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239 Cards in this Set

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DIAGNOSTIC TESTS

GOAL

A COUPLE OF BASICS DEFINITIONS
Distinguish between infected/diseased and noninfected/diseased individuals

Any device or process designed to detect a sign, substance, tissue change or response
DIAGNOSTIC TESTS

TWO TYPES

AND EXAMPLES
Pathagnomonic Tests
- Absolute Predictor
- No false positives
- False negatives possible
~~ ie dont find marker
- Culture
- Parasite Detection
- PCR

Surrogate Tests
- detection of secondary changes
- false positives
- false negatives
- Serology
- Allergy Test
~~ immunosuppresion may produce false negative
SEROLOGICAL TESTS

4 POSITIVE INTERPRETATIONS
Animal previously exposed to the infectious agent

Prior vaccination or passive antibody transfer
~~ colostrum

Cross Reactions

Lab Errors
- lack of standard processes
SEROLOGICAL TESTS

4 NEGATIVE INTERPRETATIONS
Animal non-infected or exposed

Animal recently infected/exposed

Immunologically tolerant animals
~~ PI BVD animals our favorites

Lab Errors

- lack of standard processes
DIAGNOSTIC TESTS

3 SCALES
Dichotomous Scale (yes or no)
- pregnancy
- virus isolation
- serologically positive

Ordinal Scale
- titer
- body condition score

Continuous Scale
- blood parameters
~~ RBC, WBC etc
- ELISA values
- somatic cell counts
A PERFECT TEST

3 CHARACTERISTICS
Only Exists for a Perfect Disease

If
- a certain charactersistic is ALWAYS present in patients with the disease
- that characteristic is NEVER present in patients who do not have the diseasse
- the test is able to dect that characteristic when it is present
The test is perfect and no further CLINICAL JUDGEMENT is required
A PERFECT TEST

3 RESULTS
All individuals without the disease of interest would have one uniform value for the test

All indivuuals with the diesase would have a different but uniform value for the test

All test results would be consisten with the results of the diseased or those on the non-diseased
REAL TEST
Positive and Negative results produce two Normal Curves with an area of overlap
TEST PERFORMANCE

TWO KEY FACTORS
Precision
- ability to producec consistent results wen repeated under the same conditions
- animal and laboratory conditions
- inerobserver variability
~~ ie agglutination interpretation requires experience
- intraobserver variablility
~~ ie how much sleep did you get

Accuracy aka Validity
- ability to produce correct results
TEST PRECISION

THREE FACTORS
- animal and laboratory conditions
- inerobserver variability
~~ ie agglutination interpretation requires experience
- intraobserver variablility
~~ ie how much sleep did you get
TEST ACCURACY

THREE RESULTS
Perfect Diagnostic Discrimination
- normal curve results do not overlap

Partial Diagnostic Discrimination
- normal curve results have partial overlap

No Diagnostic Discrimination
- complete overlap of normal curve results
TEST ACCURACY

HOW TO GET IT
Gold Standard
- a diagnostic method or combination of methods which determines absolutely and without error whether a disease/infection is present in an animal

OK How to REALLY get it
- 2X2 Table
~~ True Positive
~~ False Positive
~~ True Negative
~~ False Negative
- The go to town with statistical techniques
ACCURACY

WHAT COMPRISES IT
Sensitivity (Se)
- the probability that a test will correctly indentify infected animals
- TRUE POSITIVES

Specificity (Sp)
- the probability that a test will correctly identify non-infected animals
- TRUE NEGATIVES

Note
- Se and Sp DO NOT change with prevalence
SENSITIVITY

MATH DESCRIPTION
Divide True Positives by Total Diseased

Note
- total diseased = sum of True Positives and False Negatives
SPECIFICITY

MATH DESCRIPTION
Divide True Negatives by Total Non-Diseased

Note
- total Non-Diseased = sum of False Positives and True Negatives
INCREASE SENSITIVITY
Decreases number of False Negatives

Increases number of False Positives

Increase sensitivity when disease is highly contaguous or pathogenic
INCREASE SPECIFICITY
Decreases number of False Positives

Increases number of False Negatives
SELECTING A CUTOFF VALUE

BUYING AND SELLING
Purpose of test

Relative cost of false positives vs false negatives

Availability of definitive tests of High Specificity

Buying
- want high Sensitivity
~~ avoid diseased animals

Selling
- high specificity
~~ ensure sale of healthy animals
PREDICTIVE VALUES

WHAT DO THEY DEPEND ON

NAME AND DEFINE THEM
Depend on
- Sensitivity
- Specificity
- PREVALENCE

Positive Predictive Value (PPV)
- proportion of True Positives amoung the TOTAL number of positive results

Negative Predictive Value (NPV)
- proportion of True Negatives amoung the TOTAL number of negative results
PREDICTIVE VALUES

FIVE TRUTHS
Are PREVALENCE DEPENDENT measures that Characterize a Test Result

Indicate the LIKELIHOOD OF DISEASE of an INDIVIDUAL with a Given Test Result

Can be used to ESTIMATE the proportion of False Positive and False Negative Results

Are important for the understanding that TEST RESULTS MAY HAVE DIFFERENT MEANINGS FOR DIFFERENT SUBGROUPS OF A POPULATION

CANNOT be obtained by the standard 2X2 table when the Prevalence in the Table IS NOT IN AGREEMENT with the Actual prevalence in the target population
APPARENT PREVALENCE
Number of Positive Test Results
TRUE PREVALENCE
Number of Diseased Animals
PREDICITIVE VALUE RELATIONSHIPS

TO

TRUE PREVALENCE
Apparent Prevalence
- increases linearly with True Prevalence

Positive Predictive Value
- exponentially increases with True Prevalence
~~ tf if prevalence is low need to use a test with High Specificity

Negative Predictive Value
- exponentially decreases with True Prevalence
SERIAL TESTING
Animal must be positive on 1st AND 2nd test

Increases Specificity

1st Test
- Highly Sensitive
- inexpensive

2nd Test
- Highly Specific
- cost less important because testing smaller numbers
PARALLEL TESTING
Animal can be positive on 1st OR 2nd test

Increases Sensitivity

Works when
- neither test has high Sensitivity
- each test detects a DIFFERENT characteristic of disease
TEST STRATEGY

SERIAL

FIVE
Increase Specificity

Positive test result is greatest predicitive value

Rule in a disease clinically

Clinical Purpose
- use when time not crucial
- avoid excessive testing
- test and removal programs

Useful when there is an important penalty for False Positve results
TEST STRATEGY

PARALLEL

FIVE
Increase Sensitivity

Negative test result is greatest predictive value

Rule Out a disease clinically

Clinical Purpose
- Rapied assesssment of individual paitients
~~ vaccination clinics
~~ emergencies

Useful when there is an important penalty for false negative results
- ie missing a disease
DIAGNOSTIC TESTING

WHEN TO USE
Used on individuals who have a specific indication of possible illenss

Individual based

Important
- diagnostic precision and accuracy

Less Important
- acceptability of test
~~ invasivenes
~~ cost
DIAGNOSIS

5 STEPS
Establishement of Diagnostic Hypothesis

Highly Sensitve tests to rule out Specific diseases

Strong Clinical Suspicion

Highly Specific test to Rule In

Confirm or Reject the clinical suspicion
SCREENING TESTS

WHEN TO USE
Used on individuals who are Asymptomatic

Early detection of disease
- case finding

Determine status of a population
- ie infected or not

Estimate
- subclinical disease
- infection prevalence

Eradicate Diseases
SCREENING TESTS

6 EXAM HANDY THOUGHTS
Population Based

If proportion of affected individuals is likely to be small
- ie early detection of disease
- risk of high number of false positives
~~ tf increase specificity
~~ tf further study of positive individuals

Evaluation should focus on the whole process

Administration
- inexpensive
- low risk
- minimal discomfort
PURPOSE OF TESTING

SEXY SIX
Diagnosis

Screening

Monitor Vaccination Programs or Procedures

Judge Severity of Disease
- quantitiative tests

Predict Subsequent Clinical Course and Prognosis

Estimate Responsiveness to Therapy
WHY MEASURE DISEASE

THREE AMIGOS
Determine mechanism of transmission via Distrubution and trend of disease
- temporal
- spatial
- feeding
- husbandry

Assess the impact of disease on study population
- what is the risk of a given animal in the population having disease

Assess the effect of control progams to prevent or eradicate disease from the population
WHAT TO MEASURE

SEVEN
CASES
- clincal cases
- subclinical cases
- production parameters
- combinations of above

NON CASES
- may be cases in the future
- recovered cases
~~ ie immune
- required for comparison purposes
COUNTS
Static Measure

Simple enumeration of cases

Very LIMITED use in epidemiology
- requires Population at Risk
PROPORTION
Static Measure

