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Allied Health Microbiology: 19.5 Protozoan Infections of the Gastrointestinal Tract

Allied Health Microbiology
19.5 Protozoan Infections of the Gastrointestinal Tract
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table of contents
  1. Cover
  2. Title Page
  3. Copyright
  4. Table Of Contents
  5. Preface
  6. Forward
  7. Chapter 1: An Invisible World
    1. 1.1 What Our Ancestors Knew
    2. 1.2 A Systematic Approach
    3. 1.3 Types of Microorganisms
    4. Summary
  8. Chapter 2: The Cell
    1. 2.1 Spontaneous Generation
    2. 2.2 Foundations of Modern Cell Theory
    3. 2.3 Unique Characteristics of Prokaryotic Cells
    4. Summary
  9. Chapter 3: Prokaryotic Diversity
    1. 3.1 Prokaryote Habitats, Relationships, and Microbiomes
    2. Summary
  10. Chapter 4: The Eukaryotes of Microbiology
    1. 4.1 Unicellular Eukaryotic Parasites
    2. 4.2 Parasitic Helminths
    3. 4.3 Fungi
    4. Summary
  11. Chapter 5: Acellular Pathogens
    1. 5.1 Viruses
    2. 5.2 The Viral Life Cycle
    3. 5.3 Prions
    4. Summary
  12. Chapter 6: Microbial Biochemistry
    1. 6.1 Microbial Biochemistry
    2. Summary
  13. Chapter 7: Microbial Growth
    1. 7.1 How Microbes Grow
    2. 7.2 Oxygen Requirements for Microbial Growth
    3. 7.3 The Effects of pH on Microbial Growth
    4. 7.4 Temperature and Microbial Growth
    5. Summary
  14. Chapter 8: Modern Applications of Microbial Genetics
    1. 8.1 Whole Genome Methods and Pharmaceutical Applications of Genetic Engineering
    2. 8.2 Gene Therapy
    3. Summary
  15. Chapter 9: Control of Microbial Growth
    1. 9.1 Controlling Microbial Growth
    2. 9.2 Testing the Effectiveness of Antiseptics and Disinfectants
    3. Summary
  16. Chapter 10: Antimicrobial Drugs
    1. 10.1 Fundamentals of Antimicrobial Chemotherapy
    2. 10.2 Mechanisms of Antibacterial Drugs
    3. 10.3 Mechanisms of Other Antimicrobial Drugs
    4. 10.4 Drug Resistance
    5. 10.5 Testing the Effectiveness of Antimicrobials
    6. 10.6 Current Strategies for Antimicrobial Discovery
    7. Summary
  17. Chapter 11: Microbial Mechanisms of Pathogenicity
    1. 11.1 Characteristics of Infectious Disease
    2. 11.2 How Pathogens Cause Disease
    3. 11.3 Virulence Factors of Bacterial and Viral Pathogens
    4. Summary
  18. Chapter 12: Disease and Epidemiology
    1. 12.1 The Language of Epidemiologists
    2. 12.2 Tracking Infectious Diseases
    3. 12.3 Modes of Disease Transmission
    4. 12.4 Global Public Health
    5. Summary
  19. Chapter 13: Innate Nonspecific Host Defenses
    1. 13.1 Physical Defenses
    2. 13.2 Chemical Defenses
    3. 13.3 Cellular Defenses
    4. 13.4 Pathogen Recognition and Phagocytosis
    5. 13.5 Inflammation and Fever
    6. Summary
  20. Chapter 14: Adaptive Specific Host Defenses
    1. 14.1 Overview of Specific Adaptive Immunity
    2. 14.2 Major Histocompatibility Complexes and Antigen-Presenting Cells
    3. 14.3 T Lymphocytes and Cellular Immunity
    4. 14.4 B Lymphocytes and Humoral Immunity
    5. 14.5 Vaccines
    6. Summary
  21. Chapter 15: Diseases of the Immune System
    1. 15.1 Hypersensitivities
    2. 15.2 Autoimmune Disorders
    3. 15.3 Organ Transplantation and Rejection
    4. Summary
  22. Chapter 16: Skin and Eye Infections
    1. 16.1 Anatomy and Normal Microbiota of the Skin and Eyes
    2. 16.2 Bacterial Infections of the Skin and Eyes
    3. 16.3 Viral Infections of the Skin and Eyes
    4. 16.4 Mycoses of the Skin
    5. 16.5 Helminthic Infections of the Skin and Eyes
    6. Summary
  23. Chapter 17: Respiratory System Infections
    1. 17.1 Anatomy and Normal Microbiota of the Respiratory Tract
    2. 17.2 Bacterial Infections of the Respiratory Tract
    3. 17.3 Viral Infections of the Respiratory Tract
    4. Summary
  24. Chapter 18: Urogenital System Infections
    1. 18.1 Anatomy and Normal Microbiota of the Urogenital Tract
    2. 18.2 Bacterial Infections of the Urinary System
    3. 18.3 Bacterial Infections of the Reproductive System
    4. 18.4 Viral Infections of the Reproductive System
    5. 18.5 Fungal Infections of the Reproductive System
    6. 18.6 Protozoan Infections of the Urogenital System
    7. Summary
  25. Chapter 19: Digestive System Infections
    1. 19.1 Anatomy and Normal Microbiota of the Digestive System
    2. 19.2 Microbial Diseases of the Mouth and Oral Cavity
    3. 19.3 Bacterial Infections of the Gastrointestinal Tract
    4. 19.4 Viral Infections of the Gastrointestinal Tract
    5. 19.5 Protozoan Infections of the Gastrointestinal Tract
    6. 19.6 Helminthic Infections of the Gastrointestinal Tract
    7. Summary
  26. Chapter 20: Circulatory and Lymphatic System Infections
    1. 20.1 Anatomy of the Circulatory and Lymphatic Systems
    2. 20.2 Bacterial Infections of the Circulatory and Lymphatic Systems
    3. 20.3 Viral Infections of the Circulatory and Lymphatic Systems
    4. 20.4 Parasitic Infections of the Circulatory and Lymphatic Systems
    5. Summary
  27. Chapter 21: Nervous System Infections
    1. 21.1 Anatomy of the Nervous System
    2. 21.2 Bacterial Diseases of the Nervous System
    3. 21.3 Acellular Diseases of the Nervous System
    4. Summary
  28. Creative Commons License
  29. Recommended Citations
  30. Versioning

