1. Giardiasis

2. GIARDIASIS Incidence Most common intestinal protozoan in U.S.A.
Third most common protozoan worldwide
Reported from 97 countries
Outbreak sites:
Aspen and Vail, Colorado
Rome, NY ; Berlin, NH
St. Petersburg, Russia
Rocky Mtns., Cascades

3. GIARDIASIS Animal Reservoirs
Proven in western U.S. beavers
Maybe also in dogs, cattle, & deer
Beavers & cattle lose cysts in winter, but re-pass cysts in late summer (implying reinfection from human sources)

4. The wild reservoir culprit for Giardia in the western U.S.

5. GIARDIASIS Risk Factors for Transmission
Poor hygiene
Close physical contact
Venereal (in male homosexuals)
Epidemics & 50 % carrier rates in:
Day care centers
Institutions for the mentally retarded
some Indian reservations

6. GIARDIASIS Pathophysiology
Caused by protozoan Giardia lamblia
Infective dose = a few cysts
Life cycle:
Trophozoites inhabit jejunum & duodenum and cause symptoms
Some trophozoites encyst & pass in stool
Cysts are infectious
Cysts are activated ("excysted") by passage thru stomach
Some patients may be asymptomatic carriers & cyst passers

9. Giardia lamblia trophozoites in stained stool

10. Giardia lamblia cyst in stained stool

11. GIARDIASIS Symptoms Initial infection: Later, more chronic sx:
Acute diarrhea for 2 to 3 days
+/- low grade fever
Anorexia, nausea, cramping
Later, more chronic sx:
Diarrhea / foul smelling stool & flatus
Foul smelling belching
Cramping, nausea, anorexia, fatigue
Abdominal distention
May progress to malabsorption, weight loss, failure to thrive

12. GIARDIASIS Diagnosis
Fresh stool exam with iodine or methylene blue stain
Avoid recent enemas, laxatives, barium
Yield is 50 to 70 % on one stool exam; is 70 to 90 % with 3 stool exams
Other Dx tests:
Entero Test (withdrawn swallowed string)
Endoscopic duodenal biopsy
ELISA serology (but does not differentiate acute from past infection)

14. GIARDIASIS Treatment 2 most common meds (probably drugs of choice) :
Quinacrine (Atabrine)
Dose 100mg tid x 5 to 7 days (7 mg / kg / day )
Cure rate 95 %
Side effects: dizzy, toxic psychosis, taste
Metronidazole (Flagyl)
250 mg tid x 7 days (21 mg / kg / day)
High cure rate
Still not FDA approved
Side effects: disulfiram-like, ? mutagen

15. GIARDIASIS Other Treatment Meds
Furazolidine (Furoxone)
Dose 100 mg qid x 7 days (6 mg / kg / day in 4 divided doses / day x 5 to 7 days)
Cure rate 85 %
Usually well tolerated; may cause nausea / emesis
Paromomycin (Humantin)
A poorly absorbed aminoglycoside-like antibiotic
Dose 25 to 30 mg / kg in 3 divided doses x 5 to 10 days
Useful for pregnant patients