A fraction in which the numerator is included in the denominator

Dimensionless

Range
- from 0 to 1
- %
PREVALENCE

TWO TYPES
A Static Measure

Always a PROPORTION

Point Prevalence aka Prevalence
- proportion of a population affected by a disease at a given point in time
- based on EXISTING cases
- P = (# individuals having a disease at a particular point in time)/(# individulas in the population AT RISK at that point in time)

Period Prevalence
- number of cases that are KNOWN to have occurred during a SPECIFIED PERIOD of time
- sum of
~~Point Prevalence at the beginning of the period
~~ # of NEW CASES that occur during the period
~~ ie incidence
RATIO
A Static Measure

A fraction in which the numerator IS NOT included in the denominator

With or Without Dimension

Range
- 0 to infinity

ie Odds Ratio
- ratio of
~~ probalility of occurence
~~ propablility of non occurence

Note
- CANNOT convert between prevalence and odds
RELATIONSHIP BETWEEN PROPORTION AND ODDS
Proportion
- = odds/(odds + 1)

Ratio aka Odds
- = proportion/(1 - proportion)
RATE
A Dynamic Measure

The instantaneous change in disease per unit change in time

Has Dimension

Range
- 0 to infinity
CUMMULATIVE INCIDENCE
CI aka Incidence Risk

PROPORTION of disease free individuals developing a given disease of a SPECIFIED TIME

Based on NEW cases

CI =
~~ # of individuals that BECOME diseased during a particular period
~~--~~ divided by
~~ # of healthy individuals in the population at the beginning of the study

Only for the FIRST occurance of disease

For Static Populations
- all animals enter study at the same time
- remain for period of study
- only "leave" study when develop disease

Can be estimated from Incidence Density
- more accurate when Incindence Density is low
- allways underestimates CI
~~ assumes all individuals are at risk for entire period
INCIDENCE DENSITY
I aka True Incidence aka Hazard Rate

Measures the RAPITIDY with which new cases of disease develop over time

I =
~~ # of NEW cases of disease that ocuuri in a population during a paricular period of time
~~--~~ divided by
~~ sum, over all individuals, of the length of TIME AT RISK of developing disease

Demominator accounts for different time at risk for different individuals
- ie time at risk stops once animal has disease

Expressed as an ANIMAL TIME UNIT
- can exceed 1

Can be estimated (used) when animals get disease MORE THAN ONCE
- ie mastitis

Useful for DYNAMIC POPULATIONS

Does NOT have an interpretation at the Individual level
CUMULATIVE INCIDENCE

NUMERATOR

DENOMINATOR

TIME

UNIT

TYPE
NUMERATOR
- New Cases

DENOMINATOR
- Initial Population

TIME
- Duration of Period

UNIT
- None

TYPE
- Proprotion
~~ involves time
INCIDENCE DENSITY

NUMERATOR

DENOMINATOR

TIME


UNIT

TYPE
NUMERATOR
- New Cases

DENOMINATOR
- Animal Time

TIME
- Start of study until development of disease

UNIT
- Cases per animal time

TYPE
- Rate
POINT PREVALENCE

NUMERATOR

DENOMINATOR

TIME


UNIT

TYPE
NUMERATOR
- Existing cases

DENOMINATOR
- Initial Population

TIME
- Single Point

UNIT
- None

TYPE
- Proportion
PERIOD PREVALENCE

NUMERATOR

DENOMINATOR

TIME

UNIT

TYPE
NUMERATOR
- Existing/new cases

DENOMINATOR
- Midpoint

TIME
- Period

UNIT
- None

TYPE
- Proportion
CRUDE MEASURES
Ingnore structure of population
- gender
- age
- breed

Comparison of crude rates misleading if population structures differ
SPECIFIC MEASURES
Proportion or Rates in specific population subgroups
- age
- gender
- breed

Detect and explain differences in risk of disease
- proportion
- rates

Stratification

Calsculated like crude measures but limited to specific sub groups
ATTACK RATE
AR

Measure of Incidence

Period of Risk is Limited

Outbreadks of Food Borne Diseases
- limited exposure period
- specific exposure agents

ArR =
~~ # animals tath develop diseas during a specified time period following exposure
~~--~~ divided by
~~ total # of animals exposed
SURVIVAL
S

Probability of an individual with a specific disease remaining alive for a specified length of time

S = (N-D)/N

N
- # number of newly diagnosed cases under observation during the specified period of time

D - # of deaths observed in a specified period of time
MORTALITY RATES

5
Crude Death Rate =
~~ # of deaths in a given time
~~--~~ divided by
~~ Total population at risk

Cause Specific Mortality Rate =
~~ # of deaths attributable to a cause
~~--~~ divided by
~~ total # of animals

Case Fatality Rate =
~~ # of deaths attributable to a disease
~~--~~ divided by
~~ total # of animals having the disease

Age-Specific Death Rate =
# of deaths within a certain age group
~~--~~ divided by
~~ total # of animals in the age group

Proportions Mortality Rate =
~~ # deaths due to specific cause of interest
~~--~~ divided by
~~ total deaths in population
General Fertility Rate
# of live births out of the average number of females of reproductive age
DISEASE PATTERNS

NAME 3
Temporal

Spatial

Individual
EPIDEMIC CURVES

DEFINITION

4 TYPES
Temporal Pattern

Describe disease occurrence over time
- ploted as frequency histogram

Endemic
- disease occurs at expected frequency

Epidemic
- disease occurs at greater than expected frequency

Sproadic
- single case
- cluter of cases

Pandemic
- humungous epidemic
- international
ENDIMIC DISEASE

4 CRITERIA
Disease present in population of region at all times

Usually low and predictable level

Tend to have only nimor fluctuations in frequency pattern over time

A isease may be endemic at ANY level of occurence
ENDEMIC DISEASE

4 TYPES
Holoednemic
- most/all animals are affected

Hyperendemic
- high proportion of animals are affected

Mesoendemic
- moderate proportion are affected

Hypoendemic
- relatively small proportion are affected
CHANGES IN ENDEMIC DISEASES
Objective
- identify periods of high of low risk to determine possible causal factors of disease

Determination of 3 Fuerther Temporal Trends
- cyclic variation
~~ ie flu balance of new strans and immunity
- seasonal fluctuations
~~ vector borne summer fall
~~ food poisoning summer
- secular(long term) trends
~~ wont be seen without analysis

Analyses
- data plots
- time series analysis
- regression analysis
- try to determine causes of time of flucuation
~~ prediction
~~ prevention
EPIDEMIC DISEASE

4 CRITERIA
Incidence exceeds expected

Usually infectious diseases or poisoning

Point source or propagated

Outbreak
- localized epidemic
~~ area
~~ population
POINT EPIDEMIC

4 FACTORS
Single common exposure

Does not spread

Steep Curves

Often foodborne disease outbreaks
PROPAGATED EPIDEMIC

7 FACTORS
More gradual curve

Often involves vectors or carriers

Diseases with longer incubation periods
- Primary then Secondary case clusters

Cases may occur ove prolonged period of time

Ascending Curve Slope
- incubation period
- characteristics of agent
~~ ie infectivity
- characteristics of host
~~ ie susceptability
- population density
~~ ie contact rate

Plateau Duration
- availability of susceptible individuals

Decending Curve Slope
- immunity
- recovery
SPORADIC DISEASE

5 FACTORS
Infrequent diseas occurence

Irregular and unpredictable

Environmental Changes

Relaxation of control measures

Vaccination Failures
EPIDEMICS HAPPEN

WHY

3 WAYS
Introduction of an agent into a setting where it has not been previously
- ie WNV, SARS
- THE DREAD GAMBIAN RATS
- no immunity

A Recent increase in the amount or virulence of the agent
- antibiotic resistence
- AI our favorite

An enhanced mode of transmission
- more animals exposed
~~ SARS
~~ foodbourne diseases
EPIDEMIC INVESTIGATIONS

7 OBJECTIVES
Indentification of the infectious agent

Establishment of the infection source
- THAT WOULD BE STU

Establishement of the main infection transmission route and vector

Control and prevention of additional cases

Evaluate existing prevention statigies

Gain knowledge
- research

Training
EPIDEMIC INVESTIGATIONS

THE QUESTION
Are the cases in excess of the expected baseline rate for disease and setting
ESTIMATION OF THE INCUBATION PERIOD

4 NEED TO KNOWS
Index Case
- THAT WOULD BE STU

Peak

Cause

Time of exposure
- knowledge about common exposures helpful
ESTIMATION OF THE INCUBATION PERIOD

2 ASSUMPTIONS
Presence of clinical signs indicates disease

Health before onset of illness
ESTIMATION OF THE INCUBATION PERIOD

FOR PROPOGATED EPIDEMICS
Difficult
SPATIAL PATTERNS

WHAT ARE THEY FOR TWO
Variation between regions and countries
- important determinants of disease distribution
- environmental factors vary among locations

Local Patterns
- pen
- litter
- herd
- animals and managment can vary within farm
SPATIAL PATTERNS

