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Disease and Epidemiology. What is Disease? . Any condition that jeopardizes the survival of an organism in a particular environment. What is epidemiology?. The study of the causes, distribution, and control of disease in populations. . Some Characteristics of Disease.

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what is disease
What is Disease?
  • Any condition that jeopardizes the survival of an organism in a particular environment

What is epidemiology?

The study of the causes, distribution, and control of disease in populations.

some characteristics of disease
Some Characteristics of Disease
  • Change of normal appearance, behavior, or movement
  • Fever
  • Dull, inflamed eyes
  • Rough-soiled hair, fur or feathers
  • Difficulty walking or running
  • Abnormal lumps
  • Discoloration/lesions of skin
disease causing entities
Disease causing entities
  • Any agent that may bring abnormal condition to any or all of the tissues of the body via eggs, contact, food or a vector
  • 2 Types of disease causing entities:
    • Infectious agents – caused by a pathogen (bacteria, virus, parasites etc), invade the body and multiply there.
    • Noninfectious agents –caused by something other than pathogens. (carcinogens, environmental, etc.)
infectious agents pathogen an infectious disease causing agent
Bacteria

Viruses

Parasites

Prions (Mad Cow Disease)

Infectious Agents -pathogen – an infectious disease causing agent
noninfectious agents
Noninfectious agents
  • Injuries
  • Mutations, genetic
  • Poisons and chemicals
  • Poor nutrition
slide8

To grow and spread, most microorganisms prefer

  • Warm, dark environment
  • Moisture
  • Source of food
  • Human body fits the criteria!
2 reservoir
2. Reservoir
  • A place the pathogen can live
  • Human body
  • Animals
  • Environment
  • Fomites: contaminated inanimate objects-
3 portal of exit
3.Portal of Exit
  • Way of leaving the reservoir in which it has been growing:
  • Blood
  • Tears
  • Feces
  • Urine
  • Saliva
  • Draining wounds
4 means of transmission
4. Means of Transmission-
  • Needs to be transported to another reservoir

Direct person to person contact- contaminated hands most common

Indirect contact-

coming in contact with contaminated equipment, food, insect bite

5 portal of entry
5. Portal of Entry
  • Breaks in skin
  • Breaks in mucous membranes
  • Respiratory tract
  • Digestive tract
  • Circulatory system
  • Genitourinary tract
how your body fights off a causative agent
How your body fights off a causative agent
  • Mucous membranes-trap
  • Cilia – transport.
  • Coughing and sneezing-- expel
  • Hydrochloric acid in the stomach-- destroy
  • Tears in the eyes-bacteriocidal
  • Fever-destroy
  • Inflammation-white cells
  • Immune response-antibodies
6 susceptible host
6. Susceptible host
  • Large numbers of pathogens.
  • Body defenses are weak

Results in susceptible host, or a person likely to get an infection or disease

Chain of infection can be broken at any point

the spread of infectious diseases
The spread of infectious diseases
  • DIRECT CONTACT: touching or other direct contact with bodily discharges, secretions or waste, an open wound, bandage, soiled objects or infected surface; STD, blood borne
  • FECAL-ORAL – eating or…….
  • ASYMPTOMATIC CARRIER – an infected person such as“Typhoid Mary”
  • VEHICLE An inanimate object which serves to communicate disease. For example, a glass of water containing microbes, or a dirty rag, etc.
  • VECTORS (such as arthropods – “bugs”) VECTOR – A live organism that serves to communicate disease. For example, mosquitoes and other arthropods.
  • Airborne/droplet
slide17
two types of vectors: mechanical and biological. Microbes do not multiply within mechanical vectors - only physically transport microbes from host to host. In contrast, microbes must propagate within a biological vector before it can transmit the microbes.
  • mosquito (malaria, St. Louis encephalitis, dengue fever, yellow fever, West Nile virus)
  • flea (bubonic plague)
  • tick (Lyme disease, rocky mountain spotted fever, tick-borne encephalitis)
  • deer mouse (hantavirus)
  • kissing bug (Triatominae) (Chagas Disease)
  • bat(Rabies)
slide18
“Typhoid Mary” Mallon -- was a cook in the New York City in the 1900s
  • she infected 22 people with typhoid fever, one of whom died. Eventually estimates ran as high as 50 deaths attributed to her.
  • Dr. George Soper interviewed Mary, and suggested there might be a connection between the dishes she served and the outbreaks of typhoid.
  • After forcibly obtaining urine and stool samples, it was revealed she was an asymptomatic carrier of typhoid salmonella
  • In 1915, a serious epidemic of typhoid erupted among the staff of New York's Sloan Hospital for Women, with twenty five cases and two deaths. City health authorities investigated.
  • Mary was quarantined for life on North Brother Island. She became something of a celebrity, and was interviewed by journalists (who were forbidden to accept as much as a glass of water from her.) She died in 1938 of pneumonia.
charting the spread of a disease
Charting the Spread of a Disease

