(RNA VIRUSES) Lesson 16: Flaviviridae Flashcards by Danica Mae Araza

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

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The name of the family Flaviviridae is derived from the Latin word _______ meaning ________

✔ flavus
✔ yellow and referring to the virus of yellow fever

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what type of RNA is Flaviviridae

single-stranded RNA

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type of replication of Flaviviridae

Positive-sense

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Flaviviridae replicate in the

cytoplasm

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Flaviviridae two genera of veterinary importance

Flavivirus and Pestivirus

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Most viruses in this genus are transmitted by arthropods and
cause encephalitis

genus Flavivirus

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Most viruses in the genus Flavivirus are transmitted by ______ and
cause ________

arthropods
encephalitis

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which are transmitted directly or indirectly, cause bovine viral diarrhoea, border disease and classical swine fever

Pestiviruses

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Pestiviruses, which are transmitted directly or indirectly, cause what diseases?

✔ bovine viral diarrhoea
✔ border disease
✔ classical swine fever (hog cholera)

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Pestiviruses, are transmitted ________, cause bovine viral diarrhoea, border disease and classical swine fever (hog cholera)

directly or indirectly

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hog cholera also known as

classical swine fever (CSF)

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Flaviviridae

The different viruses under the genus Pestivirus are antigenically diverse, antigenically cross-reactive and display an overlapping host spectrum.

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These viruses can cross-infect
other ruminants and swine

Bovine viral diarrhoea virus
Border disease virus

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Bovine viral diarrhoea virus and border disease virus can cross-infect these animals

other ruminants and swine

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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

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Zoonotic viruses of Flaviviridae

✓ Louping ill virus
✓ Japanese
encephalitis
✓ West Nile virus

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Causes inapparent infection, acute disease
(bovine viral diarrhoea) and sporadic fatal
infection (mucosal disease).

Bovine viral
diarrhoea virus 1
and 2

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Infection of pregnant animals may result in
abortion, congenital defects or persistent
infection (immunotolerance)

Bovine viral
diarrhoea virus 1
and 2

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Important infection of pregnant ewes and
cause of abortion or congenital abnormalities
(hairy shaker lambs)

Border disease virus (sheep)

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Border disease virus cause an important infection of pregnant ewes and
cause of abortion or congenital abnormalities
like?

hairy shaker lambs (sheep)

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Economically significant disease.

Classical swine
fever (hog cholera)
virus

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Highly contagious, generalized infection that
is frequently fatal.

Classical swine
fever (hog cholera)
virus

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Present in specific regions of Europe.
Transmitted by the tick Ixodes ricinus.
Produces encephalitis in sheep

Louping ill virus

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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

1. nervous signs 2. abortion 3. 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

1. generalized infection 2. hepatitis 3. 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?

1. cytopathic (due to mutation) 2. 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

1. Group 1 (caused CSF outbreak during 1940’s and 1950’s) 2. Group 2 (European isolates) 3. 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

(RNA VIRUSES) Lesson 16: Flaviviridae Flashcards

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