Is it actually true that the bacterium was never found again?
A golf-course bag still owns the strain
The ping is a bag, not a eureka moment. Satoshi Omura's group at the Kitasato Institute in Tokyo treated soil collection as a habit, not a hunt for a headline.
Streptomyces already had a Nobel in the family - Selman Waksman's streptomycin - so Omura's bet was not romantic. Soil microbes poison their neighbours. Some of those poisons become drugs. The work is volume: thousands of cultures, most of them dead ends, a short list of broths worth shipping. From many thousand isolates he kept about fifty that looked promising. One of those fifty, sent in 1974, carried strain MA-4680, later catalogued as Streptomyces avermitilis and, after a 2002 phylogenetic pass, proposed as Streptomyces avermectinius. The sample came from ground near a golf course bordering the ocean at Kawana.
Merck's people, and later Omura himself in the Nobel lecture, said the same awkward fact out loud: exhaustive searches never found another avermectin-producing organism. The entire human and veterinary tree hangs on that one isolate. That is why this desk files the origin as a ping rather than a platform. A platform would have turned up twice. A ping is a single hit that has to be cultured, shipped, and defended. If you want the molecule's later clinical life, start here and then move to the Stromectol 3 mg monograph - do not start with a social post that skips the bag.
Fifty shipped cultures, one mouse cleared
| Desk column | Omura / Kitasato | Campbell / Merck |
|---|---|---|
| Ping they owned | Soil isolate MA-4680 | Mouse anthelmintic screen |
| What they could not do alone | In-animal worm kill at scale | Find the organism in Japan |
| Output that moved | Shipped cultures, fermentation notes | Avermectin identified, then edited |
| Later stamp | Shared 2015 Nobel | Shared 2015 Nobel |
Kitasato could grow the organism and describe the fermentation. It could not, at scale, ask whether a broth killed worms living inside an animal. That half of the job sat with William Campbell's parasitology group at Merck Sharp & Dohme Research Laboratories. Boyd Woodruff was posted alongside the Tokyo bench to keep the collaboration from becoming a polite exchange of letters. The screen they used was blunt and fast: mice infected with Nematospiroides dubius, later Heligmosomoides, fed a culture, then watched for vanished worms and vanished eggs.
One of the first fifty specially selected microorganisms cleared the gut. Unpurified broth killed the intestinal worms and wiped the faecal egg signal. Isolation chemists then had to name the causal stuff. It was not one molecule. Analytical work showed a complex of eight closely related structures, later called the avermectins, with a family resemblance to the milbemycin pesticides. Campbell's lecture is dry about the next step: fermentation people coaxed the bacterium to make more, synthetic people made hundreds and then thousands of relatives, and parasitologists ranked them. The ping had become a trace - a partnership with two benches and one organism that still has not been re-found.
Hydrogen at 22-23, and a name that died
The bacterium's product is not the tablet. The tablet is a hydrogenation of one bond, chosen after a grind of analogues.
Merck's chemists added hydrogen at the carbon 22-23 position of selected avermectins. The resulting pair - at least 90 percent 22,23-dihydroavermectin B1a and less than 10 percent B1b - is ivermectin. Campbell wrote that the logical name was hyvermectin, until someone noticed that in some languages 'hyver' means testicle. The bottle became ivermectin. The American Chemical Society later summarised the analogue hunt as a 25-fold potency gain over the worm drugs then on the shelf, with a cleaner safety margin in the host. That is the whole point of a natural-product lead: you do not swallow the broth; you swallow the edit.
US Stromectol is that edit pressed as a 3 mg tablet - microcrystalline cellulose, pregelatinized starch, magnesium stearate, butylated hydroxyanisole, citric acid. The 3 mg chip is the unit that later onchocerciasis programmes counted into weight bands. History people sometimes talk as if 'ivermectin' arrived fully formed from dirt. It did not. Dirt gave a family. A hydrogenation gave a medicine. A tablet strength gave a countable object. The working card on this site is about that object. This page is about why the object exists at all.
