IDMM Week 4 PBL

Question 1

cause of fever in a returning traveller:

1. short incubation period of less than 21 days?
2. longer incubation period of > 21 days?

Answer 1

1. likely malaria, typhoid or dengue (rickettsial diseases becoming more common)
2. likely malaria or TB–consider Hep A in un-immunized patients

Question 2

how do you distinguish between

1. malaria
2. hepatitis
3. dengue
4. typhoid fever

(distinctive symptoms)

Answer 2

1. cyclical fevers/chills (diagnosed with blood smear)
2. screened with serology
3. short duration with maculopapular rash
4. long duration with possible GI

Question 3

giardia lamblia organism class

Answer 3

intestinal protozoan flagellate

Question 4

giardia lamblia virulence mechanisms

Answer 4

adheres via ventral sucking disc to small intestine wall

Question 5

clinical presentation of travellers diarrhea due to giardia lamblia

Answer 5

incubation period 1-14 days
duration 1-3 weeks

explosive, FOUL, FROTHY diarrhea, abdominal pain, bloating, nausea, vomiting

Question 6

giardia lamblia lifecycle

Answer 6

transmitted in cyst form

ingest cysts in contaminated food, water or fecal-oral

in small intestine, the cysts turn into 2 trophozoites each

trophozoites multiply (binary fission) and remain in the lumen of the small intestine or attach to mucosa via sucking disc

cysts form as parasites transit to colon

Question 7

ascaris lumbricoides organism class

Answer 7

intestinal helminth (nematode)

Question 8

ascaris lumbrocoides virulence mechanisms

Answer 8

sheer size

Question 9

ascaris lumbricoides clinical presentation

Answer 9

may be asymptomatic

abdominal cramping
malnutrition
cough
intestinal obstruction
ectopic infection

Question 10

ascaris lumbricoides life cycle

Answer 10

adult worms live in lumen of small intestine–> females produce eggs which are passed in feces–> only fertilized eggs are infective, and these fertilized eggs are infective after 18 days- several weeks–> swallowed infective eggs, larvae hatch, invade intestinal mucosa, are carried via portal and systemic circulation to the lungs–> larvae mature in lungs for 10-14 days–> penetrate alveolar walls and ascend bronchus to throat where they are swallowed–> develop into adults in small intestine–> can live 1-2 years

Question 11

P. vivax lifecycle in human host

Answer 11

(total process involved both human and anopheles female)

1. at blood meal, infected female anopheles mosquito inoculates SPOROZOITES into human host
2. sporozoites infect LIVER cells–> mature into SCHIZONTS which rupture and release MEROZOITES
   (3. P. vivax can have dormant hypnozoites in the liver that can later cause reactivation)
3. this initial replication in the liver is called exo-erythrocytic shizogony
4. parasites then undergo asexual multiplication in erythrocytes–> erythrocytic shizogony
5. merozoites infect RBCs–> ring stage trophozoites mature into schizonts–> rupture and release merozoites
6. some develop into sexual erythrocytic stage (gametocytes)–> blood stage parasites are the clinical manifestation

Question 12

P. vivax lifecycle in anopheles mosquito

Answer 12

1. gametocytes are ingested by mosquito during blood meal
2. SPOROGONIC cycle = parasites multiply in mosquito
3. in stomach, microgametocytes (male) penetrate macrogametocytes (female) and make zygotes
4. zygotes become motile and elongate and invade midgut wall of mosquito
5. develop into oocysts
6. grow, rupture and release new sporozoites
7. go to salivary glands

Question 13

P. vivax fever cycle timing

Answer 13

48 hour cycle

Question 14

treatment of parasites

Answer 14

metronidazole
albendazole
ivermectin
praziquantel
malaria drugs