Viruses Flashcards
What are viruses?
Small, intracellular obligate parasites
WHat shape can viruses be?
Helical or icosahedrons
What are 2 examples of current viruses?
Rabies
Ebola
Viruses are classified by the Baltimore classification system. How are they classified?
morphology
Genome
Ecology
Viral genomes can be linear or segmented, single or double stranded, positive sense or negative sense. What is positive and negative sense?
Positive sense - viral strand directly codes for protein
Negative sense - viral strand is complimentary code for a protein
What 2 viruses have been eradicated worldwide and who did they affect?
Smallpox- people
Rinderpest - ruminants
How are viral infections controlled?
Biosecurity
Vaccination
Antimicrobial
How can viruses enter the body?
Ingestion Inhalationn Injection Through skin (trauma, bite, arthropod) Via mucosal membrane (oral/respiratory/reproductive)
How do viruses cause disease?
Cross mucosal barriers via blood
Identify and enter target cell
Replicate
Leave
What is viraemia?
Viruses enter blood from lymph nodes and spread rapidly
What are the 2 types of viraemia?
Primary - early infection, low level, few target cells
Secondary - large scale infection
How do viruses replicate and infect others?
Uncoat genome Positive/negative genome integration Genome replication Protein production Virus assembly and leave Transmission via saliva/faeces/respiratory
Why can viruses mutate rapidly?
No proofreading during DNA/RNA reproduction, unlike other cells. Make mistakes
Genomic integration - viruses integrate their genes into host, when host cells replicate, also replicates the virus
What is viral immunotolerance? Why do viruses do this?
Lack of immune response to antigen
Optimal virulence to increase transmission
Viruses involved with gastrointestinal disease enter the body through the oral route. What do they need to survive before they become infectious?
Immune response
Stomach acid
Bile
Why do viral GI diseases cause vomiting diarrhoea?
Aim to spread
What are examples of viral enteritis?
Norovirus Pestivirus Coronavirus Transmissible gastroenteritis virus Rotavirus Canine/feline parvovirus
What is norovirus the main cause of?
Diarrhoea in humans
What are pestiviruses?
Type of flaviviridae
E.g. bovine viral diarrhoea
What species do coronaviruses affect? What type of nucleic acids do they have
Porcine, bovine, feline
Sense RNA
Which species gets the highly infectious transmissible gastroenteritis virus? How are they protected?
Pigs
Through milk
Rotavirus is common in which animals?
Young - vaccinate dams to prevent passing to offspring
Rotarovirus infectivity is increase by which enzyme? How?
Trypsin
Releases infectious proteins
What type of nucleic acid is in feline/ canine parvovirus? It is highly infectious, which cells does it invade?
DNA
Rapidly dividing cells
What is interferon? What does it do?What can it be used to treat?
Signalling protein released as part of the innate immune response
Reduce viral replication
CPV/FPV
Which 3 viruses are involved with respiratory disease?
Orthomyxovirus (influenza)
Infectious bronchitis virus
Feline calicivirus and herpes virus
Describe equine influenza
Caused by orthomyxovirus S - nasal discharge, caugh Can be fatal Vaccines require regular updates Can be passed to dogs
Describe avian influenza
Between birds, can pass to cats
By orthomyxovirus
Replicates in GI/respiratory tract but is systemic
What causes genetic drift?
Mutations
What causes genetic shift? - radical viral changes
Reassortment (process where influenza viruses swap gene segments)
What is DIVA?
Differentiating between infected and vaccinated animals
How do you DIVA?
IBR marker vaccine
Vaccine contains only certain antibodies
