14. Protozoans: Giardiasis

Question 1

what is the pathogen that causes giardiasis

Answer 1

giardia duodenalis

Question 2

briefly describe the structure of Giardia duodenalis

Answer 2

flagellated enteric protozoan

Question 3

how is giardiasis transmitted

Answer 3

ingestion of cysts in contaminated water, food or via the faecal oral route

Question 4

what happens to ingested cysts

Answer 4

in the small intestine, excystation releases trophozoites that multiply

encystation occurs as the parasites move towards the colon

cysts pass in the faeces

Question 5

are cysts durable?

Answer 5

yes. very hardy, can survive months in cold water

Question 6

how can some trophozoites stick to the mucosa

Answer 6

using a sucking disc

Question 7

what are some of the clinical symptoms of giardia

Answer 7

diarrhoea (lasting 1 week +), nausea, belching, weight loss

Question 8

how contagious is giardia

Answer 8

highly contagious, results in clusters of cases

Question 9

can cysts be visualised under microscope

Answer 9

yes, using iodine and saline

Question 10

what is the entero test

Answer 10

string attached to weighted gelatin capsule which is ingested into the stomach. the string is then retrieved a few days later bringing giardia with it

Question 11

name an antigen detection test used to diagnose giardia

Answer 11

lateral flow assay for giardia antigens in stool samples

• mix sample with reagent and results collected in 10 mins

Question 12

what are the benefits of using ELISA over other lateral flow antigen tests

Answer 12

discriminates from other conditions such as Crohn’s disease and ulcerative colitis