Eukaryotic Parasite_ Protozoa

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• Protozoa Overview

  • General Characteristics:

    • First forms of life (unicellular eukaryotes).

    • Most are heterotrophs: Obtain nutrients from other organisms.

    • Most reproduce asexually.

  • Classified by Type of Locomotion:

    • Pseudopods:

      • "Fake feet" used for movement.

    • Flagella: Whip-like structure for movement.

    • Cilia: Hair-like projections for movement.

    • Apicomplexa: Non-motile.

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• Pseudopods Classification:

  • Amoeba:

    • Example: Entamoeba histolytica.

    • Causes Amoebic Dysentery:

      • Effects digestive system, leading to bloody diarrhea.

  • Amoeba Movement:

    • Use pseudopods and cytoplasmic streaming.

  • Active Form: Trophozoite

    • Inactive Form: Cyst

    • Route of Entry (ROE):

      • Fecal-oral, enters through mouth, exits via the digestive system.

      • Cyst survives stomach, trophozoite grows in intestines, then encysts and is released as feces.

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• Another Amoeba Example:

  • Naegleria fowleri: Causes Amoebic Meningoencephalitis:

    • Flask-shaped amoeba found in warm freshwater (lakes, ponds).

    • Can exhibit a flagellate form.

    • Enters via olfactory system, leading to severe brain pathology.

    • Symptoms: Increase in cerebrospinal fluid pressure, can lead to death.

    • Most documented survivor’s case noted.

    • Areas of concern: Dirty water exposure, particularly in Texas and Florida.

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• Ciliates:

  • Example: Balantidium coli.

    • Can cause dysentery, often asymptomatic.

  • Flagellates:

    • Trichomonas vaginalis:

      • A genital pathogen causing Trichomoniasis:

        • Symptoms: Smelly, off-color vaginal discharge.

      • Route of Entry: Direct contact, does not survive long outside host (no cyst form).

    • Giardia spp:

      • Mango-shaped protozoa.

      • Forms cysts in water; trophozoite form in hosts.

      • Causes watery diarrhea; ROE: Fecal-oral.

      • Prevention: Wash hands, avoid drinking untreated water.

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• Chronic and Acute Phase of Infection:

  • Affected individuals may become bedridden.

  • Parasites introduced through bites; can result in fever, swollen lymph nodes during acute phase.

  • Chronic Phase:

    • Affects heart, brain, or intestines.

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• Apicomplexa Overview:

  • Plasmodium spp:

    • Causative agents of malaria.

    • Common Types:

      • Plasmodium vivax: Milder form

      • Plasmodium falciparum: Malignant form.

    • Vector: Anopheles mosquito (definitive host).

    • Mechanism: Parasite in sporozoite form, undergoes sexual reproduction in the mosquito.

    • Merozoites penetrate red blood cells; ring form is diagnostic.

    • Mechanism of Adhesion: Induces adhesive knobs in RBC, allowing parasites to replicate within capillaries.

    • Treatment: Common drug is artemisinin.

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• Toxoplasma gondii:

  • Causative agent of toxoplasmosis.

    • Usually asymptomatic except in immunocompromised individuals.

    • Spread through poorly cooked food or exposure to infected cat feces.

    • Can transfer from mother to fetus (congenital infection): May cause stillbirth or severe brain/vision issues.

  • Life Cycle:

    • Sexual reproduction occurs inside the cat's body.

    • Mind-Altering Effects: Infected mice lose fear of cats.

    • Structural Forms: Tachyzoites, pseudocysts, oocysts in feces and environment.