Viruses 2.5 - Viral Encephalitis, Etc. - KMS Flashcards
What is the reservoir for Eastern Equinie encephalitis?
Eastern equine virus (alphavirus)
Enveloped +ssRNA
Reservoir: birds
What is the reservoir for Western Equine virus?
Western equine virus (alphavirus)
Enveloped +ssRNA
reservoir = birds
What is the reservoir for St. Louis encephalitis?
St Louis encephalitis virus (flavivirus)
Enveloped +ssRNA
reservoir: birds
What is the reservoir for WNV?
West Nile virus (flavivirus)
Enveloped, +ssRNA
reservoir: birds
What is the reservoir for Dengue virus?
Dengue virus (flavivirus)
Enveloped +ssRNA
reservoir: mosquitos
What is the clinical presentation for EEV?
Eastern Equine Encephalitis-Severe, rapid progression
What is the clinical presentation for WEV?
Western Equine Encephalitis - Classic encephalitis
What is the clinical presentation for St. Louis encephalitis?
St Louis encephalitis -SIADH
What is the clinical presentation for WNV?
Motor or brainstem involvement
What is the clinical presentation for Dengue virus?
Flulike syndrome; possible CNS involvement
What is the clinical presentation of Colorado Tick fever virus?
Headache behind eyes, photophobia,
rash, skin pain, sweating
Name an additional 7 entities that can cause encephalitis.
- HSV
- VXV
- Orthomyxovirus/influenza
- Enterovirus/picornavirus
- Rabies virus/rhabdovirus
- Mumps virus/paramyxovirus
- Measles virus/paramyxovirus
What is the mortality of HSV encephalitis?
70%
What are the specific clinical patterns and sequelae of HSV viral encephalitis?
Subacute, psychiatric, recurrent meningitis
Sequelae: Common
What is the mortality of VZV encephalitis?
variable
What are the specific clinical patterns and sequelae of VZV viral encephalitis?
Rash, encephalitis in 0.1-0.2% of children
Sequelae: adults worse
What is the mortality of influenza virus/orthomyxoviridae viral encephalitis?
Unknown
What are the specific clinical patterns and sequelae of influenza virus/orthomyxovirus viral encephalitis?
Guillain-Barré, myelitis
Sequelae: Parkinsonism
What is the mortality rate of enterovirus/picornavirus viral encephalitis?
Low; high for enterovirus 71
What are the specific clinical patterns and sequelae associated with enterovirus/picornavirus viral encephalitis?
Herpangina; hand, foot, mouth disease; enterovirus 71 causes rhombencephalitis
Sequelae: mild, except for enterovirus 71
What is the mortality rate of rabies virus/rhabdovirus viral encephalitis?
Virtually 100%
What are the specific clinical patterns and sequelae associated with rabies virus/rhabdovirus viral encephalitis?
Paresthesias; confusion, spasms, hydrophobia; brainstem features
Sequelae: death
What is the mortality rate of mumps virus/paramyxovirus viral encephalitis? Measles virus?
Both are low
What are the specific clinical patterns and sequelae associated with Mumps virus/paramyxoviridae viral encephalitis?
Parotitis, pancreatitis, orchitis, aseptic meningitis
Sequelae: frequent
What are the specific clinical patterns and sequelae associated with Measles virus/paramyxoviridae viral encephalitis?
Characteristic rash; myelitis
Sequelae: Frequent: mental retardation, seizures
Arboviruses are generally borne by what?
Arthropods, AKA mosquitos
“Arbovirus” is sort of an acronym: ARthropod BOrne virus
What are the 3 viral families are associated with Arboviruses?
Togaviridae
Flaviviridae
Bunyaviridae
What diseases are associated with the family Togaviridae?
- Togaviradae (enveloped +ssRNA)
- WEE, EEE, VEE encephalitis, chikungunya & rubella
What diseases are associated with the family Flaviviridae?
- Flaviviradae (enveloped +ssRNA)
- Yellow and dengue fevers, St. Louis and Japanese encephalitis, West Nile virus, hepatitis C
What diseases are associated with the family Bunyaviridae?
- Bunyaviradae (enveloped -ssRNA)
- California encephalitis, Rift Valley fever, hantavirus
What is the genetic makeup of togaviruses?
