A CASE REPORT

A 41-years old woman, suffering from fever and headache since three days, was admitted because of a tonic clonic seizure.

The patient had been complaining of chronic headache and

recurrent labialis herpes simplex. On admission physical examination revealed afebrile, able

to react to verbal stimulus and to localize pain, but confused when asked simple questions.

Routine laboratory blood analysis were normal. Brain computed tomography (CT) on admission showed

hyperintense lesion in the right parietal lobe without mass effect.

CSF analysis showed pleocytosis with WBC 100/cumm,

increased protein concentration, 88 mg/dl and glucose 48 mg/dl; smears for bacteria, fungi and mycobacteria were negative as well as cultures.

Later, based on clinical findings, CT and EEG pattern (focal right temporal alterations of cerebral activity), and PCR detection of HSV-1 DNA in the cerebrospinal fluid diagnosis of Herpes simplex encephalitis was made.

Acyclovir therapy (10 mg/kg 8 hourly) was administered for 21 days.

CSF analysis was performed again after two weeks and

revealed WBC 50/cumm, protein 55 mg/dl, glucose 54 mg/dl; cerebral images showed a reduction of hyperintense lesion in the right temporal lobe and disappearance of oedema in the frontal regions.

The patient was discharged with minimal cognitive

impairment of memory and speech.

VIRAL ENCEPHALITIS AND

ARBOVIRUSES CAUSING DISEASE OF NERVOUS

SYSTEM

Introduction

Causative agents

Pathogenesis in general

Clinical features in general

Laboratory diagnosis in general

Treatment and prevention

Introduction

Encephalitis: An inflammation of the brain characterized

sudden fever, headache, vomiting, photophobia, stiff neck

and back, confusion, impaired judgment, drowsiness, weak

muscles, clumsy and unsteady gait, and irritability.

Viral infection is the most common and important cause,

with over 100 viruses implicated worldwide.

Incidence of 3.5-7.4 per 100,000 persons per year.

Causative agents

Herpes viruses (HSV-1 & 2, VZV, EBV, CMV, herpes virus 6)

Adenoviruses

Influenza A

Enteroviruses, Poliovirus

Measles, mumps & rubella viruses

Rabies

Arboviruses :Japanese encephalitis, St. Louis encephalitis,

West Nile encephalitis virus, Eastern, Western and

Venezuelan equine encephalitis virus, Colorado tick fever.

Arenaviruses – Lymphocytic choriomeningitis virus

What is Arbovirus? Arboviruses = arthropod-borne viruses Arboviruses are maintained in nature through biological transmission between susceptible vertebrate hosts by blood-feeding arthropods Vertebrate infection occurs when the infected arthropod takes a blood meal

Family and Genus

Viruses causing Encephalitis Febrile illness Hemorrhagic fever

Togaviridae Alphavirus (mosquito borne)

Western and eastern equine encephalitis Venezuelan equine encephalitis

Chikungunya O’nyong-nyong Semliki forest Sindbis Ross river virus

Chikungunya

Flaviviridae Flavivirus Mosquito borne Tick-borne

St. Louis encephalitis West Nile Murray valley Japanese B Russian springsummer encephalitis

Dengue types 1-4 Dengue Yellow fever Kyasanur Forest disease Omsk hemorrhagic fever

Bunyaviridae a.Bunyavirus (mosquito-borne) b.Phlebovirus (Phlebotomus or mosquito-borne) c. Nairovirus (tick borne)

California encephalitis La Crossie

Chittor virus Sandfly fever Rift valley fever Nairobi sheepdisease Ganjam virus

Reovirus Orbivirus (Tick-borne)

Colorado tick Borne virus

Rhabdoviridae Vesiculovirus (mosquito borne, sandfly borne)

Vesicular stomatitis virus Chandipura virus

Major arboviruses that cause encephalitis

Flaviviridae

Japanese encephalitis

St. Louis encephalitis

West Nile

Togaviridae

Eastern equine encephalitis

Western equine encephalitis

Bunyaviridae

La Crosse encephalitis

http://www cdc gov/ncidod/dvbid/arbor/world

Properties of Arboviruses Property Alphavirus Flavivirus Bunyavirus Rhabdovirus Reovirus Symmetry Cubic Cubic Helical Bullet-shaped Cubic

Size (diameter in nm)

60-65 40-50 90-100 170X100 60-80

Nucleic Acid

ss-positive sense RNA

ss-positive sense RNA

ss-negative sense RNA

ss-negative sense RNA

ds-RNA

Pathogenesis of arboviruses in general The virus enters the body through the bite of the insect

vector. It multiplies in the reticuloendothelial system and

leads to viraemia.

The virus is than transported to the target organs, such as:

CNS in encephalitis

Capillary endothelium in hemorrhagic fevers

Liver in yellow fever.

Clinical features in general Arboviruses cause the following clinical syndromes such as:

Febrile illness with or without rash and arthralgia

Encephalitis

Hemorrhagic fever and systemic disease

Yellow fever.

