Meet Pasteur and See How Understanding Microbes Changed Lives for the Better
Part 2: Microbes as causes of disease, and the quest for vaccines
An early impression of rabies’ dangers
In October 1831 in the countryside, 9-year-old Louis Pasteur was a testimony of the suffering caused by a mad dog bite to a farmer. He smelled and heard the scream as the hot iron melted the man’s flesh to neutralize the poison. 8 people died in the atrocious agonies of the hydrophobia disease from this dog.
From microbes’ uses to microbes’ dangers
At the beginning of his career as a chemist, Pasteur was brought to the powers of microbes, the good and the bad, as he helped the industries of wine and beetroot control their fermentations.
When he was asked for help by his old friend Dumas to save the silkworm industry and found the germs causing pebrine in the parent moths, allowing breeders to select healthy eggs, Pasteur realized that this simple preventative measure could be applied to other diseases. He saw the potential of the discovery for a better future:
“It is in the power of man to make parasitic maladies disappear from the face of the globe, if the doctrine of Spontaneous Generation is wrong, as I am sure it is.” — Pasteur.
In 1872, at a time when over one woman in 20 died of child-bed fever, Pasteur attended an oration by a renowned physician on the hypothetic causes of these fevers. The doctor was suddenly interrupted by a bellowing voice, from 50-year old half paralyzed Pasteur claiming: “The thing that kills women with child-bed fever — it isn’t anything like that! It is you doctors that carry microbes from sick women to healthy ones!” Pasteur had read about Koch’s work (more about Koch in a later article), which clearly showed that germs cause diseases, and he wanted to translate this knowledge to prevent germs from killing people.
“The thing that kills women with child-bed fever — it isn’t anything like that! It is you doctors that carry microbes from sick women to healthy ones!” — Pasteur
Anthrax, and the discovery of immunity in recovered cows
One day in his laboratory, Pasteur found that microbes from the air had contaminated a bottle of boiled urine in which he had seeded anthrax germs — and to his surprise, there were no anthrax germs left, as if they had been choked by the air-borne bacilli. Wondering if the bacteria could also protect animals and humans from the disease, he and his assistants Roux and Chamberland started inoculating guinea pigs with anthrax and then shooting doses of billions of harmless bacteria into them, meant to oppose the anthrax infection. An early intuition of the huge potential of probiotics to protect against infections. Unfortunately, this experiment didn’t work. So Pasteur and his acolytes joined Louvrier who was testing his treatment to save cows from anthrax. Some cows naturally recovered from anthrax, so Pasteur proposed an experiment to asses the causality of healing: to give anthrax to 4 cows, and treat 2 of them with Louvrier’s cure. They did it. After a while, one cow died and one cow recovered in each group, treated and nontreated — questioning the efficacy of the cure.
With the two recovered cows, Pasteur had the idea of testing an even stronger strain of anthrax. 5 drops were injected into the cow’s shoulders, and everyone waited. The cows didn’t as much as shiver from the vicious inoculation, to the joy of the investigators. Pasteur solemnly affirmed:
“Once a cow has anthrax but gets better from it, all the anthrax microbes in the world cannot give her another attack — she is immune.”
Pasteur then wanted to give animals “a little attack of anthrax, a safe little attack that won’t kill”.
For the next ten years, Pasteur, Roux, and Chamberland trained their microscopes and perspectives on how to bring about immunity in dozens of diseases.
Chicken cholera, when old-tame microbes save lives
In 1880, Pasteur was manipulating the tiny microbe causing chicken cholera. He cultivated the microbes from chicken meat and fed a few drops, on bread, to cackling chicken, observing the effects of contamination, and establishing that the inoculations always caused the birds’ death.
A lot of flasks were used for culturing the microbes, some of them containing chicken cholera batches several weeks old. Before a big cleanup, Pasteur had the idea to test the old broth on chicken. Healthy birds were inoculated and soon, started demonstrating symptoms of drowsiness, stopped eating and their feathers ruffled. The next day, he came to put them in the post-mortem board, but found them perfectly happy and recovered. For the very first time.
As the team came back from holidays, there were not many volatiles left to pursue inoculations — they had decimated the stocks, and the laboratory assistants had failed to buy and breed new ones. They gathered a few new chicks and the ones that had recovered and inoculated everyone with a virulent cholera strain. The chicken who had previously healed from the disease didn’t even get the slightest sick, while the same strain killed all the new chickens in 24 hours.
“When the microbes age, they get tame… They give chicken the disease, but only a little of it… and when she gets better she can stand all the vicious virulent microbes in the world… This is our chance — this is my most remarkable discovery — this is a vaccine I’ve discovered, much more sure, more scientific than the one for smallpox where no one has seen the germ… We’ll apply this to anthrax too… to all virulent diseases… We will save lives!”
Pasteur, at age 56, started the most hectic part of his life. The trio replicated the experiments and confirmed the immunity of vaccinated chicken.
