Giardiasis

Question 1

Life cycle: What is responsible for signs and symptoms of Giardia?

Answer 1

Trophs attach to the surface lining cells and cause symptoms

Question 2

Life cycle: What part of the cyst is most important in transmission

Answer 2

Cysts have an outer wall to protect them

Question 3

Life cycle: What is Excystation?

Answer 3

Step 1 Release of parasite from cyst in the small intestine

Question 4

Life cycle: Each cyst releases how many parasites?

Answer 4

Each cyst releases 2 trophs

Question 5

Life cycle: What is Encystation?

Answer 5

formation of cyst from trophs; with giardia smooth wall cyst can contain 2 trophs

Question 6

Clinical: Describe the clinical manifestations of Giardia

Answer 6

• Acute diarrhea x 7-10 days, watery, foul-smelling (Concern with dehydration in children)
• Incubation period is 7-10 days
• Abdominal discomfort
  Chronic diarrhea =/- malabsorption, weight loss
  Asymptomatic “infection can occur”
  Occasional lactase deficiency with or after infection (important to avoid dairy, as it will prolong symptoms)

Question 7

Describe the Epidemiology of Giardia

Answer 7

HIGHLY CONTAGIOUS  (infection spreads with only 10 or more cysts)
 - Fecal oral (person to person)
 - Day care (person to person)
 - Sex practice (person to person)
 - Water
 - Foodborne (after fecal contamination)
Traveller's Diarrhea

Question 8

Describe the Diagnosis of Giardia

Answer 8

Giardia stool antigen (most cost effective) polyclonal or monoclonal antibody against cyst or trophozoite antigens is used, whether with an immunoflourscent antibody test or ELISA

• useful to dx or r/o giardia
• Ab or ELISA (highly specific/sensitive test)
• Fecal leukocytes (WBC) absent (no inflammation)
• Duodenal aspirate and/or biopsy or “string test:
• Stool for O & P (ova and parasite exam) can be negative even with infection. Organisms can be shed intermittently
• No serologic test available

Question 9

Describe the Treatment of Giardia

Answer 9

TINIDAZOLE (DOC - drug of choice)

• single dosing
• avoid dairy 1 month
• also: metronidazole (was DOC, still used)
• empiric therapy for presumed giardiasis in very selective patients= diarrhea for longer than 3 weeks or lab w/u negative but patient “at risk” by hx

Question 10

Explain prevention of Giardia

Answer 10

• proper handling/treatment of water (chlorination)
• hand washing
• avoid oral-anal
• campers: boil/treat H2O w/ chlorine/iodine
  - small volume personal water filter

Question 11

How can we prevent this disease?

Answer 11

1. Proper handling & treatment of water
2. Good personal hygiene
3. Campers & travelers to filter/boil water

Question 12

What are Trophozoites?

Answer 12

• The active form that grows and replicates by binary fission
• Protozoan enteric flagellate. Single cell protozoa