Picornaviridae Flashcards
What viruses are part of the Picornaviridae family?
Enterovirus Cardiovirus Rhinovirus Aphthovirus Hepatovirus Parechovirus
Are Picornaviridae virus’s RNA or DNA virus? ss or ds? structure?
ss (+) RNA, linear
What virus is responsible for Foot and Mouth Disease?
Apththovirus
Is Aphthovirus envelope or non-envelope virus?
No envelope
survives drying
What are the serotypes for FMDV?
Type O Type A Type Asia 1 Type SAT 1-2 Type C
What is FMDV susceptible to for inactivation? Give 4 examples
pH - > 9 : 5% acetic acid or other acids or 1-2% sodium hydroxide or other alkalis
Phenolic and quarternary ammonium compounds effective
Oxidizing agents (bleach) - environment w/o organic substances! Detergents increase effectiveness
Heat
What animals are susceptible to FMDV? What animal won’t be affected?
domestic and wild ruminants and pigs = cloven hoof animal
(cattle, buffalo, sheep, goats, camelids, deer, pigs, rabbits, mice, guinea pigs, chickens, humans)
Horses are not affected
How does FMD present?
systemic disease
high fever
vesicles on epithelial surfaces
Is FMD fatal in adults?
Not usually but will cause economic losses
Can be fatal in young animals – myocarditis
What countries are free of FMD?
North America
Australia
New Zeland
UK
How many important antigenic proteins does FMD have?
VP1
VP2
VP3
VP4
Are lab animals like rabbits,mice and guinea pigs susceptible to FMD?
Yes
What is the amplifying host for FMD? What does this mean?
Pigs
secrete large amounts of virus in breath, air borne spread
What is the sentinel host for FMD? What does this mean?
Cattle
Highly sensitive to infection by respiratory route
What is the maintenance host for FMD? What does this mean?
Sheep
Mild asymptomatic disease, can spread through flocks before detection
What is the route of infection for FMD?
inhalation
ingestion
AI
What is the incubation period for FMD?
36 hours, usually 3-10 days
How long can FMD persist?
months to years in partially immune animals, life time in some species
What causes the death of young animals with FMD?
Myocarditis
When does virus shedding start for FMD? What is the significance?
1-4 days before clinical signs appear
Before we know the animals are sick, the herd is affected
What is the infectious dose for FMDV?
< 10 particles +
What is the transmission for FMDV?
Aerosol
Direct contact
Contaminated animal products
Contaminated pastures
Wind-borne carriage of infectious aerosols
Possible passive transmission by birds and humans
What is the pathogenesis for FMD?
Large amount of virus present in mucosal secretions, milk, urine, and feces of infected animals –> infection of epithelial cells –> cytoplasmic replication –> virus assembly –> cell lysis –> virus release –> localized infection of regional lymph nodes –> virus enters blood = viremia –> dissemination to secondary sites –> increase in virus load on host –> virus collects in cornified epithelium (feet, mammary gland, mouth and tongue)
What are primary sites of FMDV replication?
At the point of entry
- soft palate
- dorsal root of pharynx
- Dermal and subdermal tissue near a skin abrasion
What are 7 factors that allow rapid spread and persistance in a population?
- antigenic variation
- large host range
- low infectious dose
- large amounts of virus b/f clinical signs develop
- no clinical signs in some species (sheep) – allows spread
- persistent infection in partially immune
- hardy virus (many routes of spread)
Will abortion occur in pregnant animals infected with FMDV? What internal organs are affected with FMD?
Yes
Pancreas and heart
What are the clinical signs and lesions of FMD?
Fever, depression, anorexia formation of vesicles Excessive salivation Smacking of the lips Vesicle rupture Lameness Abortion Hear and panceras also have lesions
What is the mortality and morbidity of FMD? Use the words high or low
High morbidity
Low mortality
What kind of vaccine is available for FMD?
inactivated vaccine - safe and effective
What can provide an animal protection of FMD?
Vaccine
Good humoral immune response following recover provides protection against the same serotype
What are problems with the FMD vaccine?
No cross protection if wrong serotype
short-lived immunity
partial protection if variant: does not prevent infection, persistent infection
Cannot distinguish b/w vaccinated and infected animal
Detection easier if no vaccination
How many vaccines are required per year for FMD if we are using it?
2-3
Adjuvanted vaccine protect for up to 1 year
What types of FMDV does the vaccine work against?
Types A, O and C
Is there a vaccination bank available for FMD in the USA?
Yes – associated with USDA
What is prevention protocal for FMD in endemic countries? FMD free countries?
ENDEMIC
- vaccination
- vaccination and slaughter
FMD free
- prevent introduction
- in face of outbreak: test and slaughter, ring-vaccination and slaughter, ring-vaccination and slaughter only sick animals
What are three options for control of FMD?
- Test and slughter (UK)
- Vaccinate and slaughter
- Vaccinate and only slaughter sick animals
How do you diagnose FMD?
Clinical signs – may confuse w/ other vesicular dz
Laboratory:
inoculated onto susceptible cells
ELISA
What samples should be collected for laboratory testing to dx FMD?
epithelium surrounding vesicle
Fluid contained within the vesicle
What are tests looking for when detecting FMD?
Viral antigen
