chikungunya , japanese enchepalitis, zika , yellow fever

1. Arboviruses
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2. Objectives
After studying this section students should be able to
1) Define arboviruses.
2) Classify arboviruses.
3) Describe chikungunya virus.
4) Describe Japanese encephalitis virus.
5) Describe zika virus.
6) Describe yellow virus.
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3. What is arbovirus ?
• Arthropod borne viruses.
• RNA viruses
• Transmitted by blood sucking insects from one vertebrate host to
other.
• Multiply inside the insect to establish harmless infection.
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4. Classification
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5. Clinical Manifestations
• Fever/rash and /or arthralgia group
• Enchephalitis
• Hemorrhagic fever group.
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6. Epidemiology
• Zoonoses – mainly endemic in animals .
• Transmission cycle.
• Humans are the accidental hosts.
• Arthropod vector.
• Climatic variation.
• Geographical distribution.
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7. Arboviruses found in india
• Common – Dengue , Japanese encephalitis , Chikungunya
• Rare -Kyasanur Foresc disease.
• West Nile,
• Sindbis,
• Crimean Congo hemorrhagic fever,
• Ganjam,
• Vellore,
• Chandipura,
• Bhanja,
• Umbre,
• Sachuperi,
• Chiuoor,
• Minnal,
• Venkacapuram,
• Dbori,
• Kaisodi and
• Sand fly fever viruses.
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8. Family Togaviridae
Contains two genera –
Alphavirus –
Fever arthritis group. Encephalitis group.
Chikungunya Eastern equine encephalitis.
Onyongnyong Western equine encephalitis
Mayaro Venezullian equine encephalitis
Ross river
Sindbis
semliki
Rubivirus
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9. Morphology-
Spherical, 50-70 nm,
ssRNA genome,enveloped.
Replicate in cytoplasm, serologically related.
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10. Fever arthralgia group
• Chikungunya fever – characterized by fever with arthralgia.
• Name derived from Makonde word kungunyala meaning bends up.
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11. Transmission
Human transmission
- Aedes mosquito bites during daytime
- Vertical.
- Blood transmission.
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12. Clinical manifestation
• Incubation period
• Acute stage
• Arthritis
• Chronic
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14. Epidemiology
Mutation in virus and vector leads to reemergence .
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16. Genotypes
• Four genotypes
• West African – current infections
• East African
• Asian genotype – before 1973
• Indian ocean genotype
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17. Lab diagnosis
• Viral isolation – For early diagnosis (0-7 d) , mosquito cell lines .
• Serum antibody detection - IgM , Ig G.
• MAC ELISA – IgM antibody Capture ELISA . Use virus lysate .
• Rapid tests – ICT (envelope antigens )
• Molecular method – RT PCR. Gene detection nsP1 and nsP4 in blood.
• Biological markers- IL1 beta, IL 6 increase, RANTES decrease.
• Haematological findings – WBC , platelets – decrease .
ESR and CRP – increase.
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18. Vaccine and treatment
• Vaccines – under trial .
• Treatment – supportive.
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19. FLAVIVIRIDAE
(MOSQUITO-TRANSMITTED) (TICK-TRANSMITTED )
Enchephalitis Haemorrhagic Enchephalitis Haemorrhagic
JE dengue Tickborne KFD
West nile yellow fever Powassan Omsk
Murray valley Louping ill
St Louis
Rocio
Fever / arthritis /microcephaly
Zika
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20. Japanese encephalitis
• Japanese B encephalitis is the leading cause of viral encephalitis in
Asia, including India.
• History
JE virus was so named because the disease
was first seen in Japan ( 1871) as "Summer
encephalitis epidemics .
But now uncommon in Japan (A ).
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21. Epidemiology
• Vector: Culex mosquito
Common vector found in India
C. tritaneniorhynchus
C. Vishnui
• Transmission cycle:
Infects non human hosts animals and birds.
Two transmission cycles are predominant.
• Pigs - Culex - Pigs
• Ardeid birds- Culex- Ardeid bird
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22. Epidemiology
• Host
Pigs – Amplifier host.
Humans are considered as dead end
Bird hosts: herons, ducks .
• Age: 85% of cases occur in children
below 15 years and 10% occur in elderly.
• Seasonal variation: common in rainy season which coincides with
maximum mosquito activity.
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23. Clinical Manifestations
• Incubation period - from 5- 15 days.
• Subclinical infection is common.
• Clinical course - divided into three stages:
1. Prodromal stage is a febrile illness.
2. Acute encephalitis stage:
convulsions, behavioral changes,
meningeal signs or paralysis.
3. Late stage and sequelae: convalescent stage
may be recovered fully or retain some neurological deficits permanently.
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24. Lab diagnosis
• IgM capture antibody ELISA – uses JERA JE recombinant antigen to
detect IgM ab.
• RT PCR. To detect envelope
E gene.
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25. Vaccine Prophylaxis for Japanese Encephalitis
• Live attenuated SA 14-14-2 vaccine:
• It is prepared from SA 14-14-2 strain of JE virus .
