Host-Pathogen Interactions 1 Flashcards
What is lethal dose 50? (LD50)
Dose of virus required to cause death of 50% of animals
What is infectious dose 50? (ID50)
Dose of virus that will infect 50% of experimental group of hosts/animals
The lower the ID50 & LD50, the ___________ virulent an organism
More
What are 4 routes of entry of virus into host?
- The skin
- Mucous membrane
- GI tract
- Respiratory tract
What are 3 ways a virus can enter host via transcutaneous injection?
- Arthropod bite
- Bite of infected animal
- Contaminated objects
What are 3 ways virus can enter host via mucous membrane?
- Conjunctiva
- Oropharynx
- Genitourinary tract/rectum
What is a disseminated infection?
Infection spreads beyond primary site of infection
What is a systemic infection?
A number of organs or tissues are infected
__________ release facilitates virus dispersal, while ___________ release provides access to underlying tissues, facilitating systemic spread
- Apical
2. Basolateral
What is viremia?
Presence of virus in blood, may be free in blood or in cell, such as lymphocytes
What are 4 types of viremia?
- Passive
- Active
- Primary
- Secondary
What is passive viremia?
Direct inoculation of virus in blood, such as bite of arthropod or contaminated syringe
What is active viremia?
Viremia following initial replication in host. Release of virions from initial site of replication to blood stream
What is primary viremia?
Initial entry of virus into blood after injection
What is secondary viremia?
Virus has replicated in major organs and once more entered the circulation
What are 3 ways virus can spread via nerves?
- Neurotrophic
- Neuroinvasive
- Neurovirulent
What is a neurotrophic virus?
Virus that can infect neural cells via neural or hematogenous spread
What is a neuroinvasive virus?
Viruses enter central nervous system after injection of a peripheral site
What is a neurovirulent virus?
Viruses that cause disease of nervous tissue, manifested by neurological symptoms and often death
T/F: Virus can exhibit low neuroinvasiveness but high neurovirulence
True
T/F: Virus exhibits neuroinvasiveness but low neurovirulence
True
Virus can exhibit high neuroinvasiveness and high neurovirulence
True
Retrograde spread of viruses travel in ____________ direction of nerve impulse flow
Opposite
Anterograde spread of viruses travel in _________ direction of nerve impulse flow
Same
What are 2 ways viruses spread through the CNS?
- Olfactory routes
2. Blood brain barrier
Acute infection is usually ___________ shedding over _______period of time
- Intensive
2. Short
Persistent infections can be shed at __________ titers for ___________ to __________
- Lower
- Months
- Years
What is viral tropism?
Specificity/affinity of virus for particular host tissue
What is a pantropic virus?
Can replicate in more than one host/tissue
What is a vesicle?
Fluid filled sac/elevation
An ulcer is an opening in skin caused by __________ of necrotic tissue
Sloughing
Nodules will have ________ borders and tumors will ____________ ____________ into dermis
- Distinct
2. Extend deep
T/F: Warts are benign skin growths that appear when virus infects top layer of skin
True
Erythema is reddening of skin, consequence of ___________ viral infection
Systemic
What are 2 ways viruses can invade the GI tract?
- Ingestion
2. Hematogenous spread, systemic infection
What are 3 types of ways viruses can cause injury to the GI tract?
- Destruction of enterocytes due to viral replication, hypersecretion
- GI disease, malabsorption, diarrhea
- Pronounced dehydration, acidosis, hemoconcentration
What are some injuries viruses do to the respiratory tract?
- Loss of ciliary activity
- Loss of integrity of lining of mucus layer
- Multifocal destruction of epithelium
- Inflammation
What are 4 types of injuries viruses can do to the CNS?
- Neuronal necrosis
- Perivascular cuffing
- Progressive demyelination
- Neuronal vacuolation
T/F: Clots form in small vessels throughout the body, however organs do not get blood, they have organ failure
True
Disseminated intravascular coagulation (DIC) will display _______________ throughout the body
Hemorrhages
What is teratogenesis?
Abnormal development or arrest in development
Virus-induced immunopathology is tissue injury mediated by __________ immune response to virus infection
Host
Virus-induced immunopathology depends on the delicate balance between ____________ and _____________ effects of host immune response
- Protective
2. Destructive
Immunopathology is tissue damage mediated by _________________ reactions
Hypersensitivity
Immunopathology is associated with ____________ diseases and _____________ disorders
- Autoimmune
2. Immunodeficiency
Immunopathology can also be ____________ mediated tissue damage
Inflammation
What are some roles of T cells?
- Cytotoxic cell mediated lysis/killing of infected host cells
- Releases of CD4+ and CD8+
Toll-like receptors are part of the __________ immune response
Innate
T/F: Antibody responses to viruses may also contribute to tissue damage
True
T/F: Infectious bursar disease is an example f immunosuppression
True
What are inapparent infections?
- Clinical signs and symptoms are not evident
- Too few cells may be infected
- Stimulate host immune response
- Possible source of virus spread
What is an acute infection?
- Short clinical course
2. Rapid clearance from host immune response
What is a latent infection?
- Persistent
- Infectious virus is not demonstrable except when reactivation occurs
- Reactivation often stimulated by immunosuppression and/or action of cytokines or hormone
What is a chronic infection?
Virus is continuously shed from or is present in infected tissue
What is a slow infection?
- Prolonged incubation period, lasting months or years
2. Slow, progressive lethal disease
