HOST PARASITE RELATIONSHIP

Question 1

The HOST-PARASITE RELATIONSHIP
Infectious disease results from the
interaction of an _____
with the ___ in its particular
______

Answer 1

infectious agent
host
environment

Question 2

The Host
Primary protective factor is RESISTANCE:
Four Types of Resistance
1)
2)
3)
4)
5)

Answer 2

1) Genetic or natural resistance
2) Species resistance
3) Age and Sex resistance
4) Immune resistance
5) nutritional

Question 3

The Host
Primary protective factor is RESISTANCE:
Four Types of Resistance
1) Genetic or natural resistance
2) Species resistance
3) Age and Sex resistance
4) Immune resistance
a.
b.

Answer 3

A. Passive or Transferred Immunity
B .Active or Acquired Immunity

Question 4

What are the three influential factors of an infectious agent?

Answer 4

• Virulence
• Tropism
• Ability to persist or to spread in the host

These factors determine how effectively an infectious agent can cause disease.

Question 5

What are the nine influential factors of the environment affecting infectious agents?

Answer 5

• Ambient temperature
• Humidity
• Spacing
• Housing/Shelter
• Moisture
• Ventilation
• Lighting
• Feeds
• Various environmental pollutants

These environmental factors can significantly impact the survival and transmission of infectious agents.

Question 6

Fill in the blank: The ability of an infectious agent to cause disease is known as _______.

Answer 6

[Virulence]

Question 7

True or False: Tropism refers to the ability of an infectious agent to spread in the host.

Answer 7

False

Tropism specifically refers to the preference of an infectious agent for a particular host tissue.

Question 8

Fill in the blank: The factor that includes ambient temperature and humidity is part of the _______ that influences infectious agents.

Answer 8

[Environment]

Question 9

What does the term ‘moisture’ refer to in the context of environmental factors influencing infectious agents?

Answer 9

The presence of water in the environment that can affect the survival and spread of infectious agents

Moisture levels can influence microbial growth and viability.

Question 10

How do bacteria generally cause disease?

Answer 10

Bacteria generally cause disease by:
* invasion
* production of toxins
* attaching or colonizing
* evading hosts defenses

These mechanisms can occur singly or in combination.

Question 11

What are the main ways viruses cause disease?

Answer 11

Viruses generally cause disease by:
* cytolysis
* maintaining steady state with the host
* integrating into the genome of the host

Cytolysis refers to the destruction of cells, often leading to disease.

Question 12

How do parasites generally cause disease?

Answer 12

Parasites generally cause disease by:
* local destruction of cells/tissues
* effects on blood circulation
* space-occupying lesions
* nutritive competition

These effects can lead to various diseases and health complications.

Question 13

What are the ways fungi generally cause disease?

Answer 13

Fungi generally cause disease by:
* invasion of living tissue
* inducing allergies or hypersensitivities
* toxicosis

Toxicosis refers to the toxic effects caused by fungal metabolites.

Question 14

How do toxins or poisons produce disease?

Answer 14

Toxins or poisons generally produce disease by:
* direct contact (causing sudden degeneration and necrosis)
* absorption (striking lesion is produced and derangement of metabolism)

Direct contact with toxins can lead to immediate tissue damage.

Question 15

What is the general term for living together or co-existence of two organisms?

Answer 15

Symbiosis

Symbiosis can involve different types of relationships between organisms.

Question 16

What are the three types of symbiotic relationships?

Answer 16

• Mutualistic
• Commensalistic
• Parasitic

Each type of relationship has different implications for the organisms involved.

Question 17

True or False: Symbiosis only refers to harmful interactions between organisms.

Answer 17

False

Symbiosis encompasses beneficial, neutral, and harmful interactions.

Question 18

Fill in the blank: Symbiosis may be __________, commensalistic, or parasitic.

Answer 18

[mutualistic]

Mutualism is a type of symbiosis where both organisms benefit.

Question 19

What is a Parasitic Relationship?

Answer 19

A relationship whereby one partner lives at the expense of another.

Parasitism often involves one organism benefiting at the cost of another, which may suffer harm.

Question 20

Define Commensalism.

Answer 20

A relationship in which there is advantage to one partner but no real disadvantage to the other.

