Arboviruses Flashcards
classification of arboviruses and characteristics of each
1- Togavirus: icosahedral nucleocapsid enveloped with + ssRNA
2- Flavivirus: icosahedral nucleocapsid enveloped with + ssRNA
3-Bunyavirus: helical nucleocapsid enveloped with - ssRNA with 3 circular segments called L, M and S
Transmission of arboviruses and extrinsic incubation and intrinsic incubation
the virus must be present in the bloodsucking vector and viremia has to be high in the host to be taken by the insect and after ingestion it replicates in the gut of the insect and then spread to another organ
Extrinsic incubation period is the obligatory length of time that must pass before the virus has replicated for the saliva of the vector to transmit it and it is usually 7-14 days.
Intrinsic incubation period is the interval between the bite and onset of symptoms
West Nile Virus properties
most common cause of neuroinvasive arboviral disease and highest number of death due to mosquitoborne encephalitis
follows Flavivirus group and has same antigenic group as SLE virus
Wild birds are the man resovoir which is transmitted by mosquitoes especially Culex species adn humans are dead end host
transmitted also from solid organ transplant
- Encephalitis w/ or w/o meningitis , fever and headache w/o enchaplitis and 80% is aysmptomatic
Lab diagonisis for WNV
detecting IgM in spinal fluid and blood
PCR
no antiviral therapy or vaccine
Eastern Equine Encephalitis Virus
EEE virus is causes the Most severe disease and highest fatality rate (50%) the virus is transmitted by swamp mosquito Culiseta among wild birds and wild birds reservoir to the principal dead end hosts horses and humans.
Encephalitis is charchaterized by sudden osnet severe headache, nausea, vomiting, fever and cahnge in mental status and rapid progressive downhill course with nuchal rigidity seizures and coma.
it has poor CNS sequelae and severe
diagnosis made by isolating the virus or demonstrating rise in ab titer
Western Equine Encepalitis Virus
more frequent but less sever than EEE virus, transmitted by culex mosquitoes among the wild bird and diagnosis by isolating the virus or observing rise in ab titer
St. Louis encephalitis Virus
causes disease on a wider geographic area
transmitted by culex mosquitoes and small birds specially english sparrows and human are deadend host
is an Urban Virus because msoquitoes prefer to breed on stagnant wastewater
causes moderately severe encephalitis with fatality rate of 10%
diagnosis by serologic testq
California Encephalitis Virus
from mosquitoes in californa
causes La Crosse encephalitis and is one of the four major encephalitis viruses in USA and is member of Bunyavirus
Transmitted by mosquito Aedes Triseriatus among forest rodents and virus is transmitted transovirally in msoquitoes
causes enteroviral meningiits or severe resembling herpes encephalitis
diagnosis y serlogic test
Colorado Tick Fever Virus
CTF is reovirus transmitted by wood tick among small rodents
mostly occurs to hikers and cause fever, headache, retroorbital pain and severe myalgia and diganosis is made by isolation of virus or detecting rise in ab titer
Yellow Fever Virus
Flavivirus with one serotype and mostly is aympotmatic
occurs in tropical regions
causes Jaundice and fever and sudden onset of fever, headache, myalagias and photophobia in sever cases
and symptoms progress to involve liver, kidney and heart and prostratation occur and shock accompained with GIT hemorrhage with Hematemesis ( black vomit)
types of yellow fever virus
1- Jungle Yellow Fever disease of monkey and transmitted by msoquitoes and monkeys are permanent host and huamns are accidental host
2- Urban Yellow fever is disease of humans transmitted by Aedes aegypti mosquito, intrinisc period is 3 to 6 days and diagnosis is made by PCR for IgM or rise in IgG
has high mortality rate and prevention is by live atteunated YFV and lasts for 10 years
