Syphilis, like the Black Death and smallpox, has earned its place in history
as a burden on mankind. Syphilis gained its notoriety for its
horrifying three stages, and caused its victims to go insane - a symptom that famously afflicted
Friedrich Nietzsche and Al Capone. With advances in immunology, syphilis no longer
poses a threat, and is easily treated. Worldwide, there's 6 million syphilis cases
reported every year, and most are cured with a simple
prescription of penicillin. However, it's worth knowing something about a disease
that ravaged Europe for 500 years, caused gruesome disfigurations,
and made its victims go insane. This is the Dark Science of syphilis. [intro music] Syphilis was first recorded in
mid-15th century Europe. It was most common among
prostitutes and johns, making the afflicted associated with
immorality and shame. It spread to North America in the
late-15th century by European navigators who were
exploring the New World. Syphilis is caused by the bacterium
Treponema pallidum, or T. pallidum, a spirochete bacteria. Its body is not spherical or rod-shaped, but rather shaped like a corkscrew,
which helps it to infect its host. Unlike other bacteria, it's not found in nature. Samples of soil, water, and even feces
are void of its presence. This is because T. pallidum is a
sensitive bacteria that requires very specific conditions to live. If left on a surface, T. pallidum can only live
for about two hours. In contrast, E. coli, a bacteria found
in the human gut, can live on a surface for several days. Even in the lab, T. pallidum is
nearly impossible to culture. The only environment where T. pallidum
is able to live is the human body. Since humans are the only reservoir
that keeps T. pallidum alive, humans are the cause of the bacteria
sticking around for over 500 years. T. pallidum is not spread through air droplets
like the common cold or even regular contact on the skin. Due to its sensitive living conditions, it has to be spread via intimate contact
on a specific surface of the body. In this case, intimate contact is defined
as kissing or sexual activity where mucosal surfaces, such as in the mouth
or genitals, make physical contact. The transfer happens when an individual
with a syphilitic legion touches a mucosal surface or a break in the skin. Once on the surface, T. pallidum excretes an enzyme
called matrix metalinoproteinase-1 or MPP-1, which breaks down
a protein called collagen - making it easier to burrow into the soft tissue. Mucosal or broken skin is required
for transfer of syphilis as this tissue is soft, very thin,
and has less surface protection, making it easier to burrow into. Regular unbroken skin or epidermis
is hard for T. pallidum to burrow into since it's thicker, rougher, and has acidic oils
on the surface that damage the bacteria. Once T. pallidum is in the body, the immune system mounts a response like
it would with any bacterial infection by inducing fever and inflammation. Then, after a couple of days, the immune response
stops, and the body goes back to normal. The immune system thinks T. pallidum is gone,
but it's not - it's just invisible. T. pallidum manages to hide from
the immune system because partway through the infection,
it shuffles a single gene in its DNA - thereby changing the sequence of proteins
on its surface. With different surface proteins, antibodies and immune cells are unable
to recognize the bacteria - permitting T. pallidum to replicate
over several weeks. The first stage of syphilis is called primary syphilis, and appears about three weeks
after the initial infection. Painless lesions called chancres appear at the site
where the bacteria entered the body. Lesions most often appear on the genitals or mouth
where there is thin, moist mucosal tissue, or where there is a break in the skin. These lesions contain hundreds of
colonies of bacteria and are highly infectious if touched. Chancres heal within three to four weeks, and after the primary infection,
T. pallidum alters its DNA and starts to evade the immune system. In between the first and second stages of syphilis, T. pallidum aggressively replicates
throughout the body, but is only able to do so every 30 hours - which, compared to other bacteria, is very slow. E. coli, for example, replicates about
every 20 minutes. This slow replication rate is not a weakness,
but rather an advantage for T. pallidum. Due to its very slow replication, T. pallidum maintains a low concentration
below the critical antigen mass. The critical antigen mass is the threshold for the number of antigens from bacteria or viruses
that must be present to elicit a response. Since T. pallidum replicates at such a slow rate, it's able to stay below the critical threshold and
avoid being seen by the immune system, thereby allowing it to spread throughout the body. Three to six weeks after the initial infection,
