Slow virus infection

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Slow virus infection

  1. 1. SLOW VIRUS DISEASES Dr.T.V.Rao MDDR.T.V.RAO MD 1
  2. 2. SLOW VIRUS DISEASES.• Animals/Humans suffer• Sheep – Scrape Visna Maedi• Incubation months to years• CNS involvement,• Genetic Predisposition.• Absence of Immune response.• Fatal Terminal Illness.DR.T.V.RAO MD 2
  3. 3. CHARACTERS OF SLOW VIRUSES 1 Incubation from months to years. 2 Illness from months to years. 3 Involvement of CNS. 4 Absence of Immune response. 5 Genetic predisposition. 6 Leads to Fatal illness.DR.T.V.RAO MD 3
  4. 4. CLASSIFICATION – 3 GROUPS• Group A Sheep Caused by Lentivirus• Group B Prions CNS• Scrapie Mink encephalopathy Kuru, Creutzfeldt-Jacob disease. Subacute spongiform viral encephalopathy Group C 2 types 1.Subacute sclerosing panencephalitis, 2.Progressive multifocal LeucoencephalopathyDR.T.V.RAO MD 4
  5. 5. HUMAN PRION DISEASE• Creuzfeldt and Jacob Disease -GJD• Gerstmann-Strasussler – GSS• Fatal Familial Insomnia –FFI• Kuru• Human transmission - Spongiform Encephalopathy.• 1 Idiopathic• 2 Familial• 3 Acquired• Location on 20 Human chromosomeDR.T.V.RAO MD 5
  6. 6. Unconventional slow viruses: Prions Prion :Proteinaceous infectious particle 1.causes spongiform encephaolpathies observed in hosts Slow Virus Diseases 2. Characteristics of diseasesHuman --long incubation periods (30 years)•Kuru before developing clinical illness•Creutzfeldt-Jakob disease (CJD)•Gerstmann-Sträussler-Scheinker (GSS syndrome)•Fatal familial insomnia (FFI)Animal•Scrapie (sheep and goats)•Transmissible mink encephalopathy•Bovine spongiform encephalopathy (BSE; mad cow disease) DR.T.V.RAO MD 6•Chronic wasting disease (mule, deer, and elk)
  7. 7. Kuru: shivering or trembling in Fore tribe of New Guinea , who used to eat dead human body. Women and children are high risk.5-19 DR.T.V.RAO MD 7
  8. 8. KURU• Kuru is a disease of man. It causes tremors and ataxia and often, in later stages, dementia. It is transmitted by rites for the dead which included autopsy and cannibalism in Fore people in Papua/New Guinea. No one born since these practices ceased has acquired Kuru. There is no evidence for transmission to fetus, transmission via milk or intimate social contact.DR.T.V.RAO MD 8
  9. 9. DR.T.V.RAO MD 9
  10. 10. SUB ACUTE SCLEROSING PAN ENCEPHALITIS (SSPE)• This disease is a rare complication of measles virus infection and develops approximately 1 to 10 years after the initial infection. It is progressive and fatal and is characterized by mental and motor deterioration. Risk factors include acquiring primary measles at an early age.• SSPE is associated with defective forms of the virus in the brain and so it is difficult to isolate infectious virus from patients. Incidence has decreased since the introduction of anti-measles vaccination.DR.T.V.RAO MD 10
  11. 11. INHERITED DISORDERS• CJD• Gerstmann Straussler Syndrome• Fatal Familial insomnia• Human to Human Kuru Iatrogenic• From Bovine to Human Variant of CJD• Investigation at Autopsy• Pr Psc Accumulates in the CNS• Detection with Western Blot test DR.T.V.RAO MD 11
  12. 12. WHAT ARE PRION DISEASES• Prion diseases are among the most intriguing infectious diseases and are associated with unconventional Proteinaceous infectious agents known as prions. Prions seem to lack nucleic acid and propagate by transmission of protein misfolding. The nature of prions and their unique mode of transmission present challenges for early diagnosis of prion diseaseDR.T.V.RAO MD 12
  13. 13. DR.T.V.RAO MD 13
  14. 14. PRIONS- Shortened form of Proteinaceous infectious particles- Prions are single molecules containing about 250 amino acids- They are abnormal variants of proteins which normally occur in cells- Prions have the ability to convert the normal forms that they come into contact with into abnormal forms DR.T.V.RAO MD 14
