Tropical diseases in the returning traveller Flashcards
some clinical presentations
fever diarrhoea cough rashes arthralgia, organomegaly, lymphadenopathy jaundice eosinophilia
fever (as the principal complaint)
malaria until proven otherwise in the returning traveller
malaria
40% of the world’s population are exposed to malaria
there are >300m cases a year in the world
>1m deaths a year - 90% in sub-saharan africa, mainly children
20% of all mortality in all >5yo in africa
malaria aetiology
transmitted by the bite of the female anopheles mosquito
protozoal infection caused by one of four species of Plasmodium in humans
P. falciparum - severe in young, non-immune, pregnant. incubation period average 7-14 days
P. vivax, ovale and malariae - often uncomplicated but chronic relapsing. incubation can be longer, up into years since vivax and ovale have a dormant stage in the liver
malaria immunity
dependant on recurrent exposure age pregnancy splenectomy G6PD deficiency, sickle cell and other haem disorders
life cycle of malaria
once a mosquito bites, it injects sporozoites into the blood. these travel to the liver where they become schizonts
schzints will then re-enter the blood where they will either enter the erythrocytic cycle
OR
they will mature into trophozoites and then gametocytes, producing more of the plasmodium, which can be taken up by another mosquito when it bites
malaria and pregnancy
parasitaemia higher
hypoglycaemia/ARDS
cerebral malaria
congenital transmission rare but foetal distress occurs
major cause of low birth weight and miscarriage in developing countries
should now be prevented by preventive malaria treatment - 3 doses of atremesin bases during pregnancy
WHO criteria for severe malaria
one or more of: cerebral malaria severe normocytic anaemia renal failure hyperparasitaemia (>5%) pulmonary oedema hypoglycaemia circulatory collapse spontaneous bleeding/DIC repeated generalised convulsions acidosis malarial hypoglobinuria (blackwater fever)
malaria investigations
thin and thick blood films and rapid diagnostic tests (RDTs)
thick films
used to estimate the parasite count which is important for prognosis and monitoring Tx
thin films
used to confirm diagnosis and determine the species
RDTs
often used in conjunction with blood films, not often used on their own
malaria management
always manage as a potentially life threatening illness
artesunate is the drug of choice for P. falciparum
quinine in non-severe malaria
severe: artesunate IV, ITU, exchange transfusion
in cerebral malaria also consider other CNS infections if no improvement after Tx
benign malaria (vivax, ovale, malariae) use chloroquine + primaquine
cerebral malaria
most severe complication of P. falciparum
clinical syndrome characterized by coma and asexual form of the parasite on peripheral blood smears
the main cause in humans is the blockage of the cerebral microvasculature by P. falciparum infected erythrocytes, which have knobs that appear on their surface causing them to stick to the endothelium
prophylaxis for travellers
mefloquine, malarone, doxycycline, chloroquine + proguanil
dengue fever
mosquito borne infection that causes severe flu like illness can sometimes lead to the potentially lethal complication dengue haemorrhagic fever
about 40% of the world’s population are now at risk
tropical and subtropical regions, mostly in urban and semi-urban areas
dengue haemorrhagic fever
leading cause of death and serious illness in children in some asian countries
no specific treatment
prevent dengue transmission by avoiding mosquito bites
HIV seroconversion
important cause of illness in the returning traveller
syndrome of fever, malaise and generalised lymphadenopathy sometimes accompanied by a macular rash
presents several weeks after exposure
underlines the importance of a good sexual Hx
typhoid
caused by salmonella typhi and salmonella typhi A,B or C 15-30m cases a year 0.5m deaths faecal-oral transmission incubation 7-14 days
signs and Sx of typhoid
Sx: fever, headache, malaise, constipation, diarrhoea
Signs: may be little to find O/E, relative bradycardia, rase spots (rare) and hepatosplenomegaly (rare)
typhoid diagnosis & treatment
culture from blood/stool/urine/bile/CSF/bone marrow
serology
Tx: ceftriaxone
schistosomiasis
200m infected globally
3 species commonly affect man: S. mansoni, haematobium and japonicum
infected after exposure to water containing cercariae (free swimming larval stage). these penetrate the skin causing initial Sx, then lay eggs in portal or urinary tract (species dep.) causing chronic damage
clinical signs of schistosomiasis
swimmer’s itch
katayama fever
chronic disease (curable if treated prior to complication)
bird flu
carried by many wild birds’ intestines, often asymptomatically
highly transmissable between wild birds and can be spread to domestic flocks where mortality is often 90% or more
many subtypes, several of which can affect humans. usually low pathogenicity
bird flu H5N1
highly pathogenic influenza virus transmitted from birds to humans since 2003
close contact with birds essential
one or two cases of human to human spread in close knit families
approx. 70% mortality in humans
potential to cause a far more devastating outbreak than swine flu
SARS
severe acute respiratory syndrome caused by SARS coronavirus
caused near pandemic in 2003 with 8000 cases worldwide and 700+ deaths
spread rapidly thanks to air travel
infectious via droplet spread
disease eventually contained by isolating cases and contacts
no cases since 2004, but there may be an animal reservoir, so eradication not claimed
viral haemorrhagic fever
syndrome of fever and haemorrhage caused by several different viruses
rare in endemic setting
can be highly transmissable, with case fatality rates up to 90% in ebola
initially transmitted by tick bites, rat urine, gorilla and monkey blood
viral haemorrhagic fever examples
ebola
lassa
CCHF
consider in unwell febrile patients with negative malaria films and incubation period less than 3 weeks
diarrhoea classification
inflammatory: with blood and mucus. results from the invasion of the colonic epithelium e.g by entamoeba histolytica or shigella
non inflammatory: with copious amounts of water secreted. e.g all viral causes or cholera
NB many pathogens can cause both e/g/ campylobacter, E coli, salmonella