T. pallidum has had time to replicate, moving on to the second stage - secondary syphilis. Secondary syphilis is much different and
more intense than primary syphilis. Primary syphilis was just a painless lesion
at the site of contact. In secondary syphilis, lesions appear on the arms,
hands, feet, chest, and back. Unlike primary syphilis, these lesions are extremely painful
and highly infectious as they harbor the treponema bacteria. Other symptoms include fever, enlarged lymph nodes,
hair and weight loss. After about four weeks,
the secondary phase resolves, and T. pallidum enters a prolonged dormant phase where it remains inactive for as long as 15 years. After secondary syphilis,
the worst appears to be over. There's an absence of symptoms
for several years, and health is not seriously affected
by the dormancy, yet T. pallidum is waiting in the shadows
to inflict its worst damage in the third stage. Between 10 and 20 years after
the initial infection, T. pallidum reactivates,
initiating tertiary syphilis - the final and most destructive phase. Once reactivated, the bacteria infects
an oddly specific area of the body - walls of blood vessels. Infection of the vasculature or blood vessels
causes chronic inflammation, which appears as large growths of
inflamed scar tissue called gummas. Gummas range in size and grow in soft tissue, causing gruesome disfigurements
if they grow large enough. Infection of the blood vessels causes
twofold damage to the body. The blood vessel itself and the organs
that receive blood from the vessel are both affected. Inflammation in blood vessels causes calcification or the buildup of calcium in the walls of the vessel. Calcification makes blood vessels narrow
and reduces blood flow - meaning less oxygen and nutrients
are getting to the organs. Two systems in the body that are
dramatically affected by this are the cardiovascular and
central nervous systems. The cardiovascular system in particular
is affected by T. pallidum because it infects the walls of the thoracic aorta - the largest artery in the body. The thoracic aorta extends from the heart
through the chest and into the abdomen, and carries a significant amount of blood. Like other blood vessels, the thoracic aorta
undergoes calcification in its vessel walls, reducing blood flow in the
largest artery in the body. Calcification also affects the aortic valve which controls blood flow into the heart. Calcification around the valve makes the
valve stiff and does not fully open, thereby reducing blood flow into the heart itself. Additionally, due to the chronic inflammation, the thoracic aorta becomes engorged with
fluid, known as an aortic aneurysm. All of these effects reduce the
heart's performance, causing palpitations, fatigue, cardiac infarction,
and even heart failure. The central nervous system is also damaged
by vascular inflammation, owing to the symptoms of insanity. Nerve cells have a very low tolerance
for hypoxia, or lack of oxygen. Even a small reduction in oxygen
can damage or even kill neurons. As nerve cells receive less nutrition,
signaling between neurons become sporadic, causing partial paralysis and motor functions,
most notable in the limbs and eyes. Regions of the brain such as the amygdala
and prefrontal cortex, which deal with emotional regulation
and logic, start to deteriorate. This affects sensory, memory,
and interpretive function - manifesting as personality changes,
memory impairment, hyperactive reflexes, and hallucinations. In the past, these effects were misdiagnosed
as insanity, but in reality is the brain gradually malfunctioning
from decreased nutrition. As tertiary syphilis progresses, damage to
the vasculature gets worse, and the central nervous system deteriorates further. Nerves associated with touch sensation degrade
to where the arms, hands, and feet cannot be consciously felt. Paralysis of the muscle becomes so severe that
standing or walking is no longer possible. Death eventually occurs from either heart failure
or neurological complications. From the first day of infection to death, syphilis can be as short as 10 years,
or as long as 30 years. Today, syphilis is not something
to be concerned about as it's easily treated with antibiotics. Victims in the past who suffered
from these dreadful stages suffered because they went untreated
for their entire. With modern medicine and treatment,
this rarely ever happens. Sometimes, science can be seen as difficult,
foreign, and even boring - yet, there are times when science grabs our attention and draws us in, yearning from more answers. Often, what draws us in are topics that are dark,
macabre, or terrifying. It's with the intention of this video
that you too were drawn in and sought to have your questions answered. Thanks for watching Dark Science.
