Exam 2: Flaviviridae Flashcards
What are the virion properties of Flaviviridae?
Virions are spherical Diameter 40-60 nm (medium sized) Inner core possible icosshedral symmetry Lipid envelope Genome: single stranded, positive sense RNA
What are the 3 genera of flaviviridae?
Pestivirus (BVDV)
Flavivirus (yellow fever virus)
Hepacivirus (hepatitis C)
What are the species of pestiviruses with animal health significance?
Bovine viral diarrhea virus 1
BVDV 2
Classic swine fever virus
What are the 2 biotypes of virus with BVDV?
Cytopathic
Non-cytophatic
Which biotype induces persistent infection with BVDV?
Non-cytophatic
Which BVDV biotype is/are virulent in cattle?
Both cytopathic and non-cytopathic may be
What are the transmission and persistence strategies of BVD?
Induction of persistently infected hosts that shed and transmit BVDV efficiently
Suppression of the host’s immune system
Transmission by various direct and indirect routes
What is the most important method of transmission for BVDV?
In utero infection
What is the main determinant of fetal response in transplacental infections?
Timing of infection during pregnancy
Describe subclinical infections from BVDV in susceptible immunocompetent nonpregnant cattle
70 to 90% of infections in adult cattle
Mild fever and leukopenia
Development of neutralizing antibodies
Describe BVDV infection in neonatal calves
Rarely seen in calves younger than 6 months
Severe enteritis, sometimes fatal
Describe venereal infections from BVDV
Semen in infected bulls contains virus
Semen quality may decrease
Seronegative cows inseminated with infective semen fail to conceive until they develop an immune response
What is immunological tolerance?
State of unresponsiveness for a particular antigen
When does immunological tolerance occur with BVDV?
When infection in utero between 80 and 125 days of pregnancy
Describe mucosal disease associated with BVDV
2 biotypes of BVDV are present
Persistent infection with non-cytopathogenic virus
Superinfection with a cytopathogenic virus
Clinical signs are similar to BVDV but more severe
What are the lesions with BVD?
Acute: erosive or ulcerative lesions in mouth, esophagus, forestomachs, abomasum and intestine
Discoloration of mucosal folds
Necrosis of lymphoid tissue
What is used to diagnose BVDV?
RT-PCR
ELISA
Ear notches
What is the main route of classic swine fever infection?
Oronasasl by direct or indirect contact with infected pigs
Indirect by contaminated feed
What does the severity of classic swine fever signs depend on?
Age of the animal and virulence of the virus
Which form of classic swine fever is always fatal?
Chronic form
What are the typical skin hemorrhages of classic swine fever?
Ears, tail, abdomen, and the inner side of the limbs
Where does primary viral replication occur with classic swine fever?
Tonsils
What does classic swine fever cause?
Severe leukopenia and immunosuppresion
What is the major lesion caused by classic swine fever?
Infarction in the spleen
Describe prenatal infections of classic swine fever
The piglets shed large amounts of virus
What should be done classical swine fever is suspected?
It should be reported immediately
Where should a sample come from when testing for classic swine fever?
Tonsils
What can transmit Flavivirus?
Mosquito
Ticks
What are viruses that fall in the Flavivirus genus?
West Nile Virus
Japanese encephalitis virus
Louping ill virus
Zika virus
What is West Nile Virus serologically related to?
St. Louis encephalitis
What are important reservoirs of West Nile Virus?
Passerines
What are the prinicpal vectors of West Nile Virus in the USA?
Culex pipiens
C. restvans
What are the 2 groups of birds infected with West Nile Virus?
Asymptomatic (carriers)
Susceptible (develop neurological disease)
What does West Nile VIrus correlate with in terms of the North American bird population?
The decline in the population
What is the range of avian West Nile Virus infections?
Subclinical to fatal with variability among species
What are the signs associated with West Nile Virus?
Neurological
In poultry, what has West Nile Virus been mostly reported in?
Ducks and geese
What is another major animal that West Nile Virus has been reported in?
Horses
What must you rule out in horses before you can confirm West Nile Virus?
Eastern Equine Encephalitis
What is Japanese encephalitis a concern for?
Travelers
What is Louping ill virus important in?
Sheep
What ticks transmit Louping ill virus?
Ixodes ricinus
Rhipicephalus appendiculatus
What are the signs associated with Louping ill virus?
Neurological
What are the flaviviruses in humans?
Yellow fever
St. Louis encephalitis
Denge
Zika virus
How is Zika virus transmitted?
Primarily though the bite of an infected Aedes species mosquito
