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The Rabbit Island Experiment
Imagine that it is 1874 and you have just been diagnosed with consumption, which we now call
tuberculosis. That’s what happened to Edward Livingston Trudeau. A few years earlier, he had nursed a
brother who ultimately died of the disease. Now, he had a fresh doctor’s degree, a young wife, a new baby,
and a terrible problem—a diagnosis that, in his time and place, was often a death sentence.
Dr. Trudeau knew all too well that a large number of people diagnosed with consumption ultimately died.
Crowded together in cities like New York, where he was living with his young family, were tens of thousands
of immigrants who were very glad to have their back-breaking factory jobs, but came home each night to
inadequate housing, food, ventilation, sanitation, and little or no leisure or relaxation time. Consumptives
labored for as long as they could draw breath as the bacterial infection in their lungs worsened and spread,
eroding blood vessels and causing bleeding and poor oxygenation, or causing the lungs to fill with fluid until
the sufferer might literally drown. Finally, exhausted consumptives would retire to their dank, crowded
apartments to be nursed by their families until they died. Often family members would themselves become
infected from their close contact and constant inhalation of organisms expelled by their sneezing, coughing,
bleeding loved one.
E.L. Trudeau, however, was not poor, nor was he a member of the factory-worker class. He decided to
travel to a place where he had spent a lot of time as a boy and a young man, the Adirondack Mountains of
upstate New York. There he could rest a bit, think, take long walks in the open air, and make a plan.
Dr. Trudeau’s condition worsened during the arduous trek north by rail and carriage. In fact, the young man
was so frail and sick that he had to be carried into the house of an Adirondack outdoorsman and wilderness
guide. But a remarkable thing happened. Dr. Trudeau began to feel better. In time, he could hike and hunt
and enjoy life with his friends. He resumed his correspondence with doctors and scientists. He sent for his
wife and child, and began to build a medical practice in the distant little outpost of Saranac Lake. And he
began to think about the cause and cure of what more and more scientists called not consumption, but
tuberculosis.
In the 19th century, a portion of the medical community believed that diseases like consumption were
caused by an unfortunate combination of bad “family blood” (after all, the poor were certainly not well-bred,
and they were more likely to become sick and to die early) and mysterious causative agents as ill-defined
as dank conditions, bad “humours,” obnoxious smells, and miasmas. But, in 1882, Robert Koch
demonstrated to most of the scientific establishment’s satisfaction that the tiny bacterium Mycobacterium
tuberculosis (MTb) caused the disease known as consumption. Moreover, he could grow pure cultures of
the finicky MTb and infect cells of experimental animals, and ultimately the animals themselves, causing the
disease. Koch said: “If the importance of a disease for mankind is measured by the number of fatalities it
causes, then tuberculosis must be considered much more important than those most feared infectious
diseases, plague, cholera and the like. One in seven of all human beings dies from tuberculosis. If one only
considers the productive middle-age groups, tuberculosis carries away one-third, and often more.” Koch’s
work, along with Louis Pasteur’s, led to the more general “germ theory of infection,” which stated that
infectious diseases were caused by germs, which was the name given to the microscopic organisms (we
know them now as viruses, bacteria, fungi, and parasites) that cause disease in people and animals.
Dr. Trudeau had followed Dr. Koch’s work with interest. He worked hard to learn how to culture MTb
organisms, and was the first to do so in the United States. Intrigued by the correlation between healthy
outdoor lifestyle and efficient anti-tubercular defense in his own case, he devised a simple experiment. The
experiment spoke to both the MTb “germ” as sole causative agent of tuberculosis and a possible therapy for
the disease. The experiment was described in his 1886 paper, “Environment in its Relation to the Progress
of Bacterial Invasion in Tuberculosis.” The following is an excerpt from that paper.
• First. What results ensue when both bacillary infection and unhygienic surroundings are made to coexist in
tuberculosis?
• Second. Are unhygienic surroundings when every known precaution has been taken to exclude the
bacillus sufficient of themselves to bring about the disease?
• Third. Is bacillary infection invariably progressive in animals placed under the best conditions of
environment attainable?
Experiments.—Fifteen rabbits were made use of and divided in three lots, each set of animals being placed
under conditions best adapted to answer in the results noted [in] the three questions already referred to.
