Question

You are off on a camping trip to the high sierra with a group of friends and one of them relays that they are scared of getting Giardia. Actually, the correct medical term is giardiasis. Fresh from a microbiology class you want to help them and proceed with a lively description of (a) the life cycle (be sure to include animal hosts), (b) symptoms one might experience if infected, (c) the availability of drugs should someone happen to contract the parasite, and finally – and most importantly –(d) how you will prevent contracting the parasite on your upcoming camping trip.

Answer 1

a. Giardiasis is caused by Giardia lamblia a flagellated protozoan that attaches firmly to intestinal wall. Humans are definite hosts and occurrence in reservoirs is not clear. The parasite may also infect other mammals. The cysts are infective stages but trophozoites may also enter through contaminated food and water. Once the cycts reach intestine they undergo excystation and attach to the intestinal walls. These trophozoites undergo multiplication by longitudinal binary fission and remain in the lumen of the proximal small bowel and undergo encystation in colon and are released out trough feces.

b. Giardiasis is the prolonged diarrhea persisting for weeks. The symptoms are malaise, nausea, flatulence, weakness, weight loss and abdominal cramps. The distinctive hydrogen sulfide odor is detected in breath and stools. Diagnosis can be done by ELISA tests and direct fluorescent-antibody test (FA).

c. Treatment is done by administration of drugs like metronidazole or quinacrine hydrochloride and nitazoxanide.

d. The infection is transmitted by contaminated water that contains cysts. Therefore infection can be prevented by precautions like drinking safe water, proper hand wash and maintenance of hygiene conditions.