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 [email protected]• 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
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
“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•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
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
Pathogenic Microbes• Frontal assault
– Short incubation– Rapid clinical
signs– Intimate
transmission
Pathogenic Microbes• Stealth assaults
– Incubation lengthy
– Slow onset of signs
– Environmental transmission
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
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
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