Merck was also surprised at the effect of avermectin. Just by injecting or having the animal drink it orally had a daramatic effect to get rid of harmful parasites and ticks. If it works on animals, it would work for humans, Omura thought. Therefore, Omura started experimets to develop a medicine for disease caused by nematodes* living inside the human body, parasites, mites and so on. *Nematodes are elongated cylindrical worms parasitic in animals or plants or free-living in soil or water. They are also called roundworms.
After confirming human safety for the enhanced form of avermectin named Ivermectin,Omura conducted a trial to treat Strongyloidiasis, which is a prevalent syndrome in southeastern Asian countries like Thailand, Vietnam, and Indonesia. Strongyloidiasis is caused by Strongyloides stercoralis, a thread-like insect of about two millimeters. They live in the small intestine. They are widely distributed among the tropic and temperate zones of the world.
Infection occurs when the young larvae living inside the soil get transferred to human skin and nails. When the nematode* grows into an adult, it lays eggs inside the human intestine. When the eggs hatch and become larvae, they would mix with human blood or lymphatic fluids and move into the lungs or intestinal tracts to grow into adults. Then they lay eggs again and keep on reproducing. There were about 40 million patients with Strongyloidiasis worldwide, but Ivermectin was successfully destroying the infection source.
Scabies, a skin disorder caused by parasitic itch mites (Sarcoptes scabiei) living on human skin was also a very troublesome condition without any special medicine. When one is infected, the skin becomes extremely itchy. A rash with small red spots appear on the surface of the skin and spreads throughout the body. But after Ivermectin was introduced, the condition healed from just taking a single dose.
In the tropical regions of Africa and South America, there has been a dangerous disease called river blindness or Onchocerciasis. Onchocerciasis had spread through tropical rivers by filarial Onchocerca worms in river water. When one is stung by a type of blackfly (Simulium), microfilariae enters the human body through the bitten wound. Later, the female microfilariae mate and give birth to the next generation. They eventually invade the eyes and cause blindness. Female adult microfilariae continue to live under the skin for 15 years.
Before Ivermectin was developed, 18 million people had been infected by this disease every year. Out of the 18 million, about 270,000 people went blind, and 500,000 people suffered damage to eyesight. To counter Onchocerciasis, Ivermectin was administered. After taking a small amount of it, people were no longer infected. Merck, which co-developed this medication with Omura named the medication "Mectizan".
In order to prevent spread of Onchocerciasis, WHO (World Health Organization) asked Merck to provide Ivermectin for free. Omura who discovered the source of this medicine, had also agreed to offer it for free. As a result, it was distributed to prevalent African tropical zone without any charge.
On September 16, 2004, Omura visited the WHO headquarters in Geneva, Switzerland, to meet the President and managers in charge of infectious disease. Omura inquired about the effectiveness of Ivermectin against Onchocerciasis. Everybody unanimously praised the great effect of Ivermectin.
“This medicine has unrivaled effect compared to any other medication for tropical disease,” they said.
Omura was very happy to hear these words, because many antibiotics are hindered by resistant bacteria at some stage. Bacteria can sometimes get used to the medicine and the medicinal effect could fade away. However, for Ivermectin, more than 300 million people per year had been taking it since 1987, but not one nematode had survived this medicine.
WHO decided to recommend strategies to bring in the whole community to take Ivermectin at the same time. If they continue this for some years, they could completely destroy Onchocerciasis someday. Ivermectin cannot kill adult microfilaria already living inside the human body, but if newly infected patients could be suppressed, the insect and the disease itself could go extinct. From 1988 onwards, Omura and Merck, offered free Ivermectin to affected countries.
After their arrival in Ghana, Omura and WHO officials took a couple of cars and drove towards the village of Asubende which is 100 kilometers north from Kumasi, the country’s second largest city. Asubende was a village surrounded by red soil and green trees. Villagers started to gather around when the visitors stopped the car. Children showed friendly smiles with bright curious eyes. They were all looking straight at Omura.
As Omura looked around, he saw a blind person holding on to a long stick which was held by a young child in front. By having the blind adult hold on to the horizontally held stick, the child in front would lead and guide the blind adult. While being helped out by other villagers, it seemed like the blind people were leading a quiet life.
“Since children here are taking Mectizan (Ivermectin), they wouldn’t infect others. Nor would they have to lose their eyesight,” explained a WHO staff. In this village with 500 inhabitants, one in every ten children come from a home with a blind person in the family. Eyesight deteriorated gradually, and many of the breadwinners or adults who were supposed to work had turned blind.
Under a big tree near the village center, people infected by lymphatic filariasis also joined the blind adults and gathered around. Microfilariae had entered into the sufferers’ lymphatic system, and affected their lymphatic vessels or lymph nodes to trigger disorders. Lymph fluid would get accumulated in one part of the body. The binding joints of the body bulged out and looked like thick tree barks. Omura utterly felt his heart sink by looking at so many people plagued by this disease.
In contrast to such adults, children who were not affected by Onchocerciasis were full of life. Omura tried to talk to the children in simple English. No one had ever heard of Japan or Tokyo. Omura looked into their eyes and asked them directly. “Do you know Mectizan?” As soon as he said so, the children gave a lively response. The interpreter introduced Omura to the children in their local language. "He is the professor who made Mectizan."
A high-pitched cheer filled the room. "Mectizan! Mectizan!" The children called out one after another. Omura trembled with awe to see the brilliant eyes of the children and their bursting youthful energy.
When these children grow up to be adults, Onchocerciasis and lymphatic filariasis will probably be extinct. The village would hopefully turn into a lively community.
The guide brought in a camera and held it up to shoot some photos. The children happily rushed to surround Omura. When Omura held out his hand to form a peace sign, the children also raised their peace signs with laughter. Being surrounded by these children’s young and wholesome energy, Omura had realized for the first time that had shed light to this part of Africa.