Epidemic Encephalitis B Epidemic Encephalitis B Dept. Of Infectious Disease Shengjing Hospital CMU.

Epidemic Encephalitis BEpidemic Encephalitis B

Dept. Of Infectious Disease

Shengjing Hospital

CMU

DefinitionDefinition

Epidemic encephalitis B is acute infectious disease caused by encephalitis B virus,usually occurs in summer &fall.The virus is transmitted by mosquito.

Pathologic lesions: cerebral parenchymaClinical feature: high fever altered consciousness convulsion meningeal irritation respiratory failure

EtiologyEtiology

Causative agent: encephalitis B virus

genus flavivirus of flaviviridae

single strain of positive-sense RNA,

virion is spheric, diameter: 15 ~ 22nm,

Resistance: unstable in environment, Sensitive to heat, disinfectants, ultraviolet rays

EtiologyEtiology

antigenicity: stable hemagglutination inhibiting Ab complement fixing Ab neutralizing Ab

EpidemiologyEpidemiologySource of infection domestic animals: pig, horse, dog poultry: chicken, duck, goose. patients:

EpidemiologyEpidemiology Route of transmission insect borne: mosquito biting , vector: mosquito, culex tritaeniorhynchus.

Survived winter mosquitoes

pigs

mosquitoes mosquitoes person

pigs

EpidemiologyEpidemiology

Susceptibility of population: universal susceptible lifelong immunity subclinical infection : overt infection

1000~2000:1

EpidemiologyEpidemiology

Epidemiologic features sporadic from July to Sep. children under 10yrs (2~6yrs) hypersporadic property

PathogenesisPathogenesis

virusmosquito biting

replication in mononuclear-phagocyte system (MPS)

onset of illness

CNS

blood streamblood-brain barrier

brief viremia

subclinical inf.

clearance

No. of virus of invasion

cellular immunity

blood brain barrier

PathologyPathology

Place of lesion: all of CNS cerebral cortex, midbrain and thalamus .

Pathologic features gross examination:

congestion hemorrhage cerebral edema soften focuses

PathologyPathology

microscopic examination: vascular lesion: endothelial cells swelling,

necrosis neuron degeneration & necrosis neurogliocyte hyperplasia & inflammatory cells

infiltration,

perivascular cuffing ,

neuronophagia.

Clinical manifestationClinical manifestation

incubation period:10~14 days (4~21days ) typical encephalitis B

Initial period crisis period convalescent period sequela period


Initial period : on the 1st to 3rd days abrupt onset fever with headache , nausea, vomiting lethargy, abdominal pain , diarrhea,


Crisis period- on the 4th ~10th days

high fever: >40 , sustained for 7~10 days.℃ altered consciousness: lethargy, confusion, delirium, stupor, semicoma, co

ma. convulsion or twitch:(40~60%) respiratory failure: 15~40%


central RF: • reason of central RF:

• lesion of cerebral parenchyma (respiratory center injury in oblongata medulla)

• cerebral edema

• brain hernia

• intracranial hypertension

• hyponatremic encephalopathy


• manifestation of central RF:

• cacorhythmic breathing

(cheyne-stokes breathing, apnea)

• brain hernia

peripheral RF:

• dyspnea, regular breathing


Other symptoms & signs of CNS

meningeal irritations (neck stiffness

Kernigs & Brudzinskis signs positive)

Deep tendon reflexes from hyperactive to disappe

ar

pathologic reflexes positive

limbs paralysis


Convalescent period

T drop to normal in 2~5 days

neurologic function regain gradually(2W)

remain some behavioral & psychologic abnormalit

ies,

aphasia, dementia, rigidity paralysis.

