Traveller's Infections (mostly parasites) (W29 and 30)

Question 1

Which part of the life-cycle of hook-worm infects the patient?

Answer 1

Filariform lava attach and penetrate skin

Question 2

Which part of the life-cycle of hook worm makes the patient sick?

Answer 2

Larva present in skin–> itch Adults present in SI: GI symptoms

Question 3

Which part of the life cycle of hook worm do you see in a specimen?

Answer 3

Egg in iodine stained fecal sample

Question 4

What is the mode of transmission of hook worm?

Answer 4

Fecal from human/ dog–> soil–> skin.

Question 5

Iodine stained mount of faeces: what is this parasite?

Answer 5

Hookworm egg

Question 6

What are the symptoms of hookworm infections?

Answer 6

Mostly asymptomatic, can get abdominal discomfort, diarrhoea, anaemia (may embed in SI and cause bleeding)

Question 7

Which parasite is typically acuired from walking around barefoor in an area with sub optimal hygeine?

Answer 7

Hookworm

Question 8

What kind of worms are hookworms?

Answer 8

Round worms

Question 9

What is the life cycle of hookworm (basic)?

Answer 9

Question 10

How long can hookworms last if not re-infected?

Answer 10

2 years

Question 11

Is hook-worm self limiting if not re infected?

Answer 11

Yes

Question 12

What is this parasite?

Answer 12

Ascaris lumbricoides

Question 13

Which part of the life-cycle of ascaris lumbricoides infects the patient?

Answer 13

Eggs are swallowed

Question 14

Which part of the life cycle of ascaris lumbricoides is seen in samples?

Answer 14

Eggs in faeces or mature worms coughed up

Question 15

Which stage of ascaris lumbricoides makes the patient sick?

Answer 15

• maturing worms in lungs can cause repiratory symptoms: dry cough/ irritation

Question 16

Describe the basic life cycle of ascaris lumbricoides

Answer 16

Key points:

infective eggs swallowed–> larvae hatch–> invade intestinal mucosa–> portal blood system–> Lungs–> mature in lungs–> ascend bronchial tree–> re swallowed–> further mature in SI–> eggs in faeces.

Question 17

How do you visualise malaria parasites?

Answer 17

Thick and thin blood films

Question 18

Returned traveller with a fever, headache and a ‘flu like’ illness. Splenomegaly and anaemia. What would you be worried about?

Answer 18

Malaria

Question 19

Which malaria displays only one trophozoite ring per RBC on thin film?

Answer 19

P. vivax

Question 20

Which malaria displays >1 trophozoite ring per RBC?

Answer 20

P. falciparum

Question 21

Which type of malaria is more resistant to antibiotics, causes life threatening disease quickly, is highly prevalent in Africa, and has no dormant stage?

Answer 21

P. falciparum

Question 22

Which type of malaria has a dormant stage in the liver, is less likely to be resistant to anti-malarials and only infects early RBCs?

Answer 22

P. vivax

Question 23

Which stage of malaria lifecyle infects humans?

Answer 23

Sporozoites are injected by a mosquito

Question 24

Which stage of malaria causes disease?

Answer 24

Merezoites lyes RBCs

Question 25

Which stage of malaria is detected in a blood film?

Answer 25

trophozoites/ schizonts

Question 26

Which kind of malaria is capable of infecting all stages of RBCs and at a higher rate (eg >1 trophozoite per RBC) leading to a greater parasitic load?

Answer 26

P. falciparum

Question 27

What is the pathogenesis of symptomatic malaria?

Answer 27

Merezoites lyse RBCs:

anaemia

RBCs get sticky and can clog up vessels, eg in the brain

lysed cells cause a systemic inflammatory response

spleenomegaly from removing damaged RBCs

hypoglycaemia because plasmodium uses up all your sugars

Question 28

What parasite is this?

Answer 28

Strongyloides stercoliasis

Question 29

What parasite is likely to have been latent in a Vietnam vet since the 70s and only become symptomatic again one he contracts chronic lymphoblastic leukemia?

Answer 29

Strongyloides stercoliasis

Question 30

What is the stage of strongyloides that infects the patient?

Answer 30

Infective larvae penetrate intact skin

Question 31

What are the symptoms of strongyloides infection (4) and which part of the life cycle is this caused by?

Answer 31

• often asymptomatic
• resp symptoms: larvae travel to lungs after penetrating skin to be re swallowed
• abdo pain: maturing/mature worms in SI
• perianal itching: larvae hatch in intestines and cause autoinfections of perianal skin

Question 32

Which stage of the strongyloides life cycle would you see in a fecal sample?

Answer 32

Larvae

Question 33

Can you get autoinfection of Strongyloides stercoliasis?

Answer 33

Yes: eggs hatch in the intestine and larvae can re infect the intestinal mucosa or perianal skin to get to the lungs and back to the intestines to mature. This results in persistent infection and over time an increase in worm load.

Question 34

How can latent stronglyloidaisis result in septicaemia in an immunosuppressed patient?

Answer 34

1. Immunosuppression as a result of disease or chemotherapy can result in
   hyperinfection
2. During the hyperinfection phase, multiple breaches of the intestinal mucosa
   result from the continuous larval migration. This facilitates the passage of
   gut microbiota through the bowel and into the tissues and circulation
3. As a result, these hyperinfected patients suffer from a high incidence of
   Gram negative septicaemia and high mortality

Question 35

Salmonella typhi/ paratyphi: gram stain, growth on HBA, MAC,

Answer 35

Gram - rods, non haemolytic on HBA, non-lactose fermenting (yellow) on MAC.

Question 36

Describe the rash caused by typhoid fever

Answer 36

Rose spots :red macules 2-4 millimeters in diameter occurring in patients suffering from enteric fever

“fine, sparse, maculopapular rash”

Question 37

Rose spots :a “fine, sparse, maculopapular rash” in a patient with fever and malaise.

What is the organism?

Answer 37

Salmonella typhi/ paratyphi

Question 38

How is salmonella typhi/ paratyphi spread?

Answer 38

fecal-oral, spread by chronic carriers (hides in gall bladder)

Question 39

Why don’t you see S. typhi in the faeces early in disease?

Answer 39

S. typhi is ingested–> invades mucosal wall–> lymph node–> primary bacteremia–> liver and spleen–> macrophages–> gall bladder (which then goes to gut), bone marrow, UT, secondary bacteremia.

Therefore early in disease in blood but not faeces.