Lecture 1: Nature of Disease

Contagion

the communication of disease from one person to another by close contact

Zoonosis

An infectious disease that is transmissible from animals to humans. Discovered by primitive Hindus when rats were first associated with the human plague.

Germ Theory of Disease

idea that infectious diseases are caused by microorganisms. Came after the downfall of the miasmatic theory.

Koch's Postulates Rules

1. The microorganism must present in all cases of disease

2. The microorganism can be isolated from the host organism and grown in pure culture, such as agar

3. The microorganism grown in the culture when inoculated into a healthy host must cause the same disease

4. The microorganism must be reisolated from the second host and grown again in a pure culture and proven to be the same as the original microorganism isolated from the first host. (All Present, isolated in pure culture, causes disease in healthy host, preisolated grows the same)

The five freedoms of animal welfare

1. Freedom from hunger/thirst

2. Freedom from discomfort

3. Freedom from pain, injury, and disease

4. Freedom from fear

5. Freedom to express normal behavior

Herd Health

Designed by herd veterinarian and producer to reduce disease incidence, provide effective diagnosis and treatment protocols, and improve productivity.

Herd Health Plan

Examples of this plan include:

-Routine Visits

-Employee training

-Records

-Economic analysis

disease

"not at ease"

Symptoms

signs of disturbances in health

Non-infectious diseases

Diseases that cannot be transmitted directly from one person to another. Can be caused by nutritional deficiencies, metabolic disorders, trauma, toxic materials, and congenital defects

Nutritional deficiencies

Lack of essential nutrients in the diet. Can include deficits in vitamins, minerals, fats, amino acids, and water

Metabolic disorders

types of diseases that include trouble breaking down certain foods and making energy (milk fever, grass tetany, and ketosis)

Trauma

a type of wound or injury. Includes cuts, tears, burns, bruises, sprains, and fractures

Toxic materials

materials that cause injury or death to an organism. Include bacterial, metallic/chemical poisons, phytotoxins, mycotoxins, and zootoxins (spiders, snakes, bees)

Congenital defects

defects present at birth. Include cryptorchidism, hernias, misplaced limbs, and atresia anus.

Infectious diseases

Diseases that are caused by infecting organisms; they can be passed from person to person, or animal to animal

Symptoms of disease

-Abnormal Temp

-Inflammation

-Depression

-Abnormal breathing

-Diarrhea

-Abortion

Tetanus

a sustained muscular contraction resulting from a rapid series of nerve impulses. Also an example of an infectious, non-contagious disease.

Skin and mucous membrane

1st line of defense! Skin, mucous, gastric juices, fecal elimination, coughing, tear gland secretions, and urination

Antibodies

Specialized proteins that aid in destroying infectious agents. Classified as agglutinins, antienzymes, antitoxins, bacteriolysins, opsonins, and precipitins

Phagocytes

Cells that ingests invading microbes. Classified as immobile (Lines the blood vessels) and free (leucocytes/white blood cells)

Vector

a transmitting agent. Can be animate or inanimate

Inanimate vectors

types of vectors including shoes, instruments, clothes, contaminated food or water, bedding, urine, feces, saliva

Animate vectors

types of vectors that include fleas, lice, ticks, humans, animals

Pathogens

organisms that cause disease

Saprophytes

a plant, fungus, or microorganism that lives on dead or decaying organic matter. Non harmful!

Bacteria

single celled microscopic organisms that multiply by binary fission

Fungi

Simple plants with no chlorophyll, so they must ingest other dead organisms or animals.

Viruses

tiny particles, smaller than bacteria and other pathogens, which must invade living cells in order to reproduce; when they invade, the cells are damaged or destroyed in the process releasing new particles to infect other cells

Protozoa

Single celled animals that are microscopic in size