Elephantiasis and river blindness are parasitic diseases straight out of a horror movie.
In both cases, insects bite humans and transmit tiny parasitic worms — which cause debilitating illnesses.
Washington University School of Medicine researchers are leading an international team in a long-term effort to eradicate the two diseases. The group recently received up to $24.7 million in grant funding from the Bill & Melinda Gates Foundation to test the safety and effectiveness of several drug regimens in sub-Saharan Africa.
Lead researcher Gary Weil has spent more than 40 years studying both diseases.
Elephantiasis — also known as lymphatic filariasis or “elephant’s foot disease” — occurs when a mosquito bites an infected person and ingests tiny parasitic worms.
That same mosquito later passes the parasite to other humans, where it develops into thread-like worms that can block lymph nodes and cause massive swelling in the limbs and genitals.
“It’s a very disabling and stigmatizing disease,” said Weil, a professor of medicine and molecular microbiology at Washington University School of Medicine.
According to the World Health Organization, more than 120 million people in 73 countries are infected with the parasite — with the highest numbers of infections in southeast Asia and sub-Saharan Africa.
A related parasitic worm causes river blindness, an infection mostly confined to Africa.
Black flies, which breed near fast-moving rivers and streams, bite humans and transmit the parasitic worm — which rapidly reproduces in the human body.
In some cases, infected people develop eye lesions that lead to permanent blindness.
The World Health Organization estimates nearly 21 million people were infected with the parasite in 2017, and of these, about 1 million had vision loss.
New efforts to eradicate river blindness
The drug currently used to treat river blindness — ivermectin — is a temporary fix, said Weil.
“The treatment doesn’t really kill them; it’s like a birth control for them,” he said. “The worms live for 10 to 15 years, so you have to keep giving [the medicine] every year for many years until they die out.”
With new funding from the Gates Foundation, Weil plans to test whether a combination of three drugs — ivermectin, diethylcarbamazine and albendazole — is more effective for treating river blindness.
Weil and his team previously demonstrated the three-drug regimen was better than conventional treatments for controlling elephantiasis, prompting the WHO to change its recommended treatment for the disease.
But treating river blindness presents some new challenges.
One of the drugs in the cocktail, diethylcarbamazine, rapidly kills the parasitic worms in the skin and eyes, which can cause inflammation and lead to blindness.
“We don’t want our public health program to cause blindness, so we have a strategy to prevent that from happening,” Weil said.
The workaround is to first give patients the drug currently used to treat river blindness — ivermectin — to reduce the number of parasites in the skin and eyes, then administer the three-drug treatment.
The team has started a series of small-scale clinical trials in Ghana to ensure there are no complications.
The Gates Foundation has committed about $6 million to the project and will review the initial results before deciding whether to release the remainder of the funding for larger community-wide studies.
The lion's share of the study should be complete by 2023, Weil said.
Public health organizations have been working for years in the hopes of eradicating elephantiasis and river blindness, but a number of logistical hurdles have slowed progress.
Mass treatment programs are “very difficult to implement” said Rachel Bick, global health research program manager in the Weil lab.
“There’s not a television in every home, and not every person has a cell phone, so it’s hard to get the information out,” Bick said, adding that it’s often challenging to reach more isolated villages.
Despite the challenges, Weil said he feels lucky to be studying diseases that could be eradicated in coming years.
“Right now, they’re still a major problem,” he said. “But there's a chance that within our lifetime, these diseases might be gone, and they’ll just be in the medical history books.”
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