WHAT DO THEY DO 3
Answer the where question

Indentify occurrences of events that happen close together in space

Generate research hypotheses
SPATIAL PATTERNS

3 VARIETIES
Random

Regular
- usually poisonings
~~ ie contaminated water

Contagious
- little clusters
INDIVIDUAL PATTERNS

7 SLICED 2 WAYS
Within Population at Risk

Individual Characteristics which affect susceptability to disease
- Age
~~ tell me about it
- Gender
- Breed
- Immune Status

Opportunities for Exposure
- Type of production
~~ ie dairy vs beef
- Management
- Feeding Practices
DESCRIPTION OF DISEASE
Simple description of disease is FIRST STEP in epidemiological investigations

Temporal Patterns
- shape of curve
- duration

Spatial Patterns
- from specific housing to the globe

Host Characteristics
- age
- sex
- breed
DESCRIPTIVE EPIDEMIOLOGY
Surveys
ANALYTICAL EPIDEMIOLOGY

3 BIGGIES
Epidemiological Associations
- statistical significance
- strength
- importance
EPIDEMIOLOGICAL STUDIES

TWO MAJOR TYPES
Observational Field Studies
- researcher has NO CONTROL
- cohort studies
- case-control studies
- cross-sectional studies
- most common

Experimental Studies aka non-observational
- experiments
- controlled
~~ clinical trials
~~ field trials
- intervention studies
- manipulation of parameters
- apply treatments to populations
CROSS SECTIONAL STUDIES

CHARACTERISTIC

OBJECTIVE
animals are randomly sample at one point in time
- WITHOUT CONSIDERING HEALTH AND EXPOSURE BEFOREHAND

Objective
- estimation of disease prevalence
- to have a snapshot of the situation at a specific moment
~~ at the same time examine for
~~-- presence of disease
~~-- exposure status
CROSS SECTIONAL STUDIES

OUTCOMES
With Disease and Exposed

With Disease and Unexposed

Without Disease and Exposed

Without Disease and Unexposed
CROSS SECTIONAL STUDIES

ADVANTAGES SEVEN
Straighforward

Allows for the study of several diseases at the same time

Data based on Representative samples
- tf can generalize

Quick

Moderate Cost

Measuring Prevalence
- tf focus for further studies

First Step for prospective studies
CROSS SECTIONAL STUDIES

DISADVANTAGES FOUR
DO NOT measure temperal sequence

Not useful for disease with LOW Frequency

Low response rates (sample size) compromise representativeness

Potential for confounding releationships between risk factors
- ie BVD and Neosporia both cause abortions
CASE CONTROL STUDIES

CHARACTERISTIC

OBJECTIVE
Animals are INTENTIONALLY CHOSEN for health status
- ie NOT randomly selected
- tf cannot show prevalence

Objective
- determine the animal health status with regard to Potential Risk Factors
- preliminary causal hypothesis
CASE CONTROL STUDIES

OUTCOMES
RETROSPECTIVE VIEW

Cases
- which were exposed
- which were unexposed

Controls aka Non-Cases
- which were exposed
- which were unexposed

Note
- effective control goups are difficult to set
- must have same exposure as cases
- ideally animals within herd
CASE CONTROL STUDIES

ADVANTAGES FIVE
Disease with low incidence or conditions developing over a long time

Evaluation of multiple risk factors for one disease

Quick

Low Cost

Indirect measurement of risk with regard to exposures
CASE CONTROL STUDIES

DISADVANTAGES FIVE
Do not provide information on the disease frequency

Not suitable for the study of rare exposures

Data collection relient on quality of past records

Selection of an unbiased control group difficuls

Only valid for ONE DISEASE
COHORT STUDIES

CHARACTERISTIC

OBJECTIVES
Units (animals or herds) are INTENTIONALY CHOSEN for their exposure status
- ie Animals are initially healthy

Objectives
- Estimation of Incidence
- Estimation of Relative Risk
- Dose-Response Relationships
~~ possible because all animals healthy at start
~~ ie vaccine efficacy
- Estimation of the Attributable Fraction
COHORT STUDIES

OUTCOMES
From a heathy Cohort monitor over time or Look retrospectively from groups

Exposed Group
- with disease
- without disease

Unexposed Group
- with disease
- without disease

Compare incidences between two groups
COHORT STUDIES

ADVANTAGES FIVE
Measures the TEMPORAL sequence of events

Several effects/diseases in one study

DIRECT disease Incidence estimates

Prospective or Retrospective

Rare Exposures
- can identify because defining groups based on exposure
COHORT STUDIES

DISADVANTAGES FIVE
Long duration if prospective
- ie have to follow course of disease


Low Frequency Diseases
- eg BSE would have feed a lot of animals to see disease

Cost

Losses during follow-up
CROSS-SECTIONAL STUDY

SAMPLING

TIME

CAUSALITY

RISK

COMPARISON OF RISKS
SAMPLING
- Random Sample

TIME
- One Point

CAUSALITY
- Association between disease and risk factors

RISK
- Prevalence

COMPARISON OF RISKS
- Prevalence Ratio
- Odds Ratio
CASE CONTROL STUDY

SAMPLING

TIME

CAUSALITY

RISK

COMPARISON OF RISKS
SAMPLING
- Diseased
- Non-Diseased

TIME
- Usually Retrospective

CAUSALITY
- Preliminary Causal Hypothesis

RISK
- None

COMPARISON OF RISKS
- Odds Ratio
COHORT STUDY

SAMPLING

TIME

CAUSALITY

RISK

COMPARISON OF RISKS
SAMPLING
- Exposed
- Non-Exposed

TIME
- Prospective
- Retrospective

CAUSALITY
- through evidence of TEMPORALITY

RISK
- Incidence Density
- Cumulative Incidence

COMPARISON OF RISKS
- Relative Risk
- Odds Ratio
CLINICAL/FIELD TRIALS

CHARACTERISTIC

OBJECTIVE
Researcher has EFFECTIVE CONTROL of study situation
- Random allocation of animals

Objectives
- Effectiveness of any type of intervention
~~ preventative etc
- Evaluation of phrmocological products
- Test a specific ie causal hypothesis
- Validate findings from observational studies
CLINICAL/FIELD TRIALS

OUTCOMES
Groups Randomized from Sample
- look forward after intervention

Treatements
- with disease
- without disease

Controls
- with disease
- without disease
CLINICAL/FIELD TRIALS

ADVANTAGES THREE
High control on study factors
- varying degrees of control

Randomization avoids systematic errors

Strongest evidenc about causal relationships
CLINICAL/FIELD TRIALS

DISADVANTAGES SIX
Large Groups

Generalization of results may be difficult
- may not apply in other managemnet situations

One effect per experiment

Duration

Cost

Ethics
- justify use or treatment of animals
- but hey there are allways lots of cats
MEASURING ASSOCIATION

THE EXAM QUESTION IS TALKING ABOUT THIS

YOU ARE THINKING ABOUT SIX THINGS
Statistical Significance

Epidemiologic meassures of Association
- relative risk
- odds ratio
- prevalence ratio
- attributable fraction
STATISITICAL SIGNIFICANCE

WHY
You need to know whether the DIFFERENCES are due to
- causes you are interesed in
- natural variation
~~ ie chance the good 'ol normal curve
HYPOTHOSES TESTING
Ho vs Ha

Ho Null Hypothesis
- Hypothesis of NO DIFFERENCE

Ha
- Hypothesis of DIFFERENCE

By means of a statistical test you can check if Ho is true
- compare observed vs expected distribution for which Ho is true
ERRORS

TWO TYPES
Type I Error
- rejection of a true Ho
- error of concluding there is a difference when there is not
- alpha is the probalbility of making a Type I error
~~ tf alpha is the LEVEL OF SIGNIFICANCE
~~ 1-alpha = CONFIDENCE
~~ P values need to be less than alpha for significance
~~ alpha typically set at 0.05

Type II Error
- failure to reject Ho when it is untrue
- error of concluding that no difference existed when in fact it did
- beta is the probability of making a Type II error
- 1-beta = probability of rejecting Ho when it is false
~~ ie the POWER OF A TEST
ERROR

POWER

CONFIDNECE
When Truth is there is a Difference

Rejecting Ho
- is Power (1-beta)
Accepting Ho
- Type II Error
- False Negative

When Truth is there is NOT a Difference

Rejecting Ho
- is Type I Error (alpha)
- False Posative
Accepting Ho
- is Confidence (1-alpha)
P VALUE
PROBABILITY that the difference OBSERVED between groups is caused by CHANCE

Provides probability of whether distribution of observations is random or not
- does not provide information about association

P value for this course
- if P <= 0.05 reject Ho
STATISTICAL SIGNIFICANCE

COMES DOWN TO TWO PARAMETERS
Sample Size
- easier to show significance if larger
- blame inconclusive results on small sample size
~~ and apply for a bigger grant

Strength of association
- ie the REAL difference between the groups
CHOOSING THE APPROPRIATE

