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

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epidemic encephalitis b

Epidemic Encephalitis B

Dept. Of Infectious Disease

Shengjing Hospital

CMU

definition
Definition
  • 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 parenchyma
  • Clinical feature:highfever
  • altered consciousness
  • convulsion
  • meningeal irritation
  • respiratory failure
etiology
Etiology
  • 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
etiology1
Etiology
  • antigenicity: stable
      • hemagglutination inhibiting Ab
      • complement fixing Ab
      • neutralizing Ab
epidemiology
Epidemiology
  • Source of infection

domestic animals:

pig, horse, dog

poultry:

chicken, duck, goose.

patients:

epidemiology1
Epidemiology
  • Route of transmission

insect borne: mosquito biting ,

vector: mosquito, culex tritaeniorhynchus.

Survived winter mosquitoes

pigs

mosquitoes mosquitoes person

pigs

epidemiology2
Epidemiology
  • Susceptibility of population:
    • universal susceptible
    • lifelong immunity
    • subclinical infection : overt infection

1000~2000:1

epidemiology3
Epidemiology
  • Epidemiologic features
    • sporadic from July to Sep.
    • children under 10yrs (2~6yrs)
    • hypersporadic property
slide10

virus

mosquito biting

replication in mononuclear-phagocyte system (MPS)

blood stream

brief viremia

blood-brain barrier

clearance

CNS

subclinical inf.

onset of illness

No. of virus of invasion

cellular immunity

blood brain barrier

pathology
Pathology
  • Place of lesion:
    • all of CNS
    • cerebral cortex, midbrain and thalamus .
  • Pathologic features
    • gross examination:
      • congestion
      • hemorrhage
      • cerebral edema
      • soften focuses
pathology1
Pathology
  • microscopic examination:
    • vascular lesion: endothelial cells swelling,

necrosis

    • neuron degeneration & necrosis
    • neurogliocyte hyperplasia & inflammatory cells

infiltration,

perivascular cuffing ,

neuronophagia.

clinical manifestation
Clinical manifestation
  • incubation period:10~14 days (4~21days )
  • typical encephalitis B
    • Initial period
    • crisis period
    • convalescent period
    • sequela period
clinical manifestation1
Clinical manifestation
  • Initial period : on the 1st to 3rd days
    • abrupt onset
    • fever with headache , nausea, vomiting lethargy,
    • abdominal pain , diarrhea,
clinical manifestation2
Clinical manifestation
  • Crisis period- on the 4th ~10th days
    • high fever: >40℃, sustained for 7~10 days.
    • altered consciousness:

lethargy, confusion, delirium, stupor, semicoma, coma.

    • convulsion or twitch:(40~60%)
    • respiratory failure: 15~40%
clinical manifestation3
Clinical manifestation
  • central RF:
    • reason of central RF:
      • lesion of cerebral parenchyma (respiratory center injury in oblongata medulla)
      • cerebral edema
      • brain hernia
      • intracranial hypertension
      • hyponatremic encephalopathy
clinical manifestation4
Clinical manifestation
    • manifestation of central RF:
      • cacorhythmic breathing

(cheyne-stokes breathing, apnea)

      • brain hernia
  • peripheral RF:
    • dyspnea, regular breathing
clinical manifestation5
Clinical manifestation
  • Other symptoms & signs of CNS
    • meningeal irritations (neck stiffness

Kernigs & Brudzinskis signs positive)

    • Deep tendon reflexes from hyperactive to disappear
    • pathologic reflexes positive
    • limbs paralysis
clinical manifestation6
Clinical manifestation
  • Convalescent period
    • T drop to normal in 2~5 days
    • neurologic function regain gradually(2W)
    • remain some behavioral & psychologic abnormalities,

aphasia, dementia, rigidity paralysis.

    • >6month - sequela
clinical manifestation7
Clinical manifestation
  • Sequela period
    • aphasia
    • dementia
    • persistent paralysis
clinical manifestation8
Clinical manifestation
  • Clinical type:
    • mild type
    • common type
    • severe type
    • fulminant type
laboratory findings
Laboratory 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
laboratory findings1
Laboratory Findings
  • Serological test:
    • specific IgM Ab: blood or CSF,

3~4d after onset, peak on 2 week

ELISA or indirect immunofluorescence

    • complement fixing Ab:

2 weekafter onset, peak on 5~6 week,

          • anamnestic diagnosis
          • epidemiologic investigation
laboratory findings2
Laboratory Findings
  • hemagglutination inhibition Ab:

5d after onset, peak on 2 week

    • diagnosis: 4 fold increase in titer
    • epidemiologic investigation
  • neutralized Ab

epidemiologic investigation

laboratory findings3
Laboratory Findings
  • pathogenic test

virus isolation:blood, CSF, brain tissue

RT-PCR : RNA

diagnosis
Diagnosis
  • Epidemiological data:
    • 7~9 month
    • <10yrs
  • Clinical manifestation:

fever, headache, vomiting, altered consciousness,

convulsion, meningeal irritation, pathologic

reflexes positive.

  • Laboratory findings:WBC, CSF, IgM
differential diagnosis
Differential Diagnosis
  • toxic bacillary dysentery

high fever,convulsion,coma.

    • <24h
    • circulatory failure: early
    • stool examination: WBC, RBC
    • CSF: normal
    • meningeal irritation: negative
differential diagnosis1
Differential Diagnosis
  • tuberculous meningitis
  • CSF, meningeal irritation
  • purulent meningitis
  • other viral encephalitis
treatment
Treatment
  • General therapy:
    • Isolation:

preventing mosquito biting, T<30℃

    • nursing: mouth, skin, eye,

turn over

clapping back

sputum aspiration

treatment1
Treatment
    • fluid & electrolyte supplementation

adult: 1500~2000ml/d

children: 50~80ml/kg/d

  • Symptomatic therapy
    • high fever: T<38℃
treatment2
Treatment
  • 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

treatment3
Treatment
  • convulsion:

fever: cooling

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

50% glucose

dexamethason

treatment4
Treatment

sedative:

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:

treatment5
Treatment
  • respiratory failure:
    • keep airway clear
      • sputum aspiration
      • turn over , clapping back, postural drainage
      • aerosolization
      • inhalation of oxygen
treatment6
Treatment
  • 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

treatment7
Treatment
  • 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
treatment8
Treatment
  • Convalescent & sequela period
    • acupuncture
    • massage
    • exercise etc.
prevention
Prevention
  • isolating patients and pig immunization,
  • killing mosquito and preventing mosquito ,
  • vaccination:

killed virus vaccine: 60~90%

slide40
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:

slide41
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