Animal Sciences 3170
Animal 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
% Final Grade
Two hourly exams
Quizzes and Homework
Final Exam
50%
25%
25%
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 Disease
1)
2)
3)
4)
5)
Nutritional
Metabolic
Trauma
Toxic Materials
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
Environment
Host
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
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
#
of
cells
in
normal
human
flora
body
population
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.
2.
3.
4.
Physical
Cellular
Immunological
Non-specific
Physical Factors - Site Specific
Respiratory
 Gastro-intestinal
 Uro-genital
 Mammary

INVADING HOST
Transmission of Pathogens
1)
2)
3)
4)
Airborne
Direct contact
Food/H2O borne
Arthropod borne
Attachment/Adherence

Specific site on host cells
Defenses Against
Adherence
pH
 Secretions
 Normal flora
 Flushing

pH
 Mouth
 Urine
 Stomach
pH
Secretory Products
Antibody
 Enzymes
 Iron chelators
 Anti-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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