Giardiasis

1. Identification

                  - a protozoan infection of the small intestine

                  - trophozoites are in lumen of small bowel

                  - cysts are infectious in stool

                  - symptoms can be sudden or severe or occur gradually

      - symptoms of fatigue and weight loss, excessive gas,

      abdominal rumblings (borborygmi) and bloating                                       - doesn’t invade tissues

-          reactive arthritis may occur

2. Infectious agent

                  – Giardia lamblia, a flagellate protozoan

3. Occurrence

• worldwide, children>adults, especially daycare centres
• most common July to October
• high incidence in travelers returning from Russia,
• contaminated municipal tap water, especially in St. Petersburg
• fewer than 3% of travelers returning from Mexico, Latin America,                                  Asia and Africa have giardia
• also known as backpacker’s diarrhea even in North America as
• parasite found in mountainous lakes and streams, transmission                                    seems largely person to person and handwashing on camping trips                              should be emphasized
• source is unfiltered surface water or shallow wells
• swimming in fresh water, swimming and wading pools
• cross contamination of water/sewer systems

4. Reservoir

                  – humans, possibly beaver and other wild and domestic

                  animals, cats, dogs and cattle

5. Transmission

                  – person to person

      - hand to mouth by transfer of cysts from feces

      - chlorine used in water treatment does not kill cysts

6. Incubation

                  – 3 to 25 days, median 7 to 10 days

7. Period of communicability

                  – entire period of infection, often months

8. Susceptibilty and resistance

                  – asymptomatic carrier rate is high

                  - infection frequently self limited

                  - AIDS patients may have more serious and

                  prolonged infection

9. Prevention

·        hand washing, educate families, personnel and inmates of          

·              institutions and adult personnel of daycare centres                                           - filter water, protect public water supply

·        boil emergency water or hypochlorite or iodine

     10.  Diagnosis

·        stool sample for parasites, ?80% pickup, consider empiric treatment

·        new antibody test, GiardEIA available from Antibodies Incorporated, 916-758-4400, very sensitive and specific

11.  Treatment

§   Metronidazole(Flagyl) 250 mg tid x 5 days, >80% cure

  or 2 grams qhs x 3

§   for children under 25 kg, 35 mg/kg in a single dose qhs for 3                             days, for children 25 to 40 kg, 50 mg/kg for 3 days

§   alternatives, quinacrine (85 to 95% cure) and albendazole                                 400 mg bid for 7 days has a variable cure rate

§   or tinidazole 2 gm once                          

furazolidone 100 mg 4 times daily for 7 to 10 days, also                                      available in suspension for young children and infants, 80%                   cure

                  - paromomycin in pregnancy

                  - Note: lactose intolerance may persist for weeks or months      following parasite eradication                 

12.  Bibliography

                  – Control of Communicable Diseases Manual, 2000

                  - Harrison’s Principles of Internal Medicine, 2001

                  - International Travel Health Guide, Rose, 2001

Jim Hayward