DISEASE
BELL WORK MONDAY, MARCH 9
What is a disease?
 What makes it a disease?


Name some animal diseases.
PATHOGENIC ORGANISM AND
DISEASE TERMS

Pathogen

microorganism that produces disease
A
living organism of microscopic dimensions
 Not all microorganisms are pathogens
 The microorganism in the pictures is not a
pathogen-does not produce a disease, in fact…
PATHOGENIC ORGANISM AND DISEASE
TERMS

Disease terminology
 agent
 transmission
 morbidity
versus mortality
 prophylaxis
 zoonosis
PATHOGENIC ORGANISM AND DISEASE
TERMS

Disease
 deviation
from normal
 infectious
disease
 noninfectious disease
 contagious (communicable) disease
 iatrogenic disease
 idiopathic disease
AGENT

Something that produces an effect
 Pathogen/micro
 Person
 animal
organism
KOCH’S “GERM” THEORY (SIMPLIFIED)

Defines an infectious disease
 The
infectious agent should be detectable in sick
animals but not healthy animals
 It should be possible to isolate and culture (grow) the
organism
 Organisms taken from the culture and introduced into
a healthy animal should cause the same disease
 The same organism should be isolated from the
second animal as well
INFECTIOUS DISEASE
Caused by microorganisms that gain entry into the
animal’s body
 How does a microorganism gain entry?


Transmission
 Bloodborne
– blood/ body fluids
 Airborne – respiratory droplets
 Fecal-oral transmission – eating, drinking, licking
contaminated food, water, objects
 Vector-borne- bloodsucking arthropods (insects such as
mosquitoes, ticks, mites) that carry the disease from one to
another
 Direct contact
BELL WORK TUESDAY MARCH 10

True or False

A pathogen is a microorganism that produces disease.


Not all microorganisms are pathogens.


True-example of microbes in rumen
Transmission has to do with whether or not a disease is
disease.


True
False-transmission has to do with how a microorganism gains entry
According to Koch’s Germ Theory (aka Koch’s Postulates) a
healthy animal could become sick if a pathogen from a sick
animal were introduced into the healthy animal.

True
BLOODBORNE DISEASE








Definition: Disease-producing microorganisms transmitted by means of blood, tissue, and
body fluids containing blood
Transmission of Pathogens
Potential exposure occurs through contact with blood, bloody saliva, vaginal
secretions, semen, and other potentially infectious bodily fluids.
Sources of Infection
Pathogens can be transmitted through open cuts, blisters, sores, acne, body
piercings, new tattoos, amniotic fluid, joint fluid, brain and spinal cord fluid, fluid
from around the heart, and body cavity fluid.
Example: Hepatitis B and C in humans
FIV, FIP, FeLV
AIRBORNE DISEASE





Definition: Disease-producing microorganisms transmitted by means of air
Transmission of Pathogens
Potential exposure occurs through aeresol, dust, liquid (droplets).
Sources of Infection
Pathogens can be transmitted by being transferred from the infected
person or animal’s mouth, nose, cut, or needle puncture. Animals receive
the disease through a portal of entry: mouth, nose, cut.


Example: Chicken Pox, Measles
Newcastle disease, Kennel Cough
VECTOR

In epidemiology, a vector is any agent (person,
animal or microorganism) that carries and
transmits an infectious pathogen into another
living organism.
 Usually
 (can
insects that feed on blood
you tell me a word that would describe this insect?)
 Epidemiology:
Study of disease
VECTOR / CARRIER

A vector is a carrier, especially the animal that
transfers an infective agent from one host to
another
 Example:
 Vector
Heartworm Disease
is the mosquito
Carries the infective agent from one dog to another dog
 The dog is a host to Heartworms because the Heartworm
completes its growth cycle in the dog


Carrier does not become infected-no sign/symptoms of
infectious disease (the mosquito does not get Heartworm
Disease)
VECTORBORNE DISEASE





Definition: Disease-producing microorganisms transmitted by means of
a vector such as mites, ticks, fleas, mosquitoes, flies, rodents
Transmission of Pathogens
Potential exposure occurs through vector/ carrier carrying
pathogen from infected animal to non infected animal
Sources of Infection
Pathogens can be transmitted by being transferred from the
infected animal by way of vector to noninfected animal through bite