• Experiment No. 1. Five rabbits were inoculated in the right lung and in the left side of the neck with five
minims of sterilized water in which was suspended a sufficient quantity of a pure culture (third generation) of
the tubercle bacillus to render the liquid quite perceptibly turbid The needle of the Koch’s inoculating syringe
was inserted subcutaneously on the left side of the neck and in the third intercostal space to a depth of
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thirty millimetres on the right side. These animals were then confined in a small box and put in a dark cellar.
They were thus deprived of light, fresh air and exercise and were also stinted in the quantity of food given
them while being themselves artificially infected with the tubercle bacillus.
• Experiment No. 2. Five healthy rabbits were placed under the following conditions: A fresh hole about ten
feet deep was dug in the middle of a field, and the animals having been confined in a small box with high
sides but no top, were lowered to the bottom of this pit, the mouth of which was then covered with boards
and fresh earth. Through this covering a small trap door was cut which was only opened long enough each
day to allow of the food, consisting of a small potato to each rabbit, being thrown to the animals. So damp
was the ground at the bottom of this pit that the box in which the rabbits were confined was constantly wet.
Thus these animals were deprived of light, fresh air, and exercise, furnished with but a scanty supply of food
while breathing a chill and damp atmosphere, though free from disease themselves and removed as far as
possible from any accidental source of bacterial infection.
• Experiment No. 3. Five rabbits having been inoculated in precisely the same manner as the animals in the
first experiment, were at once turned loose on a small island in June, 1886. It would be difficult to imagine
conditions better suited to stimulate the vitality of these animals to the highest point than were here
provided. They lived all the time in the sunshine and fresh air, and soon acquired the habit of constant
motion so common in wild animals. The grass and green shrubs on the island afforded all the fresh food
necessary and in addition they were daily provided with an abundant supply of vegetables. Thus, while
artificially infected themselves they were placed in the midst of conditions well adapted to stimulate their
vital powers to the highest point attainable.
Dr. Trudeau’s little experiment had a big impact on medical thinking at the time. His experiment offered a
rationale for opening his Adirondack Cottage Sanitarium, which offered rich and poor alike a regimen of
abundant nourishing food, lots of sunlight, plenty of rest, and as much fresh air as a person could tolerate.
Hundreds were helped, and many similar establishments were opened.
Perhaps the experiment was so successful because of the care with which Trudeau had designed its
components. It is important to identify an interesting and potentially approachable question or set of
questions before undertaking an experiment. But it is just as important to devise a clever experimental
design.
Question Set 1:
- What is the dependent variable in the Rabbit Island Experiment? What is the independent variable(s) in
the experiment? What are some of the controlled/ standardized variables? - The data from the experiment Dr. Trudeau describes is shown below in Figure 1. The Rabbit Island
Experiment ( figure 1, 2, 3 on this website ) ( sorry for the inconvenient )
https://sciencecases.lib.buffalo.edu/cs/files/tb_rabbit_island.pdf
o Describe how the figure shows the results of the experiment and describe why the rabbits are emaciated
in groups 1 and 2.
3/ Discuss how the conclusions of the Rabbit Island Experiment answers the three questions Dr. Trudeau
was attempting to answer. Does this support the germ theory of infection? Does the data suggest what
might be good environmental conditions for tuberculosis patients?
4/ What might be the effect of crowding on effective exposure rate of individual animals to MTb? (Hint:
Would you rather board an airplane for a 3-hour trip where 2 out of 300 passengers had the flu or board an
airplane where 200 out of 300 passengers had the flu?)
5/ Suppose you were the Mayor of New York City in the 1890s/early 1900s and were convinced by Dr.
Trudeau’s experiments that in your city a transmissible bacterium was causing tuberculosis and that poor
living conditions and inadequate diet were adversely affecting the ability of hundreds of people to fight the
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infection. What sort of public policies might you try to enact in order to combat the public health menace?
What obstacles might you encounter?
Tuberculosis in Social Context
E.L. Trudeau was quick to distinguish between a helpful therapy and a cure. He opened the Adirondack
Cottage Sanitarium, where poor and rich alike could come and receive the benefits of fresh air, plenty of
sunlight, rest, and abundant but simple nourishing food. Hundreds benefited. Similar institutions opened up
in the U.S., and the movement was already well underway in Western Europe. But the cure would only
come in the 1950s with the discovery of antibiotics that were effective against the mycobacterium.
