Many scientists would train and toil by Pasteur’s side, but the flinty young physician Emile Roux contributed more than any other to Pasteur’s researches into animal and human disease processes. Roux’s medical training had been temporarily disrupted when he, in a fit of anger at the director of the Val-de-Grâce Army Medical School for slighting the serious scientific effort he was expending on his student dissertation on rabies, insulted his superior and was consequently imprisoned and then expelled. As a medical graduate, Roux monastically devoted himself to the systematic study of microbes and immunity in the Pasteur laboratory at the École Normale (and later at the Institut Pasteur). In this role, he was often a thorn in the side of his master, pitting his own methodologies against Pasteur’s, always urging the elder scientist toward greater extremes of scientific rigor. “This Roux is really a pain,” Pasteur complained. “If you listened to him, he would stop you in everything you are trying to accomplish.” Still, the collaboration between the two men, which lasted from 1878, when Pasteur began to concentrate on contagious diseases, until Pasteur’s death in 1895, was an extraordinarily productive one.
Throughout his career, Pasteur was known for his diligence and tenacity: he would approach every research question with an exhaustive, meticulous zeal. Since he often took on problems of particular controversy in his own lifetime, his rigor was never wasted, as he was constantly under attack. The French scientists of the nineteenth century were not content to air their disagreements in sternly worded missives placed in relevant academic journals, as is standard today. Rather, they confronted one another face-to-face before their esteemed colleagues at the Académie des Sciences, the Académie Nationale de Médecine, or even the venerated Académie Française. Pasteur’s fastidious methodology was matched by his aggressive rhetorical manner, a combination that frequently allowed him to make a great show of toppling his rivals’ scientific theories in public—indeed, to terrific applause. These performances were a particular source of satisfaction for Pasteur.
Pasteur professed a belief in research and experiment as a means to end human misery. It was a goal both lofty and earnest. He advised his younger scientific colleagues, “Live in the serene peace of laboratories and libraries. Say to yourselves…, 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 to the good of humanity.” Pasteur’s love for children, in particular, and passion for preserving them against the morbid threat of infectious disease were to become famous. “When I see a child,” said Pasteur, “he inspires me with two feelings: tenderness for what he is now, respect for what he may become hereafter.” Much of Pasteur’s medical research focused on diseases that were particularly associated with childhood illness. Pasteur himself had lost three children to disease: two young daughters to typhoid and another to cancer. Following the death of the third daughter, Cecile, he wrote to a colleague, “I am now wholly wrapped up in my studies, which alone take my thoughts from my deep sorrow.”
Pasteur felt his calling as a scientist was ultimately to spare life and alleviate suffering, and as the secrets of microbiology revealed themselves to him over the course of his career, his conscience guided him toward new humane applications. Early in his career, he painstakingly tested and vigorously defended techniques to control microbial contamination—not just of food and drink but also of surgical wounds—and in doing so saved countless lives around the world. But as his restless mind turned toward other diseases, contagions first of France’s livestock and then of its countrymen, Pasteur began to think of a more fundamental means of preventing the morbidity and mortality caused by infection. Vaccines took hold of his imagination.
Vaccination is the induction of immunity to a disease in an otherwise vulnerable individual, accomplished through intentional exposure to some less virulent form of the disease. The practice began with variolation against smallpox infection, originating in Asia more than a millennium before Pasteur. The procedure consisted of taking a small amount of the pus from an active smallpox lesion and introducing it into a small surgical incision or directly into the nose of a patient with no history of the disease. The resulting infection was milder and less disfiguring than natural smallpox, leading to a case fatality rate of only 1 to 2 percent, as opposed to 30 percent with a natural infection. Variolation was popularized in western Europe during the early eighteenth century by England’s Lady Mary Wortley Montagu. After witnessing its successful practice during her husband’s term as British ambassador to the Ottoman Empire, Lady Montagu insisted that her three-year-old daughter be variolated a few years later when a smallpox outbreak threatened England. Much interest was generated in the British court, and within a year the Prince of Wales’s daughters Amelia and Caroline had been variolated as well. The practice immediately became widespread throughout Britain but had yet to overcome several decades of resistance in France. Only after the unexpected death of Louis XV from smallpox in 1774 did variolation become common among the French.
