Pests & History: The Plague – Q & A With Mark Smith, PHD.

Pests and History.  Believe it or not, pests have influenced history in dramatic ways.  For example:  When Marie Antoinette allegedly said “let them eat cake,” she undoubtedly was referring to the fact that there were ants in the brownies and they were ruined.   Also, the ‘face that launched a thousand ships,’ Helen of Troy, left not for the reason everyone thinks.  She moved to Troy because her house at Sparta was infested with termites.

I could go on and on.  Thankfully, I won’t.

I have always been interested in history, real history.  As an owner of a pest control company in the Boise area, my interest is also doubly piqued when I’v read how pests have impacted human society, religion, and politics.

Recently I spoke with Mark Smith, PHD, Professor of History at The College of Idaho.  We had a fascinating conversation on this very topic.  He consented to do a Q & A!  This is the first of a three part series that we’ll do on the impact of The Black Death on History:

Kirk:  Is there a time in history that pests have altered dramatically the course of human history?  

Mark Smith:  Probably the most dramatic epidemic in western civilization was the Black Death in the late middle ages.  The first reports of the disease come from the 1330s in China.  By 1347, it broke out in the area we now call Turkey.  From there, because of the regular trade routes, the disease quickly made its way to Italy aboard merchant ships, striking first in the port cities.  By late 1348, the epidemic spread throughout Europe, with devastating results.

Kirk:  How did people contract this disease?

Mark Smith:  The Black Death is caused by a bacterium:  Yersinia Pestis.  To this day, this bacterium is commonly present in rodents such as squirrels and rats.  In most years, a few cases of plague kill dogs, cats or squirrels in Idaho.  On occasion, humans also contract the disease which, with early detection, can be treated effectively with antibiotics.  The Black Death, at least at first, was spread by rats stowed away on ships, and coming ashore in port cities.  The disease spread to humans, initially, through the agency of fleas.  Fleas bite the infected rats, ingesting the bacterium which then multiplies rapidly inside the flea, clogging its gut, and inhibiting its ability to suck blood.  If that same flea, at just the right time, jumps off the rat and bites a human, rather than sucking the human’s blood, the flea effectively injects a plug filled with bacteria into the human.  At this point, the location of the bite determines the course of the disease.  If the flea bite happens to hit a lymph capillary, the bacteria enter the lymphatic system and multiply rapidly in lymph nodes.  This is the Bubonic Plague, so called because the lymph nodes swell, sometimes up the size of a softball, and those large and visible lumps were called “bubos.”  If, however, the flea bites into a blood capillary, the bacteria are injected directly into the blood stream, where they reproduce rapidly. This is called Septicemic Plague.  Ultimately Septicemic Plague can create a sort of Toxic Shock reaction as well as a type of Pneumonia.  Thus, both Septicemic and Bubonic Plague are the results of two pests: fleas and rats.  The third type of plague, however, is the most deadly:  The Pneumonic Plague.  Victims of both Septicemic and Bubonic Plague may develop Pneumonia, which causes them to cough from lungs richly infested with bacteria.  As a result, the disease becomes airborne.  Anyone breathing in the infected air near someone who has coughed up the bacteria will inhale the infection into the lungs.  The result is a highly contagious form of Pneumonia that kills very quickly.  Both Septicemic and Pneumonic Plague can kill in only a couple of days.  Bubonic Plague takes a little longer to develop, but is equally deadly.  The epidemic was called the Black Death because those infected developed large black spots on their skin. Scholars estimate that, within five years of the initial infection in Europe, some 25 million people died – nearly 1/3 of the population of Europe.  But the Black Death did not stop then.  It recurred every few years, whenever a new generation without immunity grew in sufficient numbers.  These periodic outbreaks continued to haunt Europe for centuries.  In London, outbreaks of plague continued until the great fire of 1666 wiped out much of the rat population.  The Black Death dramatically altered the course of western civilization.

Kirk:  Did people generally know how (or from what source) they got this disease?

Mark Smith:  In general, late medieval people did not know much about contagion or the sources of disease.  They did know, however, that proximity to someone who had the disease (including burial of the body) seemed to create higher instances of infection.  The results were devastating as those who could moved away from population centers, those infected seldom received care, and putrefying bodies of the victims piled up in the streets.  Most people seemed to take a spiritual interpretation of the causes of the Black Death, attributing it to God, demons, or evil in the society.

Kirk:  Did certain areas, countries, castes of people, etc. have it worse than others?

Mark Smith:  Naturally, deaths were concentrated where people lived closer together and were most likely to encounter rats.  Port cities were particularly vulnerable.  In some cases, whole towns and villages were virtually wiped out.  While nobody was exempt, wealthy nobles in their country manors were most exempt, while the poor in crowded urban or village contexts were most vulnerable.  There were also strange pockets of resistance to the disease, most notable among them, the English village of Eyam in the Peak District of Derbyshire.  When a recurrence of the Black death hit Eyam in the 17^th century, very few died.  Because they kept careful records, modern researchers in genetics have been able to test the DNA of descendants of the plague-resistant families.  They found that these families shared a CCR5-delta 32 mutation that not only seems to have conferred immunity against the plague, but also, if present in both parents, confers immunity against HIV.  Indeed, even in the middle ages, physicians learned a great deal about contagion and treatment that they could not have learned in other contexts.

Saint Sebastian Interceding for the Plague Stricken, Josse Lieferinxe, 1497–1499, The Walters Art Museum

About Mark Smith:  Check out his Bio page here:  Mark Smith, PHD.

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