Case report

1. Case report 報告人: I2 顏銘漢 指導人: 盧章智 主任

2. History • A 25-year-old woman had recently returned from a trip to the Rocky Mountains. She had been traveling with a group of campers, who had obtained their drinking water from a lake. A few days after returning home, she presented to her internist suffering from profuse(過多的) watery diarrhea, crampy epigastric pain, and foul(惡臭)-smelling flatulence (屁). She discovered that most of the other campers had reported symptoms similar to her own.

3. History • Three stool specimens were submitted for labora­tory analysis. All specimens were negative for enteric bacterial pathogens, and two were also negative for parasites. Since the specimens for ova and parasites were received in vials containing the preservatives polyvinyl alcohol and 10% formalin, no wet mounts (載片) were made to detect motility. A permanent trichromestain revealed rare, oval protozoan trophozoites, measuring 9 to 20 jjum in length and 5 to 15 jjim in width.

4. History • The broad anterior end of each trophozoite(滋養期原蟲 )contained a concave area which covered half the ventral surface. The structure of this parasite gave the overall appearance of a "smiling face" . Rare cysts, having four nuclei, and characteristic median bodies and longitudinal fibers were also seen. Typical cysts are demonstrated.

6. Questions • 1. • Which protozoan parasite is causing the camper's infection? • Which form of this parasite is infectious? • A: • Giardia lamblia. (giardiasis)梨形蟲病 • cyst

8. 2. • How is this parasite transmitted? • A: • Cysts, which are resistant to adverse environmental conditions, are passed in the feces of an infected host, and the next host is infected when it ingests cysts in food or water contaminated with feces

9. Accidentally putting something into your mouth or swallowing something that has come into contact with feces of a person or animal infected with Giardia. • Swallowing recreational water contaminated with Giardia. Recreational water includes water in swimming pools, hot tubs, jacuzzis, fountains, lakes, rivers, springs, ponds, or streams that can be contaminated with sewage or feces from humans or animals. • Eating uncooked food contaminated with Giardia. • Accidentally swallowingGiardia picked up from surfaces (such as bathroom fixtures, changing tables, diaper pails, or toys) contaminated with feces from an infected person.

10. 3. • How can this infection be controlled andprevented? • A: • Practice good hygiene. • Avoid water that might be contaminated. • Avoid food that might be contaminated. • Avoid fecal exposure during sexual activity.

11. 4. • How does this parasite attach itself to the intestinal wall? • A: • Giardia is a flagellated (having whip-like appendages for locomotion) protozoan that, in the trophozoite (active) form, attaches itself with an adhesive disk (ventral side) to the lining of the upper intestinal tract of the host animal.  There, it feeds and reproduces. 

12. Which conditionmight result as a consequence of this attachment? • 1.malabsorptive diarrhea • 2.fatty, four-smelling stools after eating • 3.milk allergy or lactose intolerance (<1 Y/O)

13. 5. • How is this infection treated? • The most common treatment for giardiasis is metronidazole (Flagyl) for 5-10 days. It eradicates the Giardia more than 85% of the time, but it often causes gastrointestinal side effects such as nausea and a metallic taste as well as dizziness and headache. • The only drug approved for treating giardiasis in the U.S. is furazolidone (Furoxone) for 7-10 days. It is approximately as effective as metronidazole.

14. Tinidazole is available outside the U.S. and is highly effective at treating giardiasis(>90%). It also can be given as a single dose and is well tolerated. • Quinacrine is very effective for treating giardiasis but is no longer available in the U.S. • Paromomycin and albendazole, though effective, are less effective than other treatments. • Occasionally, treatment fails to eradicate Giardia. In such cases, the drug may be changed or a longer duration or higher dose may be used. Combination therapy also may be effective (e.g., quinacrine and metronidazole).

15. 6. • Describe the life cycle of this parasite. • At some time in its active life, the trophozoite releases its hold on the bowel wall and floats in the fecal stream.  As it makes its journey, it transforms into an egg-like structure called a cyst, which is eventually passed in the stool.  Duration of cyst excretion, called shedding, may persist for months.  Once outside the body, the cysts can be ingested by another animal.  Then, they “hatch” into trophozoites due to stomach acid action and digestive enzymes, and the cycle repeats.

16. 7. • Describe the pathogenesis of this infection. • A significant infestation can leave millions of trophozoites stuck tight to the intestinal lining.  There, they cripple the gut’s ability to secrete enzymes and absorb food, especially fats, thereby producing the disease’s symptoms.  The symptoms typically appear one to two weeks after ingestion, with an average of nine days, but four weeks is not uncommon.  Symptoms can vanish suddenly and then reappear.  They may hide for months.  They may not appear at all.

17. 8. • How is the laboratory diagnosis of this infection made? • A: • Giardia lamblia is frequently diagnosed by visualizing the organism, either the trophozoite or the cyst in stained preparations or unstained wet mounts with the aid of a microscope. • A commercial fluorescent antibody kit is available to stain the organism. • Organisms may be concentrated by sedimentation or flotation; however, these procedures reduce the number of recognizable organisms in the sample. • An enzyme linked immunosorbant assay(ELISA) that detects excretory secretory products of the organism is also available.

18. 9. • Discuss the epidemiology of this infection. • A: • Giardiasis is more prevalent inchildren than in adults, possibly because many individuals seem to have a lasting immunityafter infection. This organism is implicated in 25% of the cases of gastrointestinal disease and may be present asymptomatically. The overall incidence of infection in the United States is estimated at 2% of the population. This disease afflicts many homosexual men, both HIV-positive and HIV-negative individuals. This is presumed to be due to sexual transmission. The disease is also common in child day care centers, especially those in which diapering is done.

19. 10. • How does the structure of these trophozoites account for the "smiling-face"appearance? • A:

20. Thanks for your attention !!!