Animal Health Midterm 1

3 references of health

• welfare

• production

• reproduction

7 stages of health spectrum

• reproduction

• production

• maintenance

• sub-optimal production

• clinical disease

• death

3 parts of disease

• subclinical disease

• suboptimal production

• welfare

Subclinical Disease

• disease that is not visible, but measurable in some way

• ex. somatic cell count

Clinical Disease

• observable, visible signs

• ex. diarrhea, mastitus, fever

Sub-Optimal Production

• below what is expected for that breed, genetic line, industry, etc

• can change over time

5 freedoms

• freedom from hunger and thirst

• freedom from discomfort

• freedom from pain, injury, disease

• freedom to express normal behaviour

• freedom from fear and distress

DAMNIT - classification of disease

• Degenerative

• anomolous

• metabolic

• neoplastic

• infectious

• trauma/toxic

Degenerative Disease

• structure is altered by age, use, disuse, biochemical changes

• ex. arthritis

Anomalous Disease

• abnormal structure/function

• may be genetic

• ex. cleft palate

Metabolic Disease

• due to nutrition, toxins, hormonal activity

• alters normal metabolism

• ex. milk fever

Neoplastic Disease

• abnormal growth of cells at the expense of normal tissue structure and function

• ex. lymphosarcoma

Infectious Disease

• caused by microorganisms that invade the body and damage normal structure and function

• mycoplasma hyopneumonia

Trauma Disease

• mechanical injury

• ex. broken bone

Toxic Disease

• caused by exogenous substance that gains access to system and damages normal structure → dysfunction

• ex. lead toxicity

Pathogen

• any disease providing microorganism or material

• bacteria, fungus, virus

Etiology

• study of the causes of disease

Infection

• invasion/multiplication of microorganisms in body tissues

• commonly causes local cellular injury b/c competitive metabolism, toxins, replication or antigen-antibody response

Pathogenesis

• process by which a pathogen produces a disease

Bacteria

• similar structure to cells

• can be non-pathogenic, opportunistic, or pathogenic

• can replicate outside of host

• responsive to antimicrobials but can form resistance

Virus

• contain some DNA or RNA

• host required for replication

• not responsive to antimicrobials

Prion

• abnormal form of PrP protein

• resistant to proteases

• somewhat host specific

• ex. mad cow disease

Mycotic Disease

• fungal

• ex. ringworm

Parasites

Can be:

• intracellular (coccidia)

• internal (intestinal worms)

• external (lice)

direct disease transmission

• direct contact between animals

fomites disease transmission

Can be:

• inanimate objects (shoe)

• object is alive but not infected - passive carrier (human hands)

• vehicle (food/water)

vector disease transmission

• invertebrate animal (insect) is required for agent life cycle and transmission

infectious secretions disease transmission

Can be:

• respiratory droplets (ex. IBRV)

• saliva (BVD)

• purulent exudate (CLA)

• feces (salmonella)

• urine (leptospira)

Epidemiology

• study of patterns of disease that exist under field conditions

3 determinants of disease

• host factors

• agent factors

• environmental factors

7 host factors

• immune status (innate, acquired)

• herd immunity

• age

• genetics (simple, phenotypic, genotypic)

• physiological state (pregnant/lactating)

• production level

• nutritional status

2 agent factors

• virulence determinants

• pathogen challenge (amount, critical load, environment)

6 environmental factors

• temperature

• humidity

• stocking density

• stall design

• bedding/flooring

• feeder design

Sufficient Cause

• alone one factor may not be sufficient, but in various combinations, disease occurs

Necessary Cause

• without this factor, disease CANNOT occur

• still may or may not be sufficient to cause disease on its own

Carrier State

• no clinical disease but can transmit an infectious agent

• may be incubating disease or stay asymptomatic

• ex. salmonella

Morbidity

• condition of being diseased

• amount of disease (frequency)

Mortality

• number of deaths as a statistic

Case Fatality

• proportion of animals with a specific disease that die

Endemic Disease

• usual frequency of occurrence of disease in population

• expected

• the normal, constant presence of disease in a population

Epidemic Disease

• an occurrence of disease to a level in excess of the expected

Sporadic Disease

• disease occurs infrequently and not readily predictable

Prevalence

• number of diseased animals / number of animals in population

• at an one point in time

Incidence

• number of new cases in a specific time period / number at risk

4 approaches for disease control

• eradication

• prevention and exclusion

• immunization

• disease management

Disease Eradication

• extinction of a species of infectious agent from a population

• population could be world, nation, farm, etc

characteristics of an eradicable disease (world)

• no carrier state

• no subclinical infection/short incubation period

• limited to one species or family (like ruminants)

• available intervention (good vaccine or test)

which diseases are eradicated world-wide

• smallpox

• rinderpest

which diseases are eradicated in canada

• brucellosis

• tuberculosis (except manitoba)

most common technique for national disease eradication - animals

• test and cull

main methods of disease eradication at a farm level

• depopulation

• selective removal

Depopulation

• large proportion or entire population of herd is removed - dependent on the disease, some require full depopulation, some only partial

Selective Removal

• deliberate euthanasia/removal of a minority of infected animals to protect the majority

• requires screening or diagnostic test to detect disease

requirements of a test - eradication

• must detect the disease agent

• test for evidence of immune response to agent

Screening Test

• applied to healthy animals

• usually before clinical disease is evident

Diagnostic Test

• confirm or classify disease - can follow up to positive screening test

• applied to abnormal or unhealthy animals

why is a diagnostic test required for selective removal

• requires a test with high sensitivity and specificity = accurate

• so we don’t remove healthy animals

Accurate Test

• test results are very close to true value or gold standard test results

Precise Test

• repeated test results are consistent with each other

Sensitivity

• ability of a test to identify truly diseased animals

• low Sn = high FN

Specificity

• ability of a test to identify truly healthy animals

• low Sp = high FP

2 factors influencing predictive value of a test

• characteristics of the test (Sp + Sn)

• prevalence of disease in the population

Disease Prevention / Exclusion

• all measures to exclude disease from an unaffected population of animals

• could be from an entire area or a population within the area

how to exclude disease from a geographic area

• exclusions at border crossings

• test animals, check vaccination status, etc.

how to exclude disease in a population within a geographic area

• closed herds/flocks

• vaccination without exposure

Disease Management

• any measures used to decrease the frequency of disease already present in a population by decreasing or eliminating causes of the disease to a level of little to no consequence

4 methods of disease management

• quarantine

• prophylactic treatment

• mass immunization

• environmental control

Quarantine

• very important for contagious diseases

• physical separation of sick animals from healthy population

Prophylactic Treatment

• treat all animals in population prophylactically at a time of known risk

• all animals treated regardless of disease status

• ex. antibiotics during common season for pneumonia

Mass Immunization

• all animals at risk within population are vaccinated

• agent is present or likely to be present

• goal: decrease clinical disease incidence or severity

Environmental Control

• ventilation

• decrease pathogen load from cleanliness

• stocking density

Health Management (HM)

• promotion of health and prevention of disease in animals within the economic/business framework of the animal owner/industry while recognizing the issues of animal welfare, human safety, environmental impact

examples of how health management is delivered

• milk production

• pregnancy rate

• growth rate

• egg production

Health Management Cycle

• decisions are made

• plans are developed and implemented

• outcomes are measured and evaluated

3 ways of defining a health management problem

• no problem problem

• old problem problem

• new problem problem

No Problem Problem

• misperception

• owner doesn’t realize there is a problem

Old Problem Problem

• a previously seen or repeated problem

• recurring problem or problem that has not responded to first approach

New Problem Problem

• disease outbreak, management changes, new barn

Promote Optimal Health

• advising people on animal management

• groups of animals

• can be local, regional, or national

Accommodate Business / Economic Realities

• companion animals - depends on level of disposable income

• food animals - depends on is the business is economically viable

Promote Animal Welfare

• set current standards that are acceptable to animals, owner, society

Promote Human and Food Safety

• antibiotic residue

• antibiotic resistance

• zoonotic disease

Consider Potential Environmental Impact

• manure management

• environmental farm plans

• carcass disposal

SMART Goal

• specific

• measurable

• achievable

• results oriented

• time framed

Specific (SMART)

• discrete aspect of management

• tied to action

• ex. decrease mortality by 1% in a year

Measurable (SMART)

• requires records

Achievable (SMART)

• constraints of people, animals, and their environment

Results Oriented (SMART)

• requires to do list

• roles and responsibility

Time Framed (SMART

• when do you evaluate success/failure

3 classes of drugs for veterinary use

• over the counter (OTC)

• prescription (Rx)

• medicated feeds

national vs. provincial drug regulations

• national level: create minimum rules

• provincial level: can make rules more strict that national ones, but not more lax

Extra-Label Drug Use (ELDU)

• any use of drug that is not specifically listed on the label

• can be changes of dose, route, frequency, indication, withdrawal time, species, etc.

• some drug families are prohibited from ELDU - because they may impact human health

Antimicrobial

• kills or inhibits microorganisms

Antibiotic

• kills or inhibits bacteria

4 reasons to use antimicrobials in vet med

• to prevent disease - during times of stress

• treatment of disease - outbreaks, individual illness

• to control disease - reduce disease spread after initial infection of some in herd

• to promote growth - no longer applicable, not used anymore

Over-The-Counter Drugs

• category IV antimicrobials only - little/no human importance

• ex. ionophores

5 rationales for classification of antimicrobials

• spectrum of activity of antimicrobials (does it work on several microbes, just one?)

• mode of action

• mechanism of resistance

• availability of alternate antimicrobial therapy

• potential for transfer of resistance

Antimicrobial Residue

• when an edible animal product has drug residues in excess of the maximum allowable limit (MRL)

Withdrawal Time

• used to prevent violative residues

• interval between the last treatment with a compound and the time when the animal can be marketed (slaughter or milked)

how is withdrawal time determined?

• determined by Health Canada

• based on time to Maximum Residual Limit (MRL)

• drug, species, and indication specific