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Animal Health
General Principles of Disease
56
Agriculture
Undergraduate 3
10/21/2014

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Term
Define Infection
Definition
Invasion and multiplication of microorganisms in body tissues - causes local cellular injury
Term
How does infection cause cellular injury?
Definition
Competitive metabolism
DNA Replication
Toxins
Antigen-Antibody Response
Term
Define Disease
Definition
Well-defined abnormalities affecting structure & fxn of an organ, organ system, tissue, or whole individual
Term
T or F: Clinical signs can be present in a 'sub-clinical disease'
Definition
False (i.e. only present with clinical disease)
Term
In which type of disease are symptoms overt?
Definition
Clinical
Term
What are the classifications of disease?
Definition
DAMNIT
Degenerative, Anomalous, Metabolic, Neoplastic, Infection, Toxic/Traumatic
Term
Describe Degenerative disease
Definition
Structure is altered by age, use/misuse, or biochemically
Term
Describe Anomalous disease
Definition
Abnormal structure and/or fxn
- may be developmental, congenital, or genetic
Term
Describe Metabolic disease
Definition
Due to nutrition, toxins, or hormonal activity that alters normal metabolism
Term
Describe Neoplastic disease
Definition
Abnormal growth of cells @ expense of normal tissue structure & fxn (i.e. cancer)
Term
Describe Infectious disease
Definition
Caused by microorganisms that invade the body and damage normal s&f (i.e. a pathogen, bacteria, viruses, parasitic)
Term
Describe traumatic disease
Definition
A mechanical injury (i.e. broken bone)
Term
Define Etiology
Definition
The study of the causes of disease
Term
T or F: The cause of a disease is synonymous with the eliologic agent
Definition
False
Term
Compare cause & causitive agent
Definition
Causitive agent: pathogen (bac., virus, etc)

Cause: other factors (like epidemiological triad)
Term
Define pathogenesis
Definition
The development of a disease
Term
Define Pathogen
Definition
Any disease-producing microorganism/material
Term
Define Epidemiology
Definition
The study of patterns of disease in a population

- The study of Frequency, Distribution, and Determinants of Health and Disease
Term
Epidemiology is to a population, as pathogenesis is to a(n) _______.
Definition
An individual
Term
T or F: Epi is simply the study of disease
Definition
False, also **productivity** of disease
Term
What are Koch's Postulates?
Definition
1. Isolate pathogen of sick animal
2. Infect healthy animal with this pathogen
** If it causes same disease as sick animal...
3. Re-isolate same pathogen
Term
Why use Koch's Postulates?
Definition
To know if a certain pathogen is the cause of a disease
Term
What are the classifications of infectious causes of disease?
Definition
Bacteria, Viruses, Prions, Mycotic, and Parasites
Term
T or F: A virus is the same size as a bacterium
Definition
Waayy false, bacteria are massive in comparison
Term
What are viruses?
Definition
- contain some nucleic acid
- require host cell to replicate
- unresponsive to traditional antimicrobial agents
Term
What are bacteria?
Definition
- like cells
- non-pathogenic, pathogenic, or opportunistic
- can replicate outside a host
- mostly resistant to antimicrobials, but can devel. resistance
Term
What are prions?
Definition
- Prion proteins (PrPs) that are improperly folded resulting in infectious or genetic disease
- resistant to proteases
- somewhat host specific
- cause TSE (Transmissible Spongiform Encephalopathy)
Term
What are mycotic infections?
Definition
fungal infections, like ringworm
Term
T or F: Parasites are only internal
Definition
False, they can be internal, external, or intracellular
Term
Define virulence
Definition
The degree of pathogenicity of a pathogen
- the severity or "fitness" of a pathogen
Term
Define predisposition
Definition
It is what predisposes an animal to infectious disease
Term
What is the goal/purpose of a pathogen?
Definition
To enhance disease transmission
Term
Define direct transmission
Definition
contact between two animals
Term
Define vector transmission
Definition
Agent requires an invertebrate host for it's own life cycle and transmission
Term
What is a fomite?
Definition
An inanimate object (i.e. boots) or one that is alive but is a passive carrier (i.e. human hands)
Term
What are some examples of disease being transmitted using infectious secretions or excretions?
Definition
Respiratory droplets, saliva, puss ("purulent exudate"), feces, urine
Term
What are the TWO broad types of disease transmission?
Definition
Horizontal & Vertical
Term
What is horizontal transmission?
Definition
b/w animals of the same generation
- infectious or contagious
Term
What is vertical transmission?
Definition
b/w animals of one generation and the succeeding generation
- dam to offspring
- in utero, or via colostrum/milk
Term
What is the difference b/w contagious vs infectious?
Definition
Contagious: capable of being transmitted from animal to animal

An infectious disease can either be contagious (ebola) or non-contagious (tetanus)
Term
What is the epidemiological triad and why is it important for disease pathogenesis?
Definition
Host, Agent, Environmental

- all three must be in perfect balance for disease to occur
Term
What are some host factors affecting disease determination?
Definition
- immune status (innate/acquired, affected by environment)
- herd immunity
- age (inevitable degen., change in prod. lvl., immune status, phys state)
- genetic
- physiologic state (preg., lactating)
- Production lvl
- Nutr'l status
Term
What are some agent factors affecting disease determination?
Definition
- virulence (can depend on cell surface & metabolic properties)
- pathogen challenge (amount, environment)
Term
What is the difference b/w necessary and sufficient cause?
Definition
Necessary: Disease will not occur without this factor

Sufficient: if present, disease WILL occur
Term
T or F: Disease is almost always multifactorial
Definition
True dat
Term
Define Carrier state
Definition
Animal doesn't have a clinical disease, but is has the potential to transmit an infectious

May be:
- amsymptomatic (never diseased)
- incubating the disease (eventually/intermittently affected)
- convalescing/recovering
Term
Define Morbidity
Definition
the condition of being diseased
- the amount of disease (frequency)
Term
Define Mortality
Definition
the number of deaths
Term
Define case fatality
Definition
the proportion of animals with a specific disease that die from it
Term
Define endemic
Definition
The predicted/expected frequency of a disease in a pop (i.e. common cold)
Term
Define Epidemic
Definition
Occurrence of (non/infectious) disease in a population that exceeds the expected level
Term
Define sporadic
Definition
Disease occurs infrequently, and not readily predictable
Term
What are the measures of disease occurrence?
Definition
- Prevalence (prop. of # diseased animals/all animals)
- Incidence (prop. of # new cases/# animals at risk)
Term
In calculating a denominator for the Incidence equation, what would we factor into deciding which species are "at risk?"
Definition
- not at risk if already diseased/infected
- not at risk if can't experience the outcome of interest (i.e. bulls can't get mastitis/pregnant, or open females can't abort)
Term
Briefly explain the iceberg concept
Definition
The number of infected/diseased individuals in a population can be higher than what is observed, because of the potential presence of sub-clinical disease
Term
In the tipping point concept, what is at either end of the scale that, if not balanced properly, could lead to disease?
Definition
Protective factors at one end, promoting health.

Risk factors at the other, promoting disease
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