Tropical Medicine; a whistle stop tour

R Johnson MBBS MRCS DTM&H

Malaria

• 2 million fatalities per year

• Almost all P. falciparum

• “tropical”

• Stable vs unstable transmission; immunity

• Simple vs complicated

Life Cycle

• Infected female anopheline mosquito• Sporozoites enter hepatocytes• Hepatic shizont once mature ruptures and

release merozoites into blood• Erythrocytic trophozoites mature into

shizonts and then precipitate sequestration• Rupture to produce merozoites or

gametocytes

Clinical Features

• The great pretender• Fever, cough, muscle aches, diarrhoea, abdo pain,

headache, seizures, haematuria• Hypoglycaemia• Anaemia; haemolysis and marrow suppression• Splenomegaly• Jaundice• Cyclical nature of fever?

Diagnosis

• Thick and thin films

• Serology

• Buffy coats

• PCR

Treatment 1

• Antipyretic

• Rehydration

• Blood transfusion

• Anti-convulsants

• Correcting hypoglycaemia

• Reducing acidaemia

• Antibiotics

Treatment 2

• Chloroquine. Non-toxic, oral or IV

• Quinine. Toxic. Effective, oral or IV

• Mefloquine. Single dose due to long half life. Toxic. Negative inotrope.

• Fansidar. Resistance!

• Artemesinins. Effective, combination therapy

Prophylaxis

• Don’t get bitten

• Dependant on area

• Dependant on what you are doing

• Dependant on time spent in malarious area

Typhoid

• Salmonella typhi and paratyphi A, B, C

• Water bourne, oro-faecal

• Infect small bowel lymphatics,

• Bacteraemia, bone marrow, spleen, liver and gallbladder

• Secondary bacteraemia and invasion of bowel

Timeline• Incubation 14 days (7-21)• Week 1, non-specific illness with fever (intermittent),

cough, diarrhoea or constipation• Week 2, rose spots, constant fever, abdo pain. Very toxic• Week 3, dehydation, metabolic mayhem. GI

haemorrhage, multiple small bowel perforations• Week 4, if reached, fever lysis and recovery.• Other presentations; meningitis, pneumonia, renal failure• Long-term sequelae; osteomyelitis, typhoid abscess,

chronic carriage

Diagnosis

• Culture; blood, marrow, csf

• Serodiagnosis; Widal test

Treatment

• Chloramphenicol

• Amoxycillin or septrin as alternatives

• MDR

• Cefotaxime

Arboviruses

• Ecological description

• Three clinical syndromes– FAR– VHF– CNS

• Supportive care

Travellers diarrhoea

• Probably majority viral

• Bacterial

• Un-exposed normal flora

• Simple; 2 doses of cipro, 3 days of trimethoprim

• Blood = dystentery; – Ameobic, shigella, campylobacter, E. coli 157