Question Set 2 - The curve shown in Figure 2 has three parts, from 1700–1800, 1800 to approx. 1955, and 1955 to
approximately 1985. The data used to produce the curve are from Western Europe, but a similar one could
be expected for the United States.
Figure 2 on this website
https://sciencecases.lib.buffalo.edu/cs/files/tb_rabbit_island.pdf
o From what you know of the history and culture of the United States and Western Europe, write a sentence
telling why each part of the curve looks the way it does.
o In looking just at this graph, what would you predict about the death rate from TB in 2000, 2010, and
2020?
In recent years, a combination of development of antibiotic resistant strains of MTb along with the creation
of a reservoir of immunocompromised people by the worldwide AIDS epidemic have contributed to a
resurgence of tuberculosis in the United States and a worldwide upswing in TB cases and deaths. This
resurgence has been accompanied by a resurgence of interest in the disease by scientists asking new
questions about the nature of true host genetic susceptibility/resistance genes for tuberculosis, about
virulence genes within the mycobacterium itself which might offer new drug targets, and about the
epigenetic factors that may influence disease predisposition and outcome in people with tuberculosis.
Tuberculosis causes nearly 2 million deaths worldwide each year. Between 1985 and 1992, cases of TB in
the United States increased by 20 percent, as shown in Figure 3.
https://sciencecases.lib.buffalo.edu/cs/files/tb_rabbit_island.pdf
The resurgence lasted until approximately 1992, then, in the United States, it began to abate. In 2005 the
TB case rate in the U.S. was 4.8 per 100,000, as the U.S. medical community brought the epidemic under
control (Centers for Disease Control & Prevention, National Prevention Information Network, n.d.).
However, in U.S. prisons and all over the world TB remains a serious health problem. In the U.S., zero
tolerance drug laws have resulted in a burgeoning incarcerated population, which constitutes a significant
reservoir of disease, with a far higher incidence rate than the general population. In New York prisons, the
incidence rate of TB is 156.0/100,000compared to the rate of 10.4/100,000 in the general population (U.S.
Agency for International Development, 2009).
Question Set 3: - Suggest 3 -5 reasons why this resurgence of TB might have occurred in the United States.
- Considering all you have learned in Parts I and II, discuss why these rates may be so much higher in
prison.
In 2006, there were 9 million new cases of tuberculosis worldwide, many of these caused by drug-resistant
strains of the mycobacterium. Scientists struggle to find new drugs that will be effective against the resistant
strains and to propose better treatment regimens involving more direct observation of treatment (DOT) to
assure patient compliance. Additionally, many have called for public acceptance and physician support for
more responsible dispensing of antibiotics. These are difficult and complex problems that require a resolve
on the part of many sectors coupled with a willingness to devote adequate resources to a fight a disease
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that most often strikes people in the poorest of places.
Additionally, it is certainly the case that many modern TB cases occur in a global incarcerated population of
approximately 8 million (U.S. Agency for International Development, 2009). Many of those incarcerated
were political prisoners taken prisoner in war zones. Conditions in the prisons include inadequate
ventilation, poor nutrition, negligent healthcare, HIV co-infection, and rampant despair. How does this
resonate with what you’ve learned of E.L. Trudeau’s experience in the late 19th century?
We know a lot about how to prevent and treat tuberculosis. There is much more to be learned. In 2010, 8.8
million people in the world fell ill with TB and 1.4 million died (World Health organization, 2012). All of the
following factors are important in causing the worldwide resurgence of tuberculosis:
(a) emergence of strains that are resistant to one or more of the available antibiotics effective against MTb;
(b) incomplete or inadequate understanding by scientists of the details of the host/pathogen interaction in
MTb infection;
(c) lack of a universally-accepted vaccine;
(d) lack of financial support for science and for public health initiatives in developing countries;
(e) famine;
(f ) geopolitical instability in the developing world; and (g) inadequate public awareness of public health
issues.
Question Set 4 - If you were a billionaire philanthropist like Warren Buffet or Bill Gates, where would you focus your efforts
against tuberculosis and why?