*Investigator must work backwards to try and determine

the index case

*The mode of transmission/vector

*The “waves” of infection

incubation period
Incubation Period
  • Time period before signs and symptoms appear
  • The delay is used for the pathogen to multiply
  • Varies with each disease:
    • Colds about 7 days
    • HIV can be 10 years
infectious disease causing agents
Pathogen - a disease causing agent (example: bacteria, viruses)

Virulence – ability of a pathogen to overcome the body’s defense & produce a disease

Host – any organism serving as a residence for a pathogen

Vector – agent/entity that delivers a pathogen to a host, intermittent host

Infectious Disease Causing Agents
bacteria
Bacteria
  • Smallest & simplest form of life
    • prokaryotic
  • Single-celled
    • Have a cell wall
  • Vary in size & shape
  • Many are beneficial
    • decompose and recycle nutrients
    • Foods – yogurt, wines, cheese
    • Aid in digestion
bacteria characteristics
Bacteria Characteristics

1. Two Domains:

Archaebacteria – live in extreme conditions

Eubacteria – all other bacteria

distinguishing characteristics of bacteria
2. Oxygen need

No oxygen (anaerobic) – such as botulism, tetanus

Oxygen required (aerobic)

Facultative anaerobic – prefers oxygen, but can survive in anaerobic conditions

Distinguishing Characteristics of Bacteria
slide25

3. Prokaryotic

No membrane bound organelles such as a nucleus or mitochondria

slide26

Microscopic

4. ________________ How big are bacteria?

http://www.cellsalive.com/howbig.htm

5. Where do they live?

Archaebacteria - live in extreme harsh environments – hot temperatures, extreme salinity for example and include halophiles, methanogens, thermophiles, sulfophilic strains

Eubacteria - bacteria we encounter on a daily basis – E. coli for example

slide27

6. Shape:

b.

a.

c.

Spherical - cocci

Helical or Spiral

Rod - bacillus

Vibrio– comma shaped

slide28

7.

Staphylococcus

Streptococcus

slide29

-Some are rigid, Some flexible

8. Have Cell Walls

9. Form Endospores in Harsh Conditions

distinguishing characteristics of bacteria30
Distinguishing Characteristics of Bacteria
  • Cell wall absorb “gram’s stain”?
    • Gram positive – retain stain in cell walls
    • Gram negative – characteristic of many pathogenic strains, may not always respond to anitbiotics
  • Ability to release toxins – waste products from metabolism
  • http://www.microbelibrary.org/microbelibrary/files/ccImages/Articleimages/keen/Gramstainkeen.htm
bacteria release toxins not good
Bacteria release toxins…………not good!!
  • Chemical substances harmful to the normal functioning of cells
    • Endotoxins – parts of bacterial cells
    • Exotoxins – wastes from bacterial cells
  • _______________- disrupt the transmission of nerve impulses.