Example: West Nile Virus, Bubonic plague

Heartworm Disease, West Nile Virus, Lyme disease
IN CLASS ASSIGNMENT
Find an example of each of the following:
 A bloodborne disease (keyword-secretions)


An airborne disease


Kennel Cough, Feline Viral Rhinotracheitis
A vector-borne disease


Felv, FIV, FIP, Canine Herpesvirus (CHV),
Heartworm, WNV, (Hantavirus, plague-animals as
vectors)
A disease transmitted by the fecal- oral route
ZOONOSIS




Zoonosis-disease that can be transmitted between
animals and humans
Hosts
Vectors (carry)
Sentinels (watch/ warn)
ZOONOSIS

Zoonosis-disease that can be transmitted between
animals and humans (under natural conditions)
 How?
Exposure of human to the infection of the animal
 If an animal has a disease and a human could get it, the
disease is said to be zoonotic

1.
2.
3.
Transmission may occur through:
Direct contact with the animal
Through a vector such as fleas or ticks
Through food contamination
 Most
at risk: young or immune suppressed (sometimes old),
also occupations that require working with diseased or
possibly diseased animals…such as veterinarians, lab
researchers, farmers and ranchers, slaughterhouses
ZOONOSIS IMPACT


apprx 60 % of human diseases are zoonotic
75% of emerging infectious diseases are zoonotic


An emerging infectious disease (EID) is an infectious disease whose
incidence has increased in the past 35 years and could increase in the
near future.
EIDs are caused by newly identified species or strains





Evolved from known infection (influenza)
Spread to new population (west nile virus)
Ecological transformation (tick borne diseases)
Reemerging infection (tuberculosis)
Most are from Livestock: pigs, chickens, cattle, goats, sheep, camels
TERMINOLOGY

Vector


Carrier


Person/animal that harbors an infectious agent with no signs of
disease
Host



Carrier that transfers an infective agent from one host to another
Living animal that “offers” food and lodging to an infectious agent
(transport host- carrier in which the organism remains alive but
no lifestage development)
Resevoir-resevoir of infectious agents


Any person, animal, etc in which an infectious agent normally lives
and multiplies
ANIMALS AS SENTINELS

Definition of sentinel animal: animal population
potentially susceptible to an infectious disease
that is being monitored/ watched for appearance
or recurrence of the pathogen or parasite

Example
 Dogs
being monitored for Rocky Mountain Spotted Tick Fever
and Ehrlichia
 Affects the human population
 Increase of dogs with disease = increase of people w/ disease
SENTINEL EVENT

Preventable disease, disability, untimely death
whose occurrence serves as a warning signal
that the quality of preventative/ therapeutic
care may need to be improved.
 Historical
animal sentinel events
 Canary
in a coal mine
 Honey bees and pollution
 Dancing cat fever
(mercury contaminated fish)
 https://www.youtube.com/watch?v=gYin9wHvyr4
 https://www.youtube.com/watch?v=ihFkyPv1jtU

EXAMPLES

Avian Flu
Transmitted by direct contact with infected
birds/poultry
 In birds symptoms are illness, decreased production,
death
 In humans typical flu symptoms; can be severe enough
to cause death
 At risk population

 Backyard
flocks
 Poultry business
 Veterinarians
EXAMPLES
Visceral Larva Migrans (larva of
roundworms)
 Fecal-oral transmission
 In animals (dogs) worms can
invade the liver, the lungs, the
uterus…parasitic and rob the
hosts food
 In humans the larvae migrate
through body tissues-lungs, liver,
eyes
 Dog, cat, racoon is host
 eggs pass through
intestines, dogs ingest
(cycle)
 Zoonosis occurs when
larvae are unknowingly
“consumed” by humans
VECTOR / CARRIER

A vector is a carrier, especially the animal that
transfer an infective agent from one host to
another
 Example:
 Vector
Heartworm Disease
is the mosquito
Carries the infective agent from one dog to another dog
 The dog is a host to Heartworms because the Heartworm
completes its growth cycle in the dog


