Host- Pathogen Interactions Flashcards
__________ refers to the ABILITY of a Virus to cause Disease in the Host.
Pathogenicity
The Virus which causes disease is called a __________.
Pathogen
__________ is the manner/ mechanism of development of a disease.
Pathogenesis
What term is used as a quantitative or relative measure of the degree of pathogenicity of the infecting virus?
Virulence
Avirulent
Not Virulent (Not harmful to the host)
T/F: Virulence is an absolute property of a virus, and depends on many variables.
FALSE!!
Virulence IS NOT an absolute property of a virus, but depends on many variables.
The dose of the virus required to cause death in 50% of the animals is called ________.
Lethal Dose 50 (LD50)
The dose of virus that will infect 50% of an experimental group of hosts/ animals is called __________.
Infectious Dose 50 (ID50)
T/F: The higher the ID50 and LD50, the more virulent the organism.
FALSE!
The LOWER the ID50 and LD50, the more virulent the organism.
Virus A has an LD50 of 80 and Virus B has an LD50 of 30. Which virus is more virulent?
A. Virus A is more virulent
B. Virus B is more virulent
C. Virus A and B has the same virulence
D. Neither virus in this case is virulent
B. Virus B is more virulent
- the lower the LD50 the more virulent the organism!!
What are the routes of entry?
- Skin
- Mucous Membrane
- GI tract
- Respiratory tract
All of the following are defenses of the skin EXCEPT:
A. Dense outer layer of keratin
B. High pH
C. Presence of Fatty Acids
D. Bacterial Flora
E. Dryness
F. Components of Innate and Adaptive Immunity
G. All of the above are defenses of the skin
B. High pH
–It should be LOW pH as one of the defenses!!
All of the following are examples of transcutaneous injections EXCEPT: A. Bite from a mosquito B. Contaminated needles C. Bite from a tick D. Inhalation of virus E. Bite from a rabid dog
D. Inhalation of virus
The 3 transcutaneous injections routes of entry via the skin are:
1- Bite of Arthropods
2- Bite of Infected Animal
3- Contaminated Objects
All of the following are defenses of the GI tract EXCEPT:
A. Mucous membrane of oral cavity and esophagus
B. Acidity of the stomach
C. Acidity of the intestine
D. Layer of mucus covering the gut
E. Lipolytic activity of bile
F. Proteolytic activity of pancreatic enzymes
G. Defensins (host defense peptides)
H. IgA
I. Scavenging Macrophages
C. Acidity of the intestine
–It should be ALKALINITY of the intestine
All of the following are defenses of the Respiratory tract EXCEPT:
A. Mucociliary blanket
B. Alveolar macrophages
C. NALT
D. BALT
E. Temperature Gradient
F. All of the above are defenses of the respiratory tract
F. All of the above are defenses of the respiratory tract
________ = presence of virus in the blood.
Viremia
What type of infection spreads beyond the primary site of infection?
Disseminated Infection
What is the infection type called when there is a number of organs or tissues that are infected?
Systemic Infection
T/F: Directional shedding of viruses from the infected epithelium is CRITICAL to subepithelial spread.
True
Apical release facilitates ___________.
Virus dispersal
Basolateral release provides access to underlying tissues, facilitating _________ spread.
Systemic
Virus may be free in blood or in a cell, such as a lymphocyte. This is an example of what?
Viremia
Initial entry of virus into the blood after infection. This is the definition of: A. Passive Viremia B. Active Viremia C. Primary Viremia D. Secondary Viremia
C. Primary Viremia
Direct inoculation of virus in blood. This is the definition of: A. Passive Viremia B. Active Viremia C. Primary Viremia D. Secondary Viremia
A. Passive Viremia
Virus has replicated in major organs and once more entered the circulation. This is the definition of: A. Passive Viremia B. Active Viremia C. Primary Viremia D. Secondary Viremia
D. Secondary Viremia
Viremia following initial virus replication in host. This is: A. Passive Viremia B. Active Viremia C. Primary Viremia D. Secondary Viremia
B. Active Viremia
A host that was directly inoculated with a virus via a contaminated syringe or from the bite of an arthropod is an example of what type of viremia? A. Passive Viremia B. Active Viremia C. Primary Viremia D. Secondary Viremia
A. Passive Viremia
Release of virions from the initial site of replication, such as lymphatics or epithelium of intestine, to the blood stream is an example of what type of viremia? A. Passive Viremia B. Active Viremia C. Primary Viremia D. Secondary Viremia
B. Active Viremia
Virus that can infect neural cells. Infection may occur by neural or hematogenous spread. This is a ________________ virus.
