Tuberculosis and HIV/AIDS Co-Infection: Epidemiology and Public Health Challenges

Transcription

1 Tuberculosis and HIV/AIDS Co-Infection: Epidemiology and Public Health Challenges John B. Kaneene, DVM, MPH, PhD University Distinguished Professor of Epidemiology Director, Center for Comparative Epidemiology

2 Overview HIV and the epidemiology of TB HIV TB TB/HIV Co-infection Effect of antiretroviral treatment on TB epidemiology Coordinated public health responses to TB and HIV/AIDS 2

3 HIV and TB HIV/AIDS Human Inmmunodeficiency Virus Cause of AIDS: Acquired Immune Deficiency Syndrome RNA Retrovirus Destroys CD4+ T cells part of the body s immune response system Two species: HIV-1 and HIV-2 Can become re-infected with new strains 3

4 HIV and TB (cont.) HIV Transmission Routes of Transmission Blood-borne Transfusion Shared needles Transplacental Sexual contact Milk from infected mothers 4

5 HIV and TB (cont.) HIV Pathogenesis Exposure Circulating HIV virus Infects T-cells HIV replicates Destroys T-cells T-cells Activated 5

6 HIV and TB (cont.) HIV Diagnosis ELISA for HIV antibodies Serum test Highly sensitive Western Blot Serum test For antibodies to specific HIV proteins 6

7 HIV and TB (cont.) HIV Diagnosis (cont.) Rapid tests Enzyme Immunoassays Test strip impregnated with antigen If antibodies present, color change Work on whole blood, serum, plasma, saliva 7

8 HIV and TB (cont.) Problems with HIV diagnostics Window period Time between infection and production of HIV antibodies, from 3 weeks 6 months FALSE NEGATIVE TEST RESULTS Patient can still transmit HIV Social Issues Privacy, availability of confidential testing Stigma around how HIV was contracted 8

9 HIV and TB (cont.) Fusion Inhibitors HIV Treatment Reverse Transcriptase Inhibitors 9

10 HIV and TB (cont.) HIV Prevention Education Reducing HIV risk Protection (e.g. condoms) Avoiding high-risk activities De-stigmatizing HIV How HIV is spread UNICEF, Uganda Ministry of Health, AIDS Control Programme Vaccines under development, but not currently available 10

11 HIV and TB (cont.) Tuberculosis Diseases caused by Mycobacterium tuberculosiscomplex bacteria Slow-growing, long incubation period Obligate intracellular pathogen Different species from different hosts M. tuberculosis in humans M. bovis in cattle BOTH can cause disease in humans 11

12 HIV and TB (cont.) Human Tuberculosis Human TB due to M. tuberculosis Known for 1000s of years Worldwide problem Chronic disease Mostly respiratory Human TB due to M. bovis Associated with contaminated dairy products, animal contact Gastrointestinal, dermal 12

13 HIV and TB (cont.) TB Routes of Transmission Respiratory Aerosols Sputum Gastrointestinal Feces Urine Integumental Mammary gland Abscesses 13

14 HIV and TB (cont.) Tuberculosis Pathogenesis Acid-fast Bacteria (AFB) Inhalation, Ingestion, Direct contact Intracelluar infection P L P L Local Tissue Reaction AFB multiply Phagosome arrest 14

15 HIV and TB (cont.) TB Diagnosis Mantoux skin test Tuberculin injected, test read after 72 hrs Other tests Sputum smear X-ray Mycobacterial culture /vph/students/practicalslides.htm 15

16 HIV and TB (cont.) Problems with TB diagnostics Skin test problems False negatives/positives with other infections Not useful if patient was vaccinated Other test problems Costly, long time period Social Issues Stigma regarding infectiousness of TB 16

17 HIV and TB (cont.) TB Treatment Standard therapy First line drugs Isoniazid, Rifampin, Pyrazinamide, Ethambutol Course of treatment in Africa lasts 8 months DOTS strategy Directly Observed Treatment Short Course Ensure patients take drugs for entire course (at least 2 months) Given to smear-positive patients 17

18 HIV and TB (cont.) TB Treatment (cont). Drug resistance Standard therapy does not work Associated with HIV infection MDR (Multi-Drug Resistant) TB XDR (extensively Drug Resistant) TB 18

19 HIV and TB (cont.) TB Prevention Vaccination Bacterin Calmette-Guérin (BCG) Education Recognizing TB Completing treatment Avoiding stigma Uganda Ministry of Health, National Tuberculosis & Leprosy Control Unit 19

20 HIV and TB (cont.) TB/HIV Co-Infection Infection with both TB and HIV TB often first manifestation of HIV TB is leading cause of death in people with HIV HIV patients have higher systemic TB TB with HIV more drug resistant (MDR-TB, XDR-TB) rates of 20