Carrier does not become infected-no sign/symptoms of
infectious disease (the mosquito does not get Heartworm
Disease)
ASSIGNMENT DUE FRIDAY

Zoonotic disease Assignment:
 Name
of Disease
 Name of organism causing disease
 Main reservoir (animals)
 Mode of transmission
 Symptoms in animal ? (reservoir)
 Symptoms in humans
HOST
A host is a person or other living animal that contributes “food and lodging” to
an infectious agent.
*Primary host/ definitive host- organism / parasite gains maturity
*Secondary/intermediate host- organism/parasite is in a larval stage
*Transport host/ Vector – a carrier in which the organism remains alive but does
not develop
Example of a disease with
an intermediate
(secondary) host:
Neospora Caninum is a
coccidian parasite that
causes disease in cattle:
Definitive (primary) host is
dog/ coyote/ fox,
intermediate host is cattle:
Oocysts in feces from dogs,
cattle graze, oocyst finish
in cattle
ZOONOSIS
Rabies
 Ringworm
 Toxoplasmosis


Cats are host
 Oocysts
(“eggs”) pass through intestines
 Oocysts are ingested-toxoplasma organisms can invade brain,
fetus (pregnant women)
 Infected cats infect other animals –oocysts form cysts in
muscle tissue-if food animal, human can become infected
 Cats become infected by eating rats
ZOONOSIS









West Nile Virus (vector borne)
BSE (food supply)
Anthrax (airborne)
Leptospirosis (blood borne/ body fluids)
Bartonella Henselae (bacteria (bacillus) that causes cat
scratch fever)
Equine Encephalitis (vector borne)
Brucellosis (mucous mebranes, milk, dairy, cheese)
Tuberculosis (airborne)
Avian Influenza (direct contact)
TESTING METHODS

Endoscopy
 visual
examination of the interior of any
cavity of the body by means of an
endoscope

Centesis
 surgical
puncture to remove fluid for
diagnostic purposes or to remove fluid or
gas
ETIOLOGY AND EPIDEMIOLOGY

Epidemiology-study of relationships determining frequency
and distribution of diseases


disease etiology, outbreak investigation, disease surveillance
and screening, biomonitoring, and comparisons of treatment
effects such as in clinical trials.
Etiology-study of disease causes/origination

The etiology of scurvy is a good example. With scurvy, sailors
going to sea often lacked fresh vegetables. Without knowing the
precise cause, Captain James Cook suspected scurvy was
caused by the lack of vegetables in the diet. Based on his
suspicion, he forced his crew to eat sauerkraut, a cabbage
preparation, every day, but he had no idea, precisely, why it
prevented scurvy. It was only about two centuries later - in 1926
that it was discovered that it was the lack of vitamin C in a
sailor's diet that was the base cause of scurvy.
CONTAGIOUS VS NONCONTAGIOUS
Contagious diseases are spread animal to animal
 Contagious diseases are also called
communicable diseases and are spread through
direct or indirect contact


An inanimate object that is contaminated with a
contagious disease is called a “fomite”
 Fomites
are sources of infection for other animals
 Water and food bowls, kennels, clothing and shoes

Not all infectious diseases are contagious

Tetanus
NOSCOMIAL INFECTIONS

Noscomial- hospital (clinic) acquired infection

Nosocomial infection—An infection occurring in a patient in a hospital or other
healthcare facility in whom it was not present or incubating at the time of
admission; or the residual of an infection acquired during a previous admission.
Includes infections acquired in the hospital but appearing after discharge, and
also such infections among the staff of the facility. (Synonym: hospital-acquired
infection
 Hygiene,
 cleaning,
disinfecting, antimicrobial,
 infection control,
 isolation
 Often resistant type, ex: MRSA,
 Highly contagious potential for fatality
ex: Parvovirus, Distemper, respiratory viruses
PROPHYLAXIS

Prophylaxis-prevention of disease and spread of
disease
 Environmental-ventilation,
cleanliness of facilities, insects,
cleanliness of objects (preventing fomites), bedding, pens
 Health/ Nutrition


(healthy animals remain resistant to most diseases)
Stress releases cortisol and epinephrine/lower immunity