Ivomec years before a human river file
The first market was veterinary, in the early 1980s. Cattle, sheep, horses, dogs - heartworm included - took the molecule years before a person with river blindness swallowed a 3 mg chip. Ivomec and its cousins became a bestseller in animal health. That chapter is not a footnote and it is not a license. It proved the chemistry worked in living hosts, paid for the human programme, and left a residue that later confused people: paste formulated for a 500 kg animal sitting on a farm-shop shelf next to a rumour.
Campbell had already flagged a human possibility while the veterinary file was still the main commercial story. Onchocerca volvulus, the filarial worm behind river blindness, looked like a target because the drug hammered microfilariae - the larval stage in skin and eye - even though it left the long-lived adults in their nodules. That gap is the reason onchocerciasis became a repeat-dose public-health file rather than a one-pill cure story. The Edinburgh desk flags it here so the history does not pretend the 1987 human approval was a sudden conversion. It was a second market built on a first one, with a different endpoint: skin-snip counts and sight, not a feedlot.
Aziz in West Africa, then an open pledge
Mohammed Aziz at Merck, working with WHO, designed and ran the West Africa clinics that moved the molecule from a veterinary win to a human onchocerciasis file. Those studies - later summarised on the US label as randomised, double-blind, placebo-controlled and comparative work in endemic West Africa, with diethylcarbamazine citrate as the old comparator - are the trial carton's job. This page only needs the hinge: once the clinics showed a single oral dose could crash skin microfilariae for months, the commercial problem flipped. The people who needed the 3 mg chips lived in places that could not buy them at a patent price.
In October 1987 Merck's then-CEO Roy Vagelos announced the company would donate Mectizan - as much as needed, for as long as needed - to control river blindness. The Mectizan Donation Program and its expert committee were stood up as an independent secretariat at the Task Force for Global Health in Atlanta, not as a marketing desk inside Rahway. That open-ended wording matters. A five-year gift dies. An open pledge lets ministries plan annual mass drug administration. Vector control under WHO's Onchocerciasis Control Programme had already spent a generation larviciding blackfly rivers in West Africa. MDA with a donated 3 mg tablet became the tool that could travel where spraying could not. The Mectizan programme history and the 2015 Nobel press release both treat that pledge as the moment the soil ping became a public-health file.
Colombia first, then three more closures
Elimination is a verification, not a vibe. WHO asks for interrupted transmission plus years of surveillance before it stamps a country.
1974
Omura's group ships a short list of cultures; MA-4680 is among the first fifty.
Mid-1970s
Campbell's mouse screen finds a broth that clears Nematospiroides; avermectins are isolated.
Early 1980s
Ivermectin launches in animals and becomes a veterinary bestseller.
1987
Human onchocerciasis use plus Merck's open Mectizan pledge; MDP secretariat opens.
2013-
WHO verifies elimination in Colombia, then Ecuador, Mexico, and Guatemala.
2015
Omura and Campbell share the Nobel Prize in Physiology or Medicine with Tu Youyou.
The Onchocerciasis Elimination Program for the Americas, later sponsored by The Carter Center, coordinated six historically endemic countries: Brazil, Colombia, Ecuador, Guatemala, Mexico, and Venezuela. Foci were smaller and more isolated than the African belt, which made high geographic and therapeutic coverage possible. Colombia stopped treatment, ran post-treatment surveillance, and became the first country in the world to receive WHO verification that onchocerciasis transmission had been eliminated. Ecuador, Mexico, and Guatemala followed. That is four closed ledgers in the Americas, not a global all-clear. Brazil and Venezuela still had harder Yanomami-area foci on the later maps. Africa remains the large remaining file.
Niger later joined the verified list on the African side, and several other countries have interrupted transmission in individual foci. Lymphatic filariasis borrowed the same donation machinery in co-endemic zones. None of that rewrites the origin story. It shows what a 3 mg onchocerciasis chip can do when coverage is high and the pledge does not expire. It also shows the limit: adults live on, so a country only closes the file after years of suppressed microfilariae and dead blackfly transmission, not after one heroic campaign season. The WHO neglected-tropical-disease pages keep the current scoreboard. This history page stops at the shape of the ledger, not today's weekly count.
