Download Fighting Disease Pathogen: a disease

Fighting Disease
Pathogen: a disease-causing microorganism
ex. parasites
How Bacterial Pathogens Work


enter body
bacteria produce TOXINS which enter bloodstream and travel throughout body
Symptoms: chills, fever, etc.
- harmful effects seen throughout body
ex. step on rusty nail
Clostridium tetani endospores enter body and begin to produce a NEUROTOXIN
that causes the body to SPASM and lock; TETANUS
- the body’s muscles CONTRACT and stay that way
- die from asphyxiation – (cannot breathe)
ex. Corynebacterium diphtheriae
- toxin prevents cell organelles from producing proteins which causes the cell to
malfunction
WEBSITES
http://www.microbes.info/resources/Medical_Microbiology/
http://www.niaid.nih.gov/final/immun/immun.htm
http://uhaweb.hartford.edu/BUGL/immune.htm
http://rex.nci.nih.gov/PATIENTS/INFO_TEACHER/immune_sys/frame2.html
http://www.bacteriamuseum.org/niches/hwfbacteria/immunesystem.shtml
DISEASES





http://research.amnh.org/exhibitions/epidemic/table4.html
http://textbookofbacteriology.net/medical.html
http://www.cbdn.ca/english/discover/discover.html
http://www.astdhpphe.org/pubs_infectious.asp
http://www.cfsan.fda.gov/%7Emow/intro.html
Comparing Viral and Bacterial Diseases
Viral diseases: organism takes over the
Bacterial diseases: organism produces
common cold
- caused by airborne rhinovirus and others
- transmitted by droplets from sneezing or
coughing
- symptoms include cough, congestion, mild
fever
- duration is about 1 week
strep throat
- caused by Streptococcus bacteria
- transmitted by droplets from coughing or
sneezing
- symptoms include high fever, very sore throat
- duration is 1–2 weeks; no long-lasting effects
hepatitis B
- caused by an enterovirus
- transmitted in the exchange of body fluids
- most people are initially asymptomatic, but
symptoms will appear 1–3 months after
infection; loss of appetite, fatigue, abdominal
discomfort, nausea, and jaundice
- long-term effects include liver cancer,
cirrhosis of the liver, and acute chronic
infection
tetanus
- caused by Clostridium tetani bacteria
- transmitted through deep puncture wounds to
the body: bacteria produce a neurotoxin that
attacks neurons
- symptoms include rigid muscle contractions,
especially in the jaw (common name:
lockjaw)
- if not caught early, can result in paralysis or
death
HIV/AIDS
- caused by a retrovirus
- transmitted in the exchange of body fluids
- symptoms include the appearance of
opportunistic diseases (rare diseases that
only show up in people with weak immune
systems)
- 100% fatal, although treatments do exist that
can prolong life for up to 15 years
botulism
- caused by Clostridium botulinum bacteria
- transmitted through improperly sterilized food
that contains the bacterial spores
- symptoms include blurred vision, difficulty
swallowing and breathing, muscle weakness,
nausea, vomiting
- 1/3 of patients will die, all within a few days of
initial symptoms
host cell and alters its function so that the viral
DNA or RNA is reproduced and new viruses
are formed
toxins that affect cells and prevent them from
functioning normally
Symptoms:
Disease in the body is recognized by symptoms. These symptoms include pain, swelling, infected
wounds, poor digestion, stiff joints, weakened bones, or just general debilitation. Symptoms are not diseases in
themselves but function as the body’s early warning system. If we neglect these warnings, or worse, turn them
off with drugs such as painkillers that suppress the symptoms, the disease remains. An analogy would be turning
off a smoke detector because the sound is annoying. The result could be that the house burns down unless you
find the cause of the smoke and extinguish it. If symptoms are ignored over a long period, it could be
irreversible (smoker’s cough _ lung cancer or emphysema).
Fever occurs when white blood cells release endogenous pyrogens that work on the
hypothalamus to raise body temperature. Most pathogenic viruses and bacteria can’t thrive in
hot environments. Some doctors suggest not taking fever reducers unless your temperature is
very high (more than 39°C).
Overview of the Body’s Defences
see book page 121
First Line of Defence (structural, non-specific)
• Skin: keeps organisms and allergens from entering the body
 sweat : contains salts and amino acids that are poisonous to bacteria
• Lysozyme: enzyme in tears, saliva, mucus secretions, perspiration; digests bacterial cell walls
• Cilia in respiratory passages: mucus helps trap inhaled bacteria and sweep up to throat
• Stomach acid: low pH kills pathogens
Second Line of Defence (cellular, non-specific)
White blood cells (leukocytes):
• Lymphocytes: found in the blood, tissue fluids, and lymph; produced in the bone marrow and thymus; produce
antibodies
• Macrophages: produced in the bone marrow; engulf pathogens by phagocytosis; once the pathogens are inside
the macrophage, it secretes lysozyme to kill the pathogens
Pus: dead WBC and bacteria
Lymphatic System:
Complex network of organs connected by a special circulatory system of vessels and nodes
- contains LYMPH: a transparent fluid containing lymphocytes
Lymphatic organs and tissues:
• Tonsils: collections of lymph tissue in the back of the throat that filter out organisms that cause infection
• Thymus: organ in which new white blood cells develop specialized functions
• Liver: white blood cells in this organ remove organisms from the blood as it flows through
• Spleen: removes abnormal cells from circulation
• Mucous membranes in the respiratory and gastrointestinal tracts: contain immunoglobulins to destroy
pathogens and allergens
• Lymph nodes: act as filters; produce antibodies to destroy invading organisms or abnormal cells
• Bone marrow: site of white blood cell formation
Third Line of Defence: Antibody Formation (specific)
• Undigested antigens stimulate the lymph nodes to produce memory cells and plasma cells.
• Plasma cells manufacture antibodies specifically shaped to deactivate the invaders.
• Antibodies circulate through the bloodstream and enter tissues to combat the remaining antigens.
• Macrophages consume and digest the deactivated antigen-antibody complex.
• Memory cells stored in lymph nodes “remember” how to produce identical antibodies if the same antigen
invades again.
Antibodies: good – protein molecules that protect the body from invaders
Antigen: bad – a foreign material that causes formation of antibodies
VERY SPECIFIC: one antibody per antigen
Immunity
1. ACTIVE IMMUNITY: the body itself manufactures antibodies to combat a
specific disease
Acquired two ways:
natural: person gets disease and body produces antibodies
- this lasts a lifetime
 artificial: injection of a vaccine
- the body recognizes this (vaccine contents) as ANTIGENS and
produces ANTIBODIES to combat the intruders
- some vaccines produce lifelong protection : diphtheria
- 3-5 years: (boosters) – small pox
- one year: influenza