Overcrowding, feeding frenzy, climate, noise, rough handling
 Minimize
exposure or susceptability to pathogens
 Vaccinations-increase animals immunity

Pets vs Herd, value/costs, allergic reactions, fibrosarcoma
 Testing
prior to obtaining
 Quarantine (incubation)
INFECTIOUS DISEASES

4 classes of agents (an agent is something that
produces an effect)
 Bacterium/Bacteria
 Virus/Viruses
 Fungus/Fungi
 Parasites/
1. BACTERIA

Staphylococci- (cocci means round) – round, clusters


Streptococci-round, chains


Leptospirosis
Endospore – oval body inside, resistant


anthrax
Spirochetes – spiral


Strangles
Bacilli – rod shaped


Skin infections, wounds, food poisoning
clostridium
Rickettsia –rod shaped, small

ehrlichia
EXAMPLES OF INFECTIOUS BACTERIAL DISEASES

Swine


Yersinia


E Coli
Mastitis
Anthrax
Canine
 Leptospirosis (Lepto)
 Ehrlichiosis (Tick Fever)
 Bordatella Bronchiseptica
(kennel cough)
Rabbit

Cattle





Horse



Pasteurella (Snuffles)
Tuleremia (vector-ticks,
flies)
Tetanus
Strangles
Cat


Enteritis
Cystitis

Cattle





Rabies - most warm blooded
animals

Dogs
 Parvovirus
 Distemper

Horses
 West Nile Virus
 Equine Encephalomyelitis
Bovine Viral Diarrhea (BVD)
Cats


Feline Panleukopenia
Calicivirus
Feline Leukemia Virus
Feline Immunodeficiency
Virus
2. EXAMPLES OF INFECTIOUS VIRUSES
BACTERIA VS VIRUSES
Is a living cell
 Prokaryote cell – No Nucleus
 Made up of cytoplasm, DNA, ribosomes,
flagella

VIRUS
Not a living cell! But are considered alive because
the reproduce, grow, develop, adapt, use energy
sources from their environment
 Made up of genetic material/ nucleic acid (DNA or
RNA) enclosed in a protein shell
 All sorts of shapes, but are extremely tiny/ cannot
see with a regular microscope
 What about Retroviruses (Feline Leukemia and
FIV):


https://www.youtube.com/watch?v=eS1GODinO8w

Viruses insert their genetic material into a living
cell
The cell becomes the virus’ host
The virus DNA/RNA becomes a part of the cells DNA
so that during cell division the virus is being replicated
and passed on
Eventually the virus’ DNA takes over, completely
changes the host cell/ kills it’s host cell and
continues to replicate and create lots more viruses
BACTERIA/VIRUSES













Ribosomes: Present / Absent
Living attributes: Living organism - Opinions differ on whether viruses are a form of life or organic
structures that interact with living organisms.
Number of cells: Unicellular; one cell / No cells; not living
Structures: DNA and RNA floating freely in cytoplasm. Has cell wall and cell membrane / DNA or RNA
enclosed inside a coat of protein.
Treatment: Antibiotics / Vaccines prevent the spread and antiviral medications help to slow
reproduction but can not stop it completely.
Enzymes: Yes / Yes, in some
Nucleus: No / No
Virulence: Yes / Yes
Infection: Localized / Systemic
Benefits: Some bacteria are beneficial (e.g. certain bacteria are required in the gut) / Viruses are not
beneficial. However, a particular virus may be able to destroy brain tumors (see
references). Viruses can be useful in genetic engineering.
Reproduction: Fission- a form of asexual reproduction / Invades a host cell and takes over the cell
causing it to make copies of the viral DNA/RNA. Destroys the host cell releasing new viruses.
Size: Larger (1000nm) / Smaller (20 - 400nm
Cell wall: Peptidoglycan/Lipopolysaccharide / No cell wall.Protein coat present instead.
PRIONS
Are proteins
 Not alive
 They do not have DNA or RNA
 They have an ability to reproduce
 Can cause inherited or transmissible diseases

PRIONS

Prion diseases are fatal and cause progressive,
neurodegenerative problems


literally, holes in the brain
The brain resembles a sponge / diseases are called
spongiform
Examples of spongiform encephalopathies are….

