Chapter 7
Infectious Diseases
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Learning Objectives
▪ Describe characteristics of bacterial infections.
▪ Identify similarities and differences between
viruses and parasites.
▪ Explain how fungal infections affect the body.
▪ Give examples of how infectious diseases
are transmitted.
▪ Recognize the importance of vectors in the
transmission of diseases.
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Learning Objectives
▪ Identify the main components of the
immune system.
▪ Compare and contrast innate and adaptive immunity.
▪ Describe how immunizations prevent infections.
▪ Critique the risks and benefits of herd immunity in
preventing infection.
▪ Outline the response of the immune system
to infection.
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Pathogens
▪ A pathogen is an invading organism that can destroy
tissues, feed off tissue, or grow and
take over space previously occupied by
healthy tissues.
▪ Bacteria, Virus, Fungus, Parasite
▪ Infection is a physiological response to a pathogen.
▪ Signs and symptoms of infections are related to the
structures that are affected, as well as how far the
infection has spread within the body.
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Bacteria
▪ Simple organisms, usually single-celled
▪ Reproduce through cell division through DNA
replication
▪ No nucleus
▪ Outer cell wall looks like a chain (peptidoglycan)
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DNA-