Neurotropic virus
Viruses that enter the central nervous system (spinal cord and brain) after infection of a peripheral site. This is a ________________ virus.
Neuroinvasive virus
Viruses that cause disease of nervous tissue, manifested by neurological symptoms and often results in death. This is a ________________ virus.
Neurovirulent virus
A virus that always enters the peripheral nervous system, but rarely enters the central nervous system (and when it does enter the CNS the consequences are almost always severe or fatal) is a virus that exhibits ___A. (high or low)___ neuroinvasiveness of the central nervous system, but ___B. (high or low)___ neurovirulence.
A. Low neuroinvasiveness
B. High neurovirulence
A virus that exhibits neuroinvasiveness of the central nervous system, but __(high or low)___ neurovirulence, is a virus in which most infections leads to invasion of the CNS, but neurological disease is mild.
Low neurovirulence
A virus that exhibits ___A. (high or low)___ neuroinvasiveness of the central nervous system, but ___B. (high or low)___ neurovirulence, is a virus that readily infects the PNS and spreads to the CNS with 100% lethality unless antiviral therapy is administered shorty after infection.
A. High
B. High
\_\_\_\_\_\_\_\_\_\_\_ spread: viruses travel in the OPPOSITE DIRECTION of nerve impulse flow. Virus invades axon terminals and then spread to Dendrite or cell body, and then cross synapse to reach next axon terminal. A. Horizontal spread B. Retrograde spread C. Vertical spread D. Anterograde spread
B. Retrograde spread
\_\_\_\_\_\_\_\_\_\_\_ spread: viruses travel in the SAME DIRECTION of nerve impulse flow. Virus invades dendrites or cell bodies and then spread to axon terminals, then cross synaptic contacts to invade dendrite of next neuron. A. Horizontal spread B. Retrograde spread C. Vertical spread D. Anterograde spread
D. Anterograde spread
Neural spread of viruses to CNS are via what 2 routes?
- Olfactory routes
2. Blood- Brain Barrier
Usually intensive shedding over short time period is classified as a(n) _________ infection.
Acute infection
_________ infection can be shed at lower titers for months to years.
Persistent
The specificity/ affinity of a virus for a particular host tissue is referred to as __________.
Tropism
____________ viruses can replicate in more than one host Organ/ Tissue.
Pantropic
A ________ is a skin injury in which there is small distinct elevation with fluid/ fluid filled sacs/ elevations.
Vesicle
A ________ is a skin injury in which there is an opening in the skin caused by sloughing of necrotic tissue, extending past the epidermis.
Ulcer
There are two types of skin injuries that are palpable, solid, with elevated mass. ____A.____ is with distinct borders. ___B._____ extend deep into the dermis.
A. Nodules
B. Tumors
________ are skin injuries that are benign (not cancerous) skin growth that appear when a virus infects the top layer to the skin.
Warts
______ are skin injuries that are solid elevations without fluid with sharp borders.
Papules
_____________ is reddening of skin, a consequence of systemic viral infection (endothelial injury in blood vessels throughout body, including those of the subcutaneous tissues).
Erythema
- Gastrointestinal disease, Malabsorption, Diarrhea
- Ingestion OR hematogenous spread, systemic infections
- Pronounced dehydration, Acidosis Hemoconcentration
- Destruction of enterocytes due to Viral replication, Hypersecretion
Put the above in order of occurrence for injury to organ/ tissues in the GI tract.
Order:
2. –> 4. –> 1. –> 3.
Virus Injury to the Organs/ Tissues of the respiratory tract can lead to all of the following EXCEPT:
A. Loss of ciliary activity
B. Loss of integrity of the lining mucus layer
C. Multifocal destruction of epithelium
D. Inflammation
E. Exudation
F. Influx of inflammatory cells
G. Obstruction of air passages
H. Hypoxia and Respiratory distress
I. Secondary bacterial infection
J. All of the above are true (i.e. none of the above are incorrect)
J.
