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12.12.05 Traveller illnesses

Travel history
  • When
  • Where
  • What
  • Who
  • How

Food poisoning organisms
  • Salmonella
  • Shigella
  • Campylobacter

Parasites
  • Investigations
    • Haemolysis
      • Very high bilirubin
      • Low Hb
    • May have slightly raised ALT, but not enough to explain the bilirubin
    • Thrombocytopaenia
    • Low glucose
    • DIC
    • Acidosis
  • Parasites are transient and correlate with fever
    • Do the blood film at the appropriate time
    • Do three before deciding it's negative

HIV
  • Common infections are CD4-dependent ones
    • Viruses
    • Protozoa
    • Fungi
    • Mycobacteria
  • Some bacteria too
    • Salmonella
    • Pneumococci
  • Parameters
    • CD4 => Disease stage
      • >200 => Only high-grade infections
      • <200 => Low-grade infections
      • <100 => Very low grade infections
    • Viral load => Speed of progression
  • Acute seroconversion 
    • Treatment is not helpful
    • Extremely infectious
  • TB
    • CD4 <200 => Probably reactivation
      • Consolidation with cavitation
      • Air bronchograms
    • CD4 <100 => Probably primary
      • Adenopathy
        • Loss of paratracheal stripe
      • Low zone
      • No cavitation

Low-grade infections in HIV
  • PCP
    • CXR often normal early on
    • Fine reticular (ground-glass) appearance later on
    • Thin-walled cysts
      • Predispose to pneumothoraces
    • Alveolar exudate
  • Candida
    • Oral candida can invade oesophagus
  • Cryptosporidium
    • Colitis - "Dilated, featureless bowel)
      • Thickened bowel wall (check opposed bowel loops)
      • Thumb printing
      • Loss of haustra
    • Remember to check for HIV before you diagnose IBD, as they can look similar
  • CMV retinitis
    • Reactivation of latent herpesvirus
    • Prevalence approx. equal to age in the healthy population
    • Haemorrhagic retinitis
  • Crytococcal meningitis
    • May not see any white cells in CSF, despite bacteria due to immunosuppression (sinister sign)
    • Check India Ink stain or CrAg in blood/CSF
  • Toxoplasma
    • Ring-enhancing lesions on MRI
      • Similar to bacterial pyogenic abscess
      • Distinguish by clinical presentation
    • Especially in unusual places
      • Thalamus, basal ganglia
  • Primary cerebral lymphoma
    • Looks very similar to toxoplasma
    • Treat as if toxoplasma and see if it changes
  • TB meningitis
    • Tends to affect the basal system rather than peripheral structures
      • Basal cisterns etc
      • => Cranial nerves often involved
    • Chronic/insidious onset
  • Progressive multifocal leucoencephalopathy (PML)
    • White matter lesions - Look a bit like MS
  • Malignancy
    • Karposi sarcoma
    • Viral leukaemia

Notes
  • Information website - nathnac.org
  • Typhoid test is a blood culture, not stool
  • Cutoff for CD4-dependent infection = 200
  • Lobar pneumonias are often pneumococcal
  • Aspiration pneumonia usually goes to the right middle lobe
  • First seizure in an adult = SOL UPO
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