1) Scrapie….in sheep and goats

2) BSE ….”Mad Cow Disease”

3) Chronic Wasting Disease…wild deer
and elk

Transmitted by inherited disease, or ingested from tissue of infected
animals (brain, spinal cord)
3. EXAMPLES OF INFECTIOUS FUNGI (MYCOSES)
Dermatophytes (Ringworm)
 Thrush (? Fungus caused by anaerobic bacteria
and mositure)
 Coccidioidomycosis (Valley Fever)

 Blastomycosis
(South East)
Histoplasmosis
 Candida (yeast infection)

4. EXAMPLES OF INFECTIOUS PARASITES
Heartworm (Dirofilaria immitis)
 Trichinella…Trichinosis
 Hookworm (Ancylostoma), Whipworm (Trichuris
vulpis), Roundworm (Toxocara)
 Giardia (protozoan)
 Coccidiosis (protozoan)

NONINFECTIOUS DISEASE CLASSIFICATIONS
Classifying diseases helps aid the veterinarian in
obtaining a diagnosis
 Helps the diagnostic process
 Clinical signs and symptoms could be the result
of several different disorders

Differential diagnosis-a list of possible causes of
disease
 Rule Outs-ruling out possible causes of disease
through diagnostic testing, observation, trial treatment

NONINFECTIOUS DISEASE CLASSIFICATIONS

Metabolic-disruption of normal chemical reactions


Anomalies – Congenital Birth Defects


Traumatic reticuloperitonitis, high rise syndrome, sucking chest
wound, diaphragmatic hernia, peritonitis, prolapsed uterus
Toxins - ingestion, inhalation, contact


DJD (osteoarthritis), Bovine Spongioform Encephalopathy (BSE)
Trauma –


Cleft palate, deaf, retinal dysplasia, dwarfism
Degenerative – progressive, permanent, longterm deterioration


Diabetes, hypothyroidism, hyperthyroidism, Cushings, Addisons
Antifreeze, misapplication of flea and tick products, warfarin (rat
poison), toads,
OTC medications, illegal drugs, plants
Immune

Immune Mediated Hemolytic Anemia (IMHA), System Lupus
Erythematosus (SLE)
Pruritis and Atopy (itchiness and hairloss) [allergies]
NONINFECTIOUS DISEASE CLASSIFICATIONS

Iatrogenic- a condition that develops as a result of treatment



Idiopathic- no explanation for underlying cause of the disease




Hyperadrenocorticism (Cushings)- can be caused by treatment for a severe
allergy problem
Surgery-excision of Thyroid glad to treat hyperthyroidism in cats…parathyroid
may also be removed causing iatrogenic hypoparathyroidism.
Idiopathic seizures
Idiopathic renal hematuria
Neoplasm - benign or malignant tumor
Nutrition –

Acute acidosis in ruminants, malnutrition, skeletal disease,
hypoglycemia, obesity
3 SEIZURE CASES
Seizure Case 1:
A 3 month old male toy poodle. The dog is strictly a house dog and does not run free,
In addition to the seizures, it has had intermittent diarrhea and is quite thin.
Differential Diagnosis (DfDx):
Developmental Disorder- brain malformation
Hypoglycemia-could be secondary to poor diet, diarrhea, intestinal parasites
Head Trauma- not likely with indoor dog
Toxins-potential for ingesting medications or illegal drugs, chocolate
Infectious causes of encephalitis- Distemper
Idiopathic epilepsy-very unlikely due to age of dog
Seizure Case 2:
A 2 ½ year old male golden retreiver. This dog is in excellent physical condition
and has been eating well. This dog is free to roam the neighborhood and
recently had one episode of vomiting and one episode where it was limping and
stiff.
DfDx:
Idiopathic epilepsy-this is high on the list because of age and breed
of dog at the onset of seizures.
Head Trauma-the recent limping and stiffness raises this possibility
Toxins- the list is long, but possibilities include insecticides,
chocolate
Liver Disease-definitely needs to be ruled out but dog has been
doing well otherwise
Infectious Encephalitis
Seizure Case 3:
A 14 year old female schnauzer. This dog had its first seizure and since that time
has not been acting normal. There has been some weight loss and a poor
appetitie, and the owners feel the dog can no longer see. The dog is strictly an
indoor dog with no history of trauma.
DfDx:
Metabolic Disease-liver dx, hypogylcemia (insulinoma in the
pancreas), Diabetes
Neoplasia- the age of the dog, the blindness, lack of normalcy after
the seizure make this a high likelihood
Ideopathic epilepsy-very unlikely with the age of the animal
PATHOGENIC ORGANISM AND DISEASE
TERMS

