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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