Characteristics of Agents of Disease Flashcards
[3] Characteristics of Agents of Diseases
- Inherent characteristics
- Characteristics directly related to man
- Characteristics related to the environment
[2] Inherent Characteristics
- Physical features
- Biologic requirements
Include morphology, motility, presence or absence of capsule, spore or cyst forms.
[inherent characteristics]
Physical features
Refers to the things needed by agent to survive.
[inherent characteristics]
Biologic requirements
[4] Characteristics directly related to man.
- Infectivity
- Pathogenicity
- Virulence
- Immunogenicity
The ability of an agent to invade and multiply in a host.
[characteristics directly related to man]
Infectivity
It is dependent on a number of factors including viability, portal of entry, susceptibility of the host, susceptible tissues and body defenses of the host.
[characteristics directly related to man]
Infectivity
Ability to produce clinically apparent illness.
[characteristics directly related to man]
Pathogenicity
Dependent on factors such as dosage, presence or absence of capsule, degree of toxigenicity, condition of the host.
[characteristics directly related to man]
Pathogenicity
Severity of the reaction produced and measured in terms of fatality.
[characteristics directly related to man]
Virulence
Infections ability to produce specific immunity.
[characteristics directly related to man]
Immunogenicity
[3] Characteristics in relation to the environment.
- reservoir
- sources of infection
- mode of transmission
Pathogenic microbe such as virus, bacteria, fungus, protozoa, rickettsia.
Infectious (causative) agent
Source of infection agent or place where the microbe could grow, survive and multiply which could be in humans, animals, food, water, soil or equipment.
Reservoir
A way or manner where an infectious agent can leave the reservoir host which could be through secretions and exudates, tissue specimens, blood, feces or urine.
Exit pathway
Airborne, direct (touching or kissing) or indirect contact (contaminated objects), droplets (coughing or sneezing), vector (insect, anthropod or animal) and vehicle (food, water or drugs).
Means of transmission
Refers to the way an infectious agent enters a host that is susceptible to infection which includes body orifices, mucous membranes, and breaks in skin.
Entry pathway
Someone who is prone to infection due to age, health or immune status. They usually include the elderly, newborn, patients who are immune suppressed, unvaccinated, and those suffering from acute or chronic illness.
Susceptible host
Refer to the mechanisms by which an infectious agent is transported from reservoir to susceptible human host.
Mode of transmission
[3] three modes of pathogen
transmission:
- Contact transmission
- Vehicle transmission
- Vector transmission
A host is exposed to infectious agents by making contact with the agent or items contaminated with the pathogen so it can reach a portal of entry into the host.
Contact transmission
[3] three types of contact transmission
- Direct contact
- Indirect contact
- Droplet
There is no intermediary between infected and uninfected individuals.
[contact transmission]
Direct contact
It encompasses such things as touching, kissing, and sexual interactions.
[contact transmission]
Direct contact
Diseases transmitted through direct contact include:
- Hepatitis A
- Staphylococcal infections
- Sexually transmitted diseases.
[contact transmission]
Direct contact
Nonliving intermediates that act as the agents of transmission by indirect contact are referred to as fomites.
[contact transmission]
Indirect contact
Takes place through intermediates:
- Tissues, Handkerchiefs
- Towels
- Bedding
- Contaminated needles (the latter easily transferring HIV and hepatitis B)
[contact transmission]
Indirect contact
It is seen in the transfer of respiratory diseases such as influenza and whooping cough.
[contact transmission]
Droplet
Usually small residues which result from evaporation of fluid from droplets emitted by an infected host.
[contact transmission]
Droplet
It can occur through sneezing, coughing, and even laughing.
[contact transmission]
Droplet
Involves pathogens riding along on supposedly clean components.
[mode of transmission]
Vehicle transmission
Air is a difficult vehicle to control.
[mode of transmission]
Vehicle transmission
Pathogens are transmitted by carriers, usually arthropods:
[mode of transmission]
Vector transmission
[2] two types of vector transmission:
- Mechanical
- Biological
Pathogens are on vector’s body parts and are passively brushed off and onto the host.
[vector transmission]
Mechanical vector
Pathogens are within the vector and transmission to the host is through a bite.
[vector transmission]
Biological vector
Goes through chain of events leading from inapparent infection to a clinical case of the disease.
The host
Range of infection, from inapparent to severe disease.
Gradient infection
Severity of illness depends on resistance of the host (immunity level).
The host
This is the total property of an individual to protect himself from an infectious agent.
Immunity
[4] Immunity
- Humoral defense
- Cellular defense
- Non-specific resistance
- Specific resistance
Action of antibodies.
[immunity]
Humoral defense
Involves white blood cells that protects our body from diseases.
[immunity]
Cellular defense
Present at the time of birth or has developed during maturation.
[immunity]
Non-specific resistance
Acquired as a result prior exposure with a foreign substance.
[immunity]
Specific resistance
Recognize some foreign objects to protect our body.
[immunity]
Specific resistance
[3] Characteristics of the Host
- Non-specific Defense Mechanisms
- Specific defense
- Mechanisms
