There’s nothing quite like a mail-order disease to propel a pathogen into notoriety. In 2001, several envelopes containing spores of the bacteria Bacillus anthracis were shipped across the United States, infecting those exposed with anthrax. This was hardly the first time B. anthracis cropped up as a prominent pathogen or agent of biological warfare; the bacterium has a sordid history as a major player in biological warfare in the past century, along with a biblical history of outbreaks.
No one really likes vaccinations. Children view the procedure with the trepidation of a victim being pursued by a madman with a butcher’s knife, while parents make soothing, inane comments to their terrified offspring, such as “the sharp, pointy weapon is nothing to be afraid of!” as they are forced to pry their children from underneath the doctor’s table (my sister was particularly prone to this type of needle-avoidance). Personally, I view my own shots with a perverse fascination, but that probably comes from being, as my parents say, ‘an unusual child.’ In general, vaccinations are viewed by both parents and patients with resigned acceptance, although in the past decade there has been an upsurge of media attention toward possible side effects. Some individuals have become leery of the procedure, choosing to keep their children unvaccinated. Just how much of these concerns are based on truth, and how much stems from misinformation?
It is important to understand the science behind vaccinations, and the process of development, before jumping to conclusions. Vaccines have provided relief from decimating diseases, even eradicating mass killers such as smallpox. They are an unparalleled scientific miracle, which utilizes the wonders of our own immune system to provide protection from deadly diseases.
Leprosy is known as the Death before Death; a disease of unparalleled historical stigma and fear that has earned the appellation kushtha, ‘eating away.’ Today, whilst its effects are none the less awful, it is known under the more innocuous title of Hansen’s Disease. In 1948, Dr. Earnest Muir wrote that leprosy was the most dreaded disease—ironically, not because it kills, but rather, because it leaves its victims alive. Leprosy and humans have a long, bitter relationship. Though it has plagued us since at least 2000 BC, we barely understand it four thousand years later and we are still wrestling with its legacy of stigmatization.
When someone mentions the plague, the Black Death often leaps to mind: an infamous, decimating disease that we tend to associate with the medieval period. However, since the beginning of recorded history the plague has sinisterly spread across the globe and wiped out up to 30-40% of the world’s population three times, as well as hundreds of smaller outbreaks. The most recent pandemic (a worldwide outbreak of disease) was less than two hundred years ago, and is arguably still going on. Several thousand cases of plague occur worldwide each year, and the plague has now been classified as a reemerging disease. While we may view the plague as an ancient disease, when we consider the facts that we lack a vaccination, there are antibiotic resistant strains, and the pathogen has been utilized for biological warfare, it is very much a modern issue.
Diabetes is a term that gets thrown around a lot these days. Whether you’re indulging in a sugary feast and a friend wryly comments on your risk of acquiring it, or you come across it in a headline, diabetes is one of the more prominent diseases of modern society. Over 20 million Americans suffer from diabetes and over 40 million have pre-diabetes . Most people know the rudimentary basis of the disease–a metabolic disorder of high blood sugar (hyperglycemia)–yet the actual pathogenesis and widespread symptoms are less well known and can be frustratingly obscure to research.
As my last post was highlighting the depressing fact that microbes are kicking our derrières in a chemical arms race, this week I’m hopefully going to alleviate any lingering doomsday gloom by examining some cases of how we have evolved resistances against infectious diseases. On that note, let’s not dwell on the fact that many of the resistances increase as a result of massive epidemics that wipe out a high percentage of a population. Instead, think of how cool it is that 95% of the population is resistant to leprosy!
The Starting Point: Population Variation
Variation within a species is the basis for evolution, as natural selection acts upon these differences. Consequently, the overall pattern of genetic diversity in a species is the result of evolutionary processes of natural selection. Demographic history such as population size and substructure, as well as migrations, mutations, genetic drift (random change in gene frequencies in a population), selective pressures, and recombination rates (creation of new combinations or forms of genes) all impact our genetic diversity . This genetic diversity is important to understand how prominent resistances come about.
Through the wide range of clinical presentations of diseases, the racial differences in severity and susceptibility to diseases, and various twin studies, researchers realized there was a correlation between our genetics and susceptibility to diseases. Human genes provide some susceptibility or, conversely, resistance to specific infectious diseases in individuals as well at the population level [4,5].
Over a third of the world is infected.
It subtly manipulates the chemicals in the human brain, influencing our behavior.
It’s been at work for thousands of years.
And now it’s coming to harvest the fruit of its labors.
Okay, the last line was added for dramatic effect. However, despite sounding like a cliché science-fiction movie, the rest is actually true! Toxoplasma gondii is a parasite that has been infecting warm-blooded creatures for thousands of years—in fact, it is one of the most common parasitic infections of animals worldwide and has even been found in arctic foxes and polar bears .