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CNSLF Micro - Viral Infections + Prions in CNS (iii) (Japanese…
CNSLF Micro - Viral Infections + Prions in CNS (iii)
Japanese encephalitis
in SE Asia
major cause of encephalitis in Asia
closely related to West Nile virus
transmitted to humans by infected mosquito, primary Culex species
humans = incidental host
maintained in an enzoontic state between mosquitos + vertebrate hosts, primarily pigs + wading birds
esp in rural agricultural areas: rice paddy fields, flood irrigation
incubation = 5-15 days
in endemic areas adults have acquired immunity from infection or immunisation - the infection is primarily seen in children
clinical presentation
most human infections asymps
<1% develop clinical disease
acute encephalitis most common
meningitis + acute flaccid paralysis, or febrile illness are other less common manifestations
case fatality rate: 20-30%
some 30-50% of survivors have serious CNS sequelae
clinical dx: neuro infection in an individual who resides/recently travelled to an endemic area
lab dx: JE virus specific IgM detection on blood or CSF
note: humans have a low level + short lived viraemia of JE virus, hence virus isolation (culture) + nucleic acid detection (PCR) not sensitive
no antiviral tx available
Prevention + Control
minimise exposure
avoidance of outdoor/night time expsoure in areas with active transmission
clothing/insecticides/insecticide txed bed nets
insecticide spraying + fogging
improved agricultural practices (centralised pig production)
immunisation = most important preventative measure
WHO recommend JE vaccine as part of routine immunisation programmes in all areas where JE infection is a public health problem
incl in the routine children immunisation schedule in Sarawak, Malaysia
Poliovirus
also an enterovirus
an important cause of paralysis before the vaccine introduced
human only reservoir, faecal oral transmission - poor hand hygiene, sewage tx
prevention
WHO polio eradication programmes - serotype 1+2 eradicated, only type 3 left (Afghanistan + Pakistan)
vaccines: live oral / inactivated IM / intradermal
clinical presentation
no or mild illness in 90-95% of cases (NB still infectious as virus shed in stool)
1-2% biphasic illness - 2-3 days of fever + GIT symptoms, appear to recover then develop fever, severe headache + other symptoms
meningitis (1-5%) usually recover
paralytic poliomyelitis (1 in 1000)
spinal polio (80%)
asymmetric paralysis
usually legs
paralysis of muscles innervated by efferent Ns from infected ant horn cells (asymmetric flaccid paralysis with no sensory loss, destruction of LMNs)
Bulbar polio
rep in motor nuclei of lower cranial Bs
weakness of tongue + pharyngeal muscles
bulbospinal (combo of above)
post-polio syndrome
30-40 yrs after paralytic polio
patients note increased weakness + muscle pain
due to loss of neurons in initially affected Ns
dx
clinical presentation
CSF - PCR
if early in illness: viral culture for poliovirus (throat secretions + faeces)
tx
supportive pain relief + physical therapy
if resp failure may need mechanical ventilation
bulbar involvement = monitor CVS closely (a/w BP fluctuations, circulatory collapse + autonomic dysfunction)