A 2015 medal does not widen the label
October 2015: the Nobel committee split the Physiology or Medicine prize. Omura and Campbell for avermectin, Tu Youyou for artemisinin. The citation was nature-derived therapies against devastating parasitic diseases. The lag was ordinary for this prize. The committee waits until impact is past argument. By 2015 the Mectizan file had decades of MDA, billions of treatments in the programme's own accounting, and those first verified closures. The medal is a stamp on a finished history, not a hunting license for new diseases.
This Edinburgh desk flags the misuse of that stamp. A soil-to-Nobel arc is catnip for people who want the tablet to be a general elixir. The history does not say that. It says one organism, one edit, one donated 3 mg chip, one larval target in onchocerciasis, and a public-health machine built around annual counts. Viral claims that treat the medal as proof the molecule 'must work' against a respiratory virus are a category error. The trial carton on this site posts the negative hospital endpoints. The working card posts the weight bands. This page posts the origin and then stops. If you need a clinician's byline on the whole set, Dr. Julian Osei signs the consult below from the infectious-disease side of this desk.
How this desk posts a soil history
Ping the bag. Trace the two benches and the hydrogenation. Flag the veterinary paste and the medal-as-license move. Post the river-blindness file: 1987 approval, open pledge, MDA, verified closures. That is the method on this page, and it is why the prose does not walk the monograph's circuit of mechanism, pharmacokinetics, and a bottom line. Those belong on the drug page. Sibling journal pieces keep the skin-snip arithmetic and the 3 mg count versus 150-200 mcg/kg in their own genres.
Readers who want a moral usually ask whether dirt can still deliver medicines. Sometimes. The easy Streptomyces finds were skimmed generations ago. Ivermectin remains a reminder that a stubborn culture collection plus an animal screen can beat a slide deck. It is also a reminder that a medicine's reputation is earned in a named disease. Onchocerciasis gave Stromectol 3 mg its human file. Nothing in Kawana, Rahway, or Stockholm automatically transfers that file to a different pathogen. Bring a named parasite to your own clinician before anyone counts chips. This desk is teaching, not a pharmacy, and Edinburgh is a byline city, not a dispensary.
Reader mail
Reader questions on this article
Answered by Dr. Julian Osei, MD · Internal medicine & infectious disease
History pings landed on this Edinburgh desk after the soil piece posted. These named readers get a full trace, not a slogan.
Yes, and the people who isolated it keep repeating it because it sounds like a boast until you sit with it. Omura's Nobel lecture says Merck and others searched exhaustively after the Kawana isolate and never found another avermectin producer. The strain from that golf-course bag remains the ancestor of the veterinary products and of every Stromectol 3 mg tablet used in onchocerciasis programmes. That is why I file the origin as a ping. A widespread soil organism would have turned up in a second country by now. This one did not. The collaboration had to keep that single culture alive and productive, which is unglamorous work and also the whole supply story.
Why credit both a Tokyo lab and a New Jersey company?
Because the job split cleanly and neither side could finish it. Kitasato was built to find odd Streptomyces, keep them stable, and describe fermentation. Merck was built to infect mice, read worm kills, purify a complex, and walk a candidate through animal safety and then human clinics. Omura selected about fifty cultures from many thousands and shipped them. Campbell's group found the broth that cleared Nematospiroides. Isolation and analogue chemistry happened on the Merck side. The 2015 prize was shared for that reason, not as a diplomatic gesture. When readers ask who 'discovered ivermectin', I say: Omura found the organism, Campbell's team found what the broth did, chemists made the 22,23-dihydro edit. All three steps sit in the file.
Did people really give this to cows before they gave it for river blindness?
They did, by several years. The early-1980s launch was veterinary - Ivomec and related brands - and it became a major animal-health product while human onchocerciasis trials were still being organised in West Africa. That order is ordinary in antiparasitic development: you learn the molecule in livestock and companion animals, then you ask whether a human filarial disease can use a related dose. What it is not is permission to raid a farm shelf. Animal pastes are concentrated for bodies many times ours and may carry other ingredients. The human file is a 3 mg tablet counted into an onchocerciasis weight band, or a 200 mcg/kg strongyloidiasis band, prescribed for a named infection. The veterinary chapter funded and de-risked that file. It does not replace it.
