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79 Cards in this Set
- Front
- Back
who studied the London cholera epidemic in 1854 and invented the 2 X 2 square for evaluation of an epidemic?
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John Snow
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What is the unit of concern of a clinician versus an epidemiologist?
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clinical: individual sick animal
epi: population of all animals: healthy, sick, and dead |
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What is the primary objective of a clinician versus an epidemiologist?
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clinician: treat and cure the sick animal
epi: maintain population health; prevent & control |
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What is the setting of a clinician versus an epidemiologist?
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clinician: hospital
epi: field (farm/kennel); setting where the disease occurs |
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What are the questions asked by a clinician versus an epidemiologist?
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clinician:
- what is the disease? - how do I treat it? - epi: - what is the disease? - who? where? when? - causes (why?) - how to prevent / control the disease |
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What is the diagnostic process of a clinician versus an epidemiologist?
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clinical:
- evaluate signs - name the disease epi: - evaluate frequency of disease occurrence - study patterns - temporal, spatial, animal determinants for intervention |
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what are the five primary goals of epidemiology?
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1. investigate/control disease with an unknown cause
2. determine origin and "behavior" of disease with a known cause 3. acquire and analyze data, produce infromation 4. assess economic impact of health and disease control 5. design and monitor intervention strategies |
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what are the three primary qualitative components of epidemiology?
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1. what is the agent?
2. how does it propagate 3. how is it manipulated in a population? |
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what are the four primary quantitative components of epidemiology?
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1. how often does it occur?
2. how rapidly does it spread? 3. "how much" are different populations/groups affected? 4. how great is the impact of prevention/control? |
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what are the four levels of disease occurrence?
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1. endemic
2. epidemic/outbreak 3. pandemic 4. free |
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what are the x- and y-axis of an epidemic curve?
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x-axis: time
y-axis: number of new cases |
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what epidemiologic figure does an epidemic curve plot?
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incidence
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an ongoing or usual presence of a "disease" in a community or group of people, animals, plants, or region, at a "constant" level or pattern of "occurrence"
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endemic
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what are the three major types of endemic patterns?
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1. sustained
2. seasonal 3. sporadic |
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what is the term associated with the way an endemic disease propagates and sustains itself?
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endemic chain of transmission
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what factor generally determines whether a disease is an epidemic?
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when the number of new cases CLEARLY exceeds the expected number of new cases in a population
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if an endemic disease was plotted on an epidemic curve for several years, what occurrence would signal an epidemic/outbreak?
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if the number of new cases exceeded the epidemic threshold of the curve
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what was critical for stopping the pandemic spread of the Black Plague?
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cutting off trade routes
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what is Phase 1 of the WHO's pandemic phase description of influenza?
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a virus discovered in animals has not yet been reported to infect humans
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what is Phase 2 of the WHO's pandemic phase description of influenza?
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an influenza virus circulating in animals has been reported to infect a human.
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what is Phase 3 of the WHO's pandemic phase description of influenza?
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animal or human-animal influenza has caused sporadic disease or small clusters of disease, but there is not sufficient human-to-human infection to sustain the outbreak
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what is Phase 4 of the WHO's pandemic phase description of influenza?
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human-to-human contact can sustain the outbreak
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what is Phase 5 of the WHO's pandemic phase description of influenza?
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the identified virus has caused sustained community-level outbreaks in two or more countries in one single WHO region.
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what is Phase 6 of the WHO's pandemic phase description of influenza?
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the identified virus has causes sustained community-level outbreaks in more than one WHO region
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what is the Post-Peak Period of the WHO's pandemic phase description of influenza?
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levels of pandemic in most countries have dropped below peak levels
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what is the Possible New Wave of the WHO's pandemic phase description of influenza?
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after the Post-Peak period, a resurgence of disease is observed.
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what is Post-Pandemic Period of the WHO's pandemic phase description of influenza?
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levels of influenza have returned to normal endemic levels in most countries
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what is the primary case?
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Primary case is the very first case that occurred; it may not be the first case reported (that is the index case)
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what is the index case?
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Index case is the first case reported (may be later than the primary case; primary case may be at an earlier date, but reported earlier)
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what is the basic reproduction number, R0, and how is its value interpreted?
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R0 = if you introduce the disease into a naïve population, what is the average amount of infections?
o If R0 = 1, then it passes from one individual to another single individual o If R0 < 1, then it disappears o If R0 >1 then it infects multiple hosts from a single person |
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what are the three things/factors required for a disease outbreak?
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1. agent
2. host 3. environment |
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what is the seasonal balace of an epidemic curve? what is the epidemic threshold?
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In an endemic disease:
seasonal balance is the moving average curve of new disease occurrences over time epidemic threshold is a curve that lies 1.645 standard deviations above the seasonal threshold curve |
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what is infectiousness?
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refers to the timing and amount of shedding of an infectious organism of a host.
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what is infectivity?
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the property of a pathogen in that how many organisms are required to successfully infect a host.
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the time from infection to clinical signs of disease
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incubation period
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what is the difference between a point common source and a continuous common source?
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a point common source is one single isolated exposure from a source, whereas continuous common source is repeated exposures of the same thing from that common source.
examples: - point common source: one group of people getting food poisoning from a single pizza one single time. - continuous common source: people split up the pizza, take it home, eat it over a period of several days and repeatedly infect themselves. |
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what does the Reed Frost Model predict and what are its variables?
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predicts the number of new cases for a propagating epidemic
variables: - number of new cases in the previous time period - the number of susceptibles (those that are not already infected or resistant) - the probability of effective contact |
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in a Reed-Frost type of epidemic curve, why do the number of predicted new cases drop off after a peak?
