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)
• 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)
• 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
• 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)
• 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
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
• 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)
• 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")
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Author & Educational Disclaimer
Author:
Dr Phillip Cockrell BM FRCP DipClinEd
Dr Phillip Cockrell is a UK Consultant Physician in Internal Medicine, currently working at Queen Alexandra Hospital, Portsmouth University Hospitals NHS Trust. He has previously worked as a registrar across Intensive Care Medicine, Gastroenterology, Cardiology, Stroke Medicine, Acute Medicine, and Respiratory Medicine.
He has held senior leadership roles including Associate Clinical Director of the Acute Medical Unit, Clinical Director of Internal Medicine, and Chief of Medicine. Dr Cockrell has over 15 years’ experience in postgraduate medical education, having lectured extensively across the MRCP syllabus and contributed to MRCP revision teaching and course development.
Dr Cockrell holds a Bachelor of Medicine (BM), Fellowship of the Royal College of Physicians (FRCP), and a Diploma in Clinical Education (DipClinEd). His teaching approach is based on structured consolidation of complex medical topics to support efficient and effective revision for postgraduate examinations.
Purpose of this content:
The material on this page is intended solely for educational purposes to support revision for the MRCP (UK) Part 1 examination. It reflects examination-relevant principles of internal medicine and is designed to aid learning and pattern recognition.
Medical disclaimer:
This content is designed for postgraduate medical examination revision and does not constitute medical advice, diagnosis, or treatment guidance and must not be used as a substitute for professional clinical judgement, local guidelines, or specialist consultation. Clinical decisions should always be made in the context of individual patient circumstances and current national guidance.