• It is cell line derived; primary hamster kidney cells are commonly used.
• Single dose - subcutaneously, followed by booster dose after 1 year.
• It is manufactured in China, but now licensed in India.
• Inactivated vaccine (Nakayama strain and Beijing strain)
• Both are mouse brain derived and formalin inactivated.
• Prepared in Central Research Institute, Kasauli (India) .
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26. • Inactivated vaccine (Beijing P3 strain): It is a cell line derived
vaccine.
• Combined vaccine – genetically engineered.
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27. Zika virus
• Zika fever: a febrile or sub-febrile illness caused by ZIKV , 2015- 16.
• Flaviviridae ( DENV, WNV, YF,JE)
• Aedes mosquitoes
• reservoir - rhesus monkey from the Zika Forest in Uganda in 1947
• ss RNA ,Genome sequenced in 2006
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28. ZIKA VIRUS - Flavivirus family
•The genome is a ~10.8 kilobase, positive
strand RNA enclosed in a capsid and surrounded
by a membrane .
•The envelope (E) glycoprotein allows attachment
of the virus particle to the host cell receptor to
initiate infection.
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29. Clinical manifestation
• About 1 in 5 people infected with
Zika virus become ill .
• Fever, rash, joint pain, or conjunctivitis.
• Others are myalgia and head ache .
• Incubation period - few days to a week.
• The illness is usually mild with symptoms lasting for several days to a
week.
• Zika virus usually remains in the blood of an infected person for
about a week but it can be found longer in some people.
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30. Risk of Zika during pregnancy
• According to pediatric neurologists in Brazil that some pregnant
women infected by zika virus have given birth to the babies with a
birth defect called microcephaly.
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31. Transmission
• Through mosquito bites:
• Zika virus is transmitted - Aedes species mosquito (A. aegypti and A.
albopictus).
•
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32. From mother to child
• A mother can pass on the virus to her newborn around the time of
birth.
• It is possible that Zika virus could be passed from a mother to her
baby during pregnancy.
• No reports of infants - through breastfeeding.
• Mothers are encouraged to breastfeed - where Zika virus is found.
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33. Through sexual contact
• Zika virus is transmitted to the people through sexual activity.
• (CDC) of the first Zika virus case acquired through sexual
transmission in Dallas County in 2016.
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34. Diagnosis
• RT PCR – RNA in urine (upto 7 d) and blood (upto 5 d).
• IgM ab detection.
Vaccines are under trial.
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35. Yellow Fever Virus
• Yellow fever - acute, febrile illness.
• Severe cases - liver dysfunction which leads to jaundice (hence the
name yellow fever), renal dysfunction and hemorrhage, high
mortality.
• Geographical distribution: endemic in West Africa and Central South
America.
• Typing: Seven genotypes, five in Africa and two in South America.
Only one serotype is known to exist.
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36. Transmission and Clinical Manifestations
• Vector: Humans - bite of Aedes aegypti.
Incubation period is - 3-6 days.
• Presence of fever, chills, headache, myalgia,
and backache-followed by nausea, vomiting,
and relative bradycardia.
• Viremic - source of infection for mosquitoes.
.
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37. Severe cases are characterized by
• Hemorrhagic manifestations
• Platelet dysfunction
• Features of liver involvemenl (hepatitis) are:
Mid-zonal necrosis and presence of counicilman bodies.
lntranuclear inclusions - hepatocytes called Torres bodies.
Appearance of jaundice.
• Renal dysfunction
• Encephalitis occurs very rarely.
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38. Yellow Fever 17 D Vaccine
• Live attenuated vaccine, prepared in allantoic cavity of chick embryo.
• No risk of encephalitis ( previously used mouse brain derived
inactivated Dakar vaccine - encephalitogenic).
• In India: Central Research Institute (CRI), Kasauli.
Available in lyophilized form and has to be
reconstituted before use.
• Dosage: Single dose, given subcutaneously.
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39. • Certificate is issued .
• Cholera and yellow fever vaccine interact with each other, hence
should not be given together (3 weeks gap to be maintained).
• Contraindications :
• Children < 9 months,
Pregnancy (except during outbreak)
HIV infected people .
People with allergy to egg.
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40. Questions ???????
REFRENCES
• Wikipedia
• Anonymous: Yellow fever outbreaks in the Americas. Disasters: Preparedness and Mitigation in
the Americas. March issue, 109,4 (2008).
• PAHO: Update on jungle Yellow fever (JYF) in Brazil, Paraguay, and Argentina. PAHO Press
Release. 11 February (2008).
• PAHO: Mobilization against yellow fever in Paraguay continues. PAHO Press Release. 26 February
(2008).
• Pastorino B, Muyembe-Tamfum JJ, Bessaud M et al.: Epidemic resurgence of chikungunya virus in
democratic Republic of the Congo: identification of a new central African strain. J. Med.
Virol. 74,277–282 (2004).
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