Slow virus diseases
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Transcript of Slow virus diseases
SLOW VIRUS DISEASES
Dr Vishal Kulkarni
MBBS MD (Microbiology)
IntroductionThe term “slow virus disease” applied to group of
infections in animals & humans characterized by
a very- Long incubation period.
- Slow but relentless course
- Terminating fatally
Concept was proposed by Singurdsson- a
veterinary pathologist
Characteristics-
Incubation period ranging from months to years
Course of illness lasting from months to years
with remission & exacerbations
Predilection for involvment of CNS
Absence of immune response
OR immune response that may actually
contribute to pathogenesis
Genetic predisposition
Invariable fatal termination
Virus Virus Family DiseaseTypical
LatencyEpidemiology
JC VirusPolyomavirus
Progressive
multifocal
leukoencephalopa
thy
Years to Life§
Unknown;
Contaminated
water?
BK Virus Polyomavirus BK Nephropathy Years to Life§
Unknown;
respiratory
spread/urine?
Rubeola
(Measles)Paramyxovirus
Subacute
Sclerosing
Panencephalitis1-10 Years
Respiratory
droplets
Rubella Togaviridae
Progressive
Rubella
Panencephalitis
10-20 YearsRespiratory
droplets
HIV Retrovirus AIDS 5-10 Years
Infected blood
or other body
fluids
Virus Virus Family DiseaseTypical
LatencyEpidemiology
HTLV 1 Retrovirus
Adult T-cell
Leukemia/Lymp
homa
10-30 Years
Infected blood
or other body
fluids
HTLV 2 RetrovirusAtypical Hairy
Cell Leukemia10-30 Years
Infected blood
or other body
fluids
Classification
Group A-
Slowly progressive infections of sheep
Visna
Maedi
Caused by serologically related non-oncogenic retro-
viruses called as lentiviruses
Another e.g.- HIV
Group B-
Comprising prion disease of CNS, scrapie,mink
encephalopathy, kuru, CJD.
Are collectively known as subacute spongioform viral
encephalopathy
Group C-
- Consisting two unrelated CNS diseases of human
beings
- Subacute sclerosing panencephalitis and
- Progressive multifocal encephalopathy
Group A diseases
Visna
- Demyelinating disease of sheep
- Characterised by paresis, paralysis & death
- It was eradicated by slaughtering of all infected
animals in 1957
Maedi
- It is slowly progressive haemorrhagic pneumonia of
sheep
Group B Diseases
Infections in animals-
- Scrapie
- Mink encephalopathy
- Bovine spongioform encephalopathy (mad cow
disease)
Infections in humans
- Creutzfeldt-Jakob disease (CJD)
- Kuru
Pathology
Infective agent is proteinaceous in nature
Devoid of DNA & RNA, known as prions
It is usually resistant to physical & chemical
agents
Can be transmitted to animals by oral or
parenteral challenge
PrP PrPSC
Stanley B. Prusiner
Proliferation of abnormal protein PrPSC.
Its accumulation in CNS disrupts
architecture & function of brain
Creutzfeldt-Jacob disease
is a subacute encephalopathy characterized by
Progressive inco-ordination, dementia & fatal termination.
Two forms
Gerstamann-Straussler- Scheinker’s syndrome
Fatal familial insomnia
can occur after
corneal transplant
contaminated injection of pitutary growth hormone
Cadaveric human dura grafts used in head injury
A varient of CJD that affected young people (<45
years) in Britain in 1996
Raised fear of infection through eating BSE
infected beef
Kuru
- Characterised by
- progressive cerebellar ataxia,
tremers
- Terminates fatally in 3-6 months
- IP- 5-10 years
- Infections believed to be due to cannibalism &
Sorcery
- A tribal custom of eating dead bodies of relatives after
ritual non sterilising cooking
Group C Diseases
Subacute sclerosing pan encephalitis ( SSPE)
- Delayed sequel of measles viral infection
- Progressive deterioration of mental & motor function
- Brain cells shows evidence of measles virus infection
- Strains isolated are defective
- May also develop as very late complication live
measles virus vaccination
- Ab in serum & CSF is characteristic
- Rare complication of Rubella virus infection
Progressive multifocal leucoencephalopathy
is a rare demyelinating disease in elderly persons
Whose immune response is impaired by
immunosuppression & malignancy
Deterioration of motor function, vision & speech
Polyoma virus has been demonstrated by electron
microscopy in brain biopsy of patients.
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