STATISTICAL TEST

5 FACTORS
Scale of Measurement of the evaluation criterion
- quantitative data
- qualitative data

Scale of measurement of the study factors
- quantitative data
- qualitative data

Existence of repeated measures
- independent samples
- related samples

Number of observations

Specific assumptions for each statistical test
- parametric techniques
~~ use if data folows normal distribution
~~ large N ie >30
~~ quantitative data
~~ lower then lower the power of test
- non-parametric techniques
~~ use when cant meet requirement for parameteric
~~ small N ie < 15
~~ qualitatiive or quantitative data
~~ has higher power than parametric when N is small
STRENGTH OF ASSOCIATION

WHEN

WHAT

3 HOWS
Check once Significance has been shown

Compare Occurances Between Groups

Relative Risk
- incidence
- Cohort Studies

Odds Ratio
- proportions
- prevalence
- incidence
- Case Control Studies
- Cohort Studies
- Cross Sectional Studies

Prevalence Ratio
- prevalence
- Cross Sectional Studies
REATIVE RISK
RR
- the relative risk of BECOMING diseased
- ie the disease is RR time more likely to occur amoung those exposed to the suspected rik factor than among those with no such exposure

The ratio of
- incidence of disease in exposed animals
~~--~~ to
- incidence of disease in unexposed animals

Range
- 0 to infinity

RR = 1
- there is not an association

RR > 1
- there is a risk factor

RR < 1
- there is a protective factor

Note
- 1 MUST BE EXCLUDED from the 95% Confidence Interval for there to be a Significant risk or protective factor
ODDS RATIO
OR
- The relative risk of BEING diseased
- DO NOT know if animals already diseased
- to measure whether of not exposure is more common in the diseased group than in the healthy group
- the odds of having the disease among those exposed to the suspected risk facor is OR times the odds of disease anoung those with no such exposure

The ratio between
- odds of disease in exposed animals
~~--~~ to
- odds of disease in unexposed animals

Range
- 0 to infinity

OR = 1
- there is not an association

OR > 1
- there is a risk factor

OR < 1
- there is a protective factor

Calculate from CROSS PRODUCT of 2X2 table

When disease is <10%
- OR ~= RR
Note
- 1 MUST BE EXCLUDED from the 95% Confidence Interval for there to be a Significant risk or protective factor
PREVALENCE RATIO
PR
- the relative risk of BEING diseased
- ie do not know if disease or exposure was first

The ratio of
- prevalence of disease in exposed animals
~~--~~ to
- prevalence of disease in unexposed animals

Range
- 0 to infinity

PR = 1
- there is not an association

PR > 1
- there is a risk factor

PR < 1
- there is a protective factor

Note
- 1 MUST BE EXCLUDED from the 95% Confidence Interval for there to be a Significant risk or protective factor
IMPORTANCE OF ASSOCIATION
To measure the effect of a factor

Determine
- Attributable Risk
- Population Attribuatable Risk
- Attributable Cause (aka etiologic) Proportion among the exposed
- Population Attributable Proportion
ATTRIBUTABLE RISK
AR

Additional risk of disease following exposure compared to that experienced by animals that are not exposed

AR = Iexposed - Iunexposed
POPULATION ATTRIBUTABLE RISK
PAR

Proportion of exposed within population times Attributable Risk

PAP = (exposed/n) x AR
ATTRIBUTABLE PROPORTION
AP

Proportion of disease in the exposed animals due to exposure

AP
= (RR-1)/RR
= (OR-1)/OR
= (PR-1)/PR
POPULATION ATTRIBUTABLE PROPORTION
AP

Proportion of disease in the population due to exposure

PAP = (proportion of exposed that are diseased) x AP
SAMPLING

WHY

OBJECTIVE
Increase the efficiency of the study

Objective
- to draw a sample which is a TRUE REPRSENTATION of the POPULATION
- tf estimate of population characteristics will have acceptable
~~ precision
~~ accuracy
SELECTING SUBJECTS

SIX DEFINITIONS
Target Population
- population at risk

Study Population
- population sampled
- ideally the same as Target Population
~~ allows extrapolation of results

Sampling Frame
- list of all sampling units in population
- ie a census of
~~ each animal
~~ each flock
~~ each farm

Sampling Unit
- each member of the sampling frame
~~ individuals
~~ flocks/herds
~~ farms

Sampling Fraction
- ratio of Sample Size : Study Population

Sample
- number of sampling units selected
SAMPLING

TWO TYPES
Non-Probabilty Sampling
- method chosen by investigator
- convenience sampling
- purposeful sampling
~~ ie specific disease
- volunteers
~~ who like Raul to cut off their head

Probability Sampling
- investigator does not chose
- all animals in population have probability of being sampled which is NOT 0
PROBABILTY SAMPLING

AIM

5 TYPES
Obtain estimates of a variable which are as close as possible to the true value for the TARGET POPULATION

Types
- simple random sampling
- systematic sampling
- stratified sampling
- cluster sampling
- multistage sampling
SIMPLE RANDOM SAMPLING
Sampling Frame Required
- ie list of individuals for headectomy

Homogeneous Population

Simple to Perform

Easy estimation of
- means
- variances
SYSTEMATIC RANDOM SAMPLING
Do NOT have Sampling Frame

Units are selected at regular intervals from STUDY POPULATION
- ie every third animal through gate

Constan of sampling must not be related to the phenomenon under measurement
STRATIFIED RANDOM SMPLING
Population is heterogeneous concerning the variable of interest

Sampling frame divided into Strata befor selection

More precise estimates

Determine a PRIORI to which Stratum each element belongs


ie Two breeds of beef cows
- divide into breed groups
- randomly select from each breed
- select number from each breed that is proportional to representation in population
CLUSTER SAMPLING
Sampling Frame is UNKNOWN
- but list of clusters is available

Clusters are randomly selected
- all animals from the selected clusters are sampled

ie Know the sows but not the piglets
- randomly select sows
- sample all piglets of selected sows
MULTISTATE SAMPLING
Large and Spread Populations

Complex Method
- more than one sampling frame
- but no sampling frame for units of interest

Not all animals within a cluster are selected

ie sample x piglets from y randomly selected sows
PROBABILITY SAMPLING

SOURCES OF ERROR

TWO TYPES

WHAT TO DO ABOUT IT
SAMPLING ERROR aka Random Error
- insufficenct precision around true value
- increase sample size
- change tha sampling procedure

SYSTEMATIC ERRORS aka Bias
- image of reality which diverges from truth

Selection Bias
- non random selection
- non inclusion
- non response

Meaurement Bias
- inaccurate measurements
~~ lack of Se and or Sp
- quality of samples taken
- poorly designed questionairs

Observational Bias
- response error

Confounding Bias
- existance of confounders
- inapporopriate choice of statistical techniques

tf change study design
HEALTH
Heath is the state of complete physical, mental and social well-bieng and not merely the absence of disease or infirmaty

or for the large animal types

Average Productin
PUBLIC HEALTH

7 CONTRIBUTORS
The Glorious Vets
- Agriculture
- Animal Health and Productin
- Food Industry
- Educations

Others
- Housing
- Public Works
- Communication
VETERINARY PUBLIC HEALTH
A component of public health activities devoted to the application of professional veterinary skills, knowledge and resources for the protection and improvement of human health

The contribution to the complete pyysical, mental and social well being of humans through an understanding and application of veterinry medical science
VETERINARY PUBLIC HEALTH

WHY
Out of 1415 species of infectious organisms known to be pathogenic to humans
- 61% are Zoonotic
- 75% of emerging pathogens are Zoonotic
VETERINARY PUBLIC HEALTH

3 DISEASE TYPES
Endemic Disease
- rabies
- brucellosis

Re-Emerging Diseases
- influenza
- leptospriosis
- salmonellosis
- AI our favorite

New Diseases
- BSE
- SARS
VETERINARY PUBLIC HEALTH

4 ACTIVITES INVOLVING

DIAGNOSIS

SURVEILLANCE

CONTROL

ERADICATION
Human protection from animal diseases ie Zoonoses
- an infectious disease transmissible under natural conditions between vertebrate animals an human beings

Food protection and safety
- to ensure the safety of all foods throoughout the process rom production, proccessing, storage and distribution to the consumtion

Emerging diseases and Antimicrobial Resistance
- infections that have newly appeared in the population
- existing infections that are rapidly increasing in incidence or geographic range

Environmental Hygiene
- study and control of the impact of animal populations on environmental health
VETERINARY PUBLIC HEALTH

3 OTHER ACTIVITES
Biomedical Models
- diagnostic and therapeutic techniques developed in animals

Disaster Response
- diseases emerge from animals

Bioterrorism
- mainly agent that affect food production
- agents that could pass to humans through food
VETERINARY PUBLIC HEALTH

6 METHODS
Epidemiology of Course
- preventative in nature
- population based

Descriptive Epidemiology

Analytical Epidemiology
- epidemiological studies
- development of models

Evaluation of diagnostic tests

Disease monitoring and surveillance

Animal health and economics
FOOD SAFETY

2 FACTOIDS
With increasing global consumption of animal derived foods there is an increased poterntial for zoonotic foodborne pathogens, including theri resistance to antibiotics, to disseminate worldwide

