Arthropods (bugs) have been associated with disease since the beginning of recorded time and have had a profound effect on shaping world history. The oldest and perhaps most well-known sequence of ecological events involving pests and disease were the 10 plagues of Egypt and the survival of the Israelites who were led by Moses in the desert for 40 years.
First Plague — Blood. That the Nile River ran red, like blood, has two possible explanations: washing of red sand into the river along its upper origin or the red protozoa known today as the red tide. In either case, the water was unfit to drink and the oxygen in the water was severely diminished, causing massive fish kills. This probably led to hordes of flies that exploited this situation in little more than a week.
Second Plague — Frogs. The plague of frogs was probably the result of water being unfit for habitation. Eventually, without a place to live and breed, massive numbers of frogs died on the land, leading to more flies.
Third Plague — Lice (or Mosquitoes). Scholars are split on whether it was lice or mosquitoes that caused the third plague. Both were present in Egypt and the consequence of either being present in large numbers is equally devastating. Body lice are known vectors of epidemic typhus and the inability of people to properly bathe and launder clothing could have led to significant mortality rates. Considering the water conditions with large amounts of organic matter, Aedes aegypti mosquitoes were probably present in large numbers and could have been involved in the transmission of yellow fever, another disease with high mortality rates.
Fourth Plague — Flies. Many believe that the fourth plague was flies, which included house flies, blow flies, flesh flies, stable flies and many other species of filth-breeding flies that took advantage of the decaying fish, frogs and by this time, human corpses. Today, scientists are aware of the many diseases carried by flies and how they contaminate food, water, wounds, etc., by walking, vomiting and defecating on these surfaces. Moses’ intuitive nature probably saved the Israelites from this plague by moving them away from this area of Egypt and instructing the people to thoroughly roast meat and to burn all that was not consumed.
Fifth Plague — Anthrax. This is a serious fly-borne disease that can cause significant mortality in domestic animals, e.g., sheep, cattle, camels, etc.
Sixth Plague — Boils. The anthrax being spread among domestic animals subsequently was spread by flies to the human population.
Seventh Plague — Hail and Lightening. In addition to killing people and animals, this initiated the physical destruction of the crops and the beginning of starvation among the survivors.
Eighth Plague — Locusts. Hordes of migratory locusts descended on the remaining crops and devoured them.
Ninth Plague — Shutting Off the Light of the Sun and Moon. The swarms of locusts were so huge that they literally darkened the skies, causing a wave of panic.
Tenth Plague — Death of the Egyptians. The catastrophic consequences of all these events were high mortality rates among the Egyptians. Besides starvation, the most plausible explanation for the high mortality rates are dysentery, cholera, typhus and yellow fever — all insect-borne diseases.
The black death or plague has been the scourge of humankind since before the beginning of the Christian era. This bacterial disease is transmitted from rodents to humans through flea bites. The first great plagues occurred between 430 B.C.E. and 690 A.C. The second plague pandemic occurred between 1050 and 1200 A.C. This episode affected parts of Asia, Africa and most of Europe. In Europe, more than 25 million people died — one quarter of the population. This led Europe into the despair of the Middle Ages. The plague destroyed entire cities and all trade was brought to a halt. One more major outbreak of plague would devastate the world from 1346 to 1349 and it is estimated that this plague pandemic killed more people than the casualties in World Wars I and II combined.
Napoleon Bonaparte suffered two major defeats as the result of arthropod-borne diseases that undoubtedly changed the course of history. In 1802, yellow fever, a mosquito-borne disease, decimated Napoleon’s fleet and troops that landed in Haiti and attempted to force the native islanders into submission. The French intended to use Haiti as their base of operations to support colonization of Louisiana. The disease caused significant losses and the armada sailed back to France, abandoning thoughts of occupying Louisiana.
Ten years later, in June 1812, Napoleon set his sights on Russia. He began this conquest with more than 420,000 men. By December the force consisted of 3,400 men. His forces obviously suffered the casualties of combat, but more significant losses were the result of starvation, cold and louse-borne typhus. The latter was suspected to be the major cause of Napoleon’s defeat in Russia, however, this disease was not actually identified for another 100 years.
These diseases have changed history and while many of them are not as problematic as they were in days gone by, new diseases, such as malaria, dengue, yellow fever and West Nile Virus, are filling their niche.
Author’s note: This column was adapted from The Deadly Triangle — A Brief History of Medical and Sanitary Entomology written by William Dwight Pierce, Ph.D.
The author is technical director of American Pest Management, Takoma Park, Md. He can be reached at rkramer@pctonline.com or 301/891-2600.