Diseases of farm animals; Etiology

Define Disease.

Alteration of a normal body function.

Define Health.

Absence of disease

What are the four main classifications of disease?

Etiology, Duration, Animal species affected, and Symptoms/Clinical signs.

Define Etiology.

Study of the cause of a disease.

Define a pathogen.

Microorganism that can lead to disease.

Name some Pathogens.

Prions, Viruses, Rickettsaie/Chlamydophillia, Bacteria, Protozoa, Fungi, Helminths, Insects.

List the Etiology non-infectious diseases.

Mechanical injury, Nutritional, Metabolic, Endocrine, Hypersensitivity, Toxicity.

What is the duration of a peracute disease?

Minutes to Hours.

What is the duration of an acute disease?

Hours to days.

What is the duration of a subacute disease?

Days to weeks.

What is the duration of a chronic disease?

Weeks to months.

What are some animal species diseases?

Hog Cholera, Caprine Arthritis-Encephalitis, Equine Infectious Anemia, Rabies, all viral pathogens.

Define a clinical symptom of disease.

A observable symptom

Define a Subclinical symptom of disease.

A non observable symptom

Define a Pathognomonic symptom of disease.

A unique and definitive clinical sign that causes that disease, an example of this is Erysipelas which causes diamond shaped lesions on swine.

What are some sources of infection.

Direct contact with clinically infected host, contact with fomites, contact with subclinical carriers, Infection from environment(soil), infection from food and water, air borne infections, blood sucking insects, organisms normally found in/on the body, and Nosocomical.

Define a Fomite.

Inanimate objects that transmit a disease.

Define Nosocomial.

Acquired from hospital/clinic.

What is a prion?

Folded infectious protein, occurs when a species eats amino acids from the same species. An example is cattle being fed feedstuffs made from the by-products of other cattle.

When where prions originally discovered?

In 1982 by Dr. Stanley Prusiner.

How do prions spread?

Replicate by converting normal prions into abnormal form, brain cells die faster as the disease progresses.

What is vertical prion or TSE transmission?

Dam to offspring, an example is a ewe that is infected transmitting to offspring through the placenta.

What is horizontal prion or TSE transmission?

From one pen mate to another.

What is a TSE?

Transmissible Spongiform Encephalopathy (Prion), transmitted by. infected feed with neurological tissue in the feed, examples include scrapie, BSE, FSE, CWD, TME, CJD, vCJD, and kuru.

Animals infected with a TSE or prion disease will show...

behavioral changes, incoordination, abnormal posture, poor appetite, and death.

What are some important things to know about viruses?

Infects all types of organisms (including bacteria), not sensitive to antibiotics, no enzyme system for energy, very small (need an electron-microscope to visualize). A virus is essentially a parasite that has to use a cell to replicate.

Are viruses living or nonliving?

Viruses are a obligate intracellular pathogen, they never replicates unless inside a living host, utilized host nucleic acid machinery, and is able to adapt to pressure from host immune system. Debatable wether it is living or nonliving.

What does a viruses structure contain?

Has a viron, nucleic acid (DNA and RNA), protein (Coat antigenic determinants also has some enzyme activity), lipids, and carbohydrates (only in envelops/hosts cellular origin).

Define a viron as it refers to a virus.

A complete virus particle.

What is the Cytocidal outcome of a virus infection?

Host cell is destroyed.

What is the Non-Cytocidal outcome of a virus infection?

Persistent infection.

What is the Latent outcome of a virus infection?

Remains "Hidden", may appear years after initial infection.

What is the Transformation outcome of a virus infection?

Oncogenic (cancer)

What are the stages of a Cytocidal viral infection.

Absorption, Penetration, Uncoating, Replication, Maturation, Release, Cell death.

What are some important things to know about a Cytocidal viral infection?

Lethal cellular damage, Shuts down host protein and RNA synthesis, Distortion of host cell, Release of host lysomosomal enzymes leading cells to digest themselves.

What are some important things to know about a Non-Cytocial viral infection?

Can occur with a fetal infection, virus can be recovered from host long after initial infection of host, and it may be due to an immunodeficiency or immunosuppression of the host.

What are some important things to know about a latent viral infection?

Virus remains "hidden", has a long incubation time (may take months to years before clinical disease occurs).

What is a Retrovirus?

An Immunodeficiency virus (Aids, HIV, and BLV).

What are some important things to know about a transformation viral infection?

Viruses contain oncogenes which become incorporated into the host cell.

What happens when oncogene affect the host cell?

Several characteristics are transformed, this includes modified cell growth patterns and alterations of cell surface.

What DNA virus is the source of Feline panleukopenia, Porcine parvovirus, and Canine parvovirus.

Parvoviridae.

What DNA virus is the source of Infectious bovine rhinotracheitis, Pseduorabies, and Equine Rhinotracheitis.

Herpetoviridae

What DNA virus is the source of Bovine papilloma virus (Warts in cattle).

Papovaviridae

What DNA virus is the source of cow pox and fowl pox.

Poxviridae

What RNA virus is the source of feline calicvirus.

Picornoviridae

What RNA virus is the source of Blue Tongue?

Reoviridae

What RNA virus is the source of diarrhea in many species.

Corona and Rotaviruses

What RNA virus is the source of rabies.

Rhabdoviridae.

What RNA virus is the source of Equine infectious anemia, Feline Leukemia Virus, Bovine Immunodeficiency Virus.

