Research from Washington University School of Medicine in St. Louis over the past decade has helped advance a global campaign led by the World Health Organization (WHO) to eliminate two neglected tropical diseases that have left tens of millions of people permanently disabled or disfigured.
Now, an international team led by Gary Weil, MD, professor of medicine and of molecular microbiology—with the assistance of up to $24.7 million in new grant funding from the Bill & Melinda Gates Foundation—plans to conduct clinical trials and related studies in Africa and Oceania that could help speed the elimination of these diseases as a public health problem. About $6 million has been committed to the project, with additional funding dependent on the results of the first wave of studies.
One of those diseases is lymphatic filariasis, which in severe cases causes elephantiasis, painfully swollen limbs that make it difficult to walk and carry out the tasks of daily life. The second disease is river blindness, known more formally as onchocerciasis, which leads to blindness and severe skin disease. Both are caused by parasitic worms that are transmitted by biting insects.
A major focus of the new effort will be on lymphatic filariasis. The WHO launched a global campaign in 2000 to eliminate the disease by 2020. While this program has successfully cut the number of people at risk of disease nearly in half—from 1.4 billion to 800 million—completely ridding communities of the microscopic worms that cause the disease has proven more difficult than expected. Better treatment regimens could accelerate the elimination process.
Lymphatic filariasis is spread by mosquitoes that carry larvae from one person to the next. Once inside a person’s body, the adult worms migrate to lymphatic vessels that drain excess fluid from tissues and return it to the bloodstream. By blocking the drainage routes, worms cause swelling in the lower limbs. Adult worms can live for years in the lymphatics, producing millions of young that travel to the bloodstream, where they are picked up by the next mosquito that bites.
The strategy will first be tested in Ghana. Success there will lead to larger studies in other countries in Africa. If successful, 18 African countries with overlapping areas of endemic river blindness and lymphatic filariasis will have a much more powerful weapon in their fight against parasitic diseases.
The grant also will allow the researchers to test other drug combinations with a goal of finding more treatment regimens that quickly and effectively kill the worms while also being safe and acceptable to the people who have to swallow the drugs. Some of these studies will include a newly approved drug called moxidectin. Moxidectin is similar to ivermectin but lasts longer in the body. It has been shown to be effective for clearing onchocerciasis parasites from the skin for at least one year.
