Traveller's Infections (mostly parasites) (W29 and 30) Flashcards
Which part of the life-cycle of hook-worm infects the patient?
Filariform lava attach and penetrate skin
Which part of the life-cycle of hook worm makes the patient sick?
Larva present in skin–> itch Adults present in SI: GI symptoms
Which part of the life cycle of hook worm do you see in a specimen?
Egg in iodine stained fecal sample
What is the mode of transmission of hook worm?
Fecal from human/ dog–> soil–> skin.
Iodine stained mount of faeces: what is this parasite?
Hookworm egg
What are the symptoms of hookworm infections?
Mostly asymptomatic, can get abdominal discomfort, diarrhoea, anaemia (may embed in SI and cause bleeding)
Which parasite is typically acuired from walking around barefoor in an area with sub optimal hygeine?
Hookworm
What kind of worms are hookworms?
Round worms
What is the life cycle of hookworm (basic)?
How long can hookworms last if not re-infected?
2 years
Is hook-worm self limiting if not re infected?
Yes
What is this parasite?
Ascaris lumbricoides
Which part of the life-cycle of ascaris lumbricoides infects the patient?
Eggs are swallowed
Which part of the life cycle of ascaris lumbricoides is seen in samples?
Eggs in faeces or mature worms coughed up
Which stage of ascaris lumbricoides makes the patient sick?
- maturing worms in lungs can cause repiratory symptoms: dry cough/ irritation
Describe the basic life cycle of ascaris lumbricoides
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.
How do you visualise malaria parasites?
Thick and thin blood films
Returned traveller with a fever, headache and a ‘flu like’ illness. Splenomegaly and anaemia. What would you be worried about?
Malaria
Which malaria displays only one trophozoite ring per RBC on thin film?
P. vivax
Which malaria displays >1 trophozoite ring per RBC?
P. falciparum
Which type of malaria is more resistant to antibiotics, causes life threatening disease quickly, is highly prevalent in Africa, and has no dormant stage?
P. falciparum
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?
P. vivax
Which stage of malaria lifecyle infects humans?
Sporozoites are injected by a mosquito
Which stage of malaria causes disease?
Merezoites lyes RBCs
Which stage of malaria is detected in a blood film?
trophozoites/ schizonts
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?
P. falciparum
What is the pathogenesis of symptomatic malaria?
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
What parasite is this?
Strongyloides stercoliasis
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?
Strongyloides stercoliasis
What is the stage of strongyloides that infects the patient?
Infective larvae penetrate intact skin
What are the symptoms of strongyloides infection (4) and which part of the life cycle is this caused by?
- 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
Which stage of the strongyloides life cycle would you see in a fecal sample?
Larvae
Can you get autoinfection of Strongyloides stercoliasis?
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.
How can latent stronglyloidaisis result in septicaemia in an immunosuppressed patient?
- Immunosuppression as a result of disease or chemotherapy can result in
hyperinfection - 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 - As a result, these hyperinfected patients suffer from a high incidence of
Gram negative septicaemia and high mortality
Salmonella typhi/ paratyphi: gram stain, growth on HBA, MAC,
Gram - rods, non haemolytic on HBA, non-lactose fermenting (yellow) on MAC.
Describe the rash caused by typhoid fever
Rose spots :red macules 2-4 millimeters in diameter occurring in patients suffering from enteric fever
“fine, sparse, maculopapular rash”
Rose spots :a “fine, sparse, maculopapular rash” in a patient with fever and malaise.
What is the organism?
Salmonella typhi/ paratyphi
How is salmonella typhi/ paratyphi spread?
fecal-oral, spread by chronic carriers (hides in gall bladder)
Why don’t you see S. typhi in the faeces early in disease?
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.