  15. 15. Prion Characteristics No antibiotics can cure disease caused by prions They are not typical of a prokaryotic organism or a eukaryotic organism All that is present in this pathogen is the protein PrPSc, the mutation of PrPC PrPSc is resistant to any form of digestion Prions are non immunogens and do not induce an immune response Prions are not easy to decompose biologically They are resistant to high temperatures & disinfectants DR.T.V.RAO MD 15
  16. 16. DR.T.V.RAO MD 16
  17. 17. HOW DOES IT SPREAD FROM ANIMAL TO ANIMAL?• Feeding cattle animal bi-products such as meat-n- bone mill that has an infected prion causes the infection in the cattle• The prions are concentrated in the brain, and spinal cord of these animals• There is no evidence that it is concentrated in the muscle mass of cattle, and they are considered safe as long as they are not in contact with the brain and spinal cord during the slaughter process DR.T.V.RAO MD 17
  18. 18. PRION HYPOTHESIS PrP is a normal cellular protein referred to as PrPc Diseased brain contains aberrant PrP which is referred to as PrPSc PrPSc has the ability to convert PrPc to itself A chain reaction follows, resulting in a cluster of tangled, nonfunctional proteins called plaques, which are aggregates of PrPSc in the brain The body defences remove these PrPSc aggregates leaving behind holes This causes degeneration of the brain cells leading to menta changes and ultimately, death DR.T.V.RAO MD 18
  19. 19. MAD COW DISEASE IN HUMANSWhen cattle brains and other cattle byproducts infected with BSE are ingested by humans, there is a risk of developing the Creutzfeldt-Jakob Disease DR.T.V.RAO MD 19
  20. 20. Epidemiology-- CJD is transmitted by injection, transplantation of contaminated tissues (corneas), contact with contaminated medical device (brain electrode), and food.-- CJD, GSS, and FFI are also inheritable.-- Kuru is due to the eating of dead body.-- variant form CJD (vCJD) in younger people (<45 years old) in UK after mad cow disease in 1980. DR.T.V.RAO MD 5-18 20
  21. 21. CJD• 1/ 1 million• Dementia, Neurological Involvement• Effects person with Genetic predisposition.• Gerstmann Strassler Scheinker syndrome• Dementia• Pr p plaques.DR.T.V.RAO MD 21
  22. 22. CJD• A Human and Animal / Fatal disease.• Neurodegenerative disorder• Spongiform changes• Reactive –Amyloidal plaques. Contain Pr P sc• Pr P sc is derived from Pr pc• Chromosome 20 is location of abnormalityOn neurons.DR.T.V.RAO MD 22
  23. 23. Origins of CJD Bovine Spongiform Encephalopathy (BSE) was first described in the UK in 1985 as a prion- based disease that affected cattle. In 1996 it was first detected in a human being It was suspected at that time (which turned out to be correct) that humans were contracting the disease from eating cows that had been infected with BSE In humans, it is has been named the Creutzfeldt- Jakob Disease (CJD) DR.T.V.RAO MD 23
  24. 24. CJD• A Human and Animal / Fatal disease.• Neurodegenerative disorder• Spongiform changes• Reactive –Amyloidal plaques. Contain Pr P sc• Pr P sc is derived from Pr pc• Chromosome 20 is location of abnormalityOn neurons. DR.T.V.RAO MD 24
  25. 25. Variant CJD in humans: section of cerebral cortex stained to show aggregates of PrPSc within plaques and more finely distributed throughout the grey matter (PrP stains brown)DR.T.V.RAO MD 25
  26. 26. PRIONS AND RESISTANCE• Formaldehyde 3.7%• Boiling, Ethanol 50%• Ionizing Radiation• House hold bleach.• Autoclaving at 121 c I1 hour Resistant to all above methods of SterilizationDR.T.V.RAO MD 26
