Host Pathogen Interactions Flashcards
Describe pathogenicity VS pathogenesis VS pathogen.
- Pathogenicity
-ability of virus to cause disease in host - Pathogenesis
-mech of development of disease - Pathogen
-virus that causes disease
Describe virulence VS avirulent.
- Virulence
-quantitative/relative measure of degree of pathogenicity of infecting virus
-not an absolute property of a virus (depends on variables) - Avirulent
-not virulent
Describe lethal dose VS infectious dose.
- Lethal dose (LD50)
-dose of virus needed to cause death of 50% of animals - Infectious dose (ID50)
-dose of virus that will infect 50% of animals
LOWER THE ID50 OR LD50 = MORE VIRULENT
Describe the routes of entry of viruses into host.
- Skin [outer layer of keratin, low pH, FA, bacterial flora, dryness, innate & adaptive immunity]
-bite (arthropod/animals), contaminated objects (needle) - Mucous membrane
- GIT [mucous membrane, acidity/alkalinity, lipolytic/proteolytic, defensins, IgA, scavenging macrophages]
- Respiratory tract [mucociliary, alveolar macrophages, NALT, BALT, temp]
Describe the subepithelial invasaion & lymphatic spread.
- Disseminated infection
-inf that spreads beyond primary site of inf - Systemic infection
-# of organs/tissues infected
Describe directional shedding of viruses from infected epithelium.
critical to subepithelial spread
1. Apical release
-virus dispersal
2. Basolateral release
-access to underlying tissue = systemic spread
Describe primary viremia VS secondary viremia.
- Primary
-initial entry of virus into blood after inf - Secondary
-virus replicated in major organs & enter circ
Describe active viremia VS passive viremia.
- Active
-release of virions from initial site of replication -> blood stream - Passive
-direct inoculation of virus in host (contaminated obj or arthropod bite) -> no initial replication elsewhere in host before
Describe how viruses spread via nerves in the host.
- Neurotropic virus
-virus infect neural cells
-inf occur via neural or hematogenous spread - Neuroinvasive virus
-virus enter CNS after inf of peripheral site - Neurovirulent virus
-virus cause disease of nervous tissue
-neurological symptoms & death
Describe examples of virus spread via nerves in host.
- Virus w low neuroinvasiveness of CNS but high neurovirulence
-enters PNS but rarely CNS
-severe consequences severe/fatal when it does - Virus w neuroinvasiveness but low neurovirulence
-inf lead to invasion of CNS but neuro disease is mild - Virus w high neuroinvasiveness & high neurovirulence
-infects PNS & spreads to CNS w 100% lethality unless antiviral therapy is given after infection
Describe retrograde VS anterograde spread.
- Retrograde
-travel in opp direction of nerve impulse flow
-invades axon terminals & spread to dendrite or cell body & cross synapse to reach next axon terminal - Anterograde
-travel in direction of nerve impulse flow
-virus invade dendrite or cell body & spread to axon terminals & cross synaptic contact to invade dendrite of next neuron
Describe other ways viruses can spread thru the CNS.
-olfactory
-BBB
Describe localized & systemic acute viral infections.
Describe acute VS persistent infections in virus shedding.
- Acute
-intensive shedding over short time period - Persistent
-shed at lower titers for months to yrs
Describe tropism VS pantropic viruses.
- Tropism
-specificity/affinity of virus for a particular host tissue - Pantropic virus
-replicate in more than one host organ/tissue
Describe virus injury to organs/tissues in the skin.
- Vesicles = fluid filled elevations
- Ulcer = opening in skin by sloughing of necrotic tissue past the epi
- Nodule/tumor = solid elevated mass w borders & deep into dermis
- Warts = benign skin growth appear when viruses infect top layer of skin
- Papule = solid elevation without sharp borders
- Erythema = red skin due to systemic viral inf
Describe virus injury to organs/tissues in the GIT.
Describe virus injury to organs/tissues in the respiratory tract.
-loss of ciliary activity
-loss of integrity of lining of mucus layer
-multi focal destruction of epi
-inflammation
-exudation
-influx of inflam cells
-obstruction of air passages
-hypoxia & respiratory distress
-2ndary bacterial inf
Describe virus injury to organs/tissues in the CNS.
-encephalitis or encephalomyelitis characterized by neuronal necrosis
-phagocytosis of neurons (neuronophagia)
-perivascular infiltrations of inflam cells (perivascular cuffing)
-neuronal vacuolation
-progressive demyelination (k9 distemper)
Describe virus injury to organs/tissues in the hemopoietic system.
-petechial (pinpoint) & ecchymotic (larger areas w ill defined margins) hemorrhages
-disseminated IV coagulation (DIC)
>clots form in small blood vessels thru out body -> organs dont get blood -> organ failure
>late stage: raw material for clot exhausted bc over use -> no clot forms = hemorrhage thru out body
-edema
-infarction
>ischemic necrosis
Describe teratogenesis VS arthrogryposis.
- Teratogenesis
-abnormal development or arrest in development of embryo or fetus
>may result in death or malformations fur antenatal period - Arthrogryposis
-joint malformations
Describe virus injury to organs/tissues in the fetus.
- Porencephaly
-BVDV - Congenital hydraencephaly
-calf showing recumbence, depression, dome shaped skull
-BVDV
Describe virus injury to organs/tissues - virus induced immunopathology.
-tissue injury mediated by host immune response to virus inf (price paid by host to clear viral inf)
-depends on balance between protective & destructive effects of the host immune response to viruses
-immunopathology = cause of damage w viruses that are non cytolytic & persistent (ex. Infected cells not immediately destroyed & immune response becomes chronic)
>if immune response clears inf by destroying small # of virus inf cells = host survives w min symptoms & no permanent damage
>if lg # of cells inf before immune induction = same immune mediated destruction can cause severe or fatal path consequences
Describe immunopathology.
-tissue damage mediated by hypersensitivity reactions
-autoimmune disease (ex. Moon blindness in horses)
-inflam mediated tissue damage (ex. Fibrosis)
-immunodeficiency disorders
