Giardia lamblia and Giardiasis | Essay Questions | Ompath Study

Practice 10 structured short- and long-answer medical questions on Giardia lamblia and Giardiasis. Review model answers for exam revision.

Essay Questions and Answers

1. Q1. ### Introduction

   Answer: - *Giardia lamblia* (also called *Giardia intestinalis* or *Giardia duodenalis*) is a protozoan parasite that causes giardiasis, an intestinal infection. - It is the only protozoan parasite found in the lumen of the small intestine (duodenum and upper jejunum). - Transmission occurs through ingestion of cysts in contaminated food and water or via direct person-to-person contact. ### Morphology of Giardia lamblia #### 1. Trophozoite (Vegetative Form) - Shape: Pear-shaped and bilaterally symmetrical. - Size: 9-21 µm long and 5-15 µm wide. - Motility: Resembles a "falling leaf" movement. - Key Features: Two nuclei with a central karyosome; four pairs of flagella (arising from a blepharoplast); axostyle (supportive rod); ventral sucking disc (for attachment); and two median bodies. #### 2. Cyst (Infective Form) - Shape: Oval or ellipsoid. - Size: 8-12 µm. - Key Features: Thick protective wall; four nuclei (in mature cysts); remnants of flagella and median bodies. - Infective Stage: Mature cysts are highly infectious and can survive in soil and water for weeks. ### Life Cycle

2. Q2. **Infective Stage**: Mature cysts are ingested via contaminated water, food, or direct fecal-oral contact.

   Answer: Model answer pending

3. Q3. **Excystation**: Occurs in the small intestine within 30 minutes of ingestion. Each cyst releases two trophozoites.

   Answer: Model answer pending

4. Q4. **Multiplication and Colonization**: Trophozoites multiply by binary fission and attach to the intestinal mucosa using their ventral sucking disc, interfering with absorption without invading tissue.

   Answer: Model answer pending

5. Q5. **Encystation**: Triggered by dehydration and bile salts in the colon; infective cysts are produced and excreted in feces.

   Answer: Model answer pending

6. Q6. **Transmission**: Cysts remain viable in the environment for weeks. Infective dose is 10–100 cysts.

   Answer: ### Pathogenesis and Clinical Features #### Pathogenesis - Adheres tightly to the intestinal epithelium causing villous atrophy and apoptosis of enterocytes. - Leads to malabsorption of fats and carbohydrates (steatorrhea). - Variant-Specific Surface Proteins (VSSP) allow the parasite to evade the immune system. #### Clinical Features - **Asymptomatic Carrier State**: 50-70% of cases. - **Acute Giardiasis**: Watery diarrhea with excess mucus (no blood), foul-smelling fatty stools (steatorrhea), epigastric pain, bloating, and temporary lactose intolerance. - **Chronic Giardiasis**: Persistent diarrhea, malnutrition, Vitamin A deficiency, and failure to thrive in children. - **Extraintestinal Manifestations**: Biliary Giardiasis (colonization of the gallbladder) causing biliary colic or jaundice. ### Diagnosis

7. Q7. **Stool Examination**: Wet mount for trophozoites and cysts; concentration techniques (zinc sulfate flotation) and Trichrome stain.

   Answer: Model answer pending

8. Q8. **Entero-Test (String Test)**: Retrieval of a swallowed string to examine for trophozoites.

   Answer: Model answer pending

9. Q9. **Serology and Molecular Tests**: ELISA for stool antigens; PCR (most sensitive).

   Answer: Model answer pending

10. Q10. **Duodenal Aspirate/Biopsy**: Used in chronic cases when stool tests are negative.

    Answer: ### Treatment #### First-Line Drugs - **Metronidazole**: 250 mg TID for 5–7 days (Adults); 15 mg/kg/day for 5 days (Children). - **Tinidazole**: 2 g single dose (Adults); 50 mg/kg single dose (Children). #### Alternative Drugs - **Furazolidone**: 100 mg QID for 7-10 days (preferred in children). - **Nitazoxanide**: 500 mg BID for 3 days. - **Paromomycin**: 25-35 mg/kg/day for 7 days (Safe in pregnancy). ### Prevention and Control - Handwashing and proper waste disposal. - Boiling water or using membrane filters (chlorination is often ineffective against cysts). - Improved sanitation and treatment of carriers.