Bloodborne pathogens Flashcards
Transmission of BB pathogens
Direct contact with infected blood fluids
Infection via contaminated needles, syringes or other unsterilised instruments
Direct infection into bloodstream by arthropod vectors e.g. mosquitoes
HIV transmission
Three routes:
- Blood/blood products or contaminated needles
- Sexually (virus is present in semen and vaginal secretions)
- Perinatally (transplacentally during delivery, ingestion of breast milk)
HIV family and types
Family - retroviridae
genus - lentivirus
HIV1 and HIV2 pathogenic for humans
HIV1 most common
HIV2 less virulent
HIV viral features
Spherical (80-100nm)
Enveloped
RNA genome
Retrovirus - uses reverse transcriptase to make DNA copy from viral RNA
Reverse transcriptase inhibitors
Zidovudine (nucleoside)
Nevirapine (non-nucleoside)
Protease inhibitors
Ritonavir
Saquinavir
HIV progression to AIDS
Exposure to HIV Seroconversion Asymptomatic Persistent generalised lymphadenopathy AIDS -related clinical features
Name some AIDS-defining features
Candidiasis of bronchi, trachea, lungs Cervical carcinoma CMV retinitis (with loss of vision) Recurrent penumonia Salmonella Wasting syndrome
Anti-retroviral therapy (ART)
Many possible regimes and combinations
Initial tx:
- 1 NRTI and 1 PI
- 2 NRTIs and 1 NNRTI
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
Prevention of HIV infection
No vaccine available yet
Screening of blood products
Needle exchange programmes
Anti-retroviral prophylaxis for needle stick injuries - avoiding high-risk sexual partners, uses of barrier contraception, effective C-section
HBV viral features
Hepadnavirus
Double-stranded DNA genome
Enveloped
HBV antigens
HBsAg - surface antigen
- Indicates infectivity
- Anti-HBsAg provided immunity and appears late
HBcAg - core antigen - appears early in infection
HBeAg - pre-core antigen - indicates high transmissibility
HBV stages of infection
Long incubation period - up to 6 months
Development of acute hepatitis
Fulminant disease carries 1-2% mortality rate
50% patients develop chronic active hepatitis - cirrhosis, hepatocellular carcinoma
HBV clinical features
Pre-icteric (jaundice) stage - malaise, anorexia, nausea, pain in RUQ (tender liver)
Icteric stage - jaundice and dark urine (bilirubin)
HBV treatment
Pegylated interferon (peginterferon) is superior compared to alpha-interferon in sustaining suppression of viral replication Anti-viral activity of nucleoside analogues e.g. oral lamivudine may be successful even in chronic HBV patients
HBV prevention
HBsAg vaccine - good protection following 3 injections over 6 month period HBV immunoglobulin Blood screening Needle exchange programmes Sexual health education
HCV viral features
Flavivirus Single-stranded RNA genome Enveloped Replicates primarily in hepatocytes Destroys liver cells Virus cannot be cultured
HCV transmission
Blood and blood proeducts
Body piercing
Haemodialysis
Sexual and vertical transmission uncommon
HCV clinical features
usually asymptomatic
Fatigue, nausea, weight loss, may rarely progress to cirrhosis, small proportion may develop hepatocellular carcinoma
HCV treatment
Interferon reduces liver transaminases in 80% patients
Ribavirun works well in combination with pegylated a-interferon
Combination therapy - sofosbuvir (nucleotide analogue) with PI and another nucleotide analogue
Monitor viral load by NAAT, no vaccine yet
HCV screening
NAAT performed on blood samples
Therefore current incidence of transfusion associated HCV is low
Malaria causes
caused by 5 species of genus plasmodium
P.falciparum, p.vivax, p.ovale, p.malariae, p.knowlesi
Malaria clinical features
fever, flu-like symptoms, p.falciparum infection can regularly progress to death, p.falciparum affects every organ - wide range of complications e.g. cerebral malaria, circulatory shock, hepatitis
malaria diagnosis
At least 3 blood films (both thick and thin) obtained from different times for microscopy
NAAT - useful for detecting drug resistance
malaria treatment and prevention
Chemotherapy kills blood stages of parasite
Resistance means tx advice should be changed regularly
Comb therapy is norm - quinine, chloroquine, doxy, proguanil, malarone
Bed nets, cover skin, repellants, prophylaxis tx for prevention
