Togaviridae.pptx

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1. Togaviridae

2. Properties of Togaviruses Toga means- Cloak Virus first time isolated from brain of horse in California Size-70 nm in diameter Positive-sense , single-stranded RNA (Reo , Birna ) Virions are spherical in shape, Enveloped, ( Picorna , Calci , Astro, Reo, Birna - NE ) Icosahedral nucleocapsid , ( Picorna , Calci , Astro, Reo, Birna , Togo, Flavi , Retro )

3. Contt .. 5' end of the genomic RNA is capped whereas the 3' end is polyadenylated Replication - cytoplasmic, ( Borna , Orthromyxo -Nucleus ) Maturation occurs via budding from the plasma membrane Agglutination goose & Chicks erythrocyte

4. Classification Alphavirus (Arthropod born virus) Rubivirus / Rebella virus (Human pathogen) Alphaviruses are transmitted b/w vertebrates by mosquitoes and certain hematophagous arthropods. Alphaviruses have wide host range , Rubiviruses infects humans only (Virus belong to Togaviridae are trans. by insect only)

5. Genus ; Alphavirus (Arthropod borne virus) Eastern equine encephalitis virus – Aedes Culiseta Western equine encephalitis virus – Culex , Culiseta Venezuelan equine encephalitis virus- Aedes , Culex Sindbis virus Chikungunya virus- Aedes Highlands virus Igho Ora virus Ross River virus Semliki forest virus Barmah Forest virus Getah virus

6. Arboviruses / Arthropod-borne Viruses Arthropod-borne viruses (arboviruses) are viruses that can be transmitted to man by arthropod vectors. Biological transmission of disease between  susceptible vertebrate  hosts by hematophagous arthropods or through transovarian or venereal transmission in arthropods.”

7. Arthropod-borne Viruses Arboviruses belong to four families: Togaviruses e.g. EEE, WEE, and VEE 2. Bunyaviruses e.g. Sandfly Fever, Rift Valley Fever, Crimean-Congo Haemorrhagic Fever 3. Flaviviruses e.g. Yellow Fever, dengue, Japanese Encephalitis 4. Reoviridae ( Orbivirus - BT, African horse sickness, Coltivirus - Colorado tick fever)

8. Transmission Cycles Man - arthropod -man e.g. dengue, urban yellow fever. Reservoir may be in either man or arthropod vector. Animal - arthropod vector - man e.g. Japanese encephalitis, EEE, WEE, jungle yellow fever. The reservoir is in an animal.

9. Man-Arthropod-Man Cycle

10. Animal-Arthropod-Man Cycle

11. Arthropod Vectors 1. Mosquitoes ( Aedes , Culex , Culeseta like) Japanese encephalitis, dengue, yellow fever , St. Louis encephalitis, EEE, WEE, VEE etc. 2. Ticks (Soft tick / hard tick etc ) Crimean-Congo haemorrhagic fever ( Hyaloma ) , various tick-borne encephalitides etc. 3. Sandflies Sicilian sandfly fever, Rift valley fever.

12. Examples of Arthropod Vectors Aedes Aegyti Assorted Ticks Phlebotmine Sandfly Culex Mosquito

13. Animal Reservoirs In many cases, the actual reservoir is not known. The following animals are implicated as reservoirs Birds Japanese encephalitis, St Louis encephalitis, EEE, WEE Pigs Japanese encephalitis Monkeys Yellow Fever Rodents VEE, Russian Spring-Summer encephalitis

14. Diseases Caused Fever and rash - this is usually a non-specific illness resembling a number of other viral illnesses such as influenza, rubella, and enterovirus infections. The patients may go on to develop encephalitis or haemorrhagic fever. Encephalitis - e.g. EEE, WEE, St Louis encephalitis, Japanese encephalitis. Haemorrhagic fever - e.g. yellow fever, dengue, Crimean-Congo haemorrhagic fever.