21 HIV and TB (cont.) TB/HIV Co-Infection (cont.) Consequences of TB/HIV co-infection 8.8 M new cases of TB 1.7 M deaths 27% of these cases in Africa 31% of these deaths in Africa Prevalence of HIV in TB patients 38% in Africa In high HIV countries (e.g. South Africa), 75% of TB cases are HIV related 21

22 HIV and the Epidemiology of TB in Africa Increased risk for TB from HIV HIV patients more likely to develop TB than uninfected people (8.3 times) Sicker HIV patients have higher rates of TB than healthier patients TB rates increase during HIV epidemics 22

23 TB-HIV Epidemiology(cont.) HIV and TB Infectiousness and Transmission Infectiousness How easily a disease is spread between hosts Depends on transmission & host susceptibility Transmission How disease is spread E.g. coughing, blood, etc. Susceptibility How easily a host can acquire an infection 23

24 TB-HIV Epidemiology(cont.) TB Infectiousness with HIV Critical period for TB infectiousness BEFORE diagnosis with TB TB is highly infectious when untreated Less infectious once TB therapy begins Length of Critical Period 1 to 3 years for patients without HIV 6 to 8 weeks for patients with HIV (increased severity of disease) Antiretroviral therapy for HIV can increase the critical period by delaying mortality 24

25 TB-HIV Epidemiology(cont.) TB Transmission with HIV Patient susceptibility Patients with HIV more easily infected HIV patients more susceptible to other forms of TB (e.g., bovine TB M. bovis) More non-pulmonary TB Systemic, gastrointestinal, neurological, etc. Higher TB mortality with HIV 25

26 TB-HIV Epidemiology(cont.) TB Control with HIV DOTS program Not sufficient to handle TB with HIV Rapid increase in numbers of TB patients Assumes patients will be smear-positive HIV TB less likely to be smear-positive Treatment Interaction of TB drugs with anti-retroviral drugs Patients with non-human TB require different drugs Misuse of TB drugs can lead to drug resistance 26

27 Public Health Responses to TB and HIV/AIDS Goals Optimize diagnosis and treatment Reduce HIV-associated TB incidence Improve HIV and TB control overall 27

28 Human Health Consequences of TB/HIV Physical: Morbidity Mortality Long-Term effects Social: Stigma, social status Economic losses Loss of population 28

29 Economic Consequences of TB/HIV Costs / Expenditures Drugs and therapeutics Hospitals and clinics Doctors, nurses, aide workers Losses Population Productivity of sick workers 29

30 Impacts : Economic High burden of disease in population Reduced food availability Lost Earnings Increased disease vulnerability Reduced work force Reduced Food production Cash crops Paid labor hours 30

31 TB-HIV Public Health Response Optimizing Diagnosis & For TB Improve DOTS Treatment Less emphasis on smear-positive diagnosis Active case finding Screen for TB in HIV clinics Optimize anti-tb chemotherapy Newer, more effective drugs and protocols Eliminate TB drugs that interact with antiretroviral HIV drugs 31

32 TB-HIV Public Health Response Optimizing Diagnosis & For TB Treatment (cont.) Prevent emergence of drug resistant TB Ensure complete treatment by patients Avoid nosocomial (hospital-acquired) infections Timely investigations and case management! 32

33 TB-HIV Public Health Response Optimizing Diagnosis & For HIV Treatment (cont.) Active case finding Screen for HIV in TB clinics Optimize anti-retroviral therapy for coinfected patients Eliminate TB and HIV drug interactions Use drugs to prevent early mortality to TB Timely investigations and case management! 33

34 TB-HIV Public Health Response Reduce HIV-associated TB Use prophylaxis (isoniazid) to prevent TB in HIV patients Avoid exposure to TB patients Prevent nosocomial infections 07Gq9qubWo07I/340x.jpg 34

35 TB-HIV Public Health Response Improving HIV and TB control Challenges Lack of trained health care workers Poor management Weak health care systems Inadequate hospitals & laboratories 35

36 TB-HIV Public Health Response Improving HIV and TB control (cont.) Strategies Better implementation of existing programs HIV testing of TB patients DOTS program Better laboratory diagnosis for TB Adequate anti-retroviral treatment Access to counseling, HIV testing and condoms to prevent spread of HIV 36

37 TB-HIV Public Health Response Improving HIV and TB control (cont.) Strategies (cont.) More widespread implementation of new interventions Most effective drug therapy for TB patients Screening all HIV patients for TB Drugs to prevent/reduce mortality by TB in HIV patients Prevent spread of TB in hospitals 37

38 TB-HIV Public Health Response Improving HIV and TB control (cont.) Strategies (cont.) Increase resources and support Train and retain new health care workers in joint HIV and TB management Increase funding for joint HIV and TB activities Increase funding of research into new and better diagnostics, treatments, and preventive measures for TB and HIV 38

39 Questions? 39