Basic concepts of diseases Flashcards
what is disease?
harmful deviation from the normal structure or functional state of an organism
epidemiology
study of incidence, distribution, and control of disease in a population
pathology
the science of the causes and effects of diseases
pathogenesis
the development of the disease and the chain of events leading to that disease
koch’s postulates
- the agent is present in every case of the disease
- the agent must be isolated from a diseased animal
- the cultured microorganism should cause the disease when introduced into a healthy animal
agent (examples)
only have to know a few
- toxicity
- dose
- pathogenicity: ability to cause disease
- infectivity: ability to infect
- immunogenicity: ability to provide immune response
- antigenic stability: agent is stable in environment long enough
- survival: does it cause death too quickly to be passed on
environment (examples)
- weather
- housing
- management
- geography
- air quality
- nutrition
- stock density
- animal movement between groups
host factors (examples)
- age
- sex
- genotype
- behavior
- nutritional status
- health status
- stress status
- reproductive status
- immune status
- innate resistance
steps during “disease” development in an animal
- exposure
- incubation
- prodromal
- decline
- convalescence
asymptomatic
no symptoms
latent
symptoms appear a long time after initial development
clinical
symptoms are present
incubation period
interval from exposure to clinical symptoms
carrier status
usually no clinical symptoms but can transmit infection for long periods
communicable (contagious, transmissible, infectious)
spread from one animal to another
non-communicable
arises from outside of hosts or from opportunistic pathogen
clinical sign (important)
something that somebody else can see, based upon physical findings
symptom (important)
the subjective experience of the patient
ex: the owner believes of what the symptoms are of their animal (animals don’t talk)
lesion
area of tissue with an abnormal structure or function
susceptible
animal at risk of developing a disease, if exposed to the agent
reservior
a long-term natural host for a disease that serves as the source of infection for other hosts
ex: a group of animals who live in that region
- Yellowstone bison can infect cattle
vector
- intermediate carrier of the disease to susceptible animals without showing symptoms of disease
- “individual”
ex: mosquito gave disease to dog
local disease
confined to a small region of the body
systematic disease
widespread disease in multiple systems of the body
primary disease
initial disease in the animal
secondary disease
follows the primary disease
portal of entry
- routes by which infectious agents can infect susceptible animal
- oral ingestion
portal of exit
- Routes by which an infectious agent exits its host
- urine & feces
DAMN IT V !!!
must remember
D - degenerative, developmental
A - anomalous
M - metabolic
N- neoplastic
I - infectious, inflammatory, immune-mediated, iatrogenic, idiopathic
T- traumatic, toxic
V - vascular
D - degenerative
- chronic, progressive, usually in older animals
ex: arthritis, cataracts
D - developmental
(congenital)
- usually in younger animals, but can also see in mature animals
ex: cleft palate, agenesis or hypoplasia of organs, “birth defects”
A - anomalous
- deviating from “normal”
ex: heart defect, liver shunt
M- metabolic
Any of the diseases that disrupt normal metabolism (including biochemical reactions)
ex: diabetes, hyperthyroidism in cats
N- neoplastic
ex: squamous cell carcinoma, lymphoma
N - nutritional
- Either deficiencies or toxicities
(too little/too much)
ex: selenium deficiency, copper poisoning in sheep/goats, obesity
I - infectious
an infectious agent is involved
ex: rabies, kennel cough
I - immune-mediated/Inflammatory
Result from abnormal function of immune system or excessive inflammatory response
ex: allergies, feline asthma, inflammatory bowel disease
I - idiopathic
Diseases we don’t know the cause of
ex: idiopathic chronic hepatitis in dogs
T - traumatic
limbs, fractures, hemorrhages
T - toxic
lead poisoning, oleander
V - vascular
Atherosclerosis, thrombus
how are diseases transmitted?
horizontal - one individual to another
vertical - from dam to offspring; “direct” transmission
routes of horizontal transmission
- direct contact
- ingestion
- inhalation
- sexual
direct transmission
- direct contact
- inoculation
- transplacental
indirect transmission
- fomite
- vector-borne
- air-borne
pathogen
a biologic agent that causes disease
pathogenicity
ability of pathogen to cause disease in host
infection
entry, development and multiplication of infectious agent
exposure
no physical response (yet)
incubation
levels of pathogen increase, physical response, but no disease yet (subclinical)
prodromal
the first signs of illness
decline
immune system kicks in or medication takes affect
convalescence
animal regains strength
what is in the epidemiologic triangle?
- host
- pathogen
- environment