15. Diagnosis Serology - usually used to make a diagnosis of arbovirus infections. Culture - a number of cell lines may be used, including mosquito cell lines. Direct detection tests - e.g detection of antigen and nucleic acids are available but again there are safety issues.

16. Prevention Surveillance - of disease and vector populations Control of vector - pesticides, elimination of breeding grounds Personal protection - screening of houses, bed nets, insect repellants Vaccination - available for a number of arboviral infections e.g. Yellow fever, Japanese encephalitis, Russian tick-borne encephalitis

17. Viral Encephalitis

18. Viral Encephalitis Western equine encephalitis (WEE) –Alpha / Toga Eastern equine encephalitis (EEE) –Alpha / Toga Venezuelan equine encephalitis (VEE)–Alpha / Toga St. Louis encephalitis (SLE) La Crosse encephalitis (LAC) Flavi virus West Nile virus (WNV) Center for Food Security and Public Health Iowa State University - 2004

19. History

20. History 1925 First arbovirus identified in the U.S. ( Sendflies ) Vesicular stomatitis 1930 WEE virus isolated in California Karl Meyer isolated agent from horse brain Center for Food Security and Public Health Iowa State University - 2004

21. History 1932 St. Louis encephalitis identified in causing human disease 1933 St. Louis encephalitis virus isolated from human brain Eastern equine encephalitis virus Isolated from equine brains Center for Food Security and Public Health Iowa State University - 2004

22. Transmission

23. Estern , Western, Venezulean produce similar clinical sign Major outbreak- VEEV VEEV- Six sub type (I to VI) Highly virulent (IAB & IC) Other non pathogenic to horse

24. Pathogenesis Outbreak during late summer and heavy rain fall season Pathogenesis Virus enter in to body through mosquito Replication at local site of biting Viremia Sign

25. Sign I.P-9 days Fever Encephalomyelitis Blindness Circling Head pressing Neurological sign most severe in EEEV

26. Lab Diagnosis History & Clinical sign Virus Isolation ( Blood, Brain, CS fluid) Cell culture- Vero, BHK 21- Produce CPE C6/36 ( Aedes albopictus ) grow but do not produce CPE Anomal inoculation ELISA VN RT PCT

27. Control Vaccination- Monovalent, Bivalent, Trivalent Vector control

28. Eastern Equine Encephalitis (EEEV) / Sleeping sickness

29. Animal EEE Incubation period: 1-8 days Severe disease Horses, pheasants, quail, ostriches, emus, puppies Clinical signs in horses Fever, anorexia, weight loss, depression CNS signs Wide stance, droopy ears, flaccid lips, hanging head Death in horses within 4 days Center for Food Security and Public Health Iowa State University - 2004

30. Western Equine Encephalitis (WEEV)

31. Animal WEE Asymptomatic Blacktail jackrabbit, kangaroo rat, Western gray squirrel, prairie dog, horse Horses with clinical signs Fever, depression, altered mentation, head pressing, ataxia, dysphagia Progress to paralysis, convulsions, death Mortality rate 20-50% Center for Food Security and Public Health Iowa State University - 2004

32. Venezuelan Equine Encephalitis (VEEV) Peste loca, Derrengadera

33. Viral Strains Subtype Cycle Pathogenic I-A I-B I-C Epizootic/ Epidemic Highly virulent for equines I-D II I-E III I-F IV V VI Enzootic/ Endemic Not for horses Limited cases in humans Center for Food Security and Public Health Iowa State University - 2004

34. Prevention and Control

35. Management of Mosquito-Borne Diseases Center for Food Security and Public Health Iowa State University - 2004 Source reduction Surveillance Biological control Chemical control Larvicide Adulticide Educating the public How to protect themselves

36. VEE as a Biological Weapon 50 kg virulent VEE particles Aerosolized over city of 5 million people 150,000 people exposed 30,000 people ill 300 deaths Center for Food Security and Public Health Iowa State University - 2004