Insects and People: Insects and Worldwide Diseases

Malaria: The Great Single Killer of Humanity

  • Agent: 4 different protozoans
  • Reservoir: human (only 1% of infected humans die, the rest are reservoirs)
  • Vector: several anopheles mosquitos
  • Target: humans only
  • Distribution: worldwide
  • Up to mid-1940’s, over 300,000,000 cases and 3,000,000 deaths per year
    • Still around 200,000,000 cases, 1-2,000,000 deaths per year
  • Symptoms: fever and chills, weakness, tired
  • Treatment: synthetic drugs (prevention)
    • Chloroquine is a medication that is used to treat malaria infection
    • Derived from a special type of tree (Cinchona tree in Peru)
    • Quinine
  • Problems: mosquito and protozoan resistance
  • Prevention
    • Remove stagnant water habitat for mosquitos
    • Prevent mosquito bites (DEET, screens, bed nets)
    • Kill them with insecticides!

 

  • Hippocrates—Was the first person to associate malaria with swamps and stagnant water
  • Sir Patrick Manson—Developed the theory that malaria was transmitted by mosquitoes to humans
  • Ronald Ross—Confirmed through experiments that Anopheles mosquitoes transmit malaria to humans

Insects in War

Napoleon's brother-in-law, General Charles Leclerc, attempted to conquer Haiti and a small country called the United States of America! How was his army of 33,000 soldiers defeated?

  • Yellow Fever – A mosquito virus – Killed 29,000 of those soldiers
  • Fact: ==Mosquito-transmitted diseases (Malaria, yellow fever, etc.) are responsible for half of all human deaths since the stone age==

Plague: Black Death

  • Agent: one species of bacteria
  • Reservoir: rodents, tolerant humans
  • Vector: rat flea
  • Target: rodents, fleas, and humans
  • Distribution: worldwide, a port disease
  • Symptoms: high fever, rapid pulse & respiration, the appearance of “bubo”
    • Bubonic, Pneumonic, and Septicemic Plague versions
  • History: almost as old as history itself
    • 1000 BC Plague of the Philistines
    • 541-544 Plague of Justinian
    • 1320-1700 Black Death throughout Europe
    • Killed 25,000,000 people by 1351
  • Repercussions many and varied
  • Disease is still around

Epidemic Typhus: Wartime Disease

  • Agent: bacteria-like microbe called rickettsia
  • Reservoir: humans and lice
  • Vector: human body louse
  • Target: humans and lice
  • Distribution: temperature regions with cold season
  • Symptoms: high fever, chills, severe headaches, confusion. Brick red spots on the body.
  • Treatment/prevention: antibiotics, lice sprays, vaccination
  • Typhus and war: world examples
    • Crusades lost 100,000s to typhus
    • Louis VII of France left with 500,000 men during the crusades and returned with only a few
    • Maximillian II of Germany failed to invade Hungary
    • Napolean defeated several times by typhus
    • Crimean War: 131,000 battle deaths, 105,000 disease deaths, 660,000 too sick to fight
  • Typhus and war: United States examples
    • 1898 Spanish-American War; 369 battle deaths, 1,939 typhus
    • WWI- 3,000,000 typhus deaths, mostly in Russia
    • WWII: malaria and typhus killed 5X more than did battles
    • Korea and Vietnam: many cases but fewer deaths

There are many other insect-vectored diseased that have shaped history and continue to do so.