ReoViruses Flashcards
Reo stands for
Resp, enteric & orphan
important reovirus genera
orbivirus genus: AHS, Equine encephalosis, BTD
Rotavirus genus: Rotavirus A-J
T/F
Bluetongue is caused by an intraerythrocytic parasite
False
whys is it called Blue tongue
farmers could observe cyanosis of tongue in clinical cases
which serotype of bluetongue disease caused a devastating outbreak in 2006
ST8
BTV is enveloped or not?
non-enveloped
How many serotypes of BTV
28 (29)
How can we know which serotype of BTV it is
with it’s VP2
What are the atypical serotypes
BTV-25,26 & 27 (28)
Why are they called atypical serotypes
- non pathogenic
- direct contact transmission
- found exclusively in small ruminants
- unable to grow in culicoides cell lines
Where was BTV-28 found?
isolated from contaminated live-attenuated sheeppox and lumpy skin disease vaccines in israel
Is BTV important
yes, has a high economical impact
why does BTV have a high economical impact
high morbidity and mortality
stillbirths, abortion
decreased BirthW
reduced milk yield & fertility rates
meat losses
vector of BTV
BTV spread naturally to susceptible hosts by the bite of blood sucking midges of genus culicoides
biological vector
which culicoides species are responsible for the transmission of BTV
C. Oxystoma
C. imicola
Where is BTV found
the culicoides vector can survive at 15° so more in southern regions
other possible route of infection other than biological vector of BTV
in utero
transplacental infection
venereal transmission through semen
(most important)
also contact/ oral
iatrogenic
mechanical vector
what is the extrinsic incubation
incubation inside the vector
4-20 dys (depends on the temperature)
what can be a mechanical vector of BTV
sheep ked, tick
BTV outbreaks
seasonal, late summer & autumn
how can BTV re-emerge after winter?
BTV possibly overwinters transplacentally in infected calves
(kind of persistent viraemia)
viraemia of in utero infected calves differs from prolonged one of adult animal
which domestic animals does BTV infect
sheep
goats
cattle
carnivores
Cattle BTV
viraemic period longer in cattle than in sheep
cattle is reservoir & amplifying host
usually asymptomatic or sub-clinical
BTV8 severe clinical signs in cattle in 2006
Goats BTV
usually asymptomatic or sub-clinical infection
but in 2006 BTV8 : severe clinical signs in goats
BTV pathogenesis
- bite of infected midges
- skin to local Ln
- 1st viraemia to secondary organs
- rep in endothelial cells & mononuclear phagocytic cells of skin
early viraemia of BTV
associated with all blood elements
later stages
exclusively associated with erythrocytes
virus effect on a cellular aspect
very strong affinity to endothelial cells, replication causes apoptosis & necrosis of endothelial cells of small blood vessels in target tissues
BTV cross protection
specific neutralising antibodies provide long-lasting protection with homologous serotype only
no cross protection at all
clinical forms of BTV
from asymptomatic to lethal
CS of BTV
fever
serous to bloody nasal discharge (mucopurulent)
hyperaemia and oedema of face (monkey face)
oral erosions
cyanosis of tongue
coronitis (lamness)
resp
muscular necrosis
cattle BTV CS
fever
conjunctivitis
nasal discharges
ulcers in oral mucosa
necrosis in lips, tongue & interdigital skin
neuro signs in calves
coronitis, interdigital disease called “dancing disease”
Goat BTV CS
mild CS
but severe with BTV8
patho of BTV
endothelial damage: coagulopathy & haemorrhages
oedema
infarction
heavy muscular degeneration & necrosis
cerebellar hypoplasia
haemorrhagic enteritis in lambs
diagnosis of BTV
RT qPCR
antibodies: AGID, ELISA
BTV DD
FMD
sheep pox
IBR
BVD-MD
MCF
panaritium
Vit E & Sel def
