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Copyright 2011. PEER.tamu.edu

Pathogens!!

Infectious Diseases are Caused by

Pathogens

•  Pathogens are microbes (microscopic living organisms) or other agents that cause diseases.

•  Ex: Foot and mouth disease is a highly contagious disease of cattle, swine, and other cloven-hoofed animals.

What are Pathogens?

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Not all microbes are pathogens!!! •  There are many

types of microbes that are actually beneficial!

•  Ex: Symbiotic bacteria found in our digestive systems

•  Ex: Normal Flora on our skin

Common Types of Pathogens

Fungi Bacteria Viruses

1. BACTERIA •  Single-celled organisms

that are prokaryotic.

•  Less than 1% of the world’s millions of bacteria are pathogenic.

•  Bacteria reproduce

rapidly and many give off toxins which damage body tissue.

Bacteria are shaped like cocci (spheres), bacilli (rods), or spirilla (spirals).

A Closer Look at the types of Pathogens:

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Common Bacterial Diseases

Disease Body System Symptoms

Examples

Dermatitis Skin Inflammation, pruritus (itching) skin lesions (bumps, blisters, scales, crusts)

Staphylococcus aureus

Keratocunjunctivitis Eye Inflammation in eye, pain, sensitivity to sunlight, tears,

“Pinkeye” is common name Staphylococcus aureus

Otitis Externa Ear Inflammation of external ear canal with reddening, drainage and itching

Staphylococcus

Rhinitis and Sinusitis Respiratory Inflammation of the membranes of the nasal passages and sinuses. Mucus nasal discharge, open-mouth breathing, sneezing.

Common Cold

Pneumonia Respiratory Deep cough and difficulty breathing

Staphylococcus aureus, including methicillin-resistant S. aureus (MRSA), Streptococcus species

Gastroenteritis Digestive Inflammation of stomach and intestines, excessive salivation, vomiting, diarrhea, straining, abdominal pain.

Salmonella

Anthrax Skin, Digestive, Respiratory

Sudden death in cattle Varied in humans depending on exposure method

Bacillus anthracis

Food Poisoning Digestive Diarrhea, Nausea, vomiting Certain E.Coli strain

Bacteria: Treatment? Cures??

A positive culture for Streptococcus bacteria

A broad spectrum antibiotic

•  Consists of a piece of genetic material (RNA) housed within a protective coat.

•  Viruses are not cells!!! Is it living…???

•  The virus reproduces by hijacking the cell of another organism (host).

•  Most viruses cause disease and are specific as to which type of cell they will attack.

•  Commonly associated with internal infections.

Rabies Virus

2. VIRUSES A Closer Look at the types of Pathogens:

Flu Virus

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Common Viral Diseases Disease Body System Symptoms Examples Hepatitis General-many organs

involved Vary from slight fever to death

Hepatitis A, B, C

Warts Skin Fibrous tumors of the skin an mucous membranes

Human papilloma virus

Pox Skin Skin lesions-bumps, blisters, pustules, and crusts

Small pox Chicken pox

Pneumonia Respiratory Labored or “flank” breathing, hard deep cough, fever, leukocytosis

Bovine Respiratory Disease (BRD)-Mannheimia haemolytica There are MANY viruses that cause Pneumonia

Meningitis and encephalitis

Nervous Invfammation of the brain covering causing blindness, paralysis, wobbling, seizures, coma and delirium

Encephalomyelitis, distemper, parvovirus, swine pseudorabies

Rabies Nervous Throat paralysis, behavior change, aggression in later stages, lack of fear

Rabies virus

•  Blood tests can also indicate a viral infection.

•  Antiviral medications are being developed, but many are cost prohibitive.

•  Vaccinations can prevent viral

infections.

Human Papilloma Virus (HPV)

Viruses: Treatment? Cures??

•  A single or multi-cellular microbe (eukaryotic).

•  Most fungi are harmless (~300 species)

•  Infects various external

and internal tissues, but more common in external tissues.

Microsporum-the fungus that causes ringworm.

3. FUNGI

A Closer Look at the types of Pathogens:

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Fungal Diseases Disease System Symptom Examples Ringworm, Jock itch Skin/Genital Circular skin lesions with hair

loss, itching, bumps or blisters

Microsporum

Athlete’s foot Skin Scaly rash, itching, burning Tinea pedis

Dandruff Skin Dry, itchy scalp Flakes of dry skin appear

Malassezia

Yeast Infection Genital Itching, irritation, thick discharge

Candida albicans

Candida Overgrowth Digestive Diarrhea, dehydration, hemorrhaging

Various Candida species

•  Anti-fungal drugs •  Topical medications •  Medicated shampoos or

soaps

Viruses: Treatment? Cures??