What made the 1987 Mectizan promise different from a normal donation?
The wording. Merck pledged Mectizan as much as needed, for as long as needed, for river blindness, rather than a fixed number of years or a fixed number of bottles. Roy Vagelos announced that in 1987 once the human data were in. An independent secretariat at the Task Force for Global Health in Atlanta, with an expert committee, then ran the allocation so ministries and NGOs could plan annual mass drug administration without a cliff. That is why onchocerciasis programmes could think in decades. A five-year gift would have died in the middle of a transmission cycle. The open pledge is also why this history page treats 1987 as a hinge equal to the soil sample: without it, the 3 mg chip stays a clinic curiosity.
Which countries actually closed their river-blindness file?
In the Americas, WHO has verified elimination of transmission in Colombia first, then Ecuador, Mexico, and Guatemala. Those four used the Onchocerciasis Elimination Program for the Americas model: small foci, high coverage, donated Mectizan, then years of post-treatment surveillance before anyone asked Geneva for a stamp. Brazil and Venezuela were the harder remaining pair on that map, especially along the Yanomami area. Africa is a larger, unfinished ledger, with individual countries and foci at different stages; Niger later reached verification. I tell readers not to flatten that into 'the world beat river blindness'. Four verified closures plus progress elsewhere is already a historic public-health file. It is not a wrap party.
If the Nobel came in 2015, does that mean the science was late?
No. The science sat in the 1970s. The prize sat in 2015 because this committee likes impact that has already happened, not a promising poster. By then you had decades of MDA, a donation programme that had become a template for other neglected diseases, and the first WHO-verified national closures. Tu Youyou's artemisinin work shared the year for the same reason: a nature-derived antiparasitic that changed a disease's map. The lag is a feature of the prize, not a slight. What I flag is the opposite error - treating the medal as if it were a 2015 discovery that somehow blesses every new use someone tweets. The medal closed a river-blindness history. It did not open a viral one.
Is ivermectin just the stuff the bacterium makes, bottled?
Not quite, and the gap is the interesting part of the history. Streptomyces avermitilis makes a family of avermectins - eight close structures in the original complex. Merck's chemists hydrogenated the 22-23 bond on selected members and landed on a defined pair that was more stable and kinder to the host. Campbell even joked that 'hyvermectin' died as a name for an accidental linguistic reason. So the 3 mg tablet is a semi-synthetic descendant, not a dried culture. That is normal natural-product work. It also explains why 'natural' is a sloppy word here. The inspiration is a soil metabolite. The medicine is an edited, quality-controlled tablet with a labelled onchocerciasis band. I send people to the drug page when they want the chemistry in clinic language.
Does this story mean soil screening is how we should still find drugs?
It means we should not pretend the well is empty, and we should not pretend it is easy. A huge share of antibiotics and antiparasitics came from actinomycetes. The cheap finds were picked over. Omura's method was stubborn volume plus a partner who could screen in animals, not a single inspired walk on a fairway. Modern labs have faster tools and also a habit of abandoning slow culture work. Ivermectin is a standing argument for keeping both. It is not an argument that the next golf course will donate a Nobel. For the disease burden this molecule actually moved, the CDC parasitic-disease pages and WHO's onchocerciasis updates are the right next read, not a nostalgia tour of dirt.
Why does an Edinburgh desk care about a Japanese golf course?
Because the 3 mg onchocerciasis chip that still appears in travel and tropical clinics here has that address on its birth certificate. Edinburgh is where this site's infectious-disease consult is signed, not where the soil was lifted. I still want a reader in Scotland to know the tablet is not a pandemic folk remedy and not a mystery powder. It is a counted object with a Kawana isolate, a Merck edit, a 1987 pledge, and a label that names Onchocerca volvulus. If your question is practical - how many chips, when to repeat, when to screen for Loa loa - jump to the working card. If your question is 'did the trials even happen', open the trial file. This page only posts the soil-to-ledger arc.
General education from a clinician, not personal medical advice. Bring your own history to your own prescriber.
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