BTV control
mass vaccination (homologous protection)
vector control
restricted zone: 20km
protection zone: 100km
surveillance zone: 150km
NOTIFIABLE
Epizootic Haemorrhagic fever which virus
Sedoviridae-Orbivirus
Which animals does Epizootic haemorrhagic fever infect
White tailed deer in the USA
Epizootic haemorrhagic disease virus (EHDV) has how many serotypes
At least 7
Important Epizootic haemorrhagic disease virus (EHDV) serotype
ST 2- Ibaraki virus, high mortality in cattle in Japan
Epizootic haemorrhagic disease virus (EHDV) vector
Mosquito and midges
Epizootic haemorrhagic disease virus (EHDV) control
NOTIFIABLE
(Domestic ruminants are also susceptible)
Epizootic haemorrhagic disease virus (EHDV) CS
Oedema, swollen head, neck, tongue
Loss of fear in humans
Lethal within 8-36hrs (100% mortality)
Differentiation of Epizootic haemorrhagic disease virus (EHDV) and BTV
qPCR
African horse sickness occurrence
Worldwide
African horse sickness causative agent
African horse sickness virus, OrbiVirus (9 serotype of diverse virulence)
Susceptibility of African horse sickness virus
Equids
Rarely: elephant, camel, dog, ferret
Epizootiology of African horse sickness
Arthropod vectors (midges (biological), mosquitoes(mechanical V), ticks (rarely, more mechanical))
Viraemia: 4-8 days
Shedding : semen, urine,discharges
Inf of carnivores : consumption of horse meat
African horse sickness Patho genesis
1st rep: lymphatic tissue
Viraemia
Lymph & blood vessel endothel damage
Oedema, haemorrhages
Pulmonary oedema, cardiopathy
African horse sickness mortality rate
Horse: 70-96!
Peracute African horse sickness CS
fever, sweating, red conjunctiva
Dyspnoe, foamy nasal discharge
Death within 24hrs
Acute form of African horse sickness CS
Resp form, death within a week
Subacute African horse sickness CS
Cardiac, oedematic form
Fever
Oedema “hippo head”
Let oedema neck &chest
Haemorrhage in conjunctiva & ventral aspect of tongue
Death of cardiac dysfunction
If survives oedema disappears within 3-8 dys
Mixed form of African horse sickness
Milder Resp signs, oedema
Chronic form of African horse sickness
Recurrent fever (in afternoon)
Mainly donkeys, zebras, immune horses
Patho of African horse sickness
Pulm. Oedema
Oedema under skin
Haemorrhages
Patho of African horse sickness
Pulm. Oedema
Oedema under skin
Haemorrhages
Diagnosis of African horse sickness
notifiable disease - lab D is needed
virus isolation: suckling mouse brain
RT-PCR
ELISA
DDx of African horse sickness
Equine viral arteritis (typically abortions)
babesiosis
anthrax
Equine infectious anaemia
prevention and control of African horse sickness in AHS free countries
restriction on equine importation from endemic countries
(permission with 30 dys quarantine, serologie and virologie)
ectoparasitic treatment
dog potential carriers
Notifiable D
outbreak control of African horse sickness
sanitary prophylaxis
slaughtering animals, insect control
vaccination on safety zone (x2)
protection for African horse sickness in endemic countries
attenuated, polyvalent vaccines (prod in ,ouse brain or cell culture)
protects for a few years
equine encephalosis occurence
southern countries of africa, in Israel too
equine encephalosis causative agent & vector
orbivirus, culicoides vector
equine encephalosis pathogenesis
similar to AHS
blood vessel damages
equine encephalosis CS
3-10 dys incubation
asymptomatic mostly
oedema of lips & eyelids
CNS signs (brain oedema)
abortion (first 5-6 months)
enteritis, liver dystrophy
equine encephalosis mortality
recovery, rarely fatal
equine encephalosis prevention & control
no vaccine
epi measures
equine encephalosis diagnosis
PCR to differentiate with AHS
elisa to detect Ab