>6month - sequela


Sequela period aphasia

dementia

persistent paralysis


Clinical type:

mild type

common type

severe type

fulminant type


T AC CV RF DC SQ

mild <39℃ lethargy - - 5~7d -

common 39~40 ℃ semicoma ± - 10d -

severe 40~41 ℃ coma + ± >2W

+

fulminant >41℃ deep coma + + death +

Laboratory FindingsLaboratory Findings

Blood picture: WBC 10~20×109 /L

neutrophil >80%

Cerebrospinal fluid - aseptic meningitis

transparent or slightly cloudy,

pressure may be elevated

pleocytosis: 50~500×106/L

protein may be elevated mildly

glucose and chloride are normal


Serological test: specific IgM Ab: blood or CSF,

3~4d after onset, peak on 2 week

ELISA or indirect immunofluorescence complement fixing Ab:

2 week after onset, peak on 5~6 week,

anamnestic diagnosis

epidemiologic investigation


hemagglutination inhibition Ab:

5d after onset, peak on 2 week

diagnosis: 4 fold increase in titer


neutralized Ab



pathogenic test virus isolation: blood, CSF, brain tissue

RT-PCR : RNA

DiagnosisDiagnosisEpidemiological data:

7~9 month

<10yrs

Clinical manifestation:

fever, headache, vomiting, altered consciousness,

convulsion, meningeal irritation, pathologic

reflexes positive.

Laboratory findings:WBC, CSF, IgM

Differential DiagnosisDifferential Diagnosis

toxic bacillary dysentery

high fever,convulsion,coma.

<24h

circulatory failure: early

stool examination: WBC, RBC

CSF: normal

meningeal irritation: negative

Differential DiagnosisDifferential Diagnosis

tuberculous meningitis

CSF, meningeal irritation

purulent meningitis

other viral encephalitis

TreatmentTreatment

General therapy:

Isolation:

preventing mosquito biting, T<30℃

nursing: mouth, skin, eye,

turn over

clapping back

sputum aspiration

TreatmentTreatment

fluid & electrolyte supplementation

adult: 1500~2000ml/d

children: 50~80ml/kg/d

Symptomatic therapy high fever: T<38℃

TreatmentTreatment physical cooling

(ice bag, alcohol bathing, cold saline enema)

drug cooling

antipyretic

subhibernation:

chlorpromazine 0.5~1mg/kg/time

phenergan 0.5~1mg/kg/time

4~6h, 3~5day

TreatmentTreatment convulsion:

fever: cooling

brain edema: 20% mannitol 1~2g/kg/time

50% glucose

dexamethason

TreatmentTreatmentsedative:

valium: adult:10~20mg/time

children: 0.1~0.3mg/ kg/ time

10% chloral hydrate:

adult:1~2g/time

children: 60~80mg/kg/time

subhibernation:

TreatmentTreatment respiratory failure:

keep airway clear• sputum aspiration• turn over , clapping back, postural drainage• aerosolization• inhalation of oxygen

TreatmentTreatment reducing cerebral edema & hernia

dehydrate :

20% mannitol :1~2g/kg/time

50% glucose , vasodilator:

654-2: adult: 20mg/time

children: 0.5~1mg/kg/time

10~30 min

TreatmentTreatment respiratory stimulant:

lobeline: adult: 3~9mg/time

children: 0.15~0.2mg/kg/time

coramine: adult: 0.375~0.75g/time

children: 5~10mg/kg/time

tracheal intubation or tracheotomy, biomotor

TreatmentTreatmentConvalescent & sequela period

acupuncture massage exercise etc.

PreventionPrevention

isolating patients and pig immunization,

killing mosquito and preventing mosquito ,

vaccination:

killed virus vaccine: 60~90%

病例分析病例分析

5 岁患儿， 8月 15 日开始发热头痛，呕吐一次，次日排稀便两次，精神不振，第三天晚间开始抽搐，神志不清。查体，T40℃，急病容，脉充实有力，呼吸略促，节律整，皮肤无瘀点、瘀斑，颈强 (+) ，克氏征 (+) ，肢体肌张力增强。辅助检查：

病例分析病例分析

血 WBC 15×109／ L，便常规 WBC 0 ～ 5个／ Hp ， CSF 细胞数 75×106／ L，糖3.5mmol/L, 氯化物 115mmol/L ，蛋白 0.45g/L

哪种诊断可能性大 ? 提供诊断依据及主要鉴别诊断治疗要点

Epidemic Encephalitis B Epidemic Encephalitis B Dept. Of Infectious Disease Shengjing Hospital CMU.

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