Evidence Based Medicine Flashcards
what is the diagnostic process
getting from differentials to working/definitive
what are four strategies for clinical diagnosis and when we use them
-pattern recognition (i.e. we know what ring worm looks like and we can recognize the issue from that)
-arborization or algorithm (challenging if many branches, very prescriptive)
-complete or exhaustive (POMA, used more commonly in referral hospitals when the simple or obvious have been ruled out, time consuming)
-hypothetico-deductive process (get presenting complaint, hx, general inspection, PE, clinical or other tests, working diagnosis. These steps help us rule things out as we go).
what do you do once you have a working diagnosis (ex cow off feed)
-treat or manage the original case
-from heard health perspective - is it a single case or is it a herd problem
-use epidemiology to approach if its a herd problem
what is the definition of epidemiology
the study of frequency, distribution, and determinants of health and disease in a population
what is the most useful type of diagnostic approach
hypothetico-deductive is the most common/useful in practice
who determined cholera and mad cow disease
cholera = john snow
MCD = john wilesmith
5 Ws of epidemiology
-what is the problem = characteristics
-who has the problem = frequency of disease
-when did the problem occur = time pattern
-where did it occur = spatial pattern
-why? what has changed = determinants
5 Ws applied to mad cow disease
-what/characteristics = down or ataxic cow. cows were very apprehensive, anxious or mad
-when= 200 new cases/month, no seasonal pattern
-where = initial cases scattered throughout brittan and most case farms only had one case
-who = older animals, more in dairy, not dependent on breed, repro status or production
-why/diagnostic hypothesis = theory is that the new prion disease of cattle is a result of catlte eating rendered sheep parts. rendering process changed to rely on continuous heat
what was the approach to BSE in canada
1st animal identified with it was in 2003 and the animal was here. feeding ruminant protein to ruminants was banned in canada in 1996 (how did we get it then?)
what impact has BSE has on the general principles of health management?
- promot optimal health; put focus on disease prevention
-prevent cows from dying of BSE
-risk of more cows becoming infected = ban of animal to animal feeding
-non-BSE countries = import restrictions, meat and bone meal ban - accomodate business/economic realities
-huge impact on beef consumption, major cost to beef industry in europe, consumer confidence in beef decreased demand
-export market disappeared overnight
-willingness to spend on prevention (likely help people start buying it again?) - promote animal welfare
-concern over diseased animals, euthanasia of sick animals
-selective cull and offspring cull
-euthanasia of healthy animal - management the health of animals promotes human and food safety
- animal diseases can have major environmental impact
-think about where the carcasses go after death/euthanasia
what is included inthe epidemiological triad
-host = or organism harbouring the disease. the who of the triangle
-agent = or microbe that causes the disease, the what of the triange
-the environment = or those external factors that cause or allow disease transmission. the where of the triangle
-all of these together cause disease
categories of disease
Degenerative
Anomalous
Metabolic
Neoplastic
Infectious/Immune Mediated
Traumatic
(DAMNIT)
what is prevention treatment and control of disease based on
management/manipulation of risk factors
uses of descriptive epidemiology (5)
-helps us to understand what disease/factors are common for host and environment
-helps us understand or assign risk or probability to diagnostic hypothesis (common things are common)
-directs us to where we focus our preventions
-important when investigating a disease outbreak
-may be a useful business tool in practice; outbreak investigation
what are some examples of host factors
age, breed, sex
why do we care about age as a host factor, what do we need to distinguish age from
-theres a physiologic effect. changes in cell or organ function that happen inevitably with the passage of time
-associated with changes in production level, immune status, physiological state (puberty, pregnancy, lactation)
distinguish from:
-increased amount of exposure (cumulative dose). not a direct age effect but rather an exposure effect
-changes in environment/housing associated with age
why do we have to worry about breed as a host factor
there are genetic factors associated with it
-simple = general characteristics of the breed. holsteins have an increased risk for DA, large breed dogs have an increased risk for hip dysplasia
-genotype = sire and dam effects within a breed. there are high and low immune responders in dairy, theres von willebrands diseases in dogs (dobermans)
-phenotypes = what you see. white pigmentation has an increased risk for cancer eye in herefords. increased risk of melanoma in horses
-environment-management = inter-relationship alters disease expression within genetically susceptible. if herefords are always kept inside, no sunlight or cancer eye
why do we have to worry about sex for host factors
-anatomically related disease = prostate cancer, cystic ovarian disease, metritis, pyometa, etc
-physiologically related disease = mastitis, pregnancy toxemia, hypocalcemia
-role of castration/spaying = increased risk of urolithiasis in steers, cats decreased risk of mammary cancer in dogs
whats the callenge with host factors
often difficult to separate host from non-host factors. animals of different ages and breeds often housed, managed and fed differently therefore the problem is separating the environmental differences from the host differences
herd immunity; types of immunity and what individual immunity depends on, definiton, what rate of disease spread depends on
immunity is a host factor. it may be related to age, and can be specific or non-specific
-acquired immunity (colostrum, vaccine induced, natural exposure)
-innate immunity (genetic origin (i.e., resistance of rabbits to myxomatosis virus in australia)
individual immunity depends on nature of agent, challenge and environment
defn = resistance of a group of animals to infection
rate at which disease may spread through a herd depends on
-number of susceptible individuals and frequency of adequate contact
temporal patterns of disease; principles of disease transmission
-# of diseased is related to # of susceptible individuals (for any given rate of contact
-if decreased # of susceptible below threshold, infection diminished. through mass vaccination
-in most cases, not all become infected
-dispersoin of animals prevented outbreaks
agent factors; problems associated
concentration or amount of agent is the challenge dose
-we dont often know the distribution of the organism in the environment
-agent may be present in nomal and diseased animals (M. hemolytica)
-presence of etiologic agent doesnt necessarily cause infection
-infection doesnt equal disease
points to ponder regarding agent factors
-examine healthy and sick animals; the presence of an organism isn always enough to cause disease. many agents are opportunistic
-what are the requirements for the agents survival? may be as important as other control measures. a clean dry environment to reduce E coli
-what circumstances allow the agent to produce the disease? other factors are often just as or more important than a vaccine
how can the risk of disease be reduced
by limiting contact (decrease animal density) and/or by boosting immunity (vaccination)
