L37: Febrile returned traveller Flashcards
Exposure to infection - air
- Influenza - respiratory, incubation period of a few days
2. Tuberculosis - respiratory, incubation period of many months
Exposure to infection - contaminated water and food
- Salmonella typhi - non-specific features, incubation days-weeks
- Salmonella enteritidis - diarrhoea, incubation for days
- Campylobacter jejuni - diarrhoea, incubation for days
- Hep A virus - jaundice, incubation for weeks
Exposure to infection - vectors
Mosquitoes
- Malaria - non-specific features, incubation for for weeks
- Dengue fever - muscle aches, incubation for days
Exposure to infection - people
- HIV - non-specific features, incubation weeks-months
2. Syphilis - variable features, incubation for weeks-months
History taking
Where have you been and what did you do? (potential organisms exposed to)
When were you there, when did you get sick? (does timeline fit with incubation period)
Malaria - where, organisms, vectors
- Often most important to consider in travellers
- Africa, India, Pakistan, SE Asia
Causative organisms: (protozoa)
- Common: plasmodium falciparum (can be fatal), plasmodium vivax (relatively benign)
- More rare: plasmodium ovale and malariae
Transmitted by Anopheles mosquitoes (forest dwelling, night feeding) - not present in Pacific east of Vanuatu (Solomons, PNG, Vanuatu high risk of malaria)
Malaria - infection
- Plasmodia in blood meal (in RBCs) travels to intestine and multiple
- Move to mosquito salivary glands
- Infected female anopheles mosquito feeds on blood and injects plasmodia sporozoites
- Sporozoites invade liver cells (in mins) and replicate forming merozoites -> burst (10 days, no symptoms)
- Merozoites released from liver and enter RBCs and replicate -> digest Hb
- After a few days, burst cell and infect further RBCs = anaemia
Malaria - symptoms
- Breakdown of Hb and erythrocyte releases products causing an immune response
- Causes shivers, rigors, fever, sweats
- Often brings infection under control, with low levels of parasite in blood remaining
Malaria - diagnosis
- Residence in malarious area
- Fever, rigor, malaise, headache, coma
- Blood film exam: at least 2 samples, examine blood for merozoites in RBCs and estimate proportion (>2% severe)
- Antigen detection in blood
Complications of plasmodium falciparum malaria
- Can affect any RBCs
- High parasite load >1% erythrocytes infected
- Inserts proteins in RBCs membrane
- Causes adherence to endothelial cells in capillaries
- Particularly in brain, kidney -> death from coma and renal failure (black urine)
Complications of plasmodium vivax malaria
- Can only infect young RBCs
- No risk of severe disease
- Some parasites stay in liver (up to 2yrs) = hypnozoites, can give relapse
Treatment and prevention of malaria
Treatment:
- P. falciparum = quinine + doxycycline to kill merozoites in RBCs (or artemether, lumefantrine)
- P. vivax = chloroquine to kill merozoite in RBCs + primaquine to kill hypnozoites in liver
Prevention:
- Avoid malarious areas
- Mosquito control
- Prophylactic drugs (doxycycline, mefloquine)
Salmonella enteritidis
- Closely related to E. coli
- Most commonly causes disease in NZ (gastroenteritis)
- From animals and birds (not humans)
- Infects colonic mucosa, causing colitis (does not invade deeper, no bacteraemia)
- Frequent diarrhoea (blood, mucus), fever, usually self-limiting
Salmonella typhi
- Common cause of persistent fever in travellers
- Acquired from humans (faeces)
- Infects macrophages of Peyers patches in terminal ileum causing bacteraemia and septicaemia
- Gallbladder colonisation after infection, released into intestine during meal
Salmonella typhi presentation and complications
- Fever, rigors, sweats, cough, headache, confusion
- Usually not diarrhoea, maybe constipation
- Risk of Peyers patches perforation leading to peritonitis, erosion of ileal blood vessels giving intestinal bleeding (death due to peritonitis)
- 10% mortality without treatment (esp. children)
- Minority have long term gall bladder colonisation and can infect others