The Ottomans had been using vaccination against smallpox long before Pasteur, possibly since 1670, and Lady Montagu reported the idea back to Europe in 1721. This process was then called “variolation” and consisted in collecting infected fluids from smallpox pustules and scratching the skin of the recipient to deliver the small quantity of pathogen directly by the blood. The recipient would then develop symptoms lasting 2 to 4 weeks, and recover, newly immune. For a disease that caused 3 out of 10 infected people to die, and the rest to live with sequels, this was a great bargain. Edward Jenner perfected the vaccine using fluids from blisters on the skin of cowpox-infected cows. He delivered his treatment since 1796, and the name of vaccination came from this disease — vacca for cow in latin.
Pasteur knew about Jenner’s work, but he thought he had brought vaccination to a new scale of understanding:
“In this case, I have demonstrated a thing that Jenner never could do in smallpox — and that is, that the microbe that kills is the same one that guards the animal from death.” — Pasteur, in a meeting of the Academy of Medicine.
Pasteur, overexcited, believed the vaccine could also protect from other diseases, as first experiments seemed to show, but he was proven wrong. Pasteur’s overstatements and extrapolations to saving humanity from disease offended doctors and brought the researcher enemies — even an invitation to a duel (where he did not go).
The great anthrax public challenge
A horse doctor named Rossignol thought Pasteur was promising much but not delivering solutions to present suffering. Farmed animals were still succumbing to anthrax. So he invited the loudmouth to a grand public experiment to demonstrate, or not, the efficacy of his proposed vaccine.
The Agricultural Society of Melun raised money to buy 48 sheep, 2 goats, and a few cows. Roux and Chamberland who had not been sleeping for a long time and were starting to drop flasks and have visions of chicken-headed guinea pigs were called back from their departure on holiday by Pasteur, for a “public demonstration that our vaccine will protect sheep against anthrax”. They dedicatedly hurried back for the attempt, which consisted in vaccinating half of the animals, and then injecting all of the animals with deadly anthrax.
The assistants, bewildered and worried, argued that the procedure was not fine-tuned and may kill some of the animals. But Pasteur roared “what worked with fourteen sheep in our laboratory will work with fifty at Melun”. They set back to work to get the vaccines ready. The day of the experiment finally came, and the three men came before the crowd and journalists, unpacked their glassware, and shot 5 drops of the first vaccine into the thighs of 24 sheep, one goat, and half of the cattle.
Twelve days later, the show was repeated, for an injection of the second vaccine, a stronger version of the bacilli. The animals bore up gracefully.
The men were anxious and coming to take the temperature of inoculated animals regularly. Thankfully, the vaccinated herd held up without symptoms.
Finally, all the animals, vaccinated and control, were brought before the jury to receive their lethal dose of anthrax on the 31st of May 1881. For the next few nights, hair grew white on the heads of the three scientists. On the 2nd of June at 2 pm, before eminent expectations, journalists, and reporters, Pasteur and his associates marched solemnly into the field and were welcomed by hurrahs. None of the vaccinated 24 sheep had so much as a fever, while 22 of the 24 non-treated were lying dead, the remaining two staggering about and oozing black blood. A triumph that changed the opinion of all the dubious minds in the audience. Pasteur, in his glory, “was a kind of Messiah who was going to lift from men the burden of all suffering”, in De Kruif’s words.
The demand for the vaccines sky-rocketed and the laboratory was quickly turned into a factory, to treat hundreds and thousands of animals.
But soon came complaints — there seemed to be quality issues and uncertainties associated with the vaccine, and the most precise of all microbe-hunters, Koch, challenged Pasteur’s statements on the vaccine properties. Why wasn’t it reliable? Because the vaccine was not pure and perfectly replicated from batch to batch — it included a wild collection of microbes that had no business in the broth.
Eradicating rabies
Instead of becoming a pharmaceutical company founder, Pasteur remained true to his work and continued seeking how he could put himself to the service of humanity. He took on the study of rabies.
Why rabies? It was not the disease killing most people, but Pasteur professed “I have always been haunted by the cries of those victims of the mad wolf that came down the streets of Arbois when I was a little boy.”
“I have always been haunted by the cries of those victims of the mad wolf that came down the streets of Arbois when I was a little boy.”
It was a very courageous choice, as the deadly virus had to be collected from the foamy jaws of contaminated mad dogs. Not only were the investigators exposed to the rabid animals’ vicinity, but they had to bring their own lips close to the beasts' fangs. Pasteur and his acolytes sucked the disease into a small glass tube to aspire virus-rich saliva from these ferocious mouths. Suck just a tiny bit too far, and rabies touches your own tongue… If this kind of work didn’t require total madness, then it must have been absolute dedication.
