Bloodborne Pathogens Flashcards
Give some examples of transmission methods of bloodborne pathogens
Viruses are very different but require contact with infected blood e.g.
• Infection via contaminated needles or other unsterilised instruments
• Direct infection into the bloodstream by arthropod vectors (e.g. mosquitoes)
• Iatrogenic through blood products (Packed red cells etc.)
Discuss Prevalence & Incidence of HIV – UK/Worldwide
• World wide as of 2019:
– 38 million people living with HIV infection
– 2.8 million of these are children
– 1.7 million people newly infected with HIV during 2019 (2.0m in 2014)
– 0.69 million died of AIDS in 2019 (1.2m 2014)
• Sub-Saharan Africa - most seriously affected
• Eastern Europe and parts of central Asia infection rates rising exponentially.
• UK in 2019 recorded 105,200 people living with HIV 4,139 new diagnoses annually
Discuss the naming/classification of HIV
• Family - retroviridae • Genus - lentivirus • HIV-1 and HIV-2 pathogenic for humans HIV-1 - most common HIV-2 – less virulent
What are the viral features of HIV?
• Spherical(80-100nm)
• Enveloped
• RNAgenome
Retrovirus – Uses reverse transcriptase to make DNA copy from viral RNA
Discuss HIV transmission
• Occurs by three routes:
– Via blood/blood products or contaminated needles
– Sexually (virus is present in semen and vaginal secretions)
– Perinatally (transplacentally during delivery, ingestion of breast milk)
What are the stages of HIV infection?
Seroconversion
Asymptomatic
AIDS
Discuss complication of HIV infection
Most complications are via reduction in T cell mediated immunity or from its psychological impact.
Patients are prone to opportunistic infections especially in respiratory tract
What are the defining conditions of AIDS?
The 5 most common AIDS-defining illnesses in the UK, in decreasing order,
• Pneumocystis jiroveci pneumonia (16.7%)
• Oesophageal candidiasis (15.2%)
• Kaposi sarcoma (13.2%)
• Mycobacterium avium–intracellular complex (9.6%)
• Cytomegalovirus retinitis (9.5%)
Discuss diagnosis of HIV infection
• Diagnosis of HIV-specific antibodies via;
– ELISA (Enzyme linked immunosorbent assay)
– Western Blotting (Technique involving gel electrophoresis)
Results may be negative up to 3 weeks post exposure so retest at 6 then 12 weeks
Testing is routine/opt out. Brief Pre test counselling should proceed testing.
How do you monitor a HIV infection?
Monitoring is very important hence viral load is measured every 3-6 months.
Serum Viral Load (Copies of Viral RNA in circulation)
• 93% of those with >55,000 copies/ml blood will develop AIDS within 9 years
• 13% of those with <1,500 copies/ml blood will develop AIDS within 9 years
Discuss treatment of HIV infection
Goal at individual level is suppress plasma HIV RNA concentrations below the limit of detection and restore immune function.
Goal at the population level is elimination of human immunodeficiency virus (HIV) transmission. In the UK this is now considered to be an achievable ambition (BHIVA report 2020)
Aim for early initiation of treatment regardless of CD4 cell count. This has clear benefit for the individual (with avoidance of morbidity and mortality), their partners (avoidance of transmission by having an undetectable viral load) and population (reduced community viral load and HIV transmissions).
Provide some examples of anti-retroviral therapy (ART)
- Nucleoside Reverse Transcriptase Inhibitors (NRTIs)
- Non-nucleoside Reverse Transcriptase Inhibitors (NNRTIs)
- Protease Inhibitors (PIs)
- Integrase inhibitors (INI)
Discuss the basic application of anti-retroviral therapy (ART)
• Many possible regimens and combinations
• Initial treatment often contain 3 total drugs:
2 NRTIs (Backbone of treatment)
+ 1 NNRTI or +1 INI or
+ PI
How does one prevent HIV infection?
- Screening of blood products
- Needle exchange programmes
- Pre exposure prophylaxis (PrEP)
- Post exposure prophylaxis (PEP)
- Antenatal antiretrovirals if HIV +ve ± Caesarean birth ± bottle-feeding
Discuss HIV as the quintessential biopsychosocial illness
Shame, sexual imperatives, pride and prejudice keep HIV underground and multiplying
What can we do as doctors to help combat the biopsychosocial nature of HIV as an illness?
Warn everyone about dangers of sexual tourism/promiscuity
Teach skills in sexual negotiation.
Explain how alcohol can undermine safe sex messages.
Promote human rights so groups driving spread of HIV aren’t driven underground. Introduce drug users to needle exchange schemes
Promote the work of STI clinics. Encourage HIV testing, eg in pregnancy Diagnose HIV early
What is HBV?
