeffrey Sachs, director of Harvard's Center for International Development.

In addition to causing immense suffering and death, malaria slows economic development by about 1.3 percent a year, the study found. That effect is compounded over time - meaning the longer malaria plagues a country, the farther it falls behind similar but malaria-free nations.

It will take an annual investment of $1 billion by the world's richest countries to significantly attack malaria, Sachs concluded. The share for the United States would cost just 75 cents per American per year, he said in a telephone briefing for U.S. reporters.

Today, the world spends only about $120 million against malaria, he said.

Malaria is one of the world's worst scourges. Drugs and insecticides have made it rare in developed countries, but in tropical, developing nations, it sickens 300 million to 500 million people every year and kills at least 1 million.

Sub-Saharan Africa is hardest hit; children are most vulnerable; and malaria is fast evolving to resist medical treatment.

The World Health Organization aims to cut malaria deaths in half by 2010, through its "Rollback Malaria" campaign unveiled in 1998. One chief strategy is bed nets treated with mosquito-killing insecticide, a cheap and proven way to prevent malaria. Yet only 2 percent of African children sleep under a bed net, says the WHO, which helped organization Tuesday's malaria summit in Nigeria.

To estimate the economic effect, Sachs added to malaria's medical costs other factors: missed schooling, neurologic damage to children, lost productivity, lack of investment by foreign corporations, lower tourism. After accounting for the effects of economic policy and other factors that influence growth, he concluded the slow-down of economic development by 1.3 percent per year, an effect compounded with passing time.

Copyright 2000 The Associated Press. All rights reserved.