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Flashcards in Bloodborne Pathogens Deck (31)
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1

How are bloodborne pathogens transmitted?

  • Direct contact with infected blood fluids. 
  • Infection via contaminated needles, syringes, or other unsterilised instruments.
  • Direct infection into the bloodstream by arthropod vectors (e.g. mosquitos).

2

How is HIV transmitted?

  • Occurs by 3 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). 

3

Describe the classification of HIV.

  • Family - retroviridae
  • Genus - lentivirus
  • HIV-1 and HIV-2 pathogenic for humans
  • HIV-1 is most common
  • HIV-2 is less virulent

4

Describe the viral features of HIV.

  • Spherical (80-100nm)
  • Enveloped
  • RNA genome
  • Retrovirus - uses reverse transcriptase to make DNA copy from viral RNA.

5

Describe the time course of HIV infection.

6

Describe the progression of HIV to AIDS.

  • Exposure to HIV
  • Seroconversion
  • Asymptomatic
  • Persistent generalised lymphadenopathy
  • AIDS-related clinical features
  • AIDS

7

What are the defining conditions associated with AIDS?

8

How does the viral load of HIV affect the development of AIDS?

  • Viral RNA copy number (viral load) in blood:
    • 13% of those with <1,500 copies/mL blood will develop AIDS within 9 years. 
    • 93% of those with >55,000 copies/mL blood will develop AIDS within 9 years. 

9

What are the available drugs for the treatment of HIV?

  • Anti-retroviral therapy (ART):
    • Nucleoside reverse transcriptase inhibitors (NRTIs). 
    • Non-nucleoside reverse transcriptase inhibitors (NNRITs). 
    • Protease inhibitors (PIs). 
  • There are many possible regimens and combinations.
  • Initial treatment often contains:
    • 1 NRTI + 1 PI
    • OR
    • 2 NRTIs + 1 NNRTI

10

Describe the diagnosis of HIV infection.

  • Diagnosis of HIV specific antibodies. 
    • ELISA
    • Western Blotting
  • NAAT used to detect viral RNA in serum. 
  • Quantitative NAAT used to measure viral load.
  • Individual testing must be preceded by counselling.
  • An initial negative result should always be followed-up.

11

Describe the prevention of HIV infection. 

  • No vaccine yet available 
  • Screening of blood products
  • Needle exchane programmes
  • Anti-retroviral prophylaxis for needlestick injuries

 

  • Avoiding high-risk sexual partners
  • Use of barrier contraception
  • Elective caesarian section

12

Describe the viral features of hepatitis B (HBV).

  • Hepadnavirus
  • Double-stranded DNA genoma
  • Enveloped

13

What are the antigens associated with hepatitis B virus (HBV)?

  • HBsAg - surface antigen 
    • Indicated infectivity
    • Anti-HBsAg provides immunity and appears late
  • HBcAg - core antigen
    • Appears early in infection
  • HBeAg - pre-core antigen
    • Indicates high transmissibility

14

How is HBV transmitted?

  • Via blood or blood products. 
  • Contaminated needles and equipment used by IV drug users. 
  • Association with tattooing, body piercing and acupuncture.

 

  • Sexual intercourse
  • Intra-uterine, peri- and post- natal infection. 
  • Contaminated haemodialysis equipment.

15

What are the stages of HBV infection?

  • Long incubation period - up to 6 months. 
  • Development of acute hepatitis.
  • Fulminant disease carries 1-2% mortality rate. 
  • 50% of patients develop chronic active hepatitis.
    • Cirrhosis
    • Hepatocellular carcinoma

16

Describe the development of an acute HBV infection which is self-limited. 

17

Describe the development of a chronic HBV infection which is persistent. 

18

What are the clinical features of HBV.

  • Pre-icteric stage
    • Malaise
    • Anorexia
    • Nausea
    • Pain in RIQ (tender liver)
  • Icteric stage 
    • Jaundice 
    • Dark urine (bilirubin)

19

Describe jaundice. What causes it?

  • Yellowish pigmentation
    • Skin
    • Sclera
    • Other mucous membranes
  • Caused by hyperbilirubinaemia

20

What are the treatments for HBV?

  • Pegylated interferon (peginterferon) is superior compared to α-interferon in sustaining suppression of viral replication. 
  • Antiviral activity of nucleoside analogues (e.g. oral lamivudine) may be successful even in chronic HBV patients.

21

What are the prevention strategies for HBV?

  • HBsAg vaccine
    • Good protection following 3 injections over a 6 month period.
  • HBV immunoglobulin
  • Blood screening
  • Needle exchange programmes
  • Sexual health education

22

What are the viral features of hepatitis C virus (HCV)?

  • Flavivirus
  • Single-stranded RNA genome
  • Enveloped 
  • Replicated primarily in hepatocytes
  • Destroys liver cells
  • Virus cannot be cultured

23

How is HCV transmitted?

  • Via blood and blood products.
  • Tattooing, body piercing and acupuncture.
  • Haemodialysis.

 

  • Sexual transmission uncommon.
  • Vertical transmission uncommon.

24

What are the clinical features of HCV?

  • Usually asymptomatic 
  • Fatigue
  • Nausea
  • Weight loss
  • May rarely progress to cirrhosis
  • Small proportion may develop hepatocellular carcinoma

25

What are the treatments for HCV?

  • Interferon reduces liver transaminases in 80% of patients. 
  • Ribavirin works well in combination with pegylated α-interferon.

 

  • Combination therapy

 

  • Sofosbuvir (nucleotide analogue)
  • Boceprevir (protease inhibitor)
  • Telaprivir (nucleotide analogue)
  • Daclatasvir (inhibits NS5A)

 

  • Monitor viral load by NAAT
  • No vaccine available

26

How is HCV screened for?

  • NAAT performedon blood samples.
  • Therefore, current incidence of transfusion-associated HCV is low. 

27

What is the cause of malaria?

  • 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 blood stream.
  • Zoonotic disease.

28

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. Examples:
    • Cerebral malaria
    • Circulatory shock
    • Hepatitis

29

How is hepatitis diagnosed?

  • At least 3 blood films (both thick and thin) obtained from different times for microscopy. 
  • NAAT - useful for detecting drug resistance. 

30

What are the available treatments for malaria?

  • Chemotherapy kills blood stages of parasite.
  • Resistance means treatment advice should be changed regularly. 
  • Combination therapy is the norm:
    • Quinine
    • Chloroquining
    • Doxycyclin
    • Proguanil
    • Malarone (= proguanil + atovaquone)
    • Artemether