There are examples of positive correlations between the levels of foodborne pathogens in food animals and the incidence of foodborne illness in humans
- ie Denmark
~~~~~~ less salmonella in prodcution chickens results in less salmonelloses in humans
FOOD PROTECTION

DEFINITION
To ensure the safety of all fodds throughout the process from production, porcessing, storage and distribution to consumption
FOOD PROTECTION

4 THREATS
Presence of infectious agents in food

Toxic substance
- chemicals
- pesticides
- residues
- dioxins
- micotoxins
- food additives

Drug and Antibiotic Residues

Novel Foods
- GMO
FOODBORNE DISEASES

DEFINITION

4 FACTOIDS
Disease, usually either infectious or toxic in nature, caused by agents that enter the body through the ingestion of food

2.1 million people died from diarrhoeal diseases in 2001
- majority attributable to contamination of food and water

30% of people are suffering from foodborne diseases each year in INDUSTRIALIZED COUNTRIES

USA
- > 250 different diseases have been linked to contaminated food or drink
- Anually
~~~- 80 million cases
~~~- 325000 hospitalizations
~~~- 5000 deaths

Outbreaks may take on massive proportions
- 1994 ice cream salmonellosis strikes 224k USA
- 1988 Clams hepatitis A 300k China
FOODBORNE DISEASE

LIST 7 TYPES
Bacterial

Viral

Parasitic

Prions

Naturally occuring toxins
- mycotoxins
- marine biotoxins
- cyanogenic glycosides
- mushroom toxins

Pesisten Organic Pollutants aka POPs
- accumulated in environment
- accumulate in those that lord it over the top of the food chain
- dioxins
- PCBs

Metals
- lead
- mercury
- cadmium
FOOD PROTECTION

5 STAGES
Preharvest
- Farm or Field

Post Harvest
- Havest or Slaughter
- Processing
- Ratail or Food Service
- Consumer
PREHAVEST FOOD SAFETY

WHAT IS IT

WHAT DOES IT CONTROL - 4

WHAT IS IT BASED ON - 4
Primarily focused on the protection of Human Health
- considered in the context of a farm to table food
- animal health is a secondary consequence

Controls
- infectious agents
- chemical residues
- drug residues
- pollutants

Based On
- good animal management proctices
- biosecurity practices
~~ ie farm sanitation
- feed selection
- animal testing and elimination
~~ surveillance
PRE HARVEST FOOD SAFETY

4 BENEFITS
Prevention of zoonotic human diseases

Control of animal diseases
- including those not pathogenic to production animals
~~~~ Ecoli
~~~~ Salmonella

Animal Welfare

Avoid Litigation
POST HARVEST FOOD SAFETY

CONTROL FOR 3

BASED ON 4
SECONDARY PREVENTION

Control and Prevention of
- sources of pathogens
- food contamination
- adulteration

Based On
- elimination of diseased or contaminated
~~~- meat
~~~- fish
~~~- milk
~~~- eggs
- Prevention of sale of objectionable animal food products
- maintaining strict hygiene during processing
- ensuring proper labelling
POST HARVEST FOOD SAFETY

SIX BENEFITS
Prevention of foodborne diseases
- main goal

Control of animal disease
- surveillance

Information regarding causes of condemnation
- prevention

Increased markentability of products
- reduce trade barriers

Consumer Confidence
- perception of safety

Inproving production efficiency
- animal selection
POST HARVEST FOOD SAFETY

3 LOCATIONS

10 ACTIVITIES
Location
- abattoirs
- porcessing plants
- retailers

Activites
- evaluation and monitoring of manufacturing practices
- inspection of processing equipment
- verification of produc formulation
- verification of labels
- issuing export certificates
- enforcing licensing
- verifying accuracy of industry grading
- evaluating sanitation procedures
- inspection of final products
- control andimplementation of in plant quality management programs
EMERGING INFECTIOUS DISEASES

WHAT ARE THEY
Infections that
- have newly appeared in the population
- have existed but are rapidly increasing in incidence or geographic range
EMERGING INFECTIOUS DISEASES

6 SPECIFIC TYPES
Actually a NEW disease

New to Country or Region

Has re-emerged
- after extinction
- after latency
- re introduction via new predisposing factors

Was always there but not DIAGNOSTICALLY proven
- neosporosis

Agent is now different
- mutation
- replacement after vaccination
- ie AI or antimicrobial resistance

New PUBLIC PERCEPTIONS produce new fears
- creates fear of a previously known disease
~~ ie txoplasmosis
~~~~ 50% of people infected in Europe
~~~~ no big deal until you get AIDS
EMERGING INFECTIOUS DISEASES

2 STEPS
Introduction of the agent into a new (susceptable) host population

Establisment and futher dissemination within the new host population

Factors that promote one or both these steps will tend to precipitate dieseas emergence
EMERGING INFECTIOUS DISEASES

2 FACTS

ONE COOL PHRASE
Numerous examples originating as Zoonoses
- SARS
- Hantavirus

Most appear to be caused by pahtogens already present in the environment

tf Emergence is due to MICROBIAL TRAFFIC
EMERGING INFECTIOUS DISEASES

MICROBIAL TRAFFIC

7 WAYS HUMANS INCREASE IT
Movement of people and animals

Ecotourism

Unusual eating habits
- fast food has high amount of industrial processing
~~~~ tf many opportunities for our little friends

Use of Exotic Animals as pets
- lets buy Roul a Gambian Rat

New Laboratory processing techniques

Genetic modifications
- porcine stress syndrome

Misuse
- antibiotics
- antimicrobial drugs
EMERGING INFECTIOUS DISEASES

MICROBIAL TRAFFIC

3 NATURAL INCREASERS
Heavy rains and flooding

Natural climate changes

Earthquakes

etc
ZOONOSES

NAME 10
Avian Influenza
- poulty

BSE
- cattle

Lyme Disease
- deer

Hantavirus
- mice

Rabies
- skunks, raccoons

Salmonellosis
- poultry, reptiles

Leistmaniasis
- dogs

West Nile Virus
- birds

Toxoplasmosis
- cats
ZOONOSIS

6 DEFINITIONS
Any disease and/or INFECTION which is naturally transmissible form animals
- ie may not be disease in animal

AGENTS of which are transmitted between vertebrate animals and people
- agents not vectors

An infectious disease transmissible under natural conditions between vertebrate animals and human beings
- can go both ways

Zoonotic agents are infectious agents which are not only confined to one host, but which can cause an infection, with or without clincal disease , in several hosts including humans
ZOONOSIS

3 NOTS
Same infectious agent can infect humans and animals but there is NO TRANSMISSION between animals and humans
- clostridium tetanus

Infectious agent is strictly transmitted between humans
- chicken pox virus

Infectious agent is striclty transmitted between animals
ZOONOSIS

4 FACTIODS
75% of emerging diseases are zoonoses

45% of reportable human diseases in California are zoonoses

50% of population in South America get infected at least once with zoonotic pathogen

More thatn 200 zoonoses currently cause a wide variety of human illness
ZOONOSES

3 REASONS TO CARE
Imapct on Health
- medical assistance for humans and animals

Impact on Economy
- losses of animals adn animal products
- loss of production

Social Impact
- decrease of human production
- rehabilition of sick
- worries
- death
ZOONOSES

7 AGENT CLASSIFICATIONS
Parasitic
- toxoplasmosis

Bacterial
- campylobacteriosis

Viral
- rabies

Fungal
- ringworm

Spirochaetal
- leptospirosis

Rickettsial
- Q fever

Prion
- BSE
USUAL RESERVOIR HOSTS

4 CLASSIFICATIONS
Direct Zoonosis
- Host
~~~~ single vetebrate animal species
- rabies
- brucellosis

Cyclozoonosis
- host
~~~~ two vertebrate animal species
~~~~ ie one sheds, one eats

Metaxoonosis
- Host
~~~~ vertebrate animal species and an invertebrate animal species
- ie vector borne

Saprozoonosis
- Host
~~~~ vertebrate animal species and a Non-Animate developmental site
- ie host sheds eggs which must spend time in environment to become infective
TRANSMISSION PATTERNS

3 CLASSIFICATIONS
Anthropoxoonosis
- Maintenance Cycle
~~~~ animal to animal
- Zoonotic Cycle
~~~~ animal to human
- rabies

Zooanthroponosis
- Maintenance Cycle
~~~~ human to human
- Zoonotic Cycle
~~~~ human to animal
- human tuberculosis

Amphixenosissis
- Maintenance Cycle
~~~~ animal to animal
~~~~ human to human
- Zoonotic Cycle
~~~~ animal to human
~~~~ human to animal
- stphylococcosis
- influenza
REVERSE ZOONOSES
Diseases of people occasionally transferred to animals and then transferred back to people
TRANSMISSION FROM ANIMALS TO HUMANS

