Exam 5 - Viral diseases

What are four main routes of entry for microbes?

1. Breaks in the skin

2. GI tract (fecal-oral route)

3. Respiratory tract

4. Urogenital tract

What are 4 types of direct transmission of microbes?

1. Horizontal contact (person to person)

2. Airborne droplets

3. Vertical contact (mother to fetus)

4. Vectors

What are three types of indirect transmission of microbes?

1. Fomites

2. Airborne

3. Food/water

Virus

Submicroscopic particles that can infect bacteria, plants, animals, and humans

What are two differences between viruses and bacteria?

-Viruses cannot replicate on their own (need a host)

-Viruses are not affected by antibiotics

How do viruses produce disease?

Replicate inside cells to cause degeneration and cell death

Virion

Complete, fully developed, infectious viral particle

Genome

Nucleic acid (RNA or DNA) that encodes genetic information to copy the virus

Capsid

Protective protein coat

Capsomere

Individual proteins that make up the capsid

Envelope

-Outer membranous layer

-Surrounds the capsid

-Not found in every virus (naked vs enveloped)

What dictates the shape/size of a virus?

Protein and nucleic acid composition

What are 5 classes of viral nucleic acids?

1. DNA or RNA

2. Single Stranded (SS) or Double Stranded (DS)

3. SS+ sense or SS- sense

4. Linear or circular

5. Segmented or non-segmented

SS+ sense

Genetic code can immediately be translated

SS- sense

Genetic code is complementary to the cell and must be converted before it can be translated

Host range

-Cells that a virus can actually infect

-Need a lock and key fit between virus and receptor on host cell

Ligand-Receptor interactions

Determines host range and allows virus to attach to and infect specific cells

What are the five steps of viral replicaton?

1. Attachment

2. Entry

3. Spread

4. Replication

5. Shedding

Attachment

-Contain attachment proteins in capsids or envelops

-Bind to specific receptors on target cell membranes

Entry

Endocytosis/phagocytoses into the cell

Spread (uncoating)

Nucleic acid and/or proteins are moved to specific locations in the cell

Replication

Nucleic acid and/or proteins take over normal cell functions to replicate

Shedding (egress)

-Viruses reassemble from created components

-Either bud or lyse from the cell

What are 5 outcomes of viral replication?

1. Necrosis

2. Apoptosis

3. Persistence/latency

4. Cell proliferation

5. Malignant transformation

What is the most effective mechanism against viral infections?

Cell mediated immunity and interferons

What are three functions of interferons?

1. Stimulate immune cells to recognize and kill infected cells

2. Trigger apoptosis in infected cells

3. Induce antiviral proteins to block viral replication

What are four examples of ds DNA viruses?

1. Adenovirus

2. Herpes virus

3. Papovirus

4. Poxvirus

Adenovirus

-Naked

-Icosahedral

What are some diseases caused by adenoviruses?

-Respiratory diseases

-Conjunctival pneumonia

-Acute hemorrhagic cystitis

-Acute gastroenteritis

Herpes virus

-Enveloped

-Spherical icosahedral

-Glycoproteins project from surface to help with entry

What diseases are caused by the herpes virus?

1. Herpes simplex I (cold sores)

2. Herpes simplex II (genital sores)

3. Varicellovirus (chicken pox/shingles)

Papovavirus

-Naked

-Icosahedral

What diseases do papovavirus cause?

-Papilomavirus

-Polyomavirus

Poxvirus

-Enveloped

-Brick shaped

-Cause progressive skin diseases

What diseases do poxvirus cause?

-Human monkey pox

-Small pox

Macule

Discolored spot on skin that is not elevated

Papule

Small, circumscribed, solid elevation of the skin

Vesicle

Small intraepidermal elevation of serous fluid

Pustule

Pus within the epidermis or glands

Hyperplasia

Spreading of lesions

What is an example of a DS DNA virus?

Parvovirus

Parvovirus

-Naked

-Icosahedral

-Smallest virus

What diseases does parvovirus cause?

-Human parvovirus B19

-Erythema infectiosum

-Joint disease syndrome

-Canine parvovirus

Canine parvovirus route of entry

Oronasal route

What does canine parvovirus target?

Tonsils and enters lymphatics

What are signs of parvovirus?

-Causes bone marrow suppression

-Cause myocarditis

-Destroys lymphoid patches in intestines

-Loss of immunity in GI tract

-Malnutrition

-Hemorrhagic diarrhea

What is are some examples of a SS+ RNA virus?

-Corona virus

-Picorna virus

-Togavirus

Corona virus

-Enveloped

-Helical

What are some diseases caused by coronavirus?

-SARS-CoV

-MERS-CoV

-Covid-19

Reservoir

Animal that can spread disease but has no symptoms themselves

Picorna virus

-Naked

-Icosahedral

What are some diseases caused by picorna virus?

-Poliovirus

-Rhinovirus (common cold)

-Hepatitis A virus

Togavirus

Envelope with spikes (help with attachment)

What are some diseases caused by Togavirus?

-Alpha virus

-Eastern equine encephalitis virus

-Yellow fever virus

-Rubella virus

What are some examples of SS- RNA viruses

-Rhabdovirus

-Orthomyxo virus

Rhabdovirus

-Envelope with spikes

-Matrix contains nucleocapsid

What are some diseases caused by rhabdovirus?

-Mumps

-Rabies

Rabies virus

-Enveloped RNA virus

-Causes rage and aggressive behavior

-Replicates in nervous tissue and saliva

-Transmitted through bite wounds

Orthomyxo virus

-Influenza virus

-Infect vertebrates

Alpha influenza virus

-Infects humans, other mammals and birds

-Causes all flu pandemics

Beta influenza virus

Infects humans and seals

Gamma influenza virus

Infects humans and pigs

Delta influenza virus

Infects pigs and cattle

How are viruses able to create different variations of itself?

-Two strains in the same host and can exchange genetics

-Combinations may be more or less virulent

What is an example of a SS RNA virus

Retroviruses

Retrovirus

-Use RNA as genetic material

-DNA inserted into the host cell

Reverse transcriptase

Converts retroviral RNA into DNA

What are diseases caused by retroviruses?

-AIDS

-Some forms of cancer (FeLV)

Feline Leukemia Virus (FeLV)

-Gamma retrovirus

-Shed in nasal secretions, saliva, urine, feces, and milk

What signs does FeLV cause?

Immune suppression and transformation of cells into cancer