Laboratory diagnosis of arboviruses in general Diagnosis is established by virus isolation or serology. Specimens Blood, CSF, brain specimen Serological tests

Haemagglutination inhibition, virus neutralization test, ELISA , complement fixation.

Detection of specific IgM antibody within 1-3 days after the onset of illness.

The detection of 4 fold or more rise in antibody titre provide a good evidence of infection.

Virus Isolation Inoculation intracerebrally into suckling mice causes

fatal encephalitis Tissue culture in vero, BHK-21 and mosquito cell lines

can be used for viral culture. Growth of the virus is detected by immunofluorescence,

haemagglutination inhibition, ELISA etc.

LABORATORY CRITERIA FOR CONFIRMATION: • Cerebrospinal fluid (CSF) isolation of the virus,

OR • A 4-fold change in serum antibodies to a specific virus (no arboviral),

OR • Antibodies to a specific virus present in CSF at a comparable or higher amount compared to serum antibodies

Japanese B encephalitis Structure and properties

Family: Flaviviridae Genus: Flavivirus Size: 40-50nm, Shape: Spherical icosahedral

capsid Lipid envelope, glycoprotein

peplomers & membrane protein Genome: ss-positive sense RNA. Four genotypes 1, 2, 3 and 4.

History of Japanese Encephalitis

• 1800s – recognized in Japan • 1924 – Japan epidemic. 6125 cases, 3797 deaths • 1935 – virus isolated in brain of Japanese patient who

died of encephalitis • 1938 – virus isolated from Culex mosquitoes in Japan • 1948 – Japan outbreak • 1949 – Korea outbreak • 1966 – China outbreak • Today – extremely prevalent in South East Asia. 30,000-

50,000 cases reported each year.

Widely distributed in Japan, China, Korea and south east Asia.

Distribution of Japanese Encephalitis

Have several extra human hosts: herons and egrets birds act as reservoir and pigs as amplifier hosts.

Mode of transmission

Culex tritaeniorhyncus: Habitat : Rice field (water logged) Water collection + submerged vegetation Pond with aquatic vegetations

Pathogenesis

The virus is transmitted by bite of mosquito (Culex tritaeniorhyncus)

Multiplication of the virus in reticuloendothelial system leading to viraemia (extraneural replication)

Invasion of CNS (cerebral cortex, thalamus, hippocampus, substantia niagra, globus pallidus, brain stem, cerebellum,spinal

cord and leptomeninges) leading to neuronal degeneration, necrosis and infiltration of inflammatory cells, with prominent perivascular accumulations (“cuffing”) of macrophages and

lymphocytes and parenchymal cellular nodules

Aseptic meningitis+ encephalitis

Clinical features I.P. 5-15 days 1. Prodromal stage: 1-6 days, fever, headache, malaise.

2. Acute encephalitic stage:

High Fever 38-40.7ºC Nuchal rigidity Focal CNS signs Characteristic attitude with head retracted and arms and knees bent and shoulders pressed to the chest, Convulsions and altered sensorium progressing to coma in many cases.

3. Late stage or sequelae:

Active inflammation subsides

Temperature and ESR normal

Neurological signs improve but residual neurological

deficits may persist (paralysis, Parkinsonism, mental

deterioration, psychiatric disorders and speech

difficulties).

Case fatality rate is 20-50%

Diagnosis 1. Isolation in mosquito cell line, mammalian cell line and

suckling mouse brain.

2. Serologic diagnosis: IgM capture ELISA which detects specific IgM in CSF and blood within 7 days of onset of disease. Paired sera taken in the first few days after onset and 2-3 weeks later will show rising antibody levels. IgG antibodies will cross react with other flaviviruses. 3. RT-PCR on early serum, CSF etc. 4. CSF- Pleocytosis and aseptic meningitis

IgM CAPTURE ASSAY

• SPECIFIC IgM Abs IN SERA : ACUTE INFECTION

• IgM Abs DEVELOP : BY 3RD- 4TH DAY

• NEGATIVE IN EARLY ADMISSION

IgM ELISA

Well coated with antigen

IgM antibody

HRP labeled anti-human IgM conjugate

TMB

JEV infected suckling mice: Day 10

(About to Die)

Newborn Swiss albino mice: Day 1

(Ready for virus isolation)

Prevention and Treatment A. Vaccines 1. Formalin inactivated mouse brain vaccine

using Nakayama strain: 2 doses in 2 weeks interval and booster dose 6-12 months later. Immunity is short lived. Inactivated(Biken) vaccine

2. The cell culture-derived inactivated JE vaccine based on the Beijing P-3 strain. Inactivated(Biken) vaccine

3. Live attenuated vaccine derived from baby hamster kidney cells from JE strain SA 14-14-2: 2 doses one year apart.

B. Mosquito Vector control: DDT, BHC, fenitrothion, malathion, sumithion (250ml/hectare spraying), larvicidal measures, use of mosquito repellants and nets.

Small species of Larvivorous fish: Top: desert killifish; middle; male guppy bottom: mosquito fish.