6 TYPES
Heirloom
- ancient origin
- agents transferred from prehisoric animals to early primates
- NOT Zoonoses

Direct
- animal to human
- no human to human

Indirect
- ie via food

Vector
- animal reservoir
- very rarely human to human

Animal to Human to Human

Now Human to Human Only
- orignially zoonoses
- now ciculates only in humans
- NOT Zoonose
ZOONOTIC DISEASES

FREQUENCY AND PATTERN

6 INFLUENCES
Nature and Extendt of human animal contacts
- pets in developed world

Socioeconomic Conditions
- contaminated water and food in developing world

Religious Belief and Cultrual Influences
- ie not eating certain species

Climate and Environmetal Disasters

Anima and Human Population Movements
- travel times are much shorter than most incubation periods

Animal Management
- intensive farming
- waste disposal
- enviromental contamination
- increased stress results in increased shedding
ZOONOTIC TRANSMISSION

5 WAYS INDUSTRIAL SOCIETIES FACILLITATE
Leisure time acitivies
- outdoor recreation

Ownership of pets
- love those gambian rats

Poor Personal Hygiene

Suburban Development
- intrudes on indigenous animal population
- revenge of bambi

Intensive animal production
ZOONOSES

8 RISK GROUPS
Agriculture

Animal product processing and namufacture

Forestry and Outdoors

Reacreation
- pets
- wild animals

Public Health Professionals

Emergency
- ie refugee camps
- loss of sanitary infrastructure

Innunosupressed Individuals
URBAN ZOONOSES

5 PATTERNS
Centripetal Trend

Pets and Exotic animals

Non-professional diseases

Children

Indirect economic losses
SYLVATIC ZOONOSES

5 PATTERNS
aka natural

Centrifugal trend

Food and Work animals

Professional Diseases

Adults

Direct economic losses
ZOONOSES

DIRECT CONTACT

PREVENTION AREAS 3
Application of basic biosecurity measures
- hand washing
~~~~ especially after handling sick animals
- treatment
~~~~ skin abrasions
~~~~ gastro intestinal diseases
- disinfection of infected premises
- change of clothing and boots between premises

Control Diseases and Risk Factors
- treatment of primary condition in animals
- rodent control
- risk factors associated with food borne diseases

Indirect beefirt of on farm food safety programs
ZOONOSES IN CANADA

3 SOURCES OF INFECTION
Direct contact with animals
- ingestion
- skin
- mucosa
- respiratory tract

Indirect Contact
- infected person
- environmental contamination
~~~~ water
~~~~ soil
~~~~ vegetables
- leisure activites

Foodborne Diseases
- salmonella swine and poultry
- compylobacter jejuni poultry
- Ecoli O157:H7 and VTEC cattle
SALMONELLOSIS

6 FACTOIDS
Disease caused by a groopu of bacteria called Salmonella

Agent is very common in environment

Disease produced usually varies with the SEROTYPE of Salmonella involved

Around 2300 different seortypes

Most Salmonella serotypes are pathogenic for humans

Worldwide Distribution
SALMONELLA SPP

NATURE OF THE BEAST

FOR 6 POINTS
Freezing does not kill

Grows
~~ 7 to 47 deg C
~~ pH 4 to 9.5

Survival
- long periods in food and manure

Easily DESTROYED BY HEATING

Sources of Infection
- infected animals contaminate
~~~~ feed
~~~~ water
~~~~ soil

Route of infection
- oral
SALMONELLOSIS

IN ANIMALS
Salmonella spp cann infect both warm and cold blooded animals
- 94% of reptiles infected

Diseases caused
- Diarrhea
~~~~ most common
~~~~ via S. typhimurium
- septicemia
~~~~ S. choeraesuis in pigs
- abortions
~~~~ S. abortusvois in sheep
SALMONELLOSIS

COMMON SEROTYPES

CATTLE
S. typhimurium

S. dublin

S. newport
SALMONELLOSIS

COMMON SEROTYPES

SHEEP
S. typhimurium

S. dublin

S. anatum

S. montevideo

S. abortusovis
SALMONELLOSIS

COMMON SEROTYPES

SWINE
S. typhimurium

S. choleraesuis
- most pathogenic
SALMONELLOSIS

COMMON SEROTYPES

HORSES
S. typhimurium

S. anatum

S. newport

S. enteritidis

S. arizonae
SALMONELLOSIS

COMMON SEROTYPES

AVIAN
S. pullorum

S. gallinarum

S. typhimurium

S. enteritidis

S. heidelberg
SALMONELLOSIS

IN ANIMALS

CARRIERS

3 TYPES
Active
- infected, recently or reactivation
- shed bacteria
- can kill young chickens

Silent
- cleared the bacteria in GIT but the bacteria is still present in lymph nodes
- shed if stressed

Passive
- salmonella is present in feces without infection
- negative if removed from contaminated environment
- ie injested but not infective

Note

A positive herd can remain positive for decades
SALMONELLOSIS

DISTRIBUTION
Mainly Poultry and Swine

Less common in Cattle
SALMONELLOSIS

IN HUMANS
Food Sources
- drinking water
- milk and dairy products
- raw meats and poultry
- eggs
- fish
- shrimp
- frog legs
- cream filled deserts
- fruit and vegetables

Direct contact
- 10% of dogs carry
- 1 - 27% of cats carry

4 million infections annually

500 deaths annually
SALMONELLOSIS

IN HUMANS

7 FACTIODS
Under Reported

Acute Symptoms
- nausea
- vomiting
- abdominal cramps
- diarrhea
- fever
- headache

Chronic Consecquences
- arthritic sypmtoms 3- 4 weeks after acute symptoms

Incubation Period
- 6 - 48 hours
- short tf easy to trace source of infection

Infective Dose
- 10k to 1M

Duration of Sysmptoms
- 1 to 2 days
- may be prolonged
~~~~ host factors
~~~~ ingested dose
~~~~ strain charcteristics

Cause of Disease
- penetration and passage of Salmonella organisms from GIT lumen into epithelium of SI
- producing inflammantion
SALMONELLOSIS

ON FARM PREVENTION

9 STEPS
Closed Herds or Flocks

Keep animals in small groups

Scrutinize purchased animals

Sterilize feed ingredients

Provide clean drinking water
- housed animals
- grazing animals

Pervent access of wild birds and rodents

Thoroughly cleanse and disinfect housing between batches

Monitor poultry breeding stock
- remove excretors

Disinfect hatching eggs and fumigate incubators
SALMONELLOSIS

KITCHEN CARES 9
Keep eggs refigerated
- no incubation < 4 deg

Throw out cracked or dirty eggs

Wash hands and cooking utensils after they have been used with eggs

Do not keep eggs warm for more than 2 hours

Refigerate leftover foods containing eggs quickly

Avoid eating raw eggs

Always cook meat and poultry

Cook stuffing separate from meat

Drink only pasteurized Milk and Juice
COLIBACILLOSIS

FACTOIDS 5
Bacterial disease caused by Echerichia coli

Normally found in the intestines of warm blooded animals

Over 200 serotypes
- most harmless

Different grops of E. coli cause gastroenteritis in humans
- Entertoxigenic ETEC
- Enterpathogenic EPEC
- Eneroinvasive EIEC

Most important in Canada
- Verotoxin producing E.coli VTEC
- O157:H7
- recognized in 1982 as cause of illness
E COLI O157:H7

5 LIFESYLE FACTS
Survies
- refrigeration
- freezing
- low pH

Low doses produce infection in ALL people

DESTROYED BY HEATING

Route of infection
- oroal

Sources of Infection
- food
~~~~ ground beef products
~~~~ raw milk
~~~~ apple juice
~~~~ alfalfa sprouts
~~~~ cole slaw
- water
E COLI O157:H7

IN ANIMALS

6 FACTOIDS
Once colonize shedding is short
- < 30 days

Animals undergoing nutritional stress are more likely to shed
- fasting may increase shedding

There is some suggestion that warmer environments increases shedding

Higher risk of shedding in younger calves

Shedding signifiicantly associated with weaning

Shedding has NOT been associated with CLINICAL symptoms ins cows
- tf silent carriers
E COLI O157:H7

IN ANIMALS

PREVALENCE
Cattle
- 43% VTEC
- 7.5% O157:H7

Poulty
- none

Swine
- 20% VTEC but non pathogenic
E COLI O157:H7

IN HUMANSS
Declining

Infective Dose
- 10 to 200
- extremely low

Incubation Period
- 3 to 8 days
- more difficult to trace back source of infection

Symptoms
- sever abdominal cramps
- watery diarrhea
- bloody diarrhea
- vomiting and nausea
- low grade fever

Complications
- hemolytic uremic syndrome
- kidney failure
- blood clotting disorders
- anemia
- CNS disease
E COLI O157:H7

ON FARM PREVENTION

6 PLANS
Note
- Not Epidemiologically Understood tf just try to prevent transmission

Seperate feed from mamure

Prevent water tank contamination

Decrease hide contamination

Transition diet modification
- reduce shedding

Continue investigation of shedding patterns in cattle

Reduce burden in GIT
- vaccination
E COLI O157:H7

FOOD PREVENTION

EIGHT EFFORTS
Note
- low infective dose
- tf assume all food contaminated

Never
- thaw food on counter
- let sit out of refrigerator > 2 hours

Use
- refrigerated ground meat within 3 to 4 days
- frozen gound meat within 3 to 4 months

Wash hands utensils and work areas after contact with raw meat

All meat, poultry and fish should be well cooked
- > 71 deg C

Nerve allow raw foods to contact
- ready to eat foods
- utensils and dishes
- serving plates

Wash all fresh fruits and vegetables thoroughly before consumption

Immunocompromised populuation should avoid consuming
- unpasteurized juice
- raw sprouts
- raw or partially cook meats

Follow the Rules of Hygiene
- hand washing
CAMPYLOBACTERIOSIS
Bacterial disease caused by genus Campylobacter

Main Serotypes responsible for human disease
- Compylobacter jejuni
~~~~ major source >90% of human disease
- Campylobacter coli
- Campylobacter lari