Retroviridae.

What is a Reckettcia pathogen?

Obligate intracellular parasite, reproduce via binary fission, require a host cell to reproduce, have both: RNA and DNA, plasma membrane, and primitive cellular structure, typically transmitted by arthropod vectors (Blood sucking Parasites).

What are some common diseases caused by Reckettsia.

Anaplasmosis (Anaplasma marginale), Potomac Horse Fever (Ehrlichia risticii), and Equine Ehrlichiosis (Ehrlichia equi)

What do Rickettsia pathogens typically do?

Typically destroy the red blood cells and turns the animal anemic.

How is Bacteria Taxonomy: Kingdom, classified.

Classified by prokaryotes (primitive cell structure), most widespread and numerous organisms, lack nucleus and membrane bound organelles, most have cell walls, no occurrence of mitosis or meiosis.

What are the three divisions of bacteria?

Archaebacteria, Eubacteria, and Mycoplasmas.

What do the two bacteria taxonomy groups class and family have in common?

They are rarely used to classify bacteria.

How does the bacteria taxonomy group genera classify bacteria.

Well defined group of organism, clearly separated from other genera by morphologic characteristics and biochemical characteristics.

How does the bacteria taxonomy group species classify bacteria.

Collection of strains that share many properties.

How does the bacteria taxonomy group subspecies classify bacteria.

May separate species based on host range or other characteristics.

What are the three ways bacteria is classified.

Gram Stain, Morphology, and Arrangement.

All pathogenic bacteria (except Mycoplasmas and Ureaplasmas)...

possess a rigid cell wall.

What are the components of a bacteria cell wall?

Peptidoglycan layer (rigidity), a thick layer (gram positive) and a thin layer (gram negative).

What color does gram positive stain?

Purple.

What color does gram negative stain?

Pink.

What are the properties of a gram positive bacteria?

Thick cell wall (20-80nm), Teichoic acids (20-40% of cell wall) help maintain structure and are Antiphagocytic, and Lipids

What are the properties of a gram negative bacteria?

Cell wall is very thin (2-3nm), Hydrophobic surface resists phagocytosis, outer membrane, lipopolysaccharide or LPS (unique to gram negative bacteria)

List some gram positive bacteria pathogens.

Streptococcus (environment), taphylococcus, Bacillus, Clostridia, ctinomyces (abscesses), Corynebacterium (Caseous Lymphadenitis disease in sheep), Listeria (circling disease), and Erysipelothrix (Erysyphillis in pigs)

List some gram negative bacteria pathogens.

Enterobacteriaceae (Escherichia, Salmonella), Pasteurella (respiratory tract), Psuedomonas (2nd invader / nosocomial), Brucella (abortion in cattle), Haemophilius (attacks all over, respiratory in the beginning), Actinobacillus (infect mouth, woody tongue), Campylobacter (fibriosis)

Bacteria is classified by morphology in what three ways.

Cocci (Circle; spherical shaped), Rods (Small, Medium, and Large), and Spriochetes (spiral shaped)

What three ways are cocci shaped bacteria arranged?

Chains, Pairs, and Clusters.

What three ways are rod shaped bacteria arranged?

Singles, Short chains, and Stacked.

Endospores are formed by...

gram positive bacteria (clostridium and Bacillus)

What are Endospores resistant to?

Heat, UV light, Desiccation., and Chemicals.

When do Endospores occur?

when there is a lack of essential nutrients

What is a Protozoa pathogen?

Single cell that has a nucleus, also contains structures that carry out specific functions for life, many shapes and sizes, They can be parasitic in moist habitats, Similarity of inner structures of protozoan and human cells make it difficult to treat infections cased by protozoan pathogens, and drugs may destroy the protozoan but may also destroy human cell.

List some protozoal pathogens that affect the small intestine.

Giardia, Coccida, Toxoplasma, and Cryptosporidia.

The protozoal pathogen Giardia causes...

diarrhea in dogs and cats.

The protozoal pathogen Coccidia causes...

Isospora and Eimeria sp.

What is the mycology of fungi and yeasts?

Eukaryotic, Have rigid cell wall but contains no chlorophyll, ubiquitous (widespread in nature), opportunistic, insensitive to most bacterial antibiotics, usually not responsible for widespread epidemics.

What are some predisposing factors for fungi and yeast pathogens?

Alteration of normal host flora (antibiotics), Immunosuppression, concurrent infections, breaks in skin, constantly moist areas of skin.

What are the two types of fungi and yeast infections.

Deep and Superficial.

Dermatophytes...

utilize keratin for growth, confined to superficial skin layers, geophillic (anywhere on the body), and are free living. Ringworm is an example.

How can a dermatophyte infection manifest?

Through subclinical carriers, classical lesions (localized), Generalized lesions with secondary bacterial infection, and raised plaque or "scales" lesions.

How can dermatophytes be transmitted?

Direct contact with infected animal, reservoir animals (rodents), and fomites.

What are the two growth forms of dimorphic fungi?

Mold(environment; mycelial) and Yeast (tissues; budding)

What are some important things to know about helminths (metazones).

Includes Flukes, roundworms, and tapeworms, Considered many celled animals with developed organs. Many are parasites, they break down body tissues, feed on blood or absorb digested food. Can be important in introducing secondary pathogens, breaks down local and systemic immunity, primarily causes subclinical losses in infected animals, heavy burdens can lead to death.