Since variolation was neither affordable nor accessible to the lower classes, it was never taken up generally as a preventative. Instead, large-scale vaccination efforts were set up only after an epidemic was in progress, limiting the ability of variolation to make a broad impact against smallpox. The physicians who carried out these procedures had no genuine scientific knowledge of why they were effective; it would be more than a century before Pasteur would popularize the germ theory and establish microbiology and immunology as fundamental medical sciences. Many physicians of the eighteenth century believed, for example, that variolation was most survivable when combined with fasting, bleeding, and mercurial purges.
One British country physician, still stricken by the memory of the noxious variolation protocol he himself underwent as a child, was motivated to find a way to diminish danger and discomfort to the patient without compromising protection against the dreaded smallpox. And so Edward Jenner set out to test the folk belief that those who handle cattle from a young age, and thus have the opportunity to be exposed to cowpox, or vaccinia, before they encounter smallpox, are protected from smallpox infection. Once this hypothesis was confirmed, he demonstrated that vaccinia could be intentionally inoculated into a naive human, conferring similar protection. His simple experiments on his neighbors and family members sufficed to convince the world that rather than being variolated with potentially deadly active smallpox, one could be inoculated with a much less virulent disease associated with altogether different species and thereby be protected from the graver infection. This humane innovation was quickly taken up around the globe; more than 100,000 were vaccinated before ten years had passed, and Jenner became an international celebrity. Immediately upon the creation of vaccine came the birth of the antivaccine movement, scientists and laypeople who claimed (much as in our present day) that vaccine was “poison.” But its use became more and more widespread, even compulsory in many places, as the decades wore on and vaccine production became standardized and improved. Altogether, it would take less than two centuries for Jenner’s vaccine to eradicate the scourge of smallpox from the earth.
Louis Pasteur favored preventative strategies against infection, and he was a great admirer of Jenner and the principle of vaccination. By the time Pasteur began his own work on communicable diseases, Jenner’s legacy was firmly established, if still not well understood. The Académie Nationale de Médecine recommended general vaccination but was still struggling to differentiate the agent of the vaccine from that of smallpox itself. Pasteur’s interest extended well beyond smallpox. He was determined to figure out the general method for immunizing patients against all of the different pathogenic microbes being cultivated in his laboratory.
Chicken cholera was the first disease to yield its secrets to the Pasteur research team. This bacterial disease of fowl was rampant in France during the 1870s, bringing misfortune to poultry farmers across the countryside. According to one of Pasteur’s assistant
s, Émile Duclaux, the breakthrough was made after the culturing of microbes was interrupted for the summer holiday. When the new academic year commenced, it was noted that the bacteria that had been set aside no longer transmitted the disease.* The formerly deadly germs produced no grave effect on experimentally infected healthy chickens. Intrigued, Pasteur took these same chickens and submitted them to a second experiment, alongside chickens that had never received inoculations. He infected both groups of animals with very fresh chicken cholera isolates, of determinately high virulence, and monitored them closely for ill effect. Shortly, Pasteur was able to observe that the birds exposed originally to the aged bacteria resisted infection with the virulent strain, too, while the naive chickens succumbed.
The significance of this finding was not lost on Pasteur. Here was induced immunity from a mortal disease—not happened upon fortuitously in the cowshed like Jenner’s, but experimentally produced in the laboratory! If chicken lives could be spared through inoculation of laboratory-attenuated microbes, it did not require much imagination on Pasteur’s part for him to suppose his method may have potential for saving human lives as well. As a nod to Jenner, Pasteur referred to his method of chicken-cholera immunization as a “vaccine.”