Neurotoxins

slide33
Bacteria exchange genetic information by conjugation-- no new cells are created-- leads to exchange of antibiotic genes

http://www.hhmi.org/biointeractive/animations/conjugation/conj_frames.htm

bacterial diseases
Bacterial Diseases

1. Anthrax - respiratory infection initially presents with cold or flu-like symptoms for several days, followed by severe (and often fatal) respiratory collapse

Cutaneous

Inhalation

slide36

3. Typhoid fever - caused by the bacteriumSalmonella Typhi. Common worldwide, it is transmitted by ingestion of food or water contaminated with feces from an infected person.

bacterial disease treatments
Bacterial Disease Treatments

ANTIBIOTICS

  • Inhibit growth of some bacteria – may disrupt cell walls, or other metabolism
  • products of fungus or competing bacteria
  • -- Ex: Penicillin, erythromycin, kanamycin, tetracycline……
  • Bacteria can _______________to become resistant to antibiotics

mutate

helpful bacteria

Make milk into yogurt!

Make antibiotics!

Treat Wastewater!

Aid Digestion!

Pesticide Control!

Also--

Decomposers/ Natural Cycle!

Bioremediation!

Food/Preservatives!

Helpful Bacteria

© Eric MacDicken

viruses46
Viruses
  • Microscopic in size – smaller than bacteria
  • Not considered to be living
  • Can cause serious, contagious disease
  • Classified by
    • type of tissue they invade,
    • appearance,
    • host they normally infect
    • Type of genetic material – DNA or RNA
virus characteristics
Virus Characteristics

DNA inside

Chicken Pox

Human Influenza

Rabies Virus

HIV

viruses structure
Viruses – Structure
  • Protein coat
  • geometric shapes
  • Receptor proteins to match virus with specific host cell
  • Genetic element
    • Either DNA or RNA strand
slide49

Two Types of Virusesa. Lytic (virulent)b. Lysogenic (temporal) – “dormant”http://highered.mcgraw-hill.com/sites/0072556781/student_view0/chapter17/animation_quiz_2.htmlhttp://www.cfoxscience.com/mrfox/apbio/Lectures/lysogenic_pathway.swf

lytic cycle
LYTIC CYCLE
  • Viral genetic element (DNA or RNA) becomes part of host cell DNA
  • Host cell produces new viruses
  • Cell lyses (is destroyed) thereby releasing viruses to invade other host cells
slide51

Virulent

  • Lytic Cycle of a Virulent Virus

--Causes disease immediately

Infectious Diseases:Viral Infection

Infectious Diseases:Viral Infection

virus reproduction process
Virus Reproduction Process
  • Absorption
  • Entry
  • Replication
  • Release
slide54

--Does not cause disease immediately

b. Temporal

Lysogenic Cycle of aTemperate Virus

Activated to produce new viruses

Remains in cell

lysogenic cycle
LYSOGENIC CYCLE
  • Considered to be “dormant”
  • Is replicated via host cell’s mitotic cycle
  • May become lytic if induced by a stimulus (such as a chemical imbalance or environmental stress)
retrovirus
Retrovirus

Dr. Stephen O'Brien's work with HIV led to a discovery that could one day help scientists treat or prevent HIV infection: People from some European populations carry a genetic mutation that prevents HIV from entering their white blood cells. O'Brien hypothesizes that this mutation, dating back 700 years, may have been a selective advantage during the bubonic plague, as it is today, with the onslaught of HIV. From Evolution: "Evolutionary Arms

http://www.whfreeman.com/kuby/content/anm/kb03an01.htm

http://www.pbs.org/wgbh/evolution/library/10/4/l_104_05.html

are viruses living
Are viruses living?

What are all living things made of?

-- don’t have complete cell parts

What do all living things need?

-- need energy from host cell

How does environment affect living things?

-- do not respond to a stimulus

How do living things reproduce?