•Enveloped and +ssRNA (25 types are human pathogens)
What is the reservoir for togaviruses?
•Virus alternates between vertebrates and arthropod vectors (mosquitos for the viruses below)
What virus genuses are associated with the togavirus family?
Alphavirus
Rubivirus
Flavivirus
Bunyaviruses
What is the reservoir associated with alphaviruses?
•Associated with birds and horses and their mosquitoes
What 3 diseases are associated with alphaviruses?
Chikungunya
Eastern and Western Equine encephalitis (EEE, WEE)
Venezuelan Equine Encephalitis (VEE)
What is the clinical presentation of Chikungunya?
1.Chikungunya: get viremia with acute febrile illness with malaise, rash and arthritis
What is the clinical presentation of EEE or WEE?
What about VEE?
1.Eastern and western equine encephalitis (EEE, WEE): get viremia (often asymptomatic)and then may invade neural tissue to cause encephalitis
1.Venezuelan equine encephalitis (VEE): get viremia with systemic manifestations (less neural involvement)
Rubivirus is associated with what?
Rubivirus (no arthropod vector) – rubella (German measles)
Congenital rubella (TORCH syndrome)
Flaviviruses are associated with what diseases?
Flaviviruses (more to follow)
•Yellow fever virus, Dengue virus, St. Louis encephalitis, Japanese encephalitis, West Nile virus, hepatitis C virus
Bunyaviruses are associated with what diseases?
Bunyaviruses
•California encephalitis, Rift Valley fever, pappataci (sandfly) fever, hantavirus pulmonary syndrome (more in emerging pathogens slides)
What is the genetic makeup of the rubella virus?
Togavirus-enveloped +ssRNA
How are rubiviruses spread?
•Enters via the respiratory route infecting respiratory tract and viremia follows
What 2 diseases are associated with rubiviruses?
German measles
Congenital Rubella Syndrome
What is the clinical presentation of German measles?
- German measles was a common, usually mild, self limiting (3 days) pediatric disease with a rash
- In adults have severe manifestations
What is the clinical presentation of congenital rubella syndrome?
- Congenital rubella syndrome affects the eyes, heart and brain
- Infection occurred during 1st trimester of pregnancy
What is the treatment and Dx for rubella infection?
- Rx- supportive
- Dx- clinical; 14-20 day incubation period (“prodrome”) followed by rash
- IgM or rising IgG against rubella
What is the prevention for rubella infection?
•Prevention - immunize with MMR live vaccine at 12-15 months and 4-6 years and non-immunized women of childbearing age
What is the clinical presentation for Dengue fever?
1.Dengue fever: virus replicates in the skin and then goes to lymphoid tissue followed by a viremia which results in fever and rash lasting 3-9 days (self-limited) but can get dengue hemorrhagic fever (immunopathologic processes produce extreme vascular permeability, shock and death and associated with serotype 2)
What is the clinical presentation for yellow fever?
1.Yellow fever: viremia with severe systemic disease (fever, headache, nausea and vomiting) followed by liver damage and intestinal hemorrhages (jaundice, shock and death)
How are flavivirus infections diagnosed and prevented?
•Dx: Symptoms and epidemiology, isolate the virus from blood or serology
•
Prevention: live vaccine against yellow fever and killed vaccines against EEE and WEE
Flaviviruses are associated with what vectors?
- Usually virus alternates between vertebrates and arthropod vectors (mosquitos for infections below)[hepatitis C virus discussed with hepatitis viruses]
- associated with birds/bird-feeding mosquitoes (SLE and WNE) and humans/human feeding mosquitos (yellow fever and Dengue fever)
What is the clinical presentation for St. Louis Encephalitis?
1.St. Louis encephalitis (SLE): viremia (usually asymptomatic), in some CNS involvement causes encephalitis inflammation and neuronal degeneration
What is the clinical presentation for West Nile Encephalitis?
1.West Nile encephalitis (WNE): viremia (usually asymptomatic), mild, flu-like cases (“West Nile fever“), more severe “West Nile encephalitis” or “West Nile meningitis” which can lead to death
Picornaviruses include what 3 clinically relevant viral entities?
Hepadnavirus
Rhinovirus
Enterovirus
Rhinoviruses includes over 100 serotypes. How are these viruses spread, how do they infect tissue, and what disease do they cause?