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because the number of susceptibles decreases (susceptibles are those that don't have the disease and are not resistant to the disease)
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what four primary effects determine the probability of effective contact?
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1. infectivity (how many organisms are required to infect)
2. population density 3. # of susceptibles and immunes 4. interaction patterns |
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what is herd immunity?
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the indirect protection of susceptible individuals brought about by the presence of immune individuals (e.g. reduces the probability of effective contact)
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what is the vaccination threshold and how is it calculated?
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the proportion of a naive population that must be vaccinated to prevent an outbreak.
VT = 1 - 1/R0 |
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what are the four phases of a typical epidemic growth curve?
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1. establishment - random effects
2. exponential growth 3. exhuastion of susceptibles 4. equilibrium/endemicity or recurrent epidemics |
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what is prevalence?
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the probability of having a disease at a particular point in time; the number of cases in a total population
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what is incidence?
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number of new cases in a known population during a specific period of time
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how is prevalance calculated?
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number of diseased
-------------------------- total population |
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how is incidence risk calculated?
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number of new cases
----------------------------- all susceptible animals free of disease at the beginning of the period |
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what is incidence risk?
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the risk of developing a disease over a given time period
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what is incidence density
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the rapidity with which new cases develop over a calculated time period
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how is mortality risk calculated?
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number of deaths over a time period
------------------------------------------------ the number of susceptibles and infected |
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what is the case fatality risk?
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the proportion of those that die from a disease in those that are infected with the diesase
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what is latency?
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the time between infection and clinical signs of a BACTERIAL infection
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what is prepatency?
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the time between infection and clinical signs of a PARASITIC infection
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what is eclipse?
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the time between infection and clinical signs of a VIRAL infection
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how do you calculate prevalence odds?
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prevalance
----------------- 1-prevalence |
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how do you calculate risk odds?
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risk
------- 1-risk |
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a group within a population that has a particular property in common (e.g. age, breed, gender)
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strata
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what is standardization?
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comparing the level of disease in different populations by adjusting for differences in the populations, such as age. It calculates the COMBINED RATE/RISK
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how does direct standardization differ from indirect stndardization?
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direct standardization compares populations to each other and adjusting for strata in both populations.
indirect standardization uses a well-defined "reference population" to make the comparison. It calculates the EXPECTED RATE/RISK (e.g. the expected incidence density). |
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what is the standard morbidity/mortality ratio
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in an indirect standardization, the number of observed cases diveded by the amount of expected cases (from the reference population)
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what is Risk Difference, and how is it calculated?
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the absolute proportion of disease cases directly attributed to exposure.
RD = (number of diseased/number of exposed) - (number of diseased/number not exposed) |
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How is Odds Ratio calculated?
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odds of disease in exposed animals
------------------------------------------------ odds of disease in non-exposed animals |
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How is Risk Ratio calculated
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the risk of disease in exposed animals
------------------------------------------ the risk of disease in non-exposed animals |
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if x animals are diseased and y animals are not diseased:
- calculate the risk - calculate the odds |
Risk = x / (x+y) - it is the proportion of diseased of the total population
odds = x / y - it is the number of animals that are diseased for every animal that is not sick |
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What are the four Koch postulates?
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A living agent is causal for a disease if:
1. It is present in all cases of the disease 2. It does not appear in other diseases 3. It can be isolated in pure culture 4. when inoculated in susceptible host creates the same disease from which it can be reisolated |
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an invertebrate that is capable of transmitting an infectious disease agent among vertebrates.
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vector
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an animate (or inanimate) object on or in which an infectious agent usually lives and depends for survival, and which therefore is often a source of infection by the agent.
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reservoir
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host who contains / harbors, and may spread an infectious disease agent
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carrier
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what are the four time scales (courses) of clinical disease?
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1. Peracute - very rapid onset and progress of symptoms (24 -48 hours)
2. Acute - rapid onset and progression (days) 3. Sub-acute - slower 4. Chronic - slow prolonged course of disease over months or years` |
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a cause, if when absent, the expected/resulting effect will not occur
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necessary cause
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a cause, if when present, the expected/resulting effect will occur
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sufficient cause
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what are the three components of the epidemiologic triad and what are some basic components that are determinants of health/disease?
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1. host: species, breed, gender, age, size, conformation, use, behavior, nutrition, immune status
2. agent: virulence, pathogenicity, gradient and outcome of infection (e.g. host response, reservoirs, severity), mode of transmission 3. environment: physical location, climate, husbandry practices, stress |
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what is transmissibility?
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how "well" can an organism be infected by an infectious agent
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what is virulence?
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how severe are the effects of an infectious agent
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what is pathogenicity?
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the proportion of infected animals that become ill
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what are the three measures taken to prevent the spread of infectious disease?
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1. exclusion
2. containment 3. elimination |
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what are the four major ways by which disease spreads?
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1. direct fecal-oral
2. direct aerosol 3. direct contact with bodily fluids 4. direct skin contact |
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what are the four major ways in which to exclude an infectious agent?
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1. prevent introduction (e.g. hand washing, protection)
2. vector control 3. vaccination 4. quarantine |
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what are the three major ways to eliminate disease from an area (not animals)
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1. cleaning
2. disinfecting 3. drying |
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what are the four VMRCVM teaching hospital biosecurity protocols?
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2. Green Dot – Healthy animals, elective surgeries
1. Yellow Dot – neonates, geriatrics, immunocompromised. 3. Orange Dot – Potentially contagious / infectious 4. Red Dot – Known contagious / infectious |