Infectious Disease

Question 1

Infection

Answer 1

the invasion and multiplication of pathogens in an individual

Question 2

Disease

Answer 2

a disorder of structure and function within the host and impacts the host (symptoms begin to show)

Question 3

Infectious diseases

Answer 3

diseases caused by pathogenic microoorganism (starts spreading)

Question 4

etiology

Answer 4

the study of disease

Question 5

Microorganism

Answer 5

any organism that is invisible to the naked eye

Question 6

list smallest to largest microbe

Answer 6

prions, viruses, bacteria, fungi, protozoa, parasites (PVBFPP)

Question 7

Commensal

Answer 7

• A microorganism that is a normal inhabitant of the animal body.
• In commensal relationships, either the microbe or host (or both) derives benefit; neither is harmed under normal circumstances

Question 8

Pathogen

Answer 8

capable of causing disease. Include both commensal and non commensal

Question 9

Obligate pathogen

Answer 9

Requires a host to survive
* never commensal
* needs to use the cell machinery
* Obligate pathogens are not commensals, but they can produce asymptomatic infections

Question 10

Commensal Pathogen

Answer 10

• A microorganism commonly found within the indigenous microbiota can cause disease in normal hosts with some regularity.

act on the host’s immune system to induce protective responses that prevent colonization and invasion by pathogens

• Not all manifest as pathogens with the same frequency, some may require significant impairment of the host’s immunity to cause disease - Opportunistic pathogens

Question 11

Environmental pathogen

Answer 11

A microorganism capable of causing disease that is transmitted to the host from an environmental source such as water or soil.

Question 12

Zoonotic pathogen

Answer 12

an infectious disease that has jumped from a non-human animal to humans.

A microorganism is a colonizer or pathogen on animals and that can be transmitted to humans either through vectors (i.e. ticks) or direct contact with the animal or its products.

Question 13

Attributes of Pathogens

Answer 13

• Enter host
• Can occur through the skin, mucosa or body’s orifices
• Commensal pathogens may skip this step, they’re “already there”
• Establish a unique habitat within the host
• Usually requires crossing physical barriers and/or breaching the
  host’s defenses
• Multiply within host
• Typically what causes disease
• Exit to infect new host
• Essential trait for obligate pathogens

Question 14

Attributes of Pathogens

Answer 14

• Enter host
• Can occur through the skin, mucosa or body’s orifices
• Commensal pathogens may skip this step, they’re “already there”
• Establish a unique habitat within the host
• Usually requires crossing physical barriers and/or breaching the host’s defences
• Multiply within host
• Typically what causes disease
• Exit to infect new host
• Essential trait for obligate pathogens (it needs to exit the host because it needs to complete the life cycle)

Question 15

What are sub-clinic outcomes of exposure to infectious agents

Answer 15

Carrier
Pathogenic elimination (non-immunity or immunity)

Question 16

What are clinic outcomes of exposure to infectious agents

Answer 16

Carrier
Pathogenic elimination (non-immunity or immunity)
Death

Question 17

Koch’s Postulates

Answer 17

1. pathogen must be found in every case of disease and not found in healthy animals
2. pathogen can be isolated and grown in pure culture.
3. a healthy subject must develop the same signs and symptoms of the disease
4. The pathogen must be re-isolated from the new host.

Question 18

Kochs Limitations

Answer 18

• Inability to isolate the organism in pure culture (commensal are already in the host)
• Inability to isolate the organism in cell-free culture
• Organisms for which a single species acts as host
• Subclinical infection
• Organisms that cause ‘distant’ infection
• Disease caused by toxins
• Diseases that require coinfection
• Organisms associated with tumors

Question 19

What are the 5 stages of infectious disease

Answer 19

1. Incubation - Pathogen multiplies without clinical signs
2. Prodromal - General and unspecific signs
3. Illness - Signs and symptoms are more severe and specific
4. Decline - Number of pathogens and clinical signs begin to decline
5. Convalescence - Return to normalcy*

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