-- need host cell to replicate

viral diseases
Viral Diseases

Common Cold

  • ___________________
  • * 200 kinds of Viruses

Symptoms include nasal discharge, obstruction of nasal breathing, swelling of the sinus membranes, sneezing, sore throat, cough, and headache.

slide60

Polio

2. ________________

  • Poliomyelitis is a crippling disease of spinal nerve cells caused by poliovirus infection.
  • The disease can strike non-immune persons of any age but affects mainly children under the age of three, and causes paralysis in one case of every 200 to 1000 infections.   
  • Preventable by vaccination. 
slide61

Tobacco Mosaic

3. ______________________

Symptoms induced can include mosaic, mottling, necrosis, stunting, leaf curling, and yellowing of plant tissues.

slide62

AIDS

4. ___________

STD

Acquired immunodeficiency syndrome, is caused by the human immunodeficiency virus, or HIV.

HIV destroys the body's ability to fight infections by attacking cells of the immune system.

slide63

Rabies

5. ______________

The vast majority of cases reported to the Centers for Disease Control and Prevention (CDC) each year occur in wild animals like raccoons, skunks, bats, and foxes.

Infects the central nervous system, causing encephalopathy and ultimately death.

slide64

STDpotential

Cold Sore

6. ______________

(Herpes simplex )

Between 50 - 80% of all people possess this virus and is spread through direct contact with an infected individual.

Once the virus has entered the body, it cannot be removed.

Only 10% of HSV1 infected people ever develop a sore.

slide65

Shingles

7. _____________

An acute infection caused by a activation of the varicella zoster virus, which also causes chicken pox.

It usually occurs during adulthood after exposure to chicken pox in childhood. The chicken pox virus remains dormant in the body.

slide66

Measles

8. _____________

Most infected children will have a rash, high fever, cough, runny nose, and watery eyes.

For every 1,000 children who get it, 1 or 2 will die from it

Spreads so easily that any child who is not immunized will probably get it, either now or later in life.

slide67

Warts

9. ___________

Non-cancerous skin growths caused by a viral infection in the top layer of the skin. Viruses that cause them are called human papillomavirus (HPV).

STD

slide68

STD

Herpes

10. _______________

HSV-2 usually produces only mild symptoms or signs or no symptoms at all.

However, HSV-2 can cause recurrent painful genital sores in many adults, and HSV-2 infection can be severe in people with suppressed immune systems.

Regardless of severity of symptoms, genital herpes frequently causes psychological distress in people who know they are infected.

slide69

Hepatitis B

11. _____________

The most common serious liver infection in the world.

It is caused by the HBV virus that attacks the liver.

HBV is 100 times more infectious than the AIDS virus. Yet, can be prevented with a safe and effective vaccine.

treatment prevention and defense
Treatment, Prevention AND Defense

1. First Level of Response: skin, mucous linings of respiratory tract

treatment prevention defense cont d

Guard/Fight Real Disease

Anitbodies Produced

Vaccine Given

Treatment/Prevention/Defense (cont’d)

2. Vaccine

3. Interferon – special proteins produced as immune response which in turn induce immune response cells to attack the antigens (viruses and bacteria)

slide72

4. Fever – elevated body temperature enhances immune response

5. Antigen – foreign substance that induces immune response

6. Immunity

slide73

http://student.ccbcmd.edu/~gkaiser/biotutorials/eustruct/phagocyt.htmlhttp://student.ccbcmd.edu/~gkaiser/biotutorials/eustruct/phagocyt.html

http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__phagocytosis.html

7. Phagocytosis – the digestion of an antigen by an immune response cell

http://www.sp.uconn.edu/~terry/Common/phago053.html

other causes of disease
Other causes of disease…
  • Parasites –

--Organism living on, in, or at the expense of another living organism

types of parasites
Types of parasites
  • Protozoa
    • Single celled
  • Helminths (worm parasites)
    • Multi-cellular
    • Tape worms, Round worms, leeches (segmented worm) – most roundworms are GOOD!!
  • Arthropods – ticks, fleas, bed bugs, flies, mosquitoes
    • Act as vectors (carriers of disease)
  • Fungi
six arthropods that affect mammals
Flies Six arthropods that affect mammals
  • Mosquitos
  • Ticks
  • Fleas
  • Lice
  • Mites