Togaviruses
fackrel@uwindsor.ca
toga.ppt
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4/13/2015
Toga Viruses
Structure
Classification
Multiplication
Clinical manifestations
Epidemiology
Diagnosis
Control
Baron’s Web Site
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Togaviridiae
Rubivirus-rubella
Alphavirus- Equine Encephalitis, Sindbis
Pestivirus- animal pathogens
 bovine
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viral diarrhea, hog cholera
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Rubella
German Measles
(first diagnosed by German doctors)
Three day Measles
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Rubella: Structure
enveloped
icosahedral
ss RNA sense
40-80 nm
30 nm core
 hemaglutinin peplomers
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+ ssRNA
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Rubella: Classification
Family Togaviridae
 genus Rubivirus only member
single serotype
three structural polypeptides
Unlike other
Togaviruses rubella is
not arthropod borne
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Rubella: Multiplication
RNA is capped and polyadenylated
 serves as mRNA -> nonstructural proteins
sense RNA -> antisense RNA
Antisense RNA template for progeny RNA
antisense RNA--> mRNA -> structural
proteins
mature at intracytoplasmic membranes
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Rubella: Clinical manifestations
Postnatal
rash
lymphadenopathy
low grade fever
Congenital
stillbirth
spontaneous abortion
birth defects
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Congential Rubella
Ocular- cataracts, retinitis, glucoma
,microphthalmaia
Heart defects- patent ductus arteriosis
Deafness- cochelar deafness, central
auditory imperception
CNS- mental retardation, encephalitis,
microcephaly
Other- hepatitis, pneumonitis
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Rubella: Pathogenesis
respiratory secretions -direct contact,
droplet
multiplies in cells of respiratory system
extends to lymph nodes, spleen
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Rubella: Epidemiology
worldwide
vaccines licenced 1969
no new epidemics
incidence ~ 100 /year
Congential rubella occurs in
unvaccinated susceptible
young women
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Rubella: Host defenses
interferon
cell mediate immunity
neutralizing antibodies
hemagglutinin inhibiting antibodies
asymptomatic reinfection possible
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Rubella: Diagnosis
Clinical manifestations- rash,
lymphadenopathy
Isolate virus respiratory tract
Detect Rubella IgM
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Diagnosis: Congenital Rubella
isolate virus - urine, CSF, blood
maternal circulating IgG- lasts 6 months
 Detect fetal or neonate IgM
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Rubella: Control
live attentuated rubella vaccine
 mumps-measles-rubella
combination
subcutaneous
15 months of age
asymptomatic in children
mild symptoms in adults
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Rubella: Control Strategies
 10-20% young women not immunized
Therefore immunize
 college students
 health care personnel
 military personnel
 after childbirth, miscarriage or abortion
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USA data 4/13/2015
Alphavirus
Encephalitis
Sindbis
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Alphaviruses are arthropod borne
(arboviruses)
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Alphavirus: Structure
icosahedral 40-50 nm
enveloped
attachment glycoprotein
ss RNA, sense, monopartite
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Alphavirus: Classification
common envelope glycoprotein
common capsid antigenic sites
26 antigenic types
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Alphavirus: Multiplication
RNA is capped and polyadenylated
 serves as mRNA -> nonstructural proteins
sense RNA -> antisense RNA
Antisense RNA template for progeny RNA
antisense RNA--> mRNA -> structural
proteins
mature at intracytoplasmic membranes
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Subgenomic mRNA
sense strand -> antisense strand
3’ one-third of antisense strand -> mRNA
mRNA -> structural proteins
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Alphavirus: Clinical
manifestations
Encephalitis viruses
 fever,
malaise, headache and/or encephalitis
Arthritis viruses
 fever,
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rash, arthralgia, arthritis
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Alphavirus: Epidemiology
mosquito-vertebrate-mosquito cycles
geographically restricted
epizootics- Venezuelan equine enchephalitis
urban epidemics- chikungunya virus
seasonal
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Alphavirus: Diagnosis
clincal manifestations
known exposure
isolate virus
detect IgM
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Alphavirus: Control
reduce mosquito populations
vaccinate vertebrate hosts- horses
vaccine humans at high risk of exposure
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