VACCINES: dead or weakened pathogens (bacterial or viral) or other antigens
2. PASSIVE IMMUNITY: antibodies given to fight infection
- temporary protection, no memory


Acquired two ways:
natural: mother passes on antibodies to baby before delivery or
through
breast milk (lasts a few months)
- immunizations begin during the first year
acquired: shot of antibody given to help fight antigen
immediately
ex. tetanus shot: an antidote to fight a possible infection of
Clostridium tetani to prevent tetanus
- the antidote or shot is derived from the plasma of an animal that
has been exposed to this antigen
- the protection lasts for 10 years
Types of active and passive immunity
ACTIVE
PASSIVE
- body manufactures it own antibodies
- antibodies are introduced into bloodstream
NATURAL
ARTIFICIAL
NATURAL
ACQUIRED
through disease
contact and recovery
through vaccination
through pregnancy and
breast-feeding
through vaccination
e.g. tetanus
Lifelong
e.g., diphtheria
Short-term Immunity
e.g., influenza, smallpox
Resisting Bacterial Infection
Transmission: spreading the disease
 HOW:





inhale dust or moisture droplets in air
direct contact – hand shake
fecal contamination – E.coli on hamburger
animal bites – insects are important VECTORS – organisms that pass on pathogens
wounds (cuts, scratches) ex. tetanus, flesh-eating bacteria
PROTECTION:





Sterilization: high temperatures destroy bacteria
Disinfectants: chemicals that can kill microorganisms on surfaces
- do not use on body
Antiseptics: slows growth of microorganisms
- can be used on body but not taken internally
Burn: destroy all infected plant or animal material
Antibacterial medication: ex. antibiotics like penicillin
 Antiseptics and disinfectants are both chemicals that destroy or impede the
growth of disease-causing organisms. An antiseptic can be used on human skin
without harming body cells; a disinfectant could harm human cells and is used
on inanimate surfaces.
Autoimmune diseases:
These are when the IMMUNE system ATTACKS a healthy body
ex. multiple sclerosis, rheumatoid arthritis
Multiple sclerosis is a chronic, inflammatory, autoimmune disease of the central nervous system (brain
and spinal cord) that causes the destruction of the covering (myelin sheath) of the nerves. Plaques resulting from
this inflammatory process that destroys normal, healthy myelin tissue are scattered throughout the central
nervous system. These plaques block the ability of the nerves to transmit nervous system signals and can cause
a wide range of neurological symptoms: loss of balance, impaired speech, extreme fatigue, double vision, and
paralysis. The exact cause of MS is not known. Current belief is that MS results from an autoimmune response in
someone genetically predisposed to develop an autoimmune disease, possibly triggered by a virus, chemical, or
something in the person’s environment. MS is the most common neurological disease affecting young adults in
Canada, and Canadians have one of the highest rates of multiple sclerosis in the world. The disease can affect
any age group. However, the diagnosis is most often made between 20 and 40 years of age, and women are
twice as likely to develop MS as men. MS is more common in Caucasians than in those of African or Asian
heritage.