Rhinoviruses (100 serotypes)
•Infection occurs person to person via the nasopharynx
•Attach via ICAM-1 receptor to respiratory epithelial cells
•Cause common cold
What is the Dx and Rx for rhinoviruses?
- Dx – clinical symptoms
- Rx – supportive
Enteroviruses include what important viruses?
(Poliovirus, Coxsackievirus, Echovirus, etc.)
How are enteroviruses spread?
•Spread via the fecal-oral route to enter via the intestinal tract and attach to receptors on intestinal epithelia
•Spread into the lymphatic circulation (lymphatic phase)
Then to the bloodstream (viremic phase)
Enteroviruses can affect the GI system. What else can they affect?
- +/- occasional neurologic phase
- Enterovirus 68 may be cause of flaccid paralysis
Where are enteroviruses found? When do most illnesses occur?
•Found worldwide Most illnesses occur in the summer and fall.
What is the Dx and Rx of enteroviruses?
- Dx. recovery of enterovirus from the throat or feces is diagnostic
- Virus may be in throat for a week and shed in the feces for several weeks
- Rx – supportive
How are polioviruses spread?
Polioviruses (3 serotypes)
•Adsorb to intestinal epithelial cells and motor neuron cells of the central nervous system
What is the clinical presentation of polioviruses?
- 90-95% of infections are subclinical
- 4-8% present with a mild fever, sore throat and headache.
- 1% get nonparalytic polio
- 0.1% get paralytic disease-bulbar polio (brainstem) or spinal polio (motor neurons)
How is poliovirus infection Dx’ed?
•Dx – culture, PCR or serology, Cowdry type B intranuclear inclusions
How is poliovirus infection prevented?
•Prevention-
Inactive (Salk vaccine) - trivalent (types 1, 2 and 3), injection at 2,4,6-18 months and at 4-6 years or oral
Sabin vaccine - attenuated, live, trivalent, produces intestinal IgA but has rare vaccine-associated paralysis (not currently recommended by CDC)
What is the common clinical presentation for Coxsackie virus?
•All cause febrile illness, rashes, upper respiratory tract disease, and aseptic meningitis
What is the clinical presentation for Coxsackie virus Group A?
•Group A - herpangina, acute hemorrhagic conjunctivitis & hand-foot-and-mouth disease
What is the clinical presentation for Coxsackie virus type B?
•Group B - pleurodynia, myocarditis, pericarditis, and hepatitis
What is the clinical presentation of an Echovirus?
Echoviruses (31 serotypes)
•Enteric Cytopathogenic Human Orphan viruses with Produce respiratory disease, febrile illness (with or without a rash), aseptic meningitis and paralytic disease
What is the genetic makeup of a Rhabdovirus?
•Rhabdovirus: bullet-shaped; -ssRNA genome with envelope (very stable to drying)
How are rhabdoviruses spread?
•Introduced through a bite wound or having a cut or sore exposed to the saliva of an live or dead infected animal, replicates at the site and then infects central nervous system tissue (encephalitis) via acetylcholine receptor with retrograde axoplasmic transport to dorsal root ganglia and spinal cord
What histological findings are associated with rhabdovirus infection?
•Neurons accumulate ribonucleoprotein as intracytoplasmic inclusions (Negri bodies)
What is the reservoir of rhabdoviruses?
- Rabies can be found in domestic and wild animals (dogs, cats, cattle, bats, foxes, skunks, raccoons)
- Airborne transmission in spaces heavily infested with bats
What are the symptoms of rabies?
- Rabies - fever, excitation, dilation of the pupils, excessive lacrimation, salivation, anxiety, hydrophobia and death
- Once symptomatic death is almost certain despite optimal supportive care
How is rabies Dx’ed?
- Dx- History of animal bite and symptoms of encephalitis
- Direct immunofluorescence of rabies virus antigen (dFA)
How is rabies treated?
- Rx- immunization against rabies within 2 days of exposure and rigorous cleansing of a bite wound (can potentially prevent infection by decreasing viral load)
- 4 vaccine doses in combination with rabies immune globulin (RIG)
- Only about half of those bitten by an infected animal actually acquire disease
How is rabies prevented?
•Prevention- vaccines for dogs and cats