Transfusion Transmitted Infections - Viruses Flashcards
What is the main issue with transfusion related infections
It can be hard to prove whether an infection is from a transfusion or is a previous infection
There will always be unknown infections that were not currently screening for or new-re-emerging strains etc e.g. Arbo virus or dengi fever etc
Talk about the history of syphilus transfusion related infections
Syphilius used to be the most common transmissible infection but penicillin almost wiped it out entirely -> there had been no positives in 20 years
However there is now 4 to 5 infection in the IBTS a year -> recurrence seen
However syphilus can only survive 4-5 days in a cold blood pack
How has our screening progressed?
We used to use fresh whole blood which wasnt screened
It was thought that albumin or fractionated products were thought to be clean
We didnt know about HepC -> only knew about HepA and HepB -> C wasnt named until the 1990s
What are the four properties of a transfusion transmitted infectious agent?
Gives rise to asymptomatic infection ‘healthy donor’
Is presentt in the blood stream, in wbcs, plasma etc
Is transmissiblle parenterally
Is able to survive storage of blood and components
What has been a major help in preventing TTIs
Volunteer donors introduced in the 1970s
What current micobiology testing do we have in place
Bacterial culture of platelets
Syphilus
Malaria since 2021
HIV
Hepatitis B, C and E
West nile virus
Anti-CM
What microbiology testing will we have in the future
prions
protozoa such as chagas, toxoplasmosis or leishmaniasis
testing for any emerging strains or re-emerging etc
Talk about our recent HepB transfusion related infection
In 2017 we had a case of TR hepatitis B
This was our first case in 20 years
It slipped through due to a statatastic error
i.e. there was so little viral particles in the sample that it depended on where you stuck the pippette into the same
How does Hepatitis B compare to HIV
Hep B is a very durable double stranded DNA virus
It can be left on needles for weeks while HIV wont survive longer than a day
HepB used to be the mosmt common healthcare infection due to needle stick injury
We currently hav nucleic acid esting in place for what?
HCV
HBV
WNV
Hiv
What is the current situation of positive results in Ireland
HIV 1 and 2 last positive in 2011
HBV 2-4 positives per year
HCV 2-4 positives per year
HTLV1/2 -> 1 in 10 years?
Syphilis -> 4-5 positives per year
Anti-CMV in 22% of donors
HEV 1 in 5000 donors but clusters
Chagas not tested for but 1:2000 US donors -> hence deferral
Talk a little on HIV and its name
HIV used to be called HTLV3
HIV and HTLV are very similar rna viruses
They insert themselves into while cells and can regrow into rna and sprout out of cells etc
Talk about HTLV
Causes tropical spastic paralysis
Its seen in the US but not really over here
Hence we only test first time donors to reduce cost -> its only an Ab test
Weve only had a single positive in 20 years so we moved to first time donors only
How does Ireland CMV levels compare to the rest of the world
We have low levels compared to over 90% in some countries, its about 40% in most countries
Talk about HEV in Ireland
Clusters seen arround abattoirs or farms
Pigs and pork meat
Associated with easter and christmas - cocktail sausages etc
Talk about chagas disease
Seen in bolivia hence we dont test for this we only defer
Whst id the residual risk of transmission of HBV, HIV and HCV
1:2 million for HBV
1:15 million for HIV
1:15 million for HCV
Why have certain viruses been increasing in frequency
International travel and migration has increased e.g. WNV incidence
Only certain mosquitos carry malaria but these have migrated north due to global warming thus were getting more positives
Talk about bacterial infection related to transfusion
Occassional contamination with microorganisms such as psudomonas, serratia, yersinia, staphs and E, Coli
can result in devastating endotoxic shock
Dependent on quality of blood taking, processing and storage protocols etc
Most likely a problem with patelets as theyre stored at 22 degrees
Highest infectious risk even though still rare
What measures are in place to reduce bacterial contamination
BacT alert for all platelets
Cleaning of site of donation thoroughly
Diverting first few mls of pack
Why is bacterial contamination still an issue even with SD treament
this is because inactivation methods such as intercept cannot guaranttee to kill bacteria as these have a cell wall
This is why BacT still recommended for platelets
What is the main benefit of NAT over Ab detection
NAT greatly shortens the winodw period of detection e.g.
HIV from 21 days to 5.6 with NAT
HCV from 58.3 days down to 4.9 with NAT+serology
HB from 38.3 to 15.6 with NAT + HBsAg
What is the main benefit of NAT over Ab detection
NAT greatly shortens the winodw period of detection e.g.
HIV from 21 days to 5.6 with NAT
HCV from 58.3 days down to 4.9 with NAT+serology
HB from 38.3 to 15.6 with NAT + HBsAg
Why is hepatitis B our main issue?
This is because even with NAT the window period remainas at 15.6 days
i.e. its undetectable for 2 weeks by either method