Malaria
Plasmodium species
• P. falciparum:
o Most severe form; high parasitaemia
o No hypnozoites (no dormant liver stage)
o Complications: cerebral malaria (confusion, seizures), severe anaemia, hypoglycaemia (esp. with quinine), acidosis, renal failure, ARDS
• P. vivax & P. ovale:
o Have liver hypnozoites → can cause relapse
o Common in Asia, South America
Diagnosis
• Blood films: thick (sensitive), thin (species ID)
• Rapid antigen tests (e.g., HRP-2 for falciparum)
Treatment
• Severe falciparum: IV artesunate (preferred) or IV quinine
• Non-severe: oral ACT (artemether-lumefantrine)
• Vivax/ovale: chloroquine (if sensitive) + primaquine for liver stage (check G6PD)
Prophylaxis
• Atovaquone-proguanil (Malarone)
• Doxycycline (avoid in pregnancy and children <8)
• Mefloquine (avoid if neuropsychiatric history)
Enteric Fever (Typhoid/Paratyphoid)
• Causative agent: Salmonella typhi or S. paratyphi
• Features:
o Prolonged stepwise fever
o Relative bradycardia ("Faget sign")
o Rose spots on trunk
o Abdominal pain, constipation common (diarrhoea less frequent early)
o Hepatosplenomegaly
Diagnosis
• Blood cultures: best yield in first week
• Stool and urine cultures later
Treatment
• Empirical: ceftriaxone or azithromycin
• Resistance common to ampicillin, chloramphenicol
Prevention
• Typhoid vaccine (Vi polysaccharide or conjugate)
Amoebiasis
• Causative agent: Entamoeba histolytica
• Features:
o Dysentery: bloody diarrhoea with mucus
o Liver abscess: RUQ pain, "anchovy paste" pus, no prominent jaundice
• Diagnosis:
o Serology (more reliable than stool microscopy)
o Imaging: single large liver lesion, usually right lobe
Treatment
• Metronidazole (kills tissue trophozoites)
• Luminal agent (paromomycin or diloxanide furoate) to eradicate cysts
Schistosomiasis
• Species:
o S. haematobium: urinary tract → haematuria, bladder fibrosis, squamous cell carcinoma risk
o S. mansoni, S. japonicum: hepatic and intestinal → portal hypertension, periportal fibrosis
Diagnosis
• Detection of eggs in urine (haematobium) or stool (mansoni)
• Serology if chronic
Treatment
• Praziquantel (effective against all human schistosomes)
Leprosy (Hansen’s Disease)
• Causative agent: Mycobacterium leprae
• Features:
o Skin: hypopigmented or erythematous patches, anaesthetic
o Peripheral neuropathy: glove-and-stocking sensory loss, claw hand, foot drop
o Lepromatous form: diffuse nodules, leonine facies
Diagnosis
• Skin smear (acid-fast bacilli)
• Skin biopsy: granulomatous inflammation
Treatment
• Multidrug therapy (MDT):
o Rifampicin
o Dapsone
o ± Clofazimine
Other Travel-Related Infections
Dengue
• Features:
o Sudden high fever ("breakbone fever")
o Severe myalgia, retro-orbital pain
o Rash ("white islands in a sea of red")
o Thrombocytopenia, plasma leakage → dengue shock syndrome
• Management:
o Supportive; avoid NSAIDs (bleeding risk)
Chikungunya
• Features:
o Severe symmetric polyarthritis, may become chronic
o Fever, maculopapular rash
• Management: supportive
Zika
• Features:
o Mild fever, rash, conjunctivitis
o Associated with congenital microcephaly, Guillain–Barré syndrome
• Transmission: mosquito, sexual, vertical
Rickettsial infections
• Examples: scrub typhus (Orientia), African tick-bite fever
• Features:
o Fever, headache, myalgia
o Eschar at bite site
o Regional lymphadenopathy
• Treatment: doxycycline
Eosinophilia clue
• Suggests helminthic or tissue-invasive parasitic infections
• Examples: strongyloidiasis, schistosomiasis, filariasis
Travel vaccinations
• Hepatitis A
• Typhoid
• Yellow fever (live; required for entry to some countries in Africa, South America)
• Rabies (especially for long stays or high-risk exposure)
• Japanese encephalitis (SE Asia travel)
Extra Revision Pearls
• Strongyloides: hyperinfection risk with steroids → check before starting immunosuppression in returning travellers
• Brucellosis: undulating fever, exposure to unpasteurised dairy
• Melioidosis (Burkholderia pseudomallei): diabetes risk, abscesses ("Vietnam time bomb")
