The world is a dangerous place. Humans live in constant contact with a
mixture of bacteria, viruses and parasites.
Evolution and modern hygiene have provided us with the means to coexist
with those that are helpful and usually survive encounters with most of the
ones that are not. Unfortunately,
victory in this conflict is unattainable because dangerous elements are
constantly changing form. Flu and the
common cold are caused by viruses that are constantly mutating into different
species. By disturbing ecologies we encounter
additional threats that must be dealt with.
Encounters with new diseases should be expected.
Harriet A. Washington has provided us with an indication
of what we should expect in an article in The
American Scholar: The Well Curve. She focuses on diseases that can affect brain
function and begins by providing a few recent discoveries as examples.
“In 1987, more than 100
Canadians developed….symptoms after dining on tainted mussels harvested off
Prince Edward Island. Short-term memory loss accompanied vomiting and diarrhea.
The victims also became disoriented and aggressive and finally were wracked by
prolonged crying jags. This new disease, christened “amnesiac shellfish
poisoning,” was caused by….several species of Pseudo-nitzschia algae. The algae produce domoic acid, a powerful
neurotoxin that destroys the ability to make memories and thrives in algal
blooms—popularly called red tides—that are incubated by warm weather.”
“Domoic acid resembles a form of
the neurotransmitter glutamate so closely that sufferers’ brains could not
discern the difference as it passed through the blood-brain barrier to cause
confusion, disorientation, seizure, coma, and sometimes death. Monterey Bay
National Marine Sanctuary scientists announced a red tide recurrence as
recently as June, followed by a mass die-off of infected anchovies, which also
threatened their mammalian predators, including man.”
A more recent discovery is even more troubling—a virus
that affects algae that somehow learned how to infect humans.
“Investigators from Johns
Hopkins, Baltimore’s Sheppard Pratt Health System, and the University of
Nebraska–Lincoln were startled to find a previously unsuspected virus, Acanthocystis turfacea chlorella virus
1, or ATCV-1, lurking in the throats of two of every five of their Baltimore
research subjects.”
The researchers who made this discovery were involved in
investigating physical attributes that might affect mental processes. They were deeply troubled by what they
learned.
“But the study’s baseline
cognitive tests unveiled the true shocker. When compared with those who did not
harbor the virus, those infected were about 10 percent slower to make
calculations and had a reduced attention span, suggesting that the virus
compromised their ability to calculate, to focus, and to process visual
information—disadvantages in the classroom, on the job, and in other familiar
learning situations.”
“The lowered mental functioning
was independent of potentially confounding factors, including age,
socioeconomic status, education, place of birth, or smoking status. Gender and
race made no difference. Repeating this experiment in a larger population
yielded the same results, and when the research team tested mice before and
after exposing them to the virus, they found 1,000 gene changes in brain regions
known to be important to memory and learning. These infected mice also took 10
percent longer to navigate a maze and showed reduced attention spans, compared
with the uninfected controls.”
These findings were newsworthy because they occurred in
wealthy western countries. Meanwhile, in
poorer counties where health surveillance and treatment are inadequate, infection
by pathogens thought to harm brain development or function are common. It is these diseases that most concern the
author. In fact she begins her piece
with this warning.
“Tropical diseases are
undermining intellectual development in countries with poor health care—and
they’re coming here next.”
Washington gathers evidence to support the notion that racial
or ethnic differences in the measurement of what wealthy western countries
refer to as IQ (not to be confused with intelligence itself) can be explained
by socioeconomic and biomedical factors such as the frequency of infection by
diseases known to affect cognitive performance.
“This take on race,
intelligence, illness, and poverty is the exact opposite of hereditarian
screeds, from Arthur Jensen’s ‘Thirty Years of Research on Black-White Differences
in Cognitive Ability’ to Charles Murray and Richard J. Herrnstein’s The Bell Curve to J. Philippe Rushton’s
musings on race, intelligence, and penis size. These broadsides and their
refutation have dominated the public debate on race and intelligence. The
authors’ theories rest on several articles of faith. One is that intelligence,
measured by IQ tests, is largely genetic and varies in a racial hierarchy, with
Asians or Caucasians usually occupying the apex and various African groups
located at the bottom.”
Her choice of title, The
Well Curve,’ is indicative of her disdain for the work of the mentioned
writers. Her faith is in the work of
others.
“….pathogens that affect cognition
have traditionally infected poor people of color in the developing world, so
their ravages and long-term effects have been more likely to go unanalyzed and
untreated. In developing countries, points out Peter Hotez, dean of the
National School of Tropical Medicine at Baylor College of Medicine in Houston,
infection by such pathogens is the norm, not a headline-worthy exception.”
“Studies like a 2010 report from
Randy Thornhill, an evolutionary biologist at the University of New Mexico, and
a 2011 research study from Carleton University in Ottawa, have strongly
correlated low average IQs from various nations with high rates of infectious
disease. A 2011 article Thornhill published in the journal Intelligence calculated that, in the United States, allowing for
education and wealth, “Infectious disease was the best predictor of average
IQ.”
