Viruses Flashcards
Viruses are:
- noncellular infectious particle
- obligate intracellular parasites
- can only live and reproduce inside other cells.
Basic Virus Anatomy
Composed of:
Nucleic Acid Core
Protein Coat (capsid)
Outer Envelope
Are all viruses the same?
There is a great variation between virus types.
Do antibiotics work against viruses?
No, they are not sensitive to antibiotics.
Are vaccinations effective against viruses?
vaccinations are generally very good at protecting host against viruses.
What is the fomite lifespan of a virus?
Some have very long fomite lives.
Nucleic Acid Core (virus)
- DNA or RNA
- ss or ds
- Contains genes needed for virus replication
Protein Coat (virus) What does it do for the nucleic acid?
It surrounds and protects the nucleic acid
Protein Coat (virus) Antigenic
Many of these proteins are highly antigenic.
- produce an immune response in host
- may be used to make vaccines
Protein Coat (virus) Host Specificity
They are responsible for host specificity.
-because they have to bind to specific receptors (ex: infect dogs, but not cats)
Outer Envelope (virus)
- only present in some viruses
- surrounds protein coat of some viruses
- made of remnants of host cell plasma membrane
- lipid bilayer
Virus Life Cycle
Adsorption/Attachment
- virus specifically recognizes host cell (protein-protein recognition)
- binds to specific receptor on host cell surface
Virus Life Cycle
Penetration
Entire virus particle or just its nucleic acid enters inside of host cell.
Virus Life Cycle
Uncoating
If virus enters cell intact, its nucleic acid comes out of protein coat.
Virus Life Cycle
Viral Replication and Protein Synthesis
- viral nucleic acid reproduces
- more viral proteins are synthesized
Virus Life Cycle
Assembly
New viral particles are assembled in the host cell from the newly made viral nucleic acid and protein.
Virus Life Cycle
Release
- virus particle are released from host cell by various mechanisms
- may be released slowly over time (“shedding”) or all at once
- may or may not kill host cell
Virus Life Cycle
6 steps
- Adsorption/Attachment
- Penetration
- Uncoating
- Viral replication and protein synthesis
- Assembly
- Release
Name the 3 outcomes of viral infection.
- No viral replication, no disease (abortive)
- Shedding (restrictive)
- Large rapid release of viral particles – cell death and host disease. (productive)
What is “shedding”?
virus
- slow steady release of viral particles
- no cell death
- may or may not cause disease of host
How do you diagnose viruses in mammals?
- Patient history very important
- Vaccination status very important
- Respiratory sounds (dorsal-viral)
- X rays
- Blood tests for virus or antibodies against the virus.
Diagnosis (virus)
How does vaccination status help?
If pt is unvaccinated, lean to viral diagnosis.
- err on side of caution
If pt is vaccinated, lean to another cause (bacterial, parasitic, etc.)
Diagnosis (virus)
What types of blood tests?
- serological tests
- ELISA (enzyme-linked immunoabsorbent assay)
What are the 3 major treatment strategies for viruses?
- supportive care
- nutrition and fluids
- antibiotics
If antibiotics are not effective against viruses, why would they be given to a patient as part of a viral treatment?
Often given to treat or prevent secondary bacterial infections.
What is a retrovirus, and what does it do?
Reverse transcriptase. They become part of the host DNA.
What does FeLV stand for?
Feline Leukemia Virus
What type of virus is FeLV?
It is a retrovirus – small ss RNA virus.
Is FeLV fatal?
It is often fatal, 2nd leading cause of death behind trauma.
Is FeLV hard to kill?
Virus is easily killed in the environment.
What are the 6 ways FeLV is transmitted?
- direct contact through saliva and nasal secretions of infected cats.
- persistently infected cats may shed virus for many years in body secretions.
- shared litter boxes, toys, food dishes
- nose to nose contact, sneezing
- queen to kitten
- some cats successfully eliminate the infection (but often become carriers)
Why can FeLV be transmitted via direct contact?
- virus mostly found in saliva
- also through urine and feces
FeLV Carrier Statistics
- 1-3% in single cat households become persistently infected
- 30% in multiple cat households become persistently infected
- infection rate increases with cat population density
What is the FeLV fatality rate?
Up to 80% fatal within 3 years of infection.
How many types of FeLV virus are there?
3 types of viruses – cat may have one or a combination of them.