Central Nervous system injury via infection of a virus, leads to encephalitis or encephalomyelitis characterized by ____A_____ necrosis, phagocytosis of neurons (= _____B_______), and perivascular infestations of inflammatory cells ( = ______C______ cuffing).
A. neuronal
B. neuronophagia
C. perivascular
What virus causes Progressive Demyelination (a CNS virus injury)?
Canine Distemper
What disease causes Neuronal vacuolation (a CNS virus injury)?
Prion
What are the 2 types of hemorrhages due to damage to endothelium, and caused by viral infection of the hemopoietic system?
1- Petechiae hemorrhage
2- Ecchymoses hemorrhage
Pin- Point/ Small spots = ___________ hemorrhage
Petechiae
Larger areas of hemorrhage, ill- defined margins = _________ hemorrhage
Ecchymoses
Clots form in small blood vessels throughout the body. Organs do not get blood which leads to organ failure. In later stages, raw material for clotting is exhausted due to over use which leads to no clot formation in later stages and causes hemorrhages throughout the body.
This above process is of which viral infection of the hemopoietic system?
Disseminated Intravascular Coagulation (DIC)
____________ is the abnormal development or arrests in development of the embryo or fetus, and may result in death or malformation during the antenatal period.
Teratogenesis.
What is defined as tissue injury mediated by host immune response to virus infection? (It is also the price paid by the host to clear a viral infection).
Virus- induced Immunopathology
T/F: Virus- induced immunopathology does not depend on the balance between the protective and destructive effects of the host immune response to viruses.
FALSE!!
Virus- induced immunopathology DEPENDS on the DELICATE BALANCE between the protective and destructive effects of the host immune response to viruses.
Which of the following is/are examples of immunopathology?
A. Tissue damage mediated by hypersensitivity reactions
B. Autoimmune diseases, e.g. moon blindness in a horse
C. Inflammation mediated tissue damage, e.g. fibrosis
D. Immunodeficiency disorders
E. A and C
F. A, C and D
G. All of the above
G. All of the above
-Cytotoxic cell mediated lysis/ killing of infected host cells, is one of the roles of ____ cells during some mechanisms of virus - induced immunopathology.
T cells
One role of T cells, during some mechanisms of virus- induced immunopathology, is the release cytokines from T cells (CD4+ and CD8+) and other cells that cause inflammation and tissue damage that becomes chronic against __________ virus infections.
persistant
What role does the Innate Immunity have in some mechanisms of virus- induced Immunopathology?
1) Toll - like receptors
2) Injury can also be mediated by free radicals, such as Nitric oxide and Superoxide.
Persistent activation of what receptors of the innate host cells by viruses, causes production of pro- inflammatory cytokines and interferons, as well as signals that recruit and activate cells involved in inflammation?
Toll- like receptors (TLRs)
T/F: Antibody responses to viruses may also contribute to tissue damage.
True
________ disease (in birds): Virus replication causes atrophy of the bursa and a severe deficiency of B lymphocytes, resulting in immunosuppression. As a result, infected birds become susceptible to other pathogens.
Infectious Bursal disease
All of the following are types of Viral Infections EXCEPT: A. Inapparent infections B. Acute Infections C. Persistent Infection D. Apparent infections
D. Apparent infections
What type of viral infection causes:
- Clinical signs and symptoms that are not evident
- Too few cells may be infected
- Stimulates the host immune response
- A possible source of virus spread
Inapparent Infections
What type of viral infection is a short-term infection?
Acute Infection
Which infection type has a short clinical course and a rapid clearance from the host immune response?
Acute Infection
During _______ infections, infectious virus is not demonstrable except when reactivation occurs.
Latent infections (a persistent infection)
T/F: Reactivation is often stimulated by immunosuppression and/ or by the actions of a cytosine or hormone during acute infection.
FALSE!
–Reactivation is often stimulated by immunosuppression and/ or by the actions of a cytosine or hormone during LATENT infection.
What 3 infections types are classified under persistent infection?
- Latent infection
- Chronic infection
- Slow infection
Acute infection followed by _________ infection - the virus is continuously shed from, or is present in infected tissue.
Chronic infection (a persistent infection)
Which infection type has a prolonged incubation period, lasting months or years, and a slow progressive lethal disease?
Slow infection (a persistent infection)
