VETT 113 Week 4 Review

The 4 most common pathogenic fungi that cause deep systemic infections in small animals include the following. (Name of disease is in parenthesis.)

Histoplasma capsulatum (Histoplasmosis) Blastomyces dermatitidis (Blastomycosis) Coccidioides immitis (Coccidioidomycosis-Valley Fever) Cryptococcus neoformans (Cryptococcosis)

obligate intracellular parasite

Cannot reproduce outside their host cell, meaning that the parasite's reproduction is entirely reliant on intercellular resources

Superficial and cutaneous mycoses

Common fungal infections limited to the skin and skin structures. • As in all infections, the outcome of a fungal infection is determined by the virulence of the infecting organism, the size of the inoculum, and the adequacy of the host defenses.

Understand the steps of viral replication.

Attachment (adsorption) stage -> Penetration step -> uncoating of genetic material -> replication -> assembly -> Release stage "Naked Virus" -> Release stage Enveloped virus

Virus

• enters the host via mucous membranes of the respiratory, gastrointestinal or urogenital tract • recognizes and binds to specific receptors on the surface of the cell.

Describe a virus.

• very small (10-400nm) -not cells -genome surrounded by a protective protein coat -depend on host cell to provide machinery they need to reproduce -formed from assembly of newly synthesized components made in a host cell

Describe / list the characteristics of protozoa.

- Unicellular - Microorganisms - Most sizes are 3-50 um - Need a microscope to view them

Subcutaneous mycoses

A group of fungal diseases that involve the skin, subcutaneous tissue, and lymphatics

With regards to the development of a fungal infection, what can occur when an animal / human is taking oral antibiotics for an extended period of time?

Antibiotic resistance can occur

What is the most common form of reproduction of protozoa?

Asexual binary fission = single organism divides into 2 organisms

What is meant by a "secondary infection"?

Bacteria move in and increase in numbers = Secondary infection - clinical signs such as pus discharge from the eyes and nose. Infection that is secondary to cause of illness

Where are protozoa commonly found?

Basically any moist environment

Opportunistic mycoses

Caused by fungi that are not true pathogens - because they can cause life-threatening systemic disease only in immunosuppressed patients.

How are viral infections diagnosed?

Clinical signs may be highly suggestive of a few viral infections • Test serum of infected animal for presence of antibodies against specific virus or viral antigens • Special lab tests (ex. Fluorescent Antibody) • Virus culture and isolation • Electron microscopy (Remember- you can NOT see viruses using a regular light microscope)

How are viruses transmitted?

Direct contact (person-to-person), Indirect contact (contaminated food, water, bodily fluids, or other objects)

How do some protozoans move?

Flagella or cilla

Describe an enveloped virus.

Have an external membrane surrounding the capsid protein. Generally easily destroyed by common disinfectants, detergents, freezing, and thawing, as the lipid membrane is easily disrupted.

Endemic mycoses

Infections caused by pathogens that are restricted geographically and are true pathogens because they have the ability to cause serious systemic infection in healthy individuals.

Can all viruses infect any tissue or any host?

No

Describe a non-enveloped virus.

No membrane around their protein capsid. Very difficult to destroy with commonly used disinfectants. Examples: Canine Parvovirus, Feline Panleukopenia, Feline Calicivirus.

Do commonly used disinfectants easily kill all viruses?

No, viruses without envelope are difficult to destroy with disinfectants

When do clinical signs develop after a host is infected with a virus? Right after infection?

No. Clinical signs develop during the release stage of the viral infection. Virions go on to infect other cells and the cycle begins again. Once enough normal cells are destroyed, clinical signs emerge. Enveloped viruses leave the cell by budding without destroying the host.

How are viruses classified?

Shape, genetic material (RNA or DNA), enveloped, non-enveloped

List some ways to help prevent viral infections.

Vaccination, Immunoglobulins, Proper nutrition; clean and adequate water supply; housing considerations, Hygiene, Stress reduction, Screening and quarantine of new animals.

Define "primary infection" as it relates to disease.

Viral infection is known as the Primary infection - damages the cells.

What is meant by a "latent infection"?

Virus is hiding dormant until stress occurs which causes the infection/virus to emerge/become reactivated. Ex) Feline respiratory viruses

If a patient has a viral infection, when would it benefit from the use of an antibiotic?

When a secondary bacterial infection has occured

Can some viruses cause cancer?

Yes, papillomavirus

host

an animal or plant that nourishes and supports a parasite

immunoglobulins

any of a class of proteins present in the serum and cells of the immune system, that function as antibodies.

lyse / lysis

disintegration of a cell by rupture of the cell wall or membrane

Pathogenic fungi

organisms that can cause disease • Fungal diseases are termed "mycoses" and are mainly superficial infections or systemic infections. • Some of the pathogenic fungi have zoonotic potential

replication

the action of copying or reproducing something

capsid

the protein coat or shell of a virus particle, surrounding the nucleic acid or nucleoprotein core.

Superficial mycoses

usually mild and non-life threatening; can cause life-threatening disease

What is meant by the term "naked virus"?

virus lacking the viral envelope. Pertain to those that only have nucleocapsid, which is a protein capsid that covers the genome of the virus.

How are viral infections treated?

• Antibiotics do NOT destroy viruses!!! However, antibiotics are useful where you have secondary bacterial infections. •Supportive care: - Fluids -Nutritional support -Treatment of clinical signs such as vomiting, diarrhea, seizures, etc. • Antiviral medications for certain viral infections

Define commensalism, mutualism, and parasitism.

• Commensalism = Type of symbiosis where it is beneficial to one organism but has no effect on the other. • Mutualism = Type of symbiosis where it is beneficial to BOTH organisms. • Parasitism = Type of symbiosis where one organism (parasite)benefits at the expense of the other organism (host).

What are the possible effects of viral infections on cells?

• Most infections cause no obvious damage to the host • Cell ruptures (lyse) releasing the viral particles • Cell remains intact and the viruses migrate out of the cell. Virus causes the cell to malfunction and clinical signs are due to this malfunction vs cell death. Example: Rabies virus • Some viruses can cause the cell to transform into a cancerous (malignant) cell. Example: Feline Leukemia Virus

What are the possible outcomes of viral infections?

• Most infections cause no obvious signs • Acute infection / illness - virus replicates, clinical signs develop, recovery or death • Chronic infection • Carriers - some animals remain infected with a virus and can shed viral particles without showing clinical signs themselves (Asymptomatic) • Latent infection - The virus may be hiding (dormant) in specific tissue and will become reactivated with stress, malnutrition, or concurrent illness. Examples: Herpes virus in humans (cold sores and genital herpes); Feline upper respiratory viruses