  27. 27. ACQUIRED PRION DISEASES• Iatrogenic CJD• Human to Human• 1974 Corneal graft• Instruments• Human growth Hormone.• Incubation 20 years Kuru Fore tribes in Papua New Guinea CannibalismShivering5-40 yearsCannibalism abolished DR.T.V.RAO MD 27
  28. 28. GROUP C• CMI absent.• Progressive Multifocal Leucoencephalopathy• May be caused by Papova virus• Leads to detoriation of Vision and Speech• Sub acute sclerosing panencephalitis. A delayed sequence of Measles Infection.• Leads to detoriation of Mental and Motor functions.• Serology / Electron Microscopy.DR.T.V.RAO MD 28
  29. 29. VARIANT OF CJD• BSE Cattle –potential Implications in human diseases.• Food chain• Young can also be infected 12-74 years• Psychiatric sensory symptoms• Ataxia Myoclones,Dementia• Accumulation of Pr psc• Amyloid plaques.• With Spongiform chains• Acquired by oral route, Possible transmission of variant CJD• Can happen through surgical Instruments.• How Many infected ? Incubation ?DR.T.V.RAO MD 29
  30. 30. Types of CJDCJD is classified into 2 forms: Classic CJD & Variant CJD Classic CJD can be transmitted to other species, however other animals cannot carry it. Sub classified into: Sporadic CJD and Iatrogenic CJD  Sporadic CJD - >85% of Classic CJD cases  Most common between 50 – 75 years  Characterized by rapidly increasing dementia  Iatrogenic CJD - < 5% Classic CJD cases  Transmission of prion via medications & surgical equipment DR.T.V.RAO MD 30
  31. 31. WHAT IS VCJDVariant Creutzfeldtt-Jakob Disease (vCJD), is caused by the consumption of BSE infected meat productsVariant CJD seems to affect mostly young patientsThe first 10 cases of variant CJD were observed in 1996, ten years after the outbreak of BSE in the UK DR.T.V.RAO MD 31
  32. 32. Clinical SymptomsCJD causes fatal degradation of brain tissue & the nervous systemThe symptoms include loss of expressiveness, muscular tremble, spasm, impaired muscle coordination, loss of memory & dementiavCJD patients also display unusual psychiatric problemsThere is no cure for CJDThe condition of the patient deteriorates, finally resulting in death DR.T.V.RAO MD 32
  33. 33. MAD COW DISEASEInitially thought to have been caused by a “slow” viruses, these were classified as “slow Viral DiseasesNow there is evidence to point out Prions as the causative factorDR.T.V.RAO MD 33
  34. 34. Mad Cow Disease: What is it? The Mad Cow Disease in Cows, Scrapie in Sheep, the Creutzfeldt-Jakob Disease in human beings belong to a class of disease called Transmissible Spongiform Encephalopathy (TSEs) Initially thought to be due to “slow viruses”, due to the long incubation period between time of infection and appearance of disease, these are now known to be caused by agents called prions. DR.T.V.RAO MD 34
  35. 35. MAD COW DISEASEScientific Name: Bovine Spongiform EncephalopathyIt is found on any type of cloven hoofed animals such as: pigs, sheep, and cattleSheep: Scrapie Spongiform Encephalopathy.There is a human form called Creutzfeldt- Jakobs Disease DR.T.V.RAO MD 35
  36. 36. DIAGNOSIS – BIOPSY• During life, a probable diagnosis is based on the clinical picture. EEG can provide useful supportive evidence in some cases. The wide range of symptoms and disease course make diagnosis difficult and prion diseases are often misdiagnosed. The final diagnosis is usually made from post-mortem examination of the brain. A brain biopsy can be used. Serology is of no use since the patient does not show an immunological response.DR.T.V.RAO MD 36
  37. 37. At Present, there is no Cure for the Mad Cow Disease(Bovine Spongiform Encephalitis) and for the Creutzfeldt-Jakob Disease Prevention is the only available optionDR.T.V.RAO MD 37
  38. 38. • Programme Created by Dr.T.V.Rao MD for Medical and Paramedical Students in the Developing world • Email • doctortvrao@gmail.comDR.T.V.RAO MD 38

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