Mad dogs in the laboratory were allowed to bite healthy dogs until the scientists had material to study. The trio — Pasteur, Roux and Chamberland — soon found that the rabies virus concentrated in the brain and spinal cord, but they were not able to cultivate it or even to see it. They used rabbits to grow the virus, but when they inoculated it to other animals, all of them died. Always. Roux and Chamberland were convinced there was no taming this germ. When all ideas were tested and no method made the virus old and gentle, the two assistants were discouraged. Until one dog recovered. Inoculated, directly into his brain, with a virulent strain, he didn’t show any symptoms. The possibility of vaccination existed.
“Do the same experiment over again — no matter if it failed last time — it may look foolish to you, but the important thing is not to leave the subject!” — Pasteur to his assistants Roux and Chamberland.
So they continued testing protocols and came up with one that showed effects: extracting a little section of infected rabbit spinal cord and hanging it to dry for 24 days in a germ-proof bottle. Injecting this shriveled tissue into the brain of a healthy dog did not deliver the deadly disease. They tested different durations and repeatedly inoculated the dogs with the dried nerves, and they stayed well. But were they immune? The day had come to test if the treatment would help them endure the virulence of the fresh virus. Two vaccinated dogs against two untreated were exposed.
New triumph! And new velleities to save the world from hydrophobia. Pasteur wanted to vaccinate all the dogs in France. But a veterinarian said with 2.5 million dogs, this was an impossible endeavor. Then Pasteur said it is not the dogs, but the people bitten by mad dogs that should be vaccinated. When someone is exposed, it takes 2 weeks before symptoms show. The protocol was tested successfully on dogs, and then came messages from unfortunates who were bitten and begged to try the vaccine. Faced with reality, Pasteur was unsure. Testing the protocols on animals was one thing, but risking the lives of people was another. For a moment, he was inclined to try it on himself, but the question was suddenly solved by a mother bringing his suffering son, bitten two days before. Two doctors said the boy was sure to die, so the test was worthwhile. For fourteen days, young Joseph received injections of weakened microbes. Day after day, everyone scrutinized signs of the disease, that never came.
This was a new soar of fame for Pasteur, a crowning of his lifelong hopes for humanity. Calls for help came from all over the world, of people he was able to save.
“My researches on the fermentation have led me naturally toward these studies to which I have resolved to devote myself without too much thought of their danger or of the disgust they inspire me” — Pasteur.
“Public usefulness and the interests of humanity enable the most disgusting work and only allow enlightened men to see the zeal that is necessary to overcome obstacles”. — Lavoisier.
Pasteur’s legacy: not only a researcher but a great communicator
For his companions, De Kruif wrote, Pasteur was “a composer of epic searchings, a Ulysses of microbe hunters.” It was, of course, important to investigate microbes' livelihoods and omnipresence. But to make a difference for the future of humanity, something more was required. The ability to make a lasting impression that could change mentalities and medical practices definitively. And that is another of Pasteur’s talents.
Pasteur the showman made a visual demonstration during a conference on germs at Paris Sorbonne. He darkened the hall, to the perplexity of the audience, and shot a single bright beam of light through the blackness. “Observe the thousands dancing specks of dust in the path of this ray. The air of this hall is filled with these specks of dust, these thousands of little nothings that you should not despise, for sometimes they carry disease and death; the typhus, the cholera, the yellow fever and many other pestilences!”
“Observe the thousands dancing specks of dust in the path of this ray. The air of this hall is filled with these specks of dust, these thousands of little nothings that you should not despise, for sometimes they carry disease and death; the typhus, the cholera, the yellow fever and many other pestilences!” — Pasteur, during a conference in the Sorbonne.
This sudden and violent appreciation of the stakes gave rise to a rumor of conversations that filled Paris, France, and beyond.
Pasteur’s work had enormous repercussions for the industries he helped when he came up with pasteurization — to make good use of bacterial fermentation in beetroot industries of alcohol and sugar, in wine and beer production, as well as for human health. He was a spokesman who spread awareness and understanding about the omnipresence of microbes in the air, surfaces, and everywhere. He contributed to changing medical practices for the betterment of public health. He is also known for prolonging Spallanzani’s experiments and demonstrating once and for all that there was no such thing as Spontaneous Generation, giving all the more reason to fight microbes and believe in the end of contagious diseases. He inspired generations after him. In the 1892 meeting held in the Sorbonne on his 70th birthday, here is the discourse he dedicated to the students:
“Do not let yourselves be tainted by a deprecating and barren skepticism, do not let yourselves be discouraged by the sadness of certain hours which pass over nations. Live in the serene peace of laboratories and libraries. Say to yourselves first: What have I done for my instruction? and, as you gradually advance, What have I done for my country? until the time comes when you may have the immense happiness of thinking that you have contributed in some way to the progress and good of humanity…”
The details and quotes are from the 1926 book Microbe Hunters by Paul De Kruif, who retraces the discoveries and characters that made the beginnings of Microbiology. De Kruif is a fantastic storyteller who learned the intimacy of those early scientists — if you liked this chronicle, I recommend you read the whole book!
