Final: Togaviridae Flashcards
Important Alphaviruses causing disease in Animals and also humans?
Eastern equine encephalitis virus
Western equine encephalitis virus
Highlands J virus
Venezuelan equine encephalitis virus
What are the equine viral encephalitis caused by alphaviruses
Western equine encephalitis virus (WEEV)
Eastern Equine Encephalitis (EEEV)
Venezuelan Equine Encephalitis (VEEV)
EEEV (eastern equine encephalitis virus)
Zoonotic disease transmitted by mosquitoes
Caused by a member of Alphavirus
Encephalitis in horses and humans
EEEV is enzootic where?
In eastern portions of North America, the Caribbean Basin, Central America, and along the northern and eastern coasts of South America
Where are the cases of EEEV in North America and when do they occur?
From the eastern and gulf coast as far as to inland sites (Texas)
Late summer and early fall, often associated with heavy rainfall
EEEV transmission cycle is maintained between passerine birds as _________/_______ hoses and Culiseta melanura as the main enzootic vector in swamp habitats.
Reservoirs;amplification
T/F: Rodents and reptiles have been found to serve as reservoirs of EEEV
True
(EEEV) Passerine birds develop high levels of _____, enough to infect enzootic ______ as well as a variety of bridge vectors.
Viremia; vectors
T/F: Humans and equines are dead-end hosts of EEEV since they do not develop sufficient viremia to transmit the virus
True
T/F: birds are able to spread EEEV if they peck or eat diseased pen mates in captivity
True
Pathogenesis of EEEV
Virus enters CNS through hematogenous route -> viral replication occurs in neurons, vascular endothelial cells and glial cells -> apoptosis of neuronal and glial cells; lesions in gray matter of cerebral cortex, thalamus, hypothalamus -> non-suppurative encephalomyelitis
Clinical signs of EEEV in horses
Hypersensitivity to sound
Periods of colic before neurological disease
Walk blindly into objects or walk in circles
Involuntary muscle mvmts (facial or should muscle tremors)
Stage of paralysis follows: inability to hold up head, head pressing or leaning back, incoordination or unnatural postures, complete paralysis
What can the horses be put in that have EEEV?
Stabilizing restraints to prevent collapse
What are the 2 forms of EEE in humans?
Systemic form: fever, malaise, arthralgia, myalgia, no CNS involvement
Encephalitic form: fever, headache, irritability, anorexia, vomiting, diarrhea, cyanosis, convulsions, coma
What is the prognosis of EEE in humans?
~1/3 of all people with EEE die
Recovered patients may suffer from permanent brain damage
T/F: Western Equine Encephalitis Virus (WEEV) is believed to have emerged from genetic recombination of an ancestral Eastern equine encephalitis virus-like virus and an ancestral Sindbis-like alphavirus
True
T/F:Epidemiological studies have shown that WEEV occurs throughout most of the Americas from the western half of North to South America
True
T/F: both the epizootic and enzootic strains of WEEV have not been identified
False, they have been ID
Epizootic North America strains are more virulent than strains that are enzootic in South America
WEEV has a high/low fatality rate in humans compared to EEEV
Low
WEEV appears to the more/less virulent than EEEV in horses
Less
T/F: epidemics of WEEV are less common, but sporadic individual cases are not
True
What are the primary amplifying hosts for WEEV?
House sparrows and house finches
What are the secondary amplifying hosts for WEEV?
Rodents, mainly black tailed jack rabbits and prairie dogs
What is the primary (enzootic) cycle of WEEV?
Between mosquitoes and birds (primary reservoirs) -> mosquitoes give to dead-end hosts (humans and horses)
What is the secondary (epizootic) cycle of WEEV?
Between mosquitos and rodents -> mosquitos give to dead end hosts
T/F: clinical signs of WEEV are the same as EEEV
True
VEEV is classified into how many antigenic subtypes?
6
What are the VEEV subtypes in the epizootic/endemic cycle? How pathogenic are they?
I-A
I-B
I-C
Highly virulent for equines
What are the subtypes of VEEV in the enzootic/endemic cycle? How pathogenic are they?
I-D I-E I-F II III IV V VI
Not virulent or virulence unknown for horses
Who is involved in the enzootic cycle of VEEV (Venezuelan Equine Encephalitis Virus)?
Between two species of mosquitos (primary vector) and rodents (amplifying hosts) -> mosquitos give to accidental or dead end hosts (human and horses)
Who is involved in the epizootic cycle of VEEV?
Between mosquitos (primary vector) and horses (amplifying hosts) -> mosquitos give it to dead-end hosts (humans)
What are the clinical signs of VEEV in horses?
Non-suppurative encephalomyelitis
Clinical signs of VEEV in humans
Normally acute, mild, systemic disease
May include headache, chills, coughing, vomiting, diarrhea, fever, myalgia, symptoms of encephalitis
In pregnant women, may cause placental damage, fetal encephalitis, abortion/stillbirth,congenital disease
Vaccination for horses against equine encephalitis
Formalin inactivated EEEV and WEEV vax are available as univalent or bivalent preparations in combo with other antigens (tetanus)
For VEEV, a tissue culture attenuated vaccine, made with a strain TC-83, is available
Vaccination for humans
No licensed vaccine against EEEV or WEEV
No licensed human VEEV vax, but TC-83 live-attenuated vax is used for lab workers and military personnel
The enzootic cycle of Venezuelan Equine Encephalitis Virus is primarily maintained between _____ and ____
Rodents and mosquitos
T/F: Western Equine Encephalitis Virus is believed to have emerged from genetic recombination of an ancestral Eastern equine encephalitis virus-like virus and ancestral Venezuelan equine encephalitis virus-like virus
False