Thornhill provides an interesting explanation for how
these diseases can affect brain development and function: these various
bacteria, viruses, and parasites compete with the brain for meager nutritional
resources. Deficient nutrition in young
children can lead to impaired brain development even without an infectious
disease.
“Thornhill’s ‘parasite-stress’
theory maintains that parasites sap the brain’s energy in several ways. The
newborn human brain uses fully 87 percent of the body’s “metabolic budget,” an
amount that diminishes with age and maturity, and if a young brain cannot meet
these initial high-energy requirements, its growth and development suffer.
Microbes and larger parasites drain this energy by feeding on tissues and
lodging in the digestive tract, where they siphon off nutrients and iron.
Additionally, viruses divert energy from their hosts to crank out copies of
themselves. This stolen energy normally would fuel brain building and other
metabolic needs of the child.”
Washington refers to these diseases that afflict more
than a billion people as NDTs (neglected tropical diseases).
“….NTDs plague extremely poor
denizens of the subtropics not only of sub-Saharan Africa, but also of Saudi
Arabia, Brazil, India, China, Indonesia, and Mexico. They are, in the words of
Peter Hotez, the dean at Baylor, ‘great disablers rather than killers’.”
The extent to which these NTDs affect cognitive
performance may still be a bit controversial, but there is no arguing that they
are physically and economically debilitating.
Young children who tend to be at least slightly malnourished in many of
these countries can only be harmed by being required to compete with parasites
for calories.
Perhaps the most interesting—and frightening— conclusion
by Washington is that these types of diseases already exist in the United
States.
“….tropical diseases—and their
neglect—are not limited to the tropics any more. They’re now very much at home
in the United States. The Big Five diseases—Chagas disease, cysticercosis,
toxocariasis, toxoplasmosis, and trichomoniasis—are quite common here among the
poor, Hotez says. ‘While sub-Saharan Africa accounts for many of the world’s
NTDs, somewhat paradoxically, most of the world’s NTDs can be found among the
poor living in wealthier countries, including the ‘Group of 20’ nations.
Houston and Texas … represent ‘ground zero’ for many of America’s neglected
tropical diseases’.”
Some explanation of a few of these will suffice to get
one’s attention. Cysticercosis describes
what follows from an infestation of the brain by tapeworm larvae. Tapeworms are usually associated with the
digestive track, but in some cases the larvae manage to reach the brain.
“Tunneling into the brain, the
larvae become encysted, cloaking themselves from the immune system with
specialized tissues. Thus ensconced and unmolested by the immune system, they
unleash the horribly versatile disease called cysticercosis.”
“Cases are more common than one
might think. Ted Nash, chief of the gastrointestinal parasites section at the
National Institutes of Health, told Discover magazine in 2012,
“Minimally, there are 5 million cases of epilepsy [worldwide] from
neurocysticercosis.” From 1,500 to 2,000 neurocysticercosis cases have been
diagnosed in the United States when confused, unconscious, or epileptic
patients are brought to the hospital and the detection of antibodies definitively
identifies the disease. Cysts near the brain’s visual cortex can blind the
carrier. Cysts near the language area can disrupt speech or comprehension.
Cysts sometimes block the flow of cerebral fluid, causing hydrocephalus, which
necessitates a shunt to relieve the pressure and prevent unconsciousness and
death. All too frequently, a tapeworm cyst causes epilepsy.”
Chagas disease
is a parasitic ailment that is usually delivered when the inappropriately named
“kissing” bug (triatominae) defecates on the skin while sucking the blood of a
person. It is a disease whose home is in
the Americas and is more prevalent in the Central American regions.
“Tropical medicine experts agree
that at least 330,000 U.S. citizens have Chagas disease, the most common
parasitic disease in the Americas, and estimates range as high as one million.
It infects six million to seven million more people in Latin America. This
chronic, silent parasitic infection leads to fatal heart or intestinal damage
in two of every five sufferers, and it also causes intellectual slowing. It can
be treated, but the lack of awareness by doctors in the United States means
that it often isn’t.”
And then there is this summary statement.
“….taken altogether, the
infections that ravage the developing world now imperil the bodies and minds of
at least 14 million U.S. residents.”
It seems unavoidable that these NTDs would find a home in
the United States. Many are endemic in
warm, tropical regions. The United
States is one of the few wealthy countries that possesses regions in which the
climate is actually warm and tropical.
As mentioned earlier, Texas and Houston are ground zero for these types
of infections. Combine the climate with
a healthcare system that has little training in recognizing these diseases,
while at the same time providing subpar medical care to the poor blacks and
Hispanics who are most at risk, and disease becomes inevitable.
Globalization and climate change are also at work. Increasing temperatures encourage diseases to
move northward. Pathogens can even be carried
by wind from distant continents. The
movement of people and large amounts of materials around the world in a
globalized economy are not helpful in containing diseases.
Yes, the world is a dangerous place. We should not expect that to change any time
soon.
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