19.5 Protozoan Infections of the Gastrointestinal Tract

Learning Objectives

  • Identify the most common protozoans that can cause infections of the GI tract
  • Compare the major characteristics of specific protozoan diseases affecting the GI tract

Like other microbes, protozoa are abundant in natural microbiota but can also be associated with significant illness. Gastrointestinal diseases caused by protozoa are generally associated with exposure to contaminated food and water, meaning that those without access to good sanitation are at greatest risk. Even in developed countries, infections can occur and these microbes have sometimes caused significant outbreaks from contamination of public water supplies.

Giardiasis

Also called backpacker’s diarrhea or beaver fever, giardiasis is a common disease in the United States caused by the flagellated protist Giardia lamblia.. To establish infection, G. lamblia uses a large adhesive disk to attach to the intestinal mucosa. The disk is comprised of microtubules. During adhesion, the flagella of G. lamblia move in a manner that draws fluid out from under the disk, resulting in an area of lower pressure that promotes its adhesion to the intestinal epithelial cells. Due to its attachment, Giardia also blocks absorption of nutrients, including fats.

Transmission occurs through contaminated food or water or directly from person to person. Children in day-care centers are at risk due to their tendency to put items into their mouths that may be contaminated. Large outbreaks may occur if a public water supply becomes contaminated. Giardia have a resistant cyst stage in their life cycle that is able to survive cold temperatures and the chlorination treatment typically used for drinking water in municipal reservoirs. As a result, municipal water must be filtered to trap and remove these cysts. Once consumed by the host, Giardia develops into the active tropozoite.

Infected individuals may be asymptomatic or have gastrointestinal signs and symptoms, sometimes accompanied by weight loss. Common symptoms, which appear one to three weeks after exposure, include diarrhea, nausea, stomach cramps, gas, greasy stool (because fat absorption is being blocked), and possible dehydration. The parasite remains in the colon and does not cause systemic infection. Signs and symptoms generally clear within two to six weeks. Chronic infections may develop and are often resistant to treatment. These are associated with weight loss, episodic diarrhea, and malabsorption syndrome due to the blocked nutrient absorption.

Diagnosis may be made using observation under the microscope. A stool ova and parasite (O&P) exam involves direct examination of a stool sample for the presence of cysts and trophozoites; it can be used to distinguish common parasitic intestinal infections. ELISA and other immunoassay tests, including commercial direct fluorescence antibody kits, are also used. The most common treatments use metronidazole as the first-line choice, followed by tinidazole. If the infection becomes chronic, the parasites may become resistant to medications.

  • Which problems can occur when trying to prevent giardiasis?

Disease Profile

Protozoan Gastrointestinal Infections

Protozoan GI infections are generally transmitted through contaminated food or water, triggering diarrhea and vomiting that can lead to dehydration. Rehydration therapy is an important aspect of treatment, but most protozoan GI infections can also be treated with drugs that target protozoans.

Figure 19.16 Details associated with the disease giardiasis, a protozoal infection of the GI tract.

Annotate

Next Chapter
19.6 Helminthic Infections of the Gastrointestinal Tract
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Copyright © 2019 by Open Stax and Linda Bruslind Allied Health Microbiology by Open Stax and Linda Bruslind is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License, except where otherwise noted.
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