Disease terminology
 Transmission-
how pathogens gain entry
 Morbidity versus Mortality
 Morbidity-
diseased animals
 Mortality –diseased animals that die
 Moribund – near death
Prevelance - amount/ number of diseased at a given time
(within a population)
Susceptibility – lacking resistance
ZOONOSIS




Zoonosis-disease that can be transmitted between
animals and humans
Hosts
Vectors (carry)
Sentinels (watch/ warn)
ZOONOSES

Zoonosis-disease that can be transmitted between
animals and humans (under natural conditions)
 How?
Exposure of human to the infection of the animal
 If an animal has a disease and a human could get it, the
disease is said to be zoonotic

1.
2.
3.
Transmission may occur through
Direct contact with the animal
Through a vector such as fleas or ticks
Through food contamination
 Most
at risk: young or immune suppressed (sometimes old),
also occupations that require working with diseased or
possibly diseased animals…such as veterinarians, lab
researchers, farmers and ranchers, slaughterhouses
EXAMPLES

Avian Flu
Transmitted by direct contact with infected
birds/poultry
 In birds symptoms are illness, decreased production,
death
 In humans typical flu syptoms, can be severe enough to
cause death
 At risk population

 Backyard
flocks
 Poultry business
 Veterinarians
EXAMPLES
Visceral Larva Migrans (larva of
roundworms)
 Fecal-oral transmission
 In animals (dogs) worms can
invade the liver, the lungs, the
uterus…parasitic and rob the
hosts food
 In humans the larvae migrate
through body tissues-lungs, liver,
eyes
 Dog, cat, racoon is host
 eggs pass through
intestines, dogs ingest
(cycle)
 Zoonosis occurs when
larvae are unknowingly
“consumed” by humans
HOST
A host is a person or other living animal that contributes “food and lodging” to
an infectious agent.
*Primary host/ definitive host- organism / parasite gains maturity
*Secondary/intermediate host- organism/parasite is in a larval stage
*Transport host/ Vector – a carrier in which the organism remains alive but does
not develop
Example of a disease with
an intermediate host:
Neospora Caninum
coccidian parasite that
causes disease in cattle:
Definitive host is dog/
coyote/ fox, intermediate
host is cattle: Oocysts in
feces from dogs, cattle
graze, oocyst finish in
cattle
VECTOR / CARRIER

A vector is a carrier, especially the animal that
transfer an infective agent from one host to
another
 Example:
 Vector
Heartworm Disease
is the mosquito
Carries the infective agent from one dog to another dog
 The dog is a host to Heartworms because the Heartworm
completes its growth cycle in the dog


Carrier does not become infected-no sign/symptoms of
infectious disease (the mosquito does not get Heartworm
Disease)
ZOONOSIS
Rabies
 Ringworm
 Toxoplasmosis


Cats are host
 Oocysts
(“eggs”) pass through intestines
 Oocysts are ingested-toxoplasma organisms can invade brain,
fetus (pregnant women)
 Infected cats infect other animals –oocysts form cysts in
muscle tissue-if food animal, human can become infected
 Cats become infected by eating rats
ZOONOSIS
West Nile Virus
 BSE
 Anthrax
 Leptospirosis
 Bartonella Henselae (bacteria (bacillus) that
causes cat scratch fever)
 Equine Encephalitis
 Brucellosis
 Tuberculosis
 Avian Influenza

TESTING METHODS

Endoscopy
 visual
examination of the interior of any
cavity of the body by means of an
endoscope

Centesis
 surgical
puncture to remove fluid for
diagnostic purposes or to remove fluid or
gas
TESTING METHODS

Imaging techniques
 radiography
 computed
tomography
 magnetic resonance imaging
 fluoroscopy
 ultrasound