In commensal relationships, one organism benefits while the other is neither helped nor harmed.

Question 21

What is Mutualism?

Answer 21

A relationship in which two organisms live together without disadvantage nor harm to one another.

Mutualism benefits both organisms involved, often enhancing their survival or reproduction.

Question 22

What is the chronologic sequence of events used by infectious microorganisms?

Answer 22

The sequence includes colonizing and invading mucosae and skin, spreading to local tissues, and causing disease.

This process is critical for understanding how infections develop and progress.

Question 23

How do infectious microorganisms commonly enter the body?

Answer 23

Ingestion, inhalation, or cutaneous penetration.

These routes are essential for the initial stages of infection.

Question 24

What do infectious microorganisms interact with upon entering the body?

Answer 24

Mucosae or skin.

This interaction is the first step in the infection process.

Question 25

If the target cell is not in mucosae or skin, where may microorganisms spread next?

Answer 25

To submucosal and subcutaneous lymphoid nodules such as in tonsils or Peyer's patches. ## Footnote These areas are important for immune response and pathogen surveillance.

Question 26

After spreading to lymphoid nodules, where do microorganisms go next?

Answer 26

To regional lymph nodes. ## Footnote Regional lymph nodes are key sites for immune activation and response.

Question 27

What systems do infectious microorganisms spread to after regional lymph nodes?

Answer 27

The circulatory and/or lymphatic systems. ## Footnote This systemic spread is crucial for the dissemination of infection throughout the body.

Question 28

True or False: Infectious microorganisms can only enter the body through ingestion.

Answer 28

False. ## Footnote They can also enter through inhalation and cutaneous penetration.

Question 29

Portals of entry. Infectious microorganisms commonly enter the body through 1. _________________, 2.__________, 3 _______________, and 4._______________

Answer 29

1.ingestion (alimentary portal) 2.inhalation (respiratory portal) 3.cutaneous penetration (skin portal) 4. ascending infection (lower urinary and reproductive portals) and interact with epithelial cells, macrophages, dendritic cells, and lymphocytes of the mucosae or skin.

Question 30

What types of cells do infectious organisms often infect?

Answer 30

Macrophages, lymphocytes, and dendritic cells ## Footnote These cells play a role in the immune response and can facilitate the spread of infections.

Question 31

How do infectious organisms spread to target cells in organ systems?

Answer 31

Via leukocyte trafficking ## Footnote This process occurs as the cells migrate through organ systems during immunologic surveillance.

Question 32

What determines cell and tissue specificity for infectious organisms?

Answer 32

Ligand-receptor interactions ## Footnote Proteins (ligands) on infectious organisms bind to receptors on host target cells.

Question 33

What are ligands in the context of infectious organisms?

Answer 33

Proteins expressed on the surface of infectious organisms ## Footnote These proteins interact with receptors on host cells.

Question 34

What happens once an infectious organism binds to a host cell receptor?

Answer 34

A sequence of events is initiated that colonizes or invades the cells ## Footnote This process can occur through phagocytosis or endocytosis.

Question 35

What are virulence determinants?

Answer 35

Factors that facilitate the colonization and invasion of host cells ## Footnote These determinants play a critical role in the infectious process.

Question 36

How do infectious organisms replicate within host cells?

Answer 36

By establishing control of normal metabolic systems ## Footnote This allows the organisms to use host cell resources for replication.

Question 37

What is the typical outcome of the infection process on host cells?

Answer 37

Cell dysfunction and/or death ## Footnote This leads to clinical disease in the host.

Question 38

Fill in the blank: Infectious organisms can invade cells through _______.

Answer 38

Phagocytosis or endocytosis ## Footnote These are processes by which cells engulf substances.

Question 39

True or False: The primary role of macrophages, lymphocytes, and dendritic cells is to support the immune response.

Answer 39

True ## Footnote These cells are integral to the body's defense mechanisms.

Question 40

Deposition of infectious microorganisms. Infectious microorganisms inhaled through the nostrils are deposited on mucosa of the nasal turbinates, nasal pharynx, and/or the conductive system of the respiratory tract. The site of deposition depends on the physical properties of the agent such as size, shape, weight, and electrostatic charge.