Pasteur’s new vaccine soon attracted naysayers on several fronts: those who fought against all science based upon the germ theory; the anti-vaccinists (who had already honed their rhetoric against the Jennerian vaccine); and those scientific rivals who would have invented the chicken-cholera vaccine themselves if their own methodology had been more sound. Pasteur was in the midst of preparing his findings for the Académie Nationale de Médecine when his arguments with his rivals in that body became so heated that he received an invitation to duel from the aging surgeon Jules Guérin. (The sixty-year-old, hemiplegic Pasteur was delicately extricated from the challenge by friends in the Académie.)
To test the broader utility of his method, Pasteur turned his attention to a second veterinary disease, one with greater economic importance for French and European agriculture: anthrax. While capable, in rare instances, of dealing a farmer or veterinarian a grisly death, anthrax was most feared across rural Europe for its ability to depopulate a prosperous farm, leaving behind an indefinitely contaminated field. Spurred on by Robert Koch’s pioneering paper, Pasteur set out to attenuate the isolated anthrax bacillus in a similar manner as he had done with chicken cholera. He was soon successful: after achieving partial success with heat deactivation, the Pasteur team ultimately found that temperamental anthrax was best attenuated chemically, with carbolic acid treatment.* In the end, the pathogen proved no less amenable to laboratory domestication than chicken cholera had.
The furor among France’s scientists and medical men created by Pasteur’s announcement of the anthrax vaccine was so intense, so fevered, as to demand some public proof of his claims. The influential veterinarian Hippolyte Rossignol accused Pasteur of “microbiolatry” in an editorial in his Veterinary Press. He invited Pasteur to perform a public demonstration on Rossignol’s own Pouilly le Fort farm in the pastoral Brie region east of Paris. Pasteur accepted the challenge, eager for a means of advancing his doctrine of vaccination. He devised a simple experimental protocol: twenty-five sheep would be vaccinated against anthrax, fifty including these would be infected, an additional ten would serve as untreated controls. All sixty would be monitored for subsequent ill health. The demonstration, carried out during May 1881, was witnessed in its various stages by a large rabble of farmers, physicians, pharmacists, newspapermen, and, especially, veterinarians—many of whom remained as skeptical of Pasteur’s vaccine as they were of the germ theory that gave birth to it. Far away from the pasture where the vaccine trial took place, some of Europe’s most ardent germ theory supporters, Robert Koch and his assistants, suspicious that Pasteur’s strong public assertions regarding microbial attenuation rested on as-yet-unstable science, voiced their stern disbelief as well.†
Great excitement was focused on the final stage of the trial, when the vaccinated and unvaccinated groups would both be injected with virulent anthrax. At the last-minute insistence of one of the more passionately skeptical veterinary observers, a triple dose of live anthrax was administered to each of the experimental animals. Pasteur himself vigorously shook the vial of anthrax prior to each inoculation, in order to prevent uneven distribution of the virulent principle. Other veterinary spectators demanded that the injections proceed with careful alternation between vaccinated and unvaccinated subjects. Pasteur assented indifferently to the various dictates of the veterinary crowd, never backing down from his assertion that “[t]he twenty-five unvaccinated sheep will perish; the twenty-five vaccinated ones will survive.”
Pasteur projected complete confidence but was privately anguished as he waited to learn the fate of the herd. As the hours ticked by and the only news from Rossignol’s farm was of a sick ewe from the vaccinated group, Pasteur’s resolve began to waver. But two days after the inoculation, all twenty-five of the unvaccinated sheep were dead, while all of the vaccinated sheep had survived. “As M. Pasteur foretold at two o’clock 23 sheep were dead,” the Times of London observed. “Two more died an hour later. The sheep which had been vaccinated frolicked and gave signs of perfect health. Farmers now know that a perfect prevention exists against anthrax.”
Pasteur was roundly congratulated, especially by France’s veterinarians, who had become his newest allies—allies who would prove extremely useful as his research progressed into the most fearsome disease known to that profession.
