Onchocerciasis, also known as river blindness, is a parasitic disease caused by the filarial nematode Onchocerca volvulus (O. volvulus). River blindness is on the World Health Organization’s list of 20 neglected tropical diseases. As a neglected tropical disease, river blindness is mainly prevalent in tropical areas and mostly affects impoverished communities with a high infection rate in women and children. Moreover, 99% of individuals infected with the disease live in 31 African countries. Current estimates show that close to 18 million individuals are infected with onchocerciasis worldwide, and of these individuals, almost 300,000 people have been permanently blinded by the disease. As such, river blindness is the second leading cause of blindness worldwide.
The disease is transmitted to humans by black flies, which reproduce in rivers and streams. The black flies carry the nematode larvae and when a black fly bites a human, the nematode larvae is transferred to the human host. The larvae then reproduce within the human host and accumulate in large numbers in the skin and eventually travel to the eyes and other organs to cause permanent blindness. Current treatment for river blindness relies on the antiparasitic drug ivermectin, which helps to control the spread of the nematode larvae throughout the body but does not eliminate or kill the adult O. volvulus nematodes that cause the disease. Additionally, it appears the nematode larvae may develop resistance to ivermectin. As such, there is an urgent need for drug discovery programs that can help combat river blindness.
Researchers from Washington University School of Medicine in St. Louis recently announced that the National Institutes of Health have granted their research team 5.5 million dollars to discover and develop drugs against river blindness. A lead researcher on the team, Dr. Makedonka Mitreva, said, “we are pleased to be doing this type of global health research, seeking new treatments for infections that tend to be neglected in terms of the amount of research and funding dedicated to them, even as they affect so many millions of people.”
The researchers have used phenotypic screening of drug libraries of approved drugs to identify whether any of the drugs can be repurposed to treat and kill adult O. volvulus nematodes. This research was recently published in the journal Pathogens, where the researchers discovered 13 drugs that may be affective in killing adult nematodes and treating river blindness. The next step in the process is to modify and optimize the structure of the identified drugs and then test them in the laboratory to determine their efficacy. As Dr. Mitreva said, “the World Health Organization has a goal of eliminating river blindness by 2030, and we believe developing effective treatments against the adult worms […] will be required to meet this goal.” This study and the future research from the team at Washington University will greatly improve the lives of the millions of individuals living with O. volvulus infection.
Sources: World Health Organization; Pan American Health Organization; The Lancet; Washington University in St. Louis; Pathogens