Geographic Distribution
- worldwide
CAMPLYLOBACTER SPP

LIFESYLE 7
Optimum growth 42 deg C
- bird temp
- will not grow below 30 deg C
- will not mutiply on chilled food but survives
~~~~ SURVIVES BETTER INSIDE REFIGERATOR THAN IN ENVIRONMENT

Likes Acid Environment
- ph 4.9

Salt Sensitive
- >2% inhibits

Does not survive well in food processing environments

Route of Infection
- oral

Sources of Infection
- poultry
- birds
- cattle
- household pets

Antibiotic Resistance
- especially Quinalones
CAMPYLOBACTERIOSOSIS

IN SWINE
Most herds infected with C.coli
- but without disease
- C. coli responsible for < 5% of human cases

High prevalence of C. jejuni in USofA
- role in human cases
CAMPYLOBACTERIOSOSIS

IN CATTLE
C. jejuni
- 40 to 80% of cattle
- 80% of farms

C. coli
- 20% of cattle

Gastrointestinal Disease
- C. jejuni

Venereal Disease
- C. jejuni
- reduced fertility in bulls and cows
- abortions

Most Human outbreaks associated with raw milk
CAMPYLOBACTERIOSOSIS

IN BROILERS
Asymptomatic
- silent carriers

C. Jejuni
- 40% of flocks in Denmark
- 35 to 80% broilers and retail chicken in Alberta
CAMPYLOBACTERIOSOSIS

IN SHEEP
Abortions
CAMPYLOBACTERIOSOSIS

IN HUMANS
Most common diarrheal disease

Infective Dose
- minimum 400

Incubation period
- 2 to 5 days

Asymptomatic
- usually

Enteritis
- diarrhea
- fever
- mild cramps
- self limiting in 95% of cases
- Duration 1 week
- infectious dose 10k

Extraintestinal Infections
- bactermia in 1 in 1000 cases
- Arthritis
- brusitis
meningitis
- Guillain-Barre syndrome

Emergence of Antibiotic Resitannt strains
- quinolones
CAMPYLOBACTEROSIS

PREVENTION ON FARM 4

WHY IS IT DIFFICULT
Difficult because of large bird reservoir

Avoid horizontal transmission from environment to bird flocks
- via strict hygeine in closed housing

Use chlorinated water

Immunization of older birds

No viable methods for reduction of campylobacter on cattle farms
CAMPYLOBACTERIOSIS

PREVENTION FOOD
Wrap fresh meats in plastic bags at the market to prevent blood from dripping on other foods

Refrigerate foods promptly

Cutting boards and counter used for food preparation should be washed immedialtely after use

Avoid eating raw or undercooked meats

Avoid eating raw eggs or foods containing raw eggs

Avoid drinking raw milk

Handwashing befor and after food preparation

Hand washing after handling pets
WHAT DO ALL VETS HAVE IN COMMON
Involvement in Public Health
VETERINARY INFRASTRUCTURE

ROLE
Pivitol

Veterinary infrastructure of a country is an important NEGOTIATING TOOL in International Trade
UPSTREAM

DOWNSTREAM
Better to find out why more bodies are falling in the river than to build a better rescue and recovery system

ie Take care of the problem during
- Food Production
- Food Processing
- tf hire more vets
PREVENTION

3 STAGES
Primary
- Susceptability Stage
- lower risk of exposure
- lower consequence of exposure
- ie vaccination program

Seconday
- Subclincal Stage
- Early Detection
- Prompt Intervention
- ie Pen Riders in Feedlot

Tertiary
- Clincal Disease
- Recovery
- Death
FOOD SAFETY

PRE-HARVEST
All activities aimed at protecting the health of the food animals while they are on the farm
- Herd health programs
- individual animal medicine
- prevent or reduce
~~ infectious
~~ parasitic
~~ chemical
~~ physical harm

Goal is to establis complete balance between
- Host Factors
- Agent Factors
- Enviromental Factors

By directly protecting the health of animals by reducing disease, we are supplying healthy animals to the food chand and performing and importan food safety activity
- Glorious but what about infectious agents that are pathogenic to people but do not cause disease in animals
~~ Ecoli O157:H7
~~ salmonella
FOOD SAFETY

PRE HARVEST

PRODUCER GROUPS
Goal science Based Practices which are DEFENSIBLE to the Global Community
- Absence of Evidence is NOT Evidence of Absence

Developing New Codes of Practice
- voluntary

Developing On Farm Food Safety Programs

Problem Based Research
ON FARM FOOD SAFETY PROGRAM

DEFINITION

BENEFITS 3
A comprehensive plan to reduce foodborne illness through a variety of interventions

Benefits
- Maintaining or expanding international trade
- increased management effectiveness and cost saving
- increased consumer confidence
ON FARM FOOD SAFETY PROGRAM

HOW

WHAT
Farmer organizations recognized increased demands made by retailers and consumers

Proactive
- farmer driven
- farmer friendly

Flexible
- can be adapted

Commodity Based
- specific to production species

Based on HACCP-like Principles
- Hazard Analysis and Critical Control Points

Not about doing something different, more about writing down what you do
- Write what you do
- Do what you write
ON FARM FOOD SAFETY PROGRAM

WHAT IS THE DIFFERENCE

BETWEEN FARMERS AND PUPPIES
Puppies are CUTE when the whine

sorry this whole thing is starting to look like a sunshine enema...
ON FARM FOOD SAFETY PROGRAM

4 STEPS TO SUCCESS
Committed operator and well trained staff
- people have to believe in the value of the program

Assessing the hazards

Identifying
- Good Management Practices (GMPs)
- Critical Control Points (CCPs)
- enable control or elimination of hazards

Implementing the plan and documenting actions
FOOD SAFTEY HAZARDS

IDENTIFY 3
Physical
- broken needles

Chemical
- drug residues
- toxicities
- poisonings

Biological
- bacterial
- viral
- parasitic
- prions
ON FARM FOOD SAFETY PROGRAM

HAZARDS

CANT LIVE WITH THEM

CANT LIVE WITHOUT THEM
Some hazards CAN be controlled, reduced or eliminated
- Antimicrobial Residue
~~ call GFaRAD
- broken needles
~~ indentify
~~ segregate
~~ communicate

Some hazards CANT easily be controlled, reduced or eliminated
- bacteria that do not harm the animal but are pathogenic to humans
- cmpylobacter
- salmonella
- Ecoli O157:H7
GOOD MANAGEMENT PRACTICES

WHAT

KEY ELEMENTS 9
aka GMPs

Based on Good Production Practices and Standard Operating Procedures (SOPs)

Key Elements of GMPs
- Animal Handling
- Indentifying health problems
- Pharmaceutical practices
- Premise and Equipment
- Maintenance
- sanitation
- Cleaning and Disinfection
- Waste Disposal
- record Keeping
GOOD MANAGEMENT PRACTICES

BIOLOGICAL HAZARDS

EXAMPLES 5
Controlling Access

Cleaning
- all in all out

Shipping clean animals and birds
- ie poultry flock sheets
~~ verify feed withdrawel times to facillitate empty GIT
~~~~ tf lower contamination

Medications and Vaccines
- proper disposal of dead or diseased animals

Minimize Stress
- increased stress = increased shedding
- ie stage closer to shipping areas
- adequate space
- good handling facilities
~~ injury prevention
STANDARD OPERATING PROCEDURES

WHAT ARE THEY

2 EXAMPLES

WHAT DO THEY REQUIRE
Step by Step Procedures

Vaccination SOPs
- vaccine protocol
- what vaccine
- when
- for which animals

Clinical Disease SOPs
- frequency of inspection
- what to do when sick identified
- how to treat

Requires Training of Personel
FOOD SAFETY RESEARCH

ON FARM

WHY
As food industry works through processes it will continue to indentify areas where there are
- GAPS in KNOWLEDGE
- fancy that

