Ecology of HIV and TB

TB
1. Mycobacterium tuberculosis
2. > lungs; hide inside macrophages (innate); form tubercle; hidden
  1. w/out treatment > eye, nerve tissue, spleen, GI tract, kidney.. death
    1. suffer undernutrition
    2. vertebrae collapse
  2. bone lesions follow spread of bacilli in blood stream: spine, hip, knee
    1. seen in arch record
      1. diagnosis using lipid markers
3. timetable of progression in adolescents (UK Medical Council, 1972)
  1. 10% of total infected; 4.3% developed clinical symptoms after 1 year; 2.1% 1 -2 yrs; 1.7% 2 - 10 yrs; 8% in total after 10 yrs
    1. immune system 'walls off'
4. globalisation
  1. est to have emerged approx 40,000 yrs ago coinciding w expansion out of Africa; demographic expansion in almost all lineages coincide w human expansion in last 200 yr (Wirth et al., 2008)
5. historical records: interpret w caution; different names and understandings e.g. consumption; classical hindu, Babylonian, Chinese and Roman texts all describe the signs n symptoms of TB
6. public health
  1. 1882: Koch - bacterial cause understood
    1. 1922: vaccination w BCG
      1. 1943: streptomycin, antibiotic
        Post WWII British vaccination program; demolition of slums; mass chest x rays
        successful public health response (Swerdlow, 1987)
        BUT resurgence in UK in those born overseas; Lancet targeted Indians but also SSA, Pakistan
        TB - higher incidence in homeless, alcoholics, injected drug users and those w HIV (reemergence linked to HIV epidemic)
        multiple drug resistant TB (MDR TB) e.g. to isoniazid, rifampicin
  2. DOT - directly observed therapy
    1. detection of infection; 6 - 8 months directly observed medication
7. >1 mil new cases reported in India & China in 2007
8. HIV prev in new TB cases above 50% in Southern Africa (WHO)
Human Immunodeficiency Virus
1. primarily spread through unprotected anal or vaginal sex (95% of cases in UK) but also from mother during pregnancy, through sharing needles
2. transmitted in bodily fluids (semen, vaginal, anal, breast milk)
3. end of 2012 just under 100,000 w HIV in UK
  1. high risk groups are gay an bisexual men and African men and women
    1. WHO est 34 mil
      1. 2.7 mil new infections in 2010; 21% below peak of epidemic in 1997
4. symptoms: flu like symptoms 2 - 6 weeks post infection aka 'seroconversion illness';
  1. after often no symptoms for several years aka 'asymptomatic HIV infection'; spreads and damages immune system
    1. late stage: diarrhoea, white spots on tongue, swollen glands; at risk of TB, pneumonia
      1. AIDS - syndrome not disease; collection of signs and symptoms all caused by HIV
    2. CD4 T cell count per cubic mil of blood; strength of immune system
      1. man: 400 -1600; women slightly higher; sharp drop following infection; stabilise at 500
        even when well millions of CD4 cells infected every day and lost, millions more produced to replace; w/out treatment CD4 will fall over time
      2. T cells part of adaptive immune system; HIV attaches to CD 4 receptor; copies; causes lysis of CD4 cell invades others
    3. viral load test
      1. 'copies' of HIV per mil of blood
        high viral load usually correlates w low CD4
5. SSA: in some countries over 20% of adults; fastest spread happening in E Europe & C Asia (increased by 250% between 2001 - 2011)
  1. over 50% of those eligible for treatment are not recieveing it
    1. increasing HIV + 50+s; 21% in 2010

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Ecology of HIV and TB

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