Diseases
Submitted by Callie Parr and used in cooperation with the University of Illinois at UrbanaChampaign.
The materials that appear in this document may be freely reproduced for
educational/training activities. There is no requirement to obtain special permission for
such uses. We do, however, ask that the following statement appear on all
reproductions:
DISEASES, by CALLIE PARR
Materials produced for classroom use in conjunction with permission from the University of
Illinois Agricultural Education Program.
This permission statement is limited to the reproduction of material for educational/training
events. Systematic or large-scale reproduction or distribution (more than one hundred
copies per year)—or inclusion of items in publications for sale—may be done only with
prior written permission. Also, reproduction on computer disk or by any other electronic
means requires prior written permission. Contact the University of Illinois Agricultural
Education Program to obtain special permission.
The University of Illinois and its affiliated entities, in addition to the individual submitting
the materials, assumes no liability to original work or activities therein.
Diseases
Disease
• Can be broken down into infectious and
non-infectious diseases
• Infectious diseases are a result of
pathogens.
-Viruses
- Bacteria
- Protozoa
- Fungi
- Parasites
• Pathogens are carried by vectors.
- animals - insects
- inorganic surfaces
Koch’s Postulates
• Used to detect infectious diseases.
– The infectious agent should be detectable in
sick animals and not in healthy ones.
– It should be possible to isolate and culture the
organism.
– Organisms taken from the culture introduced
into healthy animals should cause the same
disease.
– The same organism should be isolated from
the second animal as well.
Ways a pathogen can enter the body
•
•
•
•
•
Wounds – breaks in the skin
Respiratory – breath it in
Mucus membranes – eyes, nose, mouth
Bites – insect bites (same as wound)
Ingestion – eat it (contaminated food/water)
Course of a disease
• Exposure – no physical response yet
• Incubation – levels of pathogen increase
• Prodromal – the first signs of illness
– Fever, muscle aches
• Decline – either immune system kicks in or
medication takes effect
– If not, then enter chronic illness
• Convalescent – animal regains strength
Bacterial Infections
• 4 major categories of bacteria by shape
– Staphylococcus
– Streptococcus
– Bacillus
– Spirochete
Bacterial Infections
• Sickness is a result of toxins released by the
bacteria.
– Exotoxins – excreted by cells
– Endotoxins – released when cells die
• Treatable with antibiotics
• Immune System fights with phagocytes
– Blood cells that surround and destroy pathogens
Common Bacterial Diseases
Strangles
• Streptococcus equi
• Horses
• Swollen lymph glands in neck, fever, reduced
appetite, nasal discharge, abortion
• Highly contagious
Scours (E. Coli diarrhea)
•
•
•
•
Escherichia coli
All species
Animals less than 2 weeks old
Severe diarrhea leading to dehydration and
death
• Preventable with medication
Pneumonia
• Rhodococcus (equi)
• All (horses)
• Nasal discharge, fever, respiratory difficulty,
inflammation that can spread to joints.
• Treatable with antibiotics
Leptospirosis
• Leptospirosis sp.
• All species
• Abortions, fever, anemia, jaundice
Pinkeye
• Moraxella bovis
• Cattle
• Inflamed conjunctiva, cloudy cornea,
sensitivity to light, fluid discharge from eye
• Treatable with topical ointment or systemic
antibiotic
• Highly contagious
Foot Rot
• Fusobacterium necrophorum
• Cattle, sheep, goats
• Deep infection of the cloven section of the
hoof, foul odor, pain, lameness
• Preventable with clean facilities
• Treatable with antibacterial soaps
Rain Scald/Rot
• Dermatophilus congolensis
• Horses, cattle, sheep, goats
• Crusting of the skin at the base of the hair
follicle mostly on the back and rump
• Similar to cradle cap in babies
• Most prevalent in animals exposed to
excessive moisture
• Treatable with antibacterial soaps
Lockjaw
• Clostridium tetani
• Horses, cattle, sheep, goats
• Muscle spasms, locked jaws, stiffness of joints,
death
• Enters through punctures and/or breaks in
skin (lives in soil naturally)
• Preventable with booster shot
Greasy Pig Disease
• Swine
• Staphylococcus hyicus
• Reddened skin, anorexia, fever, thickened skin
with purulent (pus) discharge
Lyme Disease
•
•
•
•
Borrelia bugdorferi
All species
Spread by ticks
Chronic arthritis, lethargy, loss of appetite,
paralysis
Viruses
What is a Virus
• No cell wall, no organelles, maybe not even be
considered living
• DNA or RNA surrounded by a protein coat
• Hijack a healthy cell and program it to create
new viruses
• Destroys host cell in process
• Often dies of suppressed immune system or
reaction to enzymes released by cells
Treatment
• Prevent with vaccine
– modified live
– killed
• Body’s natural immune system
• Very limited anti-viral medications
Shipping Fever
• Cattle
• Bovine Respiratory Syncytial Virus, Bovine
Virus Diarrhea, Infectious Bovine
Rhinotracheitis, Parainfluenza-3
• High Fever, nasal discharge, coughing
Panleukopenia
• Cats
• Feline parvovirus
• Fever, vomiting, extreme diarrhea, anorexia
Feline Leukemia
• Cats
• Retrovirus
• Chronic weight loss, anemia, anorexia, tumors
Equine Infectious Anemia
• Retrovirus
• Horses
• Fever, hemolytic anemia (breakdown of red
blood cells), icterus (jaundice/yellowing),
weight loss
Canine Distemper
• Canine distemper virus
• Dogs
• Fever, nasal discharge, seizures, pneumonia
Rabies
• All species
• Rhabdovirus
• Paralysis, inability to swallow (foaming at
mouth), aggression, stupor, brain lesions
Pseudorabies
• Pigs
• Herpesvirus
• Shaking, ataxia (gross uncoordination),
convulsions, seizures, fever
Fungal Infections
Fungal infections
• Usually spread by spores or direct contact
• Spores very resistant to heat, moisture, or
dryness
• Treatable with fungicides
Ringworm
• Red, crusty/flaky ring on the skin that expands
outwards
• Has nothing to do with worms
• Microsporum or Trichophyton
• Live in hair folicles
Others
•
•
•
•
Blastomycosis (canine)
Sporotrichinosis (feline, canine)
Cryptococcosis (feline, canine)
Histoplasmosis (feline, canine)
Parasites
What is a Parasite?
• Any organism that lives off another organism
and causes harm
• Detrimental to host’s health in many ways
– Compete for nutrients and “starve” the host
– Damage tissues of the host
– Release toxins into the host
– Suck the blood causing anemia
– Serve as a vector for bacteria or viruses
Life cycle
• May parasites have a complex life cycle that
help them survive and spread from one
host to another.
– Egg, larvae, pupa, adult or egg, nymph, adult
• Definitive host is the animal that carries the
mature parasite.
• Intermediate host carries the immature
(egg or larvae) parasite.
Example
A dog (definitive host) has a tapeworm (parasite). The
head of the tape worm attaches to the lining of the
small intestine causing malnourishment. As the
parasite develops, segments containing the eggs
break off and exit the anus (look like grains of rice).
The segments rupture releasing the eggs. A flea
larva (intermediate host) on the dog eats the eggs.
When the flea matures it jumps onto another
animal. The animal bites at the fleas, ingesting the
contaminated flea. The tapeworm eggs are released
in the second dog’s stomach and move to the small
intestine where they hatch and implant completing
the cycle.
Intestinal Parasites
• Typical clinical signs
– Diarrhea
– Vomiting
– pot-bellied
– dull coat
– poor weight gain
– Anemia
– coughing
Common Internal Parasites
Roundworms
• Dogs and Cats
• Toxocara canis/cati or Toxascaris leonina
• Ingested eggs hatch into larvae in the intestine.
Lavae travel through liver and lungs. The larvae are
then coughed up and re-swallowed where they
develop into adults and attach in the intestine. Eggs
are shed in the feces.
• Passed through ingestion of feces, mother’s milk,
placental wall, eat infested animals (rabbits, rats)
Hookworms
• Dogs and cats
• Ancylostoma sp. or Uncinaria sp.
• The larvae are ingested and develop into
adults which attach to the intestinal lining and
suck blood. Eggs are released in the feces
where they hatch into larvae.
• Ingest larvae, placental wall, mother’s milk,
through the skin of the food pads.
Tapeworms
• Dogs and cats
• Dipylidium caninum, Taenia pisformis/ taeniaeformis
• Requires an intermediate host
• eggs/larvae must be ingested
Heartworms
• Dogs
• Dirofilaria immitis
• Adult worms live in the major vessels and
chambers of the heart. Clog the blood flow.
• Transmitted by mosquitoes (intermediate
host)
• Incubation time is about 6 months
Strongylosis
• Strongylus sp.
• Horses
• Eggs passed in the feces develop into larvae.
Larvae migrate into blood stream causing
damage, enter large intestine and mature,
then release eggs.
• Horse eat the larvae as they graze
Bot flies
• Horses
• Gasterophilus intestinalis/nasalis
• Flies lay eggs on horse’s legs which get licked
and ingested. Larvae travel down esophagus
into the stomach. Then they are passed out
through feces to develop into flies.
Trichostrongyles
• Ruminants
• Hemonchus, Ostertagia, Trichostrongylus,
Cooperia, Bunostomum
• Eggs passed through feces and consumed by
grazing. Develop into larvae and adults in
stomach and intestine.
• Able to go dormant during winter.
Coccidiosis
• Ruminants
• Species of protozoa including Eimeria sp.
• Oocyst (egg) passed in feces. Ingested and
goes through several stages of development
being absorbed into the lining of the
intestines.
Common External Parasite
• Mostly blood suckers
– Fleas
– Ticks
– Mites
– Various flies
– Mosquitoes