From anthrax, Pasteur turned his attention next to another veterinary disease, but one with widely understood consequences for people. Rabies, and its associated illness in humans, hydrophobia, did not claim so many French lives as others did. That said, it had a prominent place in the French imagination. For each one of the few hundred deaths from rabies registered each year in France, there were several bitten Frenchmen—or, more frequently, French children—who, along with their loved ones, spent many months in the agony of uncertainty: Would the wound lead to a grisly death from hydrophobia? In Pasteur’s youth, when his own village had been terrorized by the rabid wolf, the danger was viscerally understood. But even as the scientist aged, the debate about whether rabies was a contagion or a spontaneous occurrence raged on among France’s prominent biologists, physicians, and veterinarians.
Pasteur’s collaborator Roux believed that Pasteur selected rabies as a subject for research as a calculated bit of stagecraft, so that his ideas about vaccination would attract maximum public interest. “This malady is one of those that cause the smallest number of victims among humans,” Roux later wrote. “If Pasteur chose it as an object of study, it was above all because the rabies virus has always been regarded as the most subtle and the most mysterious of all, and also because to everyone’s mind rabies is the most frightening and dreaded malady…. He thought that to solve the problem of rabies would be a blessing for humanity and a brilliant triumph for his doctrines.”
The Pasteur laboratory received its first mad dogs from M. J. Bourrel, the former army veterinarian whose 1874 survey had found the anti-contagionists ascendant. Bourrel had been studying rabies for some years without penetrating very deeply into its mysteries. He had, however, localized its contagious principle to the rabid animal’s saliva; given this fact, he recommended the precautionary measure of filing down the teeth of all dogs at large, so that should they become infected, they might not be able to penetrate skin and transmit the deadly agent. Bourrel could provide no better preventative than this, as his search for a rabies cure had led nowhere. He wrote in 1874 that his efforts in the laboratory had shown only that rabies is “impenetrable to science until now.” In the summer of 1880, while assisting him in the laboratory, Bourrel’s own nephew suffered the bite of a rabid dog and died following several days of torturous agony.
In December of that year, Bourrel provided the Pasteurians with two terrifying specimens of canine rabies for study. The
first suffered from dumb, or paralytic, rabies. Its mute affliction was wretched to witness: a paralyzed, slack jaw, failing to support a limp, foam-covered tongue, and, above this, eyes full of “wistful anguish.” The second dog, a victim of the more common furious form of the disease, terrorized the laboratory, menacing the scientists with its enraged, bloodshot gaze, its unpredictable lunges and fits, and its unforgettably mournful, hallucinatory howls.
During the same month, a doctor named Odilon Lannelongue contacted Pasteur about a five-year-old patient, bitten on the face one month prior to hospitalization, now racked by all the classic symptoms of rabies: restlessness, convulsions, aggression, hydrophobia. The child suffered mightily for fewer than twenty-four hours in the hospital and then died, his mouth full of the viscous mucus he had been unable to swallow. Within four hours after the child’s death, Pasteur collected a sample of the mucus. Upon his return to the laboratory, he inoculated some of the diluted mucus into a group of rabbits—a procedure, published more than a decade earlier by the veterinarian Pierre Victor Galtier, proven to determine whether rabies was present in the saliva of suspect dogs. But the rabbits inoculated with the child’s mucus surprised Pasteur, and contradicted precedent, by dying too quickly: they died in only thirty-six hours, when it should have taken weeks. Rabbits inoculated with saliva from those dead rabbits died nearly as rapidly. Moreover, the rabbits died of apparent respiratory failure, not neurological disease as would be typical of rabies. Dr. Lannelongue and his colleague Dr. Maurice Raynaud, after repeating the experiment themselves, eagerly announced proof that the child had died of rabies. If they were correct, this also would represent the first documented case of human-to-animal transmission of the disease.
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