Finals: Picornaviridae Flashcards
Picornaviruses were the first demonstrated as a ______ _____ that caused disease in animals by Loeffler and Frosch in 1898
Filterable agent
The filterable agent of Picornaviruses caused what?
Foot-and-mouth disease (FMD)
Picornaviruses have played a big role in what?
Development of virology
What are the 8 Picornaviridae genera?
Aphtovirus Teschovirus Erbovirus Hepatovirus Enterovirus Cardiovirus Kobuvirus Parechovirus There are two more proposed
What virus was removed from the Picornaviridae in 2006 to be reclassified to Enterovirus?
Rhinovirus
What are the virion properties of Picornaviruses?
Non-enveloped, ss, positive sense RNA viruses
Icosahedral symmetry
Genomic RNA is infectious
Picornaviruses are stable in what?
Mucous and feces
Can withstand strong sunlight
Unstable in aerosols
High humidity favors survival for several hours
Sodium carbonate is an effective disinfectant
Where does the replication of Picornavirus occur?
In the cytoplasm
Most Picornaviruses enter cells through endocytosis or fuse with the cell membrane
Poliovirus does not enter cells through endocytosis: VP4 and the amino terminal of VP1 relocate to the virion surface. VP1 makes a pore in the cell membrane allowing injection of viral capsid into the cell
Tell me about foot-and-mouth disease virus (FMDV)
Picornaviridae, Aphthovirus
There are 7 distinct serotypes, and not cross protective
Inactivated at pH below 6.5 and above 11
Survives in milk, milk products, bone marrow
When was the last reported case of Foot-and-mouth disease in the US?
1929
When were the last reported cases of foot-and-mouth disease in Canada and Mexico?
1953
FMDV is a disease of who?
A disease of cloven hoofed animals
It should not be confused with hand, foot and mouth disease in humans caused by coxsackie virus A6, A10, A16 or enterovirus 71
What are the clinical signs of FMDV infection?
Incubation of 2-12 days
Early clinical signs include fever excessive salivation and nasal discharge (cattle).
Lesions (initially vesicles) on the buccal area and in the buccal cavity (snout in pigs).
Vesicles on the coronary bands and interdigital space
Recover in two weeks unless secondary infections arise
Abortion
Death in young animals
Lesions on teats
What are the clinical signs of FMDV in goats and sheep
Mild, if any, signs
Fever, oral lesions, lameness
Make recognition of infection and prevention of spread difficult
Maintenance hosts
What is the relevance of FMDV?
Highly contagious trans-boundary animal disease.
Cause major socio-economic losses due to:
-loss of livestock production
-limitation of international trade in livestock and animal products
What are the morbidity and mortality of FMDV?
Morbidity 100% in susceptible animal population.
Mortality less than 1%: higher in young animals infected with highly virulent virus strains, animals generally destroyed to prevent spread.
What is the transmission of FMDV?
Respiratory aerosols: proper temperature and humidity, survives 1-2 days in human respiratory tract
Direct contact: ingestion of infected animal parts, artificial insemination, biologicals, hormones
Indirect contact via fomites
How do we clinically diagnose FMDV?
Clinically, vesicular diseases are indistinguishable!!!
Salivation, lameness with vesicles - requires further testing.
Tranquilization may be necessary to complete examination.
What is the proper way for sample collection for testing for FMDV?
Before collecting or sending any samples, the proper authorities should be contacted.
Notify authorities and wait for instructions before collecting samples.
Samples should only be sent under secure conditions and to authorized laboratories to prevent the spread of the disease.
What are the laboratory diagnosis for FMDV?
Lab tests: Virus isolation and ID Antigen or nucleic acid detection* Complement fixation ELISA and virus neutralization
What are the clinical signs on FMDV in cattle?
Oral and hoof lesions, salivation, drooling, lameness, abortions, death in young animals, “panters”
Disease indicators
What are the clinical signs of pigs with FMDV?
Severe hoof lesions, hoof sloughing, snout vesicles, less severe oral lesions.
Amplifying Hosts
How do we treat FMDV?
There is no treatment available - DO NOT ATTEMPT ANY TREATMENT
For FMD-free countries an outbreak could result in quarantine, euthanization and disposal
Vaccines are available: ramifications are many.
How do we prevent FMDV?
USDA APHIS: Strict import restrictions. Prohibit live ruminants, swine, and their products from FMD-affected countries.
>450 FADD to investigate suspicious lesions
State planning/training exercises
Biosecurity protocols for livestock facilities
What is the disinfection of FMDV?
Effective solutions include: 2% sodium hydroxide (lye) 4% sodium carbonate (soda ash) 5.25% sodium hypochlorite (household bleach) 0.2% citric acid
Areas must be free of organic matter
What are the vaccines for FMDV?
Killed vaccine, serotype specific
Huge implications if vaccination is done
Tell me about Enterovirus
Are ubiquitous and occur in all vertebrates
Same cause disease of economic importance in swine and poultry
Cause of swine vesicular disease
Cause of polioencephalomyelitis
Tell me about Swine vesicular disease virus (SVDV)?
The virus is enzootic in Italy
Resistant to ambient temperature and to sodium carbonate
Can be transmitted in pork productions
Virus can survive neutral pH at 4C for 160 days
Is swine vesicular disease virus found in North America?
Not at all.
So the USA and Canada it is referred to as a foreign animal disease.
Pigs are the only natural host for the swine vesicular disease virus.
What is the transmission swine vesicular disease virus?
Virus infects swine via skin abrasions and mucosa by ingestion and inhalation.
Direct contact among infected swine or with their excretions.
What are the clinical signs of SVDV?
Sudden appearance of lameness
Fever - transient
Vesicles appear at the junction between heel and coronary bands.
Lesions on the snout, lips and tongue
Occasionally, some pigs may develop encephalomyelitis - ataxia, circling and convulsions
What is the pathogenesis of SVDV?
Infection is through fecal-oral route
Replication is in the gastrointestinal tract - predominantly
But skin abrasions may also act as portals of entry, particularly feet.
Pigs can become viremic within 24 h and vesicles appear by 48 h
Virus is excreted in large amounts in feces
How do we diagnose SVDV?
The case should be treated as if it was FMD
Rapid tests should be performed to rule out FMD
RT-PCR, particularly multiplexed assays which can detect multiple agents at once.
ELISA can be performed IF enough vesicular fluid is collected.
Virus isolation in swine kidney cells - can produce CPE after 6 h
What are the DDx for SVDV?
Foot-and-mouth disease
Vesicular stomatitis
Vesicular exanthema of swine
Chemical or thermal burns
NO VACCINE!!
Tell me about sanitary prophylaxis
On-going vesicular disease surveillance program with tracing and humane slaughter of all test positives and contacts
Control of vehicles used for transporting pigs
Thorough disinfection of premises, transport vehicles, and equipment
