Tropical diseases in the returning traveller

Question 1

some clinical presentations

Answer 1

fever
diarrhoea
cough
rashes
arthralgia, organomegaly, lymphadenopathy
jaundice
eosinophilia

Question 2

fever (as the principal complaint)

Answer 2

malaria until proven otherwise in the returning traveller

Question 3

malaria

Answer 3

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

Question 4

malaria aetiology

Answer 4

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

Question 5

malaria immunity

Answer 5

dependant on recurrent exposure
age
pregnancy
splenectomy
G6PD deficiency, sickle cell and other haem disorders

Question 6

life cycle of malaria

Answer 6

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

Question 7

malaria and pregnancy

Answer 7

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

Question 8

WHO criteria for severe malaria

Answer 8

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)

Question 9

malaria investigations

Answer 9

thin and thick blood films and rapid diagnostic tests (RDTs)

Question 10

thick films

Answer 10

used to estimate the parasite count which is important for prognosis and monitoring Tx

Question 11

thin films

Answer 11

used to confirm diagnosis and determine the species

Question 12

RDTs

Answer 12

often used in conjunction with blood films, not often used on their own

Question 13

malaria management

Answer 13

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

Question 14

cerebral malaria

Answer 14

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

Question 15

prophylaxis for travellers

Answer 15

mefloquine, malarone, doxycycline, chloroquine + proguanil

Question 16

dengue fever

Answer 16

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

Question 17

dengue haemorrhagic fever

Answer 17

leading cause of death and serious illness in children in some asian countries
no specific treatment
prevent dengue transmission by avoiding mosquito bites

Question 18

HIV seroconversion

Answer 18

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

Question 19

typhoid

Answer 19

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

Question 20

signs and Sx of typhoid

Answer 20

Sx: fever, headache, malaise, constipation, diarrhoea
Signs: may be little to find O/E, relative bradycardia, rase spots (rare) and hepatosplenomegaly (rare)

Question 21

typhoid diagnosis & treatment

Answer 21

culture from blood/stool/urine/bile/CSF/bone marrow
serology

Tx: ceftriaxone

Question 22

schistosomiasis

Answer 22

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

Question 23

clinical signs of schistosomiasis

Answer 23

swimmer’s itch
katayama fever
chronic disease (curable if treated prior to complication)

Question 24

bird flu

Answer 24

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

Question 25

bird flu H5N1

Answer 25

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

Question 26

SARS

Answer 26

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

Question 27

viral haemorrhagic fever

Answer 27

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

Question 28

viral haemorrhagic fever examples

Answer 28

ebola
lassa
CCHF
consider in unwell febrile patients with negative malaria films and incubation period less than 3 weeks

Question 29

diarrhoea classification

Answer 29

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