GAPs
- ie Camplyobacter jejuni
~~ high in Poultry and also Hogs
~~ human sources of infection not actually identified
- ie did Johnny get his nasty Ecoli infection from
~~ the goat at the petting zoo
~~ or the burger on the way there

Developing therapies for reduction of comensual infection in food animals by agnets pathogenic to humans
- ie probiotics to reduce Ecoli in beef cattle
- vaccinations
- lytic phage therapy
- therapies must be acceptable to producers and consumers
FOOD SAFETY

PRE HARVEST

VETERINARIANS ROLE

SUMMARY 5 POINTS
Keep doing what we do best
- desingningand implementing herd health programs
- treating individuals animals

Education in herd health and management to help producers make sound decisions

Applied Research

Auditors of ON Farm Food Safety Programs
- currently raising awareness
- regulatory component not yet identified
~~ will involve vets
INFECTIOUS HUMAN MORTALITY

TOP 5 SOURCES
Account for 85%

Diarrheal Disese
- food
- water

Measles

Mumps

AIDS

Malaria

TB
- food sourced

tf 2 of Top 5 Food Borne
FOOD BORNE ILLNESS

6 STUPENOUS STATISTICS
USofA?
- 1 in 4 affected annually
- 7.6 M cases/year
- 32 K hospitalizations
- 500 Deaths

World Wide
- 1.6 B cases/year
- 2.1 M deaths/yeare

tf Eating is RISK BEHAVIOR in most parts of world
CFIA'S MANDATE

3 PILLARS
Safe Food

Consumer Protection

Market Access
CANADIAN FOOD SAFETY SYSTEM

3 PRINCIPLES
Heatlh of the population must remain Paramount

Policy decisions must be based on Scientific Evidence

All sectors and jurisdictions must collaborate to protect consumers
FOOD BORNE DISEASE

WHO DEFINITION
Any disease of an infectious or toxic nature caused by or thought ot be caused by the consumption of Food or Water

Occurs when there has been a failure to adequately control the hygeine and temperture of the WHOLE food chain
MEAT INSPECTION PROGRAM

WHEN

WHAT

WHO
National Meat Inspection
- founded 1907
- response to human TB
- manily aquired from cattle
- not practicle to test cattle
~~ tf inspect carcasses in central location

Ensures that meat and poultry products are safe and wholesome

Involved in
- Federal Plants
- Domestic Plants
~~ licensed by Province
FEDERAL PLANTS

VETERINARY INVOLVEMENT

8 WAYS
Humane Transport
- animal health
- animal advocate

Antemortem and Postmortem Dispositions
- public health
- animal health

Sanitation
- public health

Sampling and Testing
- disease surveillence
- public health
- animal health

Labeling
- weight fraud
- allergies via ingredients
- public health

Imports
- public health

Exports
- Economic
- must be licensed to export

Auditing
- conformation to procedure
- public health
VETERINARY MEAT INSPECTION

5 WHYS
Sound, safe, non-adulterated, correctly labeled meat products
- public health

Identify Disease in flocks and herds
- animal health
- public health


Collect data on disease occurence in animals
- report to OIE re Country Status
- animal health

Prevent introduction of exotic animal diseases
- animal health
- public health

Provide produces and operators with Export outlets
- economic
FOOD BORNE DISEASE

2 TYPES
Most are Bacterial

Infection
- living organisms
- takes time for illness to develop
- ie Listeria Monocytogenes
~~ 21 days for symptoms
~~ hard to investigate

Intoxication
- Preformed toxins from bacterial
- symptoms develop rapidly
- 6 to 8 hrs or less
FOOD BORNE DISEASE

SOURCES 3
Directly form animals
- salmonella
- camplyobacter
- E.coli

Environemtal
- Clostridia
- Listeria
- Bacillus

Human Reservoir
- staphylococcus
- viruses
~~ ie Norwalk like on cruise ships
FOOD BORNE DISEASE

TRANSITION
VISIBLE TO INVISIBLE

Historically
- food, meat or milk carried pathogen

Currently
- contamination during or subsequent to production
- often part of Normal Intestinal Flora of animals
~~ tf not clinical disease to animal

Identification of Infection
- challenging
- requires more education
CONSUMER DEMANDS

CHANGE
Post WWII
- just wanted Cheap Meat

Currently
- demand for guaranteed, wholesome, environmental and animal welfare friendly product
- concern for residues and genetic modifications
HACCP

3 BULLETS
Pervention of potential food safety hazards rather than detection problems in finished product
- driven in '60s by NASA
~~ no cosmotic diarrhea

Based on sound technological nand scientific principles

Indentifies and prioritizes Intervention at Critical Conrol Points (CCPs)
HACCP

WHO

WHERE
Plant is responsible for writing and implementing their system effectively

CFIA approves the system and audits it regularly to ensure compliance

Now a Condition of License

Moving towards Farm Based HACCP programs
HACCP SYSTEM

5 WHATS
Product Description
- identify end user and tf risks
~~ ie adult vs infant consumer

Plant Schematic
- movement of product and inedibles
- avoid cross contamination

Flow Diagram

Prerequisite Programs
- premises
- transportation
- storage
- equipment
~~ cleaning
~~ calibration ie temperature
- personel
~~ training
~~ hygiene
- sanitation
- pest control
- recalls
- monitoring
- actions
- verification

HACCP Plans
- CCPs
CRITICAL CONTROL POINTS

DEFINITION
Any point, step or procedure at which control can be applied and a food sfety hazard can be prevented, eliminated or reduce to an acceptable level
- time at temperature
- refrigeration
- addition of sodium nitrate curing agent
~~ prolongs shelf life
~~ chemical hazard
~~ mixed with salt to avoid over consumption
- metal detection
ANTIBIOTIC RESISTANCE

HUMAN MEDICINE 3

VETERINARY MEDICINE 3
HM

Perscription of Antibiotics for viral infections

Non perscription use
- especially developing world

Incomplete course

VM

Low level use for Growth Promotion

Prophylaxis

Incomplete Course
ANTIBIOTIC RESISTANCE

CONSISTENT THEMES 7
Resistence develops in bacteria when antibiotics are given to animals

Bacteria spread from animals to humans

Some of these bacteria cause disease in humans

Impact of resistance on human health UNKNOWN
- perception of significant problem

Relative contribution of animal or human use not known

Policy changes expected to have negative consequences for agriculture

Issues are complex
- We don't know much
ANTIBIOTIC RESISTANCE

5 REASONS TO CARE
More difficult and expensive to prescibe for resistant strains

Resistant strains are more virulent
- tf more severe disease

Increased in number of cases

Enhanced spread of infection or duration of shedding

Cost
ANTIBIOTIC RESISTANCE

5 ACTIONS
Surveillance

Education

Infection Control

Reductions in Consumption

Canadian Integrated Program for Antimicrobial Resistance Surveillance (CIPARS)
CIPARS
Canadian Integrated Program for Antimicrobial Resistance Surveillance

Nationally Integrated

Information on Antibiotic use

National abattoir project
- enteric
~~ clinical disease in animals
- commensal
~~ animal unaffected

Public health laboratories
- enteric

Provides for monitoring of trends in resistance in animal and human populations
- perception vs reality
DISEASE CONTROL

NON ANTIMICROBIAL METHODS

7
Biosecurity

Quarantine

Vaccination
- prevent rather than treat

Selective Sourcing

All in All out
- disinfect inbetween

Laboratory Testing
- treatment delays

Sanitation

Farm Entry Restrictions
RESIDUES VS RESISTANCE
Residues produce Resistance

BUT

Resistance DOES NOT produce residues
CHEMICAL RESIDUES

DEFINITION
A substance having pharmacological action, their metabolites and other substances transmitted to animal products and which are likely to be harmful to human health

Requirement to differentiate between safe and unsafe concentrations
CHEMICAL RESIDUES

7 EXAMPLES
Antimicrobials

Pesticides

Hormones

beta-agonists
- clymbuteral used in veal calves
~~ remember the murdered Italian vet

Herbicides

Heavy Metals
- contaminated construction materials

Fungicides
CHEMICAL RESIDUES

3 CONSUMER CONCERNS
Drug Resistance

Alergies
- ie penecillan residues

Toxicity
- long term consumption
DRUG RESIDUES

HOW
Occur due to problems in CLEARANCE RATES

Off Label Use
- overdose
- diferent route
~~ IM vs IQ
- more frequent intervals
- different species
- LIABILITY
~~ cover your ass

Technical Erros
- injection between muscle bellies
- amount per site
~~ < 10 mls
- site choice
~~ neck usually better than butt

INflammatory Reactions

Labelling Errors
- non updated withdrawal times
CHEMICAL RESIDUES

AND CFIA
CFIA performs random weekly sampling for antibiotics in plant

Testing for other residues done regularly according ot sampling plan from Ottawa
FOOD SAFETY

REMEMBER ON THING
Remember that every food animal you treat is NOT
- a steer
- a pig
- a chicken

It is Someones
- steak
- ham
- drumstick

It could be for someone young, old or immunosuppressed

It could even be yours