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Epidemic Encephalitis B

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

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

  2. 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

  3. 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

  4. Etiology • antigenicity: stable • hemagglutination inhibiting Ab • complement fixing Ab • neutralizing Ab

  5. Epidemiology • Source of infection domestic animals: pig, horse, dog poultry: chicken, duck, goose. patients:

  6. Epidemiology • Route of transmission insect borne: mosquito biting , vector: mosquito, culex tritaeniorhynchus. Survived winter mosquitoes pigs mosquitoes mosquitoes person pigs

  7. Epidemiology • Susceptibility of population: • universal susceptible • lifelong immunity • subclinical infection : overt infection 1000~2000:1

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

  9. Pathogenesis

  10. 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

  11. Pathology • Place of lesion: • all of CNS • cerebral cortex, midbrain and thalamus . • Pathologic features • gross examination: • congestion • hemorrhage • cerebral edema • soften focuses

  12. Pathology • microscopic examination: • vascular lesion: endothelial cells swelling, necrosis • neuron degeneration & necrosis • neurogliocyte hyperplasia & inflammatory cells infiltration, perivascular cuffing , neuronophagia.

  13. Clinical manifestation • incubation period:10~14 days (4~21days ) • typical encephalitis B • Initial period • crisis period • convalescent period • sequela period

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

  15. 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%

  16. 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

  17. Clinical manifestation • manifestation of central RF: • cacorhythmic breathing (cheyne-stokes breathing, apnea) • brain hernia • peripheral RF: • dyspnea, regular breathing

  18. 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

  19. 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

  20. Clinical manifestation • Sequela period • aphasia • dementia • persistent paralysis

  21. Clinical manifestation • Clinical type: • mild type • common type • severe type • fulminant type

  22. Clinical manifestation

  23. 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

  24. 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

  25. Laboratory Findings • hemagglutination inhibition Ab: 5d after onset, peak on 2 week • diagnosis: 4 fold increase in titer • epidemiologic investigation • neutralized Ab epidemiologic investigation

  26. Laboratory Findings • pathogenic test virus isolation:blood, CSF, brain tissue RT-PCR : RNA

  27. 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

  28. Differential Diagnosis • toxic bacillary dysentery high fever,convulsion,coma. • <24h • circulatory failure: early • stool examination: WBC, RBC • CSF: normal • meningeal irritation: negative

  29. Differential Diagnosis • tuberculous meningitis • CSF, meningeal irritation • purulent meningitis • other viral encephalitis

  30. Treatment • General therapy: • Isolation: preventing mosquito biting, T<30℃ • nursing: mouth, skin, eye, turn over clapping back sputum aspiration

  31. Treatment • fluid & electrolyte supplementation adult: 1500~2000ml/d children: 50~80ml/kg/d • Symptomatic therapy • high fever: T<38℃

  32. 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

  33. Treatment • convulsion: fever: cooling brain edema: 20% mannitol 1~2g/kg/time 50% glucose dexamethason

  34. 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:

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

  36. 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

  37. 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

  38. Treatment • Convalescent & sequela period • acupuncture • massage • exercise etc.

  39. Prevention • isolating patients and pig immunization, • killing mosquito and preventing mosquito , • vaccination: killed virus vaccine: 60~90%

  40. 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：

  41. 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

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