22.3 Your Health and Protists

Your Health and Protists

Section Objective

  • Identify examples of harmful and helpful protists.

Protists and Humans

  • Protists can affect human beings negatively, directly, and indirectly.
  • Harmful effects:
    • Diseases in humans: African sleeping sickness, amoebic dysentery, Giardiasis, and malaria.
    • Diseases in livestock: Increases the cost of treating livestock, injures livestock production, and leads to higher prices for consumers.

Beneficial Protists

  • Essential and beneficial to humans and other organisms.
  • Examples:
    • Cattle depend on commensal protists in their digestive tract to digest the cellulose in hay and grass.
    • Humans also have commensal protists in their digestive tracts.
    • Protists are responsible for increased oxygen levels as they are the largest photosynthesizers on Earth.
    • Integral part of the food chain: They make up much of the plankton in the oceans.
    • Essential in recycling important chemicals in the environment, such as phosphorus, carbon, and nitrogen.

Malaria

  • One of the deadliest diseases in the world, accounting for up to three million deaths annually.
  • Infects an estimated one hundred million people at a time.
  • Symptoms: Fever, confusion, sweating, severe chills, and intense thirst.
  • Causes of malaria-related deaths: Brain damage, kidney failure, or anemia.

Malaria Life Cycle

  • Spreads to humans through mosquito bites and is caused by species of Plasmodium.
    • During mosquito bites, mosquitoes inject approximately 1,000 protists through its saliva.
  • Stages of malaria infection:
    • Sporozoite: The infective phase, which is the first stage of malaria infection.
    • Merozoite: Results in the infection of the liver, during which the sporozoites rapidly divide and produce millions of cells.
      • Within 48 hours, the merozoites infect red blood cells, causing them to rupture, releasing more merozoites and toxic substances.
    • Cycle of fever and chills: Repeated every 48-72 hours.
    • Gametes: Some of the merozoites develop into gametes in the final stage.
  • The malaria parasite matures inside the mosquito before it can infect other humans because mosquitoes cannot regurgitate food or mix saliva with food.

Check Your Understanding

  • Which of these diseases is not caused by protists?
    • A. Malaria
    • B. Amoebic dysentery
    • C. Giardiasis
    • D. Smallpox
    • E. African sleeping sickness
  • Answer: D. Smallpox

Treating and Preventing Malaria

  • Medications used since the 1650s: Primaquine and Chloroquine.
    • These medications are derivatives of quinine, a chemical derived from the bark of the cinchona tree of South America.
  • The spread of malaria is controlled by:
    • Reducing mosquito populations through means such as spraying insecticides.
    • Reducing breeding grounds.
    • Using mosquito predators such as the mosquito fish.