19. Viral encephalitis (Tick, West Nile, Equine, Japanese and other)

viral encel general (general transmission, pathology)

mosquito transmit

severe brain inflammation

West nile virus ae

rna virus

fam : flaviviridae

genus : arbovirus

spp : flavivirus

wnv general (listed? zoonosis? hosts

WOAH

zoonotic

primary: host birds

also affects: mammals especially horse

wnv epizoo

endemic america, africa, europe (france, greece, germany)

wnv transmission

vector : mosquito (culex, aedes)

wnv pathogenesis

inject mosqui - enter blood - hemorh and congestion

spread to cns - encephalitis

wnv cs birds

encephalitis

fever

stiff neck

disorientation

tremors

muscle weak

paralysis

death

wnv cs horse

most do not develop clinical disease

encephalomyelitis (spinal cord and brain infection)

listlessness, weakness, inability to swallow, anorexia, depression, stumbling, incoordination, fever, death

wnv human cs

wn fever - non-specific

wn encephalitis (immunosuppressed) - cns =, convulsion, paralysis, coma

viral encephal dg

cs

isolation

pcr

serology (elisa, vnt)

viral encephal tx

none

symptomatic, supportive

equine encephalitis ae

rna virus

togavirus

alphavirus

EEEV, WEEV, VEEV

ee 3 spp ae

- eastern eq encephalitis virus

- western eq encephalomyelitis virus

- venezuelan eq encephalitis virus

ee general (listed? zoonosis?)

WOAH (all three)

zoonotic (all three)

ee epizoo

mainly America

panama 2021

east-west - bird-mosquito cycle

Venezuelan - rodent/bird/mosquito cycle - human and horse accidental dead-end host

ee transmission

vector: mosquito (also ticks in WEEV)

rodent by contact, aerosol, ingest

ee pathogenesis

inject by mosquito - LN - replicates in macrophages/neutrophils - leukopenia, fever, lymphopenia - viremia - cns - brain damage, death

ee pathology (what causes cs?)

cortical and thalamic lesions, brain stem deficits

ee cs horse

depression, quiet

cns: impaired vision, head pressing, circling, can’t swallow, ataxia, paralysis, convulsion, death

death 2-3d after cs high mortal

ee cs human

flu-like (sudden fever, muscle pain, headache)

then meningoencephalitis, seizure, coma

1/3 people with EEEV will die (mortality lower in WEEV, VEEV)

ee pm lesions

haemorrhages

congestion cns

japanese encephalitis ae general (classification, listed? zoonosis?)

JEV, flavivirus, flaviviridae

WOAH

zoonotic

je epizoo

japan

some part asia

je transmission

vector : mosquito (culex, aedes)

je pathogenesis

LN - replicate in macrophages +neutrophils - lymphopenia - viremia

je cs horse

mostly asymptomatic

je cs pigs

reproductive disorders

infertility, abort, stillbirth, weak offspring

je cs human

flu-like

fever, coma, mortal 30%

tick-borne encephalitis ae

rna virus

fam : flaviviridae

genus : flavivirus

spp : tick borne encephalitis virus

tbe general (listed? zoonosis? system? hosts?)

WOAH

zoonotic

cns

ru

birds

rodent

car

horse

human

tbe 3 subtypes

- western europe

- siberian

- far eastern (russia, asia, china)

tbe epizoo

seasonal: april-october

endemic: europe, asia

10,000-12,000 human cases annually

tbe transmit

main: small rodents; accidental: humans

(large animals don’t contribute to maintenance of the disease)

tick bite vector Ixodidae (transstadial, transovarial)

ingest unpasteurised milk

tbe pathogenesis

replicate at site of infect - in lymphatic syst + bloodstream - viraemia - cns

tbe cs ru

asymptomatic

shed in milk

7-10d follow infect

tbe dog cs

cns

apathy

excitement

ataxia

paralysis of limbs and facial nerve

abnormal spinal reflex

nystagmus

tbe human cs

inapparent

viraemic: flulike (headache, weak, nausea)

30% case cns meningitis, vomit, paralysis

acute: death

tbe dg

cs, seasonality, epizoo. situation

histo: meningoencephalitis

biochem: leukopaenia, thrombocypenia; increased WBC in blood and CSF

serology: vnt, elisa

RT-PCR

sample blood csf

tbe tx

symptomatic, supportive

antiinflammatory drugs: NSAIDs, prednisolone

sedation: diazepam

fluids: restore electrolytes due to vomiting

mannitol (decrease excess fluid in brain)

vaccinate in endemic areas

outbreak ctl

tick, rodent ctl

remove tick asap

hyperimmune serum to limit severity

serologic screening of milk tank in endemic

outbreak prevent

vaccinate - endemic

tick elimination - fipronil

pasteurise milk

rotation pasture

rodent control

competent authorities ctl

- isolation, treatment, movement restrict

- insect ctl

- surveillance 100km (as all mosquito-borne diseases)

competent authorities prevention methods

- insect repellent, full-length clothes, avoid dusk/dawn, damage habitats of mosquitoes (standing water), fly nets

- rodent ctl

- vaccinate endemic

sanitation tbe

- tick activity depends on humidity, T° (wet summer, mild winter)

- ascaricides, permethrin, amitraz

- inactive by 56° 30min, ether, chloroform, pasteurise dairy

resistance in environment (WNV, EEEV, WEEV, VEEV)

wnv : cool, moist

EEEV, WEEV : no

VEEV: dried blood, exudate

disinfection viral encephalitis

-Ethanol (70%), formaldehyde (2%), UV light, heat, low pH, and sun

- Insect control: pyrethroids (sodium channel blockers-disrupt axonal transmission)

B) Which mosquito genera transmit which diseases?

- remove standing water

aedes (dengue)

anopheles (malaria)

culex (wnv, encephalitis, tularemia)

B) Mosquito Life Cycle

complete metamorphosis

eggs laid in fresh or polluted water

only females bite

adults survive 2 weeks

B) Mosquito ctl method

- mechanical (adhesive, light, traps)

- physical (T°, steam, uv, heat, radiation)

- biological (fungi, egg parasite)

- chemical (fungicide, aerosols, spray, fumigants)