CNS Infections- Viral Encephalitis

Question 1

During encephalitis, viral replication occurs in ______, leading to severe CNS dysfunction which causes manifestations.

Answer 1

brain parenchyma

Question 2

The brain is not a ____ for viral infection. Infections in the CNS are usually a secondary infections, occurring weeks, months, years after the initial infection.

Answer 2

POE

Question 3

Few survive viral encephalitis, and those who do have ___________

Answer 3

serious emotional disorders and learning deficits

Question 4

The most frequent etiologic agents are

Answer 4

1. Arboviruses

2. Herpes simplex virus-1 (HSV-1)

Question 5

The etiologic agents that can cause BOTH focal and diffuse encephalitis:

Answer 5

1. Non-polio enterovirus
2. Herpes simplex virus 1 (HSV-1)
3. Arbovirus

Question 6

The etiologic agents of FOCAL encephalitis only:

Answer 6

rarely polio virus or rabies

Question 7

Describe Arbovirus

Answer 7

1. Arthropod-borne viruses (arboviruses)
2. Zoonotic agents
3. Association with chronic infection in the reservoir host.
4. Humans are generally the dead end host.
5. Disease in the reservoir, if it occurs, is similar to human disease if POE is same

Question 8

Togaviridae group comprises most arthropod-borne viruses and Rubella, also includes:

Answer 8

Alphavirus and Flavivirus

Question 9

Alphavirus includes

Answer 9

1. Eastern equine encephalitis (EEE) is caused by EEEVirus.
2. Western equine encephalitis (WEE) is caused by WEEVirus.
3. Venezuelan equine encephalitis (VEE) is caused by VEEVirus.
   * *equine viruses**

Question 10

Flavivirus (flavi = Latin for yellow, includes yellow fever, dengue, hepatitis C agents, also Japanese encephalitis virus and Nipah virus which are an important disease agents in Asia; includes:

Answer 10

1. St. Louis encephalitis (SLE) is caused by SLEVirus.
2. West Nile Encephalitis (WNE) is caused by WNVirus.
3. Powassan encephalitis (POW) is caused by POWVirus

Question 11

Bunyaviridae - bunyavirus includes:

Answer 11

1. California virus
2. Jamestown canyon virus
3. La Cross viruses (LAC) virus

(called the California encephalitis group, highest incidence in California, Midwest and southeast US)

Question 12

Reoviridae group (respiratory, enteric orphans) includes:

Answer 12

1. Rotaviruses

2. Coltiviruses–> Colorado tick fever is caused by CTFVirus (rare in US)

Question 13

Arboviruses cause two primary syndromes in humans:

Answer 13

1. hemorrhagic fever

2. encephalitis/meningitis

Question 14

Arboviruses are the primary cause of _________, but also cause _________.

Answer 14

epidemic encephalitis

benign, aseptic meningitis

Question 15

Seasonality

Answer 15

summer months when humans are outdoors.

Question 16

Vectors are primarily

Answer 16

mosquitoes and ticks

• Colorado tick fever and Powassan fever virus are spread by ticks
• The rest of the arboviruses are spread by mosquitoes

Question 17

Reservoir

Answer 17

Zoonosis (many animals, but primarily birds and small mammals in US)

Survival of virus by alternating between vertebrate host (reservoir) and arthropod host (vector)

Question 18

Primary virus replication (viremia) occurs with each arbovirus having specific target cells, such as endothelial cells of the capillaries, macrophages, monocytes, erythrocytes, and the reticuloendothelial system (liver, spleen, lymph nodes) → symptoms are _________

Answer 18

either no or mild symptoms

Question 19

A second round of replication in reticuloendothelial cells can occur immediately after the primary round, producing a second viremia, which may yield sufficient virus to attack___________, depending upon the specific virus → symptoms are __________

Answer 19

brain, liver, skin, vasculature, kidney

symptoms are severe

Question 20

In humans, during the first and second rounds of replication, the viremia is usually low, resulting in mostly ______________

Answer 20

asymptomatic infections and humans being incidental hosts.

