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99% Invisible
99% Invisible

Drug Story: Ivermectin

May 26, 2026 • 48m

Summary

⏱️ 10 min read

Overview

This episode of 99% Invisible features Drug Story, a podcast exploring the history of ivermectin—a miracle drug that revolutionized treatment for parasitic diseases like river blindness and hookworm. The episode traces ivermectin's discovery in Japanese soil, its life-saving impact in Africa and beyond, and its controversial pivot during COVID-19 when it became central to debates about medical freedom, misinformation, and the erosion of trust in scientific institutions.

The Hookworm Epidemic in the American South

In the early 1900s, parasitologist Charles Stiles discovered that hookworms were endemic in the southern United States, affecting an estimated 40% of the population. The parasite caused severe anemia and lethargy, contributing to stereotypes about lazy Southerners. With funding from John D. Rockefeller, Stiles launched a campaign involving treatment with thymol, building outhouses, and distributing shoes to prevent infection through bare feet. This effort laid the groundwork for the national public health infrastructure but faced opposition from groups defending medical freedom against government intervention.

  • Charles Stiles identified hookworms as causing widespread anemia and lethargy in the South, affecting 40% of the population
  • Hookworm larvae enter through bare feet, travel through the bloodstream to lungs, are coughed up and swallowed, then attach to intestines
  • The Rockefeller Sanitary Commission implemented three strategies: treatment with thymol, building outhouses, and distributing shoes
  • The National League of Medical Freedom opposed federal health initiatives, arguing for medical freedom and alternative treatments
" Hookworm larvae live in the soil and burrow through to reach their target, human feet, where they quickly slip into the pores of bare skin. This might cause a rash, It was called ground itch. But the worm is in. "
" my hobby may be summarized in the two words, clean up. In our filthy American habits of daily life, I see the cause of more preventable sickness and preventable death than I do in any other one factor. "

River Blindness and the Global Parasitic Crisis

River blindness, caused by the parasite Onchocerca volvulus transmitted through black fly bites, devastated communities in sub-Saharan Africa. The disease affected 20 million people worldwide, causing hundreds of thousands to go blind or suffer impaired vision. When the worm larvae entered the eyes, they triggered immune responses leading to inflammation and blindness, often striking people in their productive years and devastating entire villages as young people fled and families collapsed under the burden of caring for blind relatives.

  • River blindness affected 20 million people worldwide, with hundreds of thousands blinded or visually impaired
  • Black flies transmit Oncocerca volvulus larvae, which grow under the skin; when larvae enter the eyes, immune reactions cause blindness
  • The World Bank used DDT to kill black fly populations in the 1970s, but it was dangerous to environment and human health
" Blindness often comes to men and women in their prime productive years. Sons or daughters must drop out of the workforce to care for a blind parent. Marriages and parenthood are less common. Eventually, young people flee the village. "

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