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.