Hepatitis B Virus
Discuss transmission of HBV
- Blood or blood products
- Contaminated needles and equipment used by intravenous drug users
- Association with tattooing, body piercing and acupuncture
- Sexual intercourse
- Intra-uterine, peri- and post-natal infection
Discuss the viral features of HBV
Classification - Hepadnavirus
• Double-strandedDNA genome
• Enveloped
Discuss HBV antigens
• Hepatitis B ‘surface’ Antigen (HBsAg) - Indicates infectivity
Anti-HBs (Antibody) provides immunity & appears late
• Hepatitis B ‘early’ Antigen (HBeAg) – Indicates high transmissibility
Discuss stages of infection in HBV
• Long incubation period - up to 6 months
• Development of acute hepatitis
• Fulminant disease carries 1-2% mortality rate
5-10% patients develop chronic active hepatitis
– Cirrhosis
– Hepatocellular carcinoma
Why are some HBV infections acute?
They are self limited
What are the clinical features of HBV?
• Pre-icteric Stage – Malaise – Anorexia – Nausea – Pain in right upper quadrant (tender liver) • Icteric Stage – Jaundice – Dark urine (bilirubin)
Discuss jaundice in the icteric phase of HBV infection
• Yellowish pigmentation caused by hyperbilirubinaemia.
Noticeable on;
- Skin
- Sclerae
Discuss treatment of HBV
The aim is to prevent Liver cirrhosis and Hepatocellular Carcinoma. Monitor for clearance of HBsAg (risk of both is much higher if HBsAg and HBeAg +ve)
• Avoid alcohol.
• Immunize sexual contacts
• Patient with Chronic Hepatitis B should be referred for antivirals, eg pegylated (PEG) interferon alfa-2a
Discuss prevention of HBV
• HBsAg vaccine – Effective following 3 injections over a 6 month period • Blood screening • Needle exchange programmes • Sexual health education
What is HCV?
Hepatitis C Virus
What are the viral features of HCV?
Classification – Flavivirus • Single-stranded RNA genome • Enveloped • Replicates primarily in hepatocytes • Destroys liver cells • Virus cannot be cultured
Discuss HCV transmission
• Blood products (However screening via a Nucleic acid amplification test (NAAT) equates to a low incidence of transfusion associated HCV)
• IV drug use
• Tattooing, body piercing and acupuncture
Sexual transmission less common
Vertical transmission less common
Discuss the clinical features of HCV
Usually asymptomatic however may report;
• Fatigue
• Nausea
• Weight loss
Those infected 50% will spontaneously clear virus, around 50% develop chronic infection
• May rarely progress to cirrhosis
• Small proportion may develop hepatocellular carcinoma
Discuss HCV treatment
- Interferon reduces liver transaminases in 80% of patients
- Ribavirin works well in combination with pegylated α-interferon
- Combination therapy
- Monitor viral load by NAAT
- No vaccine available yet
Fuck
Malaria
Discuss the worldwide infection of malaria
- > 1.5 billion people live with the threat of malaria
- > 229 million cases in 2019 (94% in Africa)
- 1 million children under 5 die each year in Africa alone
- 2000 reported cases per year in UK
What is the cause of malaria?
• Single celled parasites
• Caused by 5 species of the genus Plasmodium – P. falciparum
– P. vivax
– P. ovale
– P. malariae – P. knowlesi
• Female Anopheles mosquito injects sporozoa into the bloodstream
• Zoonotic disease
How many hosts are involved in the life cycle of malaria?
2 hosts
What are the different phases in the life cycle of malaria in humans
Hepatic phase and erythrocytic phase
What are the clinical features of malaria?
• Fever
• Flu-like symptoms
• P. falciparum infection can rapidly progress to death
• P. falciparum affects every organ – wide range of complications (cytoadherence) e.g.
– Cerebral malaria
– Circulatory shock
– Hepatitis
How does one diagnose malaria?
- At least 3 blood films (both thick and thin) obtained from different times for microscopy
- NAAT – useful for detecting drug resistance
What is the therapeutic management of malaria?
Chemotherapy kills ‘erythrocytic phase’ of parasite in active infection
Resistance means exact regime is based on local resistance patterns Combination therapy is the norm and many variations exist;
Uncomplicated Plasmodium Ovale/Vivax/Malariae
Chloroquine
*P. Ovale/Vivax need 14d of Primaquine to treat liver stage and prevent relapses
Uncomplicated Plasmodium Falciparum
Riamet (Artemether + Lumefantrine)
Discuss malaria prevention
- Sleep under bed nets
- Cover exposed skin between dusk and dawn
- Use of mosquito repellants
- Prophylactic treatment
- Vaccines currently being developed
