MICRO L8 P1 Foodborne Intestinal Parasites Overview

Foodborne Intestinal Parasites

• Foodborne intestinal parasites are a concern for public health.
• Various parasites cause intestinal disease, including Entamoeba histolytica, Giardia intestinalis, and Taenia.
• Ascaris lumbricoides is also a parasite that causes intestinal issues.

Entamoeba histolytica

• Causes intestinal disease:

  • Intestinal amebiasis: intestinal infection.
  • Amebic dysentery: invasion of intestinal mucosa.
  • Extra-intestinal amebiasis: infection of organs outside the intestine.

• Morphology:

  • Trophozoites: Exhibits rapid, unidirectional movement using pseudopods.
    • Contains a single nucleus.
    • Can contain red blood cells, bacteria, yeast, and other debris in the cytoplasm. E. histolytica is the only intestinal amoeba that exhibits this.
  • Cysts: Are spherical to round and smaller than trophozoites.
    • Mature cysts contain 1-4 nuclei (quadrinucleated)
    • Red blood cells, bacteria, and yeast are not found in the cyst stage.

• Life Cycle:

  • Once the infective cyst is ingested, excystation occurs in the small intestine.
  • A single cyst produces motile trophozoites that settle in the large intestine and replicate.
  • Trophozoites can migrate to other organs like the liver, potentially causing abscess formation (extra-intestinal amebiasis).
  • Encystation occurs and cysts are released in human feces. Cysts are very resistant to various environmental conditions.

• Epidemiology:

  • Transmission routes include ingestion of cysts in food.
  • Houseflies and cockroaches can be vectors by spreading cysts on unprotected food.
  • Improperly treated water supplies can spread the infection.

• Clinical Symptoms:

  • Infected patients can be asymptomatic (asymptomatic carrier state).
  • Amebic colitis: An intestinal infection characterized by diarrhea, abdominal pain, and cramping.
  • Amebic dysentery: A condition marked by blood and/or pus and mucus in the stool.
  • Symptomatic Extraintestinal Amebiasis: Abscess formation in the right lobe of the liver leads to upper right abdominal pain, fever, nausea, and potential vomiting.
  • Intestinal damage and malabsorption can also occur, leading to diarrhea, nutrient loss, impact on appetite and food intake, anemia, and/or micronutrient deficiencies.

The Flagellates

• Categorized into groups:
  • Intestinal flagellates (Giardia intestinalis)
  • Urogenital flagellates (Trichomonas vaginalis)
  • Hemoflagellates (Trypanosoma and Leishmania spp)
• Movement via flagella in their trophozoite form.

Giardia intestinalis

• Description: Intestinal flagellate that colonizes and reproduces in the small intestine.

• Causes: Diarrheal illness known as giardiasis, also known as "traveler's diarrhea" in less-developed countries.

• Morphology:

  • Trophozoites: Motile stage with bilateral symmetry (similar anatomical parts on opposite sides).
    • Two nuclei.
    • Four pairs of (8) flagella.
    • Sucking discs for attachment and nourishment.
  • Cysts: Typical oval with a thick cell wall.
    • Immature cysts contain two nuclei
    • Mature cysts (infective stage) contain four nuclei

• Life Cycle:

  • Infection occurs via ingestion of cysts in contaminated water, food, or the fecal-oral route (hands).
  • In the small intestine, excystation releases trophozoites which attach to the mucosa.
  • Encystation occurs in the colon.
  • Trophozoites are detected in diarrheal feces. Cysts are more common in formed (non-diarrheal) feces.

• Impact on Nutrition:

  • Malabsorption of nutrients, interfering with absorption of carbohydrates, fats, proteins, fat-soluble vitamins (A, D, E).
  • Leads to nutritional deficiencies.
  • Lactose intolerance due to intestinal damage.
  • Chronic diarrhea and nutrient loss, leading to weight loss, appetite loss, delayed cognitive development and learning difficulties.
  • Disruption of gut microbiota and immune function.

Explore the critical aspects of foodborne intestinal parasites, focusing on Entamoeba histolytica, Giardia intestinalis, and Taenia. This quiz covers their impact on public health, including the diseases they cause and their morphological characteristics. Test your knowledge about these major intestinal pathogens.