(RNA VIRUSES) Lesson 16: Flaviviridae Flashcards
General description of Flaviviridae
- The viruses are spherical, 40–60 nm in diameter with an icosahedral capsid and a tightly adherent envelope containing two or
three virus-encoded proteins depending on the genus - Positive-sense, single-stranded RNA
- Replicate in the cytoplasm
- Has Two genera of veterinary importance, Flavivirus and Pestivirus
The name of the family Flaviviridae is derived from the Latin word _______ meaning ________
✔ flavus
✔ yellow and referring to the virus of yellow fever
what type of RNA is Flaviviridae
single-stranded RNA
type of replication of Flaviviridae
Positive-sense
Flaviviridae replicate in the
cytoplasm
Flaviviridae two genera of veterinary importance
Flavivirus and Pestivirus
Most viruses in this genus are transmitted by arthropods and
cause encephalitis
genus Flavivirus
Most viruses in the genus Flavivirus are transmitted by ______ and
cause ________
arthropods
encephalitis
which are transmitted directly or indirectly, cause bovine viral diarrhoea, border disease and classical swine fever
Pestiviruses
Pestiviruses, which are transmitted directly or indirectly, cause what diseases?
✔ bovine viral diarrhoea
✔ border disease
✔ classical swine fever (hog cholera)
Pestiviruses, are transmitted ________, cause bovine viral diarrhoea, border disease and classical swine fever (hog cholera)
directly or indirectly
hog cholera also known as
classical swine fever (CSF)
Flaviviridae
The different viruses under the genus Pestivirus are antigenically diverse, antigenically cross-reactive and display an overlapping host spectrum.
These viruses can cross-infect
other ruminants and swine
Bovine viral diarrhoea virus
Border disease virus
Bovine viral diarrhoea virus and border disease virus can cross-infect these animals
other ruminants and swine
Viruses in the family Flaviviridae that cause OIE-listed diseases.
- Japanese encephalitis virus
- West Nile virus
- Bovine viral diarrhoea virus 1
- Bovine viral diarrhoea virus 2
- Classical swine fever virus
Zoonotic viruses of Flaviviridae
✓ Louping ill virus
✓ Japanese
encephalitis
✓ West Nile virus
Causes inapparent infection, acute disease
(bovine viral diarrhoea) and sporadic fatal
infection (mucosal disease).
Bovine viral
diarrhoea virus 1
and 2
Infection of pregnant animals may result in
abortion, congenital defects or persistent
infection (immunotolerance)
Bovine viral
diarrhoea virus 1
and 2
Important infection of pregnant ewes and
cause of abortion or congenital abnormalities
(hairy shaker lambs)
Border disease virus (sheep)
Border disease virus cause an important infection of pregnant ewes and
cause of abortion or congenital abnormalities
like?
hairy shaker lambs (sheep)
Economically significant disease.
Classical swine
fever (hog cholera)
virus
Highly contagious, generalized infection that
is frequently fatal.
Classical swine
fever (hog cholera)
virus
Present in specific regions of Europe.
Transmitted by the tick Ixodes ricinus.
Produces encephalitis in sheep
Louping ill virus
Louping ill virus is transmitted by the _________
tick Ixodes ricinus
Louping ill virus is transmitted by the tick Ixodes ricinus.
Produces what disease in sheep?
encephalitis
Nervous signs, abortion and congenital
tremor are features of the disease
Classical swine
fever (hog cholera)
virus
FLAVIVIRIDAE
features of the disease
caused by classical swine
fever (hog cholera)
virus
- nervous signs
- abortion
- congenital
tremor
Widespread distribution in Asia.
Transmitted
by mosquitoes. Water birds are reservoir
host.
Japanese
encephalitis
Japanese
encephalitis
is transmitted
by?
mosquitoes
are reservoir
host of Japanese
encephalitis
Water birds
West Nile virus
are transmitted by?
mosquitoes
are the
natural hosts of West Nile virus
birds
Sporadic cause of serious CNS
disease in humans and horses
West Nile virus
Occurs in parts of sub-Saharan Africa.
Causes generalized infection, hepatitis and
abortion. Transmitted by mosquitoes
Wesselsbron virus
Wesselsbron virus causes what conditions
- generalized infection
- hepatitis
- abortion
Wesselsbron virus is transmitted by?
mosquitoes
Outbreaks of progressive paresis and
paralysis in turkeys in Israel and South
Africa. Mosquito-borne virus
Israel turkey
meningoencephalitis
virus
Israel turkey
meningoencephalitis
virus
causes an outbreaks of these conditions in turkeys in Israel and South
Africa.
progressive paresis and
paralysis
Mosquito-borne virus
Israel turkey
meningoencephalitis
virus
Infection with this virus is common in cattle
populations worldwide
bovine viral diarrhoea virus (BVDV)
bovine viral diarrhoea virus (BVDV) geographical distribution
Worldwide
The virus is responsible for acute disease (bovine viral diarrhoea) and a chronic
syndrome associated with persistent infection (mucosal disease).
bovine viral diarrhoea virus (BVDV)
chronic
syndrome associated with persistent infection
mucosal disease
Isolates of BVDV can be segregated into two genotypes now considered
separate species.