FeLV Symptoms
- fever, depression, loss of appetite, swollen lymph nodes, rhinitis, gingivitis, etc. very wide range of symptoms.
- immunodeficiency leading to secondary infections
- cancer – esp. lymphosarcoma and bone marrow disorders
- anemia - leukemia
What happens if the cat does not die from FeLV?
They become a carrier.
How is FeLV diagnosed?
There are many blood tests available.
How do you treat a cat with FeLV?
You give supportive care.
Is there a vaccination for FeLV?
Yes. It is effective, but not completely.
What does FIV stand for?
Feline Immunodeficiency Virus
What is FIV?
Feline form of HIV.
What type of virus is FIV?
A retrovirus (ss RNA)
What is another name for FIV?
Also called FTLV – Feline T-lymphotrophic T cell lentivirus.
How is FIV transmitted?
Mostly through blood transfer, e.g. bite wounds from other cats.
What are the 3 major stages of FIV?
- Acute Stage
- Latent, Asymptomatic State
- AIDS Stage
How long does the acute stage last in FIV, and what are the symptoms?
- lasts 2-9 weeks
- fever, neutropenia, enlarged lymph nodes
How long does the latent stage last in FIV, what are the symptoms?
- up to 10 years
- minor if any clinical signs
- cat is a carrier
How long does the AIDS stage last in FIV, what are the symptoms?
- months to a few years
- severe weight loss, opportunistic infections,
- immunodeficiency, tumors, etc.
What is the outcome of FIV?
Death
Are the symptoms of FIV similar to another virus?
Yes. symptoms may be similar to FeLV (gingivitis, chronic diarrhea, fever, conjunctivitis, rhinitis, swollen glands, appetite loss, depression, etc.
How is FIV prevented?
Vaccination
What does neutropenia mean?
Decrease in neutrophil, white blood cells.
What does FPV stand for?
Feline Panleukopenia Virus
Is FPV serious?
Yes, it is a very serious disease.
What is another name for FPV?
Feline Distemper (VERY different from Canine Distemper or Parvo)
What type of virus is FPV?
A parvovirus. Very small ss DNA virus.
Is FPV fatal, why?
Highly. It kills the diving cells in the immune systems and GI systems.
Is FPV able to survive in the environment?
Yes, virus can survive extreme temperatures and humidity for years – can also survive many common disinfectants. This makes it very contagious.
Is FPV contagious?
Yes, it is very contagious.
How is FPV transmitted?
- sharing food, water, bedding, litter boxes with other cats
- mostly by contact with feces of another cat
- also by direct contact with infected cat
- in utero from infected mother to offspring
What happens when offspring is infected with FPV in utero?
cerebellar hypoplasia in offspring
Is FPV severe?
It is very sever and often fatal, some cats die suddenly.
How quickly to cats get sick once they have contracted FPV?
Cats can get sick within a few days of infection.
What are the symptoms of FPV?
- depression, loss of appetite, fever, vomiting, diarrhea
- pregnant cat may have stillborn kittens.
Is FPV preventable?
Yes, vaccinations are VERY effective.
What does FIP stand for?
Feline Infectious Peritonitis
Is FIP serious?
It is very serious and often fatal.
What cause FIP?
A feline coronavirus (large RNA virus).
Are there other feline coronaviruses and are they harmful?
- there are a variety of feline coronaviruses in the environment.
- almost all of them are basically harmless.
What about benign strains of coronavirus?
They can spontaneously mutate to the disease forming virus and cause illness.
What is an example of a coronavirus mutation?
FECV mutates to FIPV
What is the percentage of cats with feline coronavirus that develop FIP?
1% to 5%
Can cats be carriers of coronavirus?
Yes, there are asymptomatic carriers of benign Coranaviruses.
Can you test a cat to tell if it has FIP or is a carrier of a benign strain?
Diagnostic tests do not distinguish between carriers of harmless virus and those with FIP.
Is FIP easily transmitted?
Yes, VERY easily.
How is FIP transmitted?
ingestion of viral particles from feces ( or saliva) of infected cats.
Where is FIP prevalent?
- multiple cat households, over 50%-70%
- may be up to 20% infection rate in catteries, as it is difficult to prevent.
Where is FIP not prevalent?
In single cat homes.
What are the 2 forms of disease with FIP?
Wet Form (acute)
Dry Form (chronic)
– both caused by the same virus
- depends on strength of infected cat’s immune response