Asymptomatic infections are the most common*

Question 21

S/S

Answer 21

Mild, self-limiting flu-like illness (1 of 5 persons infected) lasting about 1 week, URT symptoms (coryza), fever, chills, sore throat, headache, nausea, vomiting, muscle weakness &/or myalgias, arthralgias, maculopapular rash.

Question 22

CNS disease may manifest as

Answer 22

1. Mild, self-limiting aseptic meningitis.
2. acute, fulminant, diffuse, encephalitis (can be focal) and death.
3. +/- acute flaccid paralysis

will see signs of meningoencephalitis: lethargy, irritability, drowsiness, acute flaccid paralysis, seizures, may evolve into coma, then death due to immunopathology (brain edema) and/or myocarditis

Question 23

Differential

Answer 23

1. Arboviruses
   2. enteroviruses
   3. herpes viruses.
   4. rabies virus (dumb rabies)

Question 24

CSF sample will show

Answer 24

protein and glucose levels as per viral infection and mononuclear pleocytosis.

Question 25

Treatment/Prevention

Answer 25

Treatment is supportive Prevention goal: limiting the vector population US military has human vaccines for Eastern Equine Encephalitis and Western Equine Encephalitis

Question 26

Eastern Equine Encephalitis (EEE):

Answer 26

- vectors are mosquitos - This disease has worst mortality rate; survivors are more likely to manifest with serious neurological sequelae * *Of all arbovirus agents of encephalitis, EEEV is unique in that infection often (not always) causes EEE. Asymptomatic infection is NOT the norm!!**

Question 27

Western Equine Encephalitis (WEE):

Answer 27

- vectors are mosquitos - rural residence is highest risk factor * **Most benign form of encephalitis***

Question 28

St. Louis Encephalitis (SEE):

Answer 28

- vectors are mosquitos - Midwest - Leading cause of epidemic arboviral encephalitis in US before West Nile Virus epidemic in 2002

Question 29

West Nile Encephalitis (WNE): | IMPORTANT

Answer 29

- Closely related to St. Louis encephalitis (cross-reacts serologically with SLE) * *Most common arbovirus infection in the US today**

Question 30

Transmission of west nile besides mosquitoes

Answer 30

1. Transfusions (4 cases) 2. in utero 3. case of a women with WNE passed infection to child via breast milk 4. Organ transplants

Question 31

S&S of WNE

Answer 31

- flu-like symptoms (moderate to high fever or chills, anorexia, malaise, muscle aches, joint pain, respiratory symptoms) - nausea, vomiting, diarrhea - maculopapular rash spreading from the trunk to head and limbs - frontal headaches of >7days duration - eye pain

Question 32

West Nile Encephalitis is West Nile fever with S/S of one or more of the following

Answer 32

1. meningitis 2. encephalitis 3. parkinsonism – tremors (obviously not in limb(s) with flaccid paralysis) 4. Focal symptoms of muscle weakness/ascending, asymmetrical diffuse flaccid paralysis: - diminished deep-tendon reflexes/areflexic leg weakness, - EMG velocity studies demonstrate axonal-type polyneuropathy affecting anterior horn cells or their axons vs. demyelination - No muscle or sensory pain/loss is noted

Question 33

Treatment for WNE

Answer 33

Ribavirin is efficacious in vitro (in cell culture) studies

Question 34

During WNE in CSF you'll see

Answer 34

plasma cells

Question 35

California (CAL) Encephalitis Serogroup

Answer 35

- La Cross (LAC; Midwestern, Southeastern US) is the most important cause of arboviral pediatric encephalitis in the USA - Jamestown canyon and other CAL groups rarely cause disease in humans - Seizures may occur during illness, some patients who recover from illness will experience seizures as sequelae