PID BLOCK 2 Flashcards
Virology
Study of viruses and viral diseases
Virologist
someone who studies viruses
Why is vet virology important?
causes high rate of mortality and morbidity in animals
impacts food safety and security
causes economic loss and is expensive to control and prevent
Zoonosis
viral diseases transmitted from animal to human
What is a virus?
- non living entities
- contains DNA or RNA surrounded by a protein (capsid)
-sometimes has a lipid envelope
-no organelles
-cant make proteins or energy by themself
-OBLIGATE INTRACELLULAR PARASITE
-dormant outside of cell
-cant multiply by division
Capsid
protein shell of a virus that holds the DNA/RNA
- made of capsomeres held together with non covalent bonds
Nucleocapsid
capsid + nucleic acid (DNA or RNA)
Lipid envelope
- lipid bilayer that covers the capsid
- glycoproteins present on the surface of the envelope (appears as spikes)
-derived from host cell
What is a naked virus?
Does not contain lipid envelope
Pleomorphism
ability of virus to alter shape or size
(Filament shaped, bullet shaped, tadpole shaped, rod shaped, brick shaped, spherical
Steps of virus replication
- Attachment
- Penetration
- Uncoating
- Synthesis of nucleic acid and protein
- Assembly and Maturation
- Release in large #’s
Classifications of viruses
- Nature of virus genome and genetic diversity
- Virus replication strategies
- Virus morphology
What is the international committee on Taxonomy of Viruses? (ICTV)
develops, refines, and maintains virus taxonomy
How to diagnosis Viral infections
- Clinical signs
- Necropsy
- Histopathology
- Cultivation/isolation
- Inoculation in eggs
- Electron microscopy
- ELISA
- PCR/RT-PCR
Serology
detection of viral antigen or host antibody against virus (ELISA)
How to treat viruses?
- Antiviral drugs
- Immune system stimulation- interferon therapy
- Synthesize antibodies or admin of natural antiserum (antibodies)
Prevention of viruses
- Vaccination
- Proper hygiene
- Eliminate arthropod vectors
- Quarantine and culling
Pathogenicity
ability of a virus to cause disease in host (harm the host)
Pathogen
the virus that causes disease
Pathogenesis
mechanism of development of a disease (HOW it causes disease)
Non pathogenic virus vs pathogenic viruses
Non-path - does not cause disease
Path- causes symptoms (ex: sick in the hospital)
Virulence
degree of pathogenicity (how bad is it)
Avirulent
Not harmful to the host
Lysis in viruses
Cell explodes and virus is able to infect new cells
Apoptosis
cell dies so virus cant replicate/ cause more harm
Impacts of virus replication
- Cell death
- Fusion of cells (multinucleation)
- No apparent change (latent, persistent)
- Transformation (normal to malignant
Virus properties that affect virulence
- Genetic variation
- Route of entry
- Affinity of virus to host organs
- Dose of infection
- Immune evasion
How is virulence measured?
LD 50 (Lethal dose reference)- dose req. to cause death in 50% of population
(A virus with LD 30 will cause more harm than a virus with LD 50)
How does a virus spread through the body?
- Local infection of epithelial surfaces
- Subepithelial invasion and lymphatic spread
- To the blood stream
Viremia
Presence of virus in the blood
Can be primary of secondary
Primary vs Secondary Viremia
Primary: initial entry of virus in blood
Secondary: Virus multiplied in organ and enters blood to affect another organ
Types of viral infection?
Disseminated: spreads beyond primary site
Systemic: # of organs/tissues infected
Neurotropic Virus
can infect neural cells but could decide hematogenous spread
Neuroinvasive Virus
enters central nervous system (CNS)
Neurovirulent Virus
causes disease of nervous tissue.
Neuro symptoms and often death
Tropism
affinity for a specific tissue
Ex: Enteric vs resp virus
Pantropic virus
can replicate in more than one host
Outcomes of viral injury
- Cell lysis
- Apoptosis
- Malignant transformation
- Persistent infection
- Immunosupression
Acute vs Persistent infection
Acute- intensive shedding over short period
Persistent- shed at low levels for months-years
Virus Injury to Skin
Can be localized or disseminated
- Vesicle (small elevation of fluid)
- Ulcer (opening of skin by necrosis)
- Nodules (solid, elevated mass)
- Warts (benign skin growth)
- Erythema (reddening of skin)
What is a reservoir?
Habitat or population where infectious agent resides
DOES NOT mean illness
Individual can be killed but pathogen can remain in population
What is the chain of infection?
- Reservoir
- Portal of exit
- Mode of transmission
- Portal of entry
- Susceptible host
- Germs (infectious agent)
Vertical mode of transmission
- anything repro, from mom to baby
1. Transovarial
2. Perinatal
3. Eggs/ transplacental
Horizontal mode of transmission
Direct or Indirect
Direct is contact or droplets/airborne
Indirect is vector or vehicle
Indirect vs Direct mode of transmission
Indirect
1. intermediary
2. Distance, long period of time
Ex: touching an ATM
Vector of Vehicle
Direct:
1. From reservoir to susceptible host
2. Little space, short time period
Ex: sneezing on someone
Contact of Droplets/airborne
Vehicle transmission
Inanimate object that serves to communicate disease
- Ex: water, food, soil
Ex of an indirect route
Vector transmission
Arthropods that carry and transmit pathogens
Mechanical vs Biological
Ex of indirect route of transmission
Mechanical vector
Carries pathogen from one host to the next without self being infected (Ex flies)
Ex of indirect route of transmission
Biological vector
Pathogen will change/multiply/develop while in vector (Ex tick)
Ex of indirect route of transmission
What is the main portal of entry for transmission?
The eyeballs
Who is a more susceptible host?
Young, old, pregnant, immune supressed (YOPI)
What makes up a nucleic acid?
- Nitrogen base
- 5 carbon sugar (ribose of deoxyribose)
- 3 phosphate groups
How are DNA sequences read?
From 5’ to 3’ from sense strand
What is a pyrimidine?
6 carbon ring
C,T, U
What is a purine?
2 joined carbon rings
A, G
DNA vs RNA
DNA:
- Double stranded, deoxyribose
- Thymidynic acid
- A, T pairing
- Nuclear location
- Stable
RNA:
- single stranded, ribose
- Uridynic acid
- A, U pairing
- Cytoplasmic location
- Labile
Transcription
DNA to RNA
Translation
RNA to protein
Silent mutation
mutation with no function change
Missense mutation
Change in function (produces a dif protein)
Nonsense mutation
change in termination/STOP codon
premature termination
Frameshift mutation
inserting or deleting a number or base pair other than a multiple of 3
Transformation
acquisition of new genetic markers by incorporation of added DNA
Ex: even after mouse dies bacteria contains DNA that can be extracted and transformed
Chain of transmission
- Infectious agent
- Reservoir
- Portal of exit
- Mode of transmission
- Portal of entry
- Susceptible host
Fomite
contaminated object, transmits disease on a limited scale
Ex of indirect transmission
