Picornaviridae Flashcards
Picornaviridae virion properties
- non enveloped virions
- virion is rounded and smooth
- 27 nm diameter
- icosahedral symmetry
- differences in stability to low pH
Picornaviridae genome
Single molecule of linear positive RNA
Significance of icosahedral symmetry
Allows for efficient assembly that does not require energy
- most efficient shape that can hold the most volume with the least amount of effort
- more geometric, rigid due to capsule
Non-enveloped properties of picornaviridae
Allows virus to infect via oral route and survive conditions of the GIT
Picornaviridae genera
- aphthovirus
- avihepatovirus
- cardiovirus
- enterovirus
- teschovirus
- tremovirus
Foot and Mouth Disease is a member of the ______ family
Aphthovirus
- is a vesicular disease!!
FMD symptoms
Fever, loss of appetite, depression, and marked drop in milk production
- drooling of saliva due to vesicular stomatitis
Vesicles of FMD
Tongue, gums, interdigital skin, coronary band of feet, teats
- vesicle rupture: denuded ulcerative lesions
FMD aftosa
7 serotypes, 60 subtypes
- no cross protection!!
- cloven hoofed animals
- inactivated at pH 6.5 and above 11
- survives in milk, milk products, bone marrow, lymph glands
Cross protection
Immunity against one serotype is not or incompletely effective against other serotypes
FMD is not seen in _______
Horses!
- common in cattle and swine
FMD serotypes
- A
- O
- C
- SAT-1
- SAT-2
- SAT-3
- Asia 1
What are the 3 forms of animal transmission for FMD?
- respiratory aerosols: requires proper temp and humidity
- -> survives 1-2 days in human respiratory tract
- direct contact: ingestion of infected food or animal parts, artificial insemination of biologicals, hormones
- indirect contact via fomites
Humans become ________ for 1-2 days when working with infected animals
Asymptomatic carriers
FMD morbidity and mortality
Morbidity: 100% in animal population (US, Canada, Mexico)
Mortality: less than 1%
- higher in young animals and highly virulent virus strains
- animals generally destroyed to prevent spread
FMD in the US
Disease is not present in the US, but the population is highly susceptible
FMD clinical signs in cattle
Oral lesions
- vesicles on tongue, dental pad, gums, soft palate, nostrils, muzzle
- excess salivation, drooling, serous nasal discharge
FMD leison progressivity
Oral lesions heal within days
- may become infected with bacteria leading to prolonged lameness and mucopurulent nasal discharge
- mortality in adult cattle is low
- calves younger than 6 months: possible mortality due to myocarditis
FMD clinical signs in pigs
- hoof lesions: lameness, lesions on coronary band, heel, interdigital space (more severe than in cattle)
- snout vesicles
- oral vesicles are less common, drooling is rare
FMD clinical signs in sheep and goats
Mild, if any signs
- fever
- oral lesions
- lameness
- makes diagnosis difficult
Clinical susceptibility and epizootiology
- cattle: best indicator due to prominent clinical signs
- pigs: best amplifier
- sheep: silent shedders
High mortality in calves with FMD due to ________
Myocarditis and myocardial necrosis
- causes acute death
FMD virus and hosts
Aphthovirus
- cattle, sheep, swine are susceptible
- horses are resistant
Swine vesicular disease virus and hosts
Enterovirus
- swine are susceptible
- cattle, sheep, horse are resistant
Vesicular stomatitis virus and hosts
Rhabdovirus
- cattle, sheep, swine, and horses are susceptible
Vesicular exanthema of swine virus and hosts
Coronavirus
- swine and horses are susceptible
- cattle, sheep are resistant
FMD in wildlife
May act as reservoirs
- may or may not show clinical signs
FMD diagnostic samples
- vesicular epithelium
- vesicular fluid (best sample!)
- oesophageal-pharyngeal fluids
- serum (acute and convalescent)
Collection of OP fluids
Use a probe inserted into the esophagus
- collect all fluid in the area
- mix with transport media for viruses
- pink color is normal (pH is normal)
- yellow color: pH is acidic and virus is dead
FMD antigen detection
- virus isolation (in vitro or in vivo)
- complement fixation
- ELISA
FMD antibody detection
- virus infection associated antigen!
- virus neutralizaiton
- ELISA
FMD nucleic acid detection
RT-PCR
- common and efficient way to diagnose
National Animal Health Laboratory Network
Cooperative effort between
- Animal and Plant Health Inspection Service
- National Institute of Food
- Agriculture American Association of Veterinary Laboratory Diagnosticians
Vesicular diseases
Economical and trade problems
- all vesicular diseases are clinically similar
- diagnostics are necessary
- notifiable disease
Recommended actions if FMD is suspected
Should be reported immediately upon diagnosis or suspicion of disease
Swine vesicular disease
Enterovirus
- sporadically in Europe and Asia
- vesicles between heel and coronary band
- lameness
- 10% of cases vesicles are seen on snout, lips, and tongue
- looks similar to FMD without diagnostics!!
Equine Rhinovirus 1
Aphthovirus (Rhinitis A virus)
- severe systemic and respiratory signs in horses
- nasal discharge, pharyngitis, lymphadenitis, cough
- viral shedding in feces
Avian encephalomyelitis
Tremovirus
- neurological disease
- young chickens (1-21 days old)
- dullness, progressive ataxia, tremors, weight loss, blindness, paralysis
- no gross lesions!!
Histopath of avian encephalomyelitis
Mononuclear encephalomyelitis
Avian encpehalomyelitis has _______ transmission
Vertical
- get disease from hens through the egg, chick will hatch infected
- could also be infected through feces (horizontal transmission) –> 3-4 weeks clinical signs
Encephalomyocarditis
Cardiovirus
- natural host are rodents
- transmitted from rodents to humans, monkeys, horses, cattle, and swine
- myocarditis with fatalities
Porcine polioencephalomyelitis
Aka: Teschen/Talfan disease
- Teschovirus
- neurological diseases in swine with paralysis
- may be related to stillbirth, fetal mummification, embryonic death infertility
Duck viral hepatitis
Avihepatovirus
- severe disease of ducks
- ducks younger of 3 weeks
- mortality can approach 100%
- extensive hepatic necrosis
- located primarily in Asia