ENUMERATE
✓ BVDV 1 (classical BVDV isolates)
✓ BVDV 2 (atypical BVDV
isolates)
Both BVDV 1 and BVDV 2 can exist as one of two biotypes based on their activity in cell cultures: what are these two?
- cytopathic (due to mutation)
- non-cytopathic (common
in cattle)
Cell culture activity of BVDV 1&2 due to mutation
cytopathic
Cell culture activity of BVDV 1&2 common in cattle
non-cytopathic
Bovine viral diarrhoea virus 1 and BVDV 2 produce similar clinical syndromes in cattle. However, only non-cytopathic BVDV 2 isolates have been associated with?
thrombocytopenia
haemorrhagic syndrome
Bovine viral diarrhoea virus 1 and BVDV 2 produce similar clinical syndromes in cattle. However, only __________isolates have been associated with thrombocytopenia and a haemorrhagic syndrome.
non-cytopathic BVDV 2
TAKE NOTE: FLAVIVIRIDAE
Animals exposed to BVDV for the first time transiently shed the virus in the early stages of infection and may transmit infection to other animals
The most important mode of transmission of BVDV 1&2 (Flaviviridae) is through ________, which shed the virus in all excretions and secretions and are efficient transmitters of the infection
persistently infected animals
These infections (1% of infected population) are produced following foetal infection before day 120 gestation with non-cytopathic strains.
Persistent infections
FLAVIVIRIDAE
Transmission of infection of BVDV is largely dependent on?
husbandry practices
FLAVIVIRIDAE
are the primary host of BVDV but the virus is capable of infecting most even-toed ungulates (ovine)
Cattle
Cattle are the primary host of BVDV but the virus is capable of infecting most of these animals.
even-toed ungulates (ovine)
is based on clinical presentation of the disease
tentative diagnosis
The detection of seroconversion and persistently infected (PI) animals are required to confirm ongoing infection in a herd. Done thru the ff techniques
✔ cell culture
✔ immunoflourescence techniques ✔ molecular and serological techniques
PI means
persistently infected
is a very contagious and frequently fatal disease of pigs
Classical swine fever (Hog Cholera)
Classical swine fever (Hog Cholera) divided into three major groupings:
ENUMERATE
- Group 1 (caused CSF outbreak during 1940’s and 1950’s)
- Group 2 (European isolates)
- Group 3 (common in Asia)
Classical swine fever (Hog Cholera) Group 1
caused CSF outbreak during 1940’s and 1950’s
Classical swine fever (Hog Cholera) Group 2
European isolates
Classical swine fever (Hog Cholera) Group 3
common in Asia
are the only natural hosts of CSFV
pigs and wild boar
is the main means of transmission of CSFV
direct contact (between infected and susceptible animals)
In enzootic areas the main means of disease spread caused by CSFV is by?
movement of infected pigs
Classical swine fever (Hog Cholera)
Congenital infections with low-virulence strains may result in the birth of persistently infected piglets with a specific immune tolerance to the virus but which may subsequently develop late-onset
The virus does not persist for long in the environment but can survive for long periods in protein-rich media such as meat or body fluids in cool condition
Classical swine fever (Hog Cholera)
Classical swine fever (Hog Cholera) does not persist for long in the environment but can survive for long periods, in what type of media?
protein-rich media such as meat or body fluids in cool condition
The incubation period of CSFV
5-10 days
Classical swine fever (Hog Cholera)
Pigs are usually infected by what route?
oronasal route
Classical swine fever (Hog Cholera)
Pigs are usually infected by the oronasal route and the ______ is the primary site for viral multiplication.
tonsil
Classical swine fever (Hog Cholera)
Pigs are usually infected by the oronasal route and the tonsil is the primary site for viral multiplication. The virus spreads to the draining regional __________before entering the bloodstream.
lymph nodes
Classical swine fever (Hog Cholera)
Late in this phase, the virus invades parenchymatous organs
viraemic phase
Classical swine fever (Hog Cholera)
Late in the viraemic phase, the virus invades these organs
parenchymatous organs
is responsible for the multiple haemorrhages seen in acute CSF
Degeneration of endothelial cells in conjunction with a severe thrombocytopenia
Degeneration of endothelial cells in conjunction with a severe thrombocytopenia
is responsible for the multiple haemorrhages seen in acute CSF. _________ on the surface of the kidneys and in the lymph nodes are the most consistent findings.
Petechiae
if present, is considered highly characteristic of acute
swine fever
Splenic infarction
Degeneration of endothelial cells in conjunction with a severe thrombocytopenia
is responsible for the multiple haemorrhages seen in acute CSF. Petechiae on the surface of these organs are the most consistent findings.
kidneys and lymph nodes
is present in most CSFV-infected pigs
non-suppurative encephalitis
Classical swine fever (Hog Cholera)
The principal CNS lesion is?
perivascular cuffing
In pregnant sows the CSFV may cross the placenta. Infection early in gestation typically results in?
resorption or abortion
In pregnant sows the CSFV infection late in gestation may result in?
protective immune response and the birth birth of healthy piglets
Classical swine fever (Hog Cholera):
may be sufficiently characteristic for a provisional diagnosis to be made, but laboratory confirmation is essential, particularly in the case of infections with low-virulence strains.
history and clinical signs
Classical swine fever (Hog Cholera):
is essential, particularly in the case of infections with low-virulence strains
laboratory confirmation