DISEASES, by CALLIE PARRMaterials produced for classroom use in conjunction with permission from the University of Illinois Agricultural Education Program.

DiseasesSubmitted by Callie Parr and used in cooperation with the University of Illinois at Urbana-

Champaign. The materials that appear in this document may be freely reproduced for

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Diseases

Disease

• Can be broken down into infectious and non-infectious diseases

• Infectious diseases are a result of pathogens. -Viruses - Protozoa - Parasites - Bacteria - Fungi

• 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.

ExampleA 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