Animal Sciences 3170Animal Sciences 3170Animal Sciences 3170Animal Sciences 3170

Animal DiseasesAnimal Diseases

ASC 3170• Host – Pathogen Interaction• Management• System Specific Diseases

Tissue Specific Diseases

TEXT• None• Supplemental Reading • Website

– http://www.oardc.ohio-state.edu/as413/

My Contact• Joe Hogan hogan.4@osu.edu• Phone 330-263-3801

Tentative Exam Schedule

• See syllabus

Quizzes & Homework• Announced – no pop quizzes• No make-up quizzes• No make-up homeworks

Make-up Exams• Discretion of Hogan

Final Grade

Terminology• Pandemics/Epidemic/Endemics• Antibodies/Antibiotics• Virus/Bacteria/Fungi/Protoza• Host Defense

– Cellular– Immunity– Innate– Induced

Terminology Confusion

Disease• Specific disorder or

illness

Latin meaning• Disease

– “Not at ease”

Disease • Infectious

– Living agent

• Non-infectious– Nonliving agent

Non Infectious Disease1) Nutritional2) Metabolic3) Trauma4) Toxic Materials5) Congenital Defects

Infectious Disease• Agents infect/invest

Infectious Agents•Bacteria•Virus•Protozoa•Fungi •Parasites

Infectious Disease Process

• Enter host

• Multiply

• Evade host defenses

• Harm host

The Holy Triangle

Host

Environment

Pathogen

Infectious Diseases• Contagious

– Animal to animal transfer

• Non contagious– Environmental

to animal transfer

Transmission•Direct

–Cough–Aerosol–Touch

Transmission •Indirect

–Vectors–Fomites

Vector• organism that transmits a

particular disease or parasite from one animal to another

Fomites• inanimate objects that transmits a

particular disease or parasite from one animal to another

Fomites

“demics”• Relating to population or area

Epidemic• Rate of disease in a population

greater than expected

Endemic• Disease is maintained at a

relatively constant rate in the population without the need for external input

Pandemic• Epidemic of worldwide (large

geographical area) distribution

J.M. Helfrich 1995

Host Parasite

Host Parasite•Interaction dynamic•Interaction dynamic

Host Parasite Interaction

Commensalism

•No harm•No benefit

Host Parasite Interaction

Parasitism •One lives @ expense of other

PARASITES - HOST• Successful Parasites co-

evolve with Host

Host Parasite Interaction

Mutualism – both benefit

Objective of pathogens• Reproduce

Pathogenicity

• Capacity to infect

Virulence • Degree of pathogenicity

ID• Infectious dose = minimal # of

pathogens needed to establish a disease.– Pathogen specific– Range 1 to 108

ID50

• Infectious Dose 50• Gold standard for virulence• Number of organisms required to

produce an infection in 50% of the test animals– Specified time– Specified route

LD50

• Lethal Dose 50• Number of organisms or toxin

required to cause death in 50% of the test animals– Specified time– Specified route

LD50 Toxin

Pathogen Types• May change category

– Host– Life Cycle– Environment

Obligate Pathogens

•Associated only with disease

Opportunistic or Potential Pathogens

• Normal flora• Disease when host

compromised

Human Normal Flora

Bacterial normal flora

population

# of cells in human

body

Pathogen Assault

Pathogenic Microbes• Frontal assault

– Short incubation– Rapid clinical

signs– Intimate

transmission

Pathogenic Microbes• Stealth assaults

– Incubation lengthy

– Slow onset of signs

– Environmental transmission

HOST

Host •Final Host

–Parasite reaches sexual maturity or replicates

Host•Intermediate Host

–Essential– Temporary environment for development

Host•Reservoir Host

–Harbors pathogens that infect others

HOST DEFENSES

Innate Defenses•Inherent to host

Innate = Intrinsic• No Prior Exposure Needed

Host Defenses•Inducible Defenses

Inducible Defenses•Due to exposure

Defense mechanisms

1. Physical

2. Cellular

3. Immunological

4. Non-specific

Physical Factors - Site Specific

RespiratoryGastro-intestinalUro-genitalMammary

INVADING HOST

Transmission of Pathogens

1) Airborne

2) Direct contact

3) Food/H2O borne

4) Arthropod borne

Attachment/Adherence

Specific site on host cells

Defenses Against AdherencepHSecretionsNormal floraFlushing

pH

MouthUrineStomach

pH

Secretory Products

AntibodyEnzymes Iron chelatorsAnti-toxins

Gut

Dermal

Vagina

Normal Flora

Occupies attachment sites Produce by-products that are competitive

Model for Commensals

Flushing Action Urinary tract Mammary gland Nasal secretion

Bacterial Attachment Factors

Proteins Glycocaylx

Bacteria Counter with Pili

Upper Respiratory

Nasal hairs Turbulence Mucous

•Drain

•Swallow

•Cililiary esculator

Rabbit Lung Cilia

Upper Respiratory Tree

Dermal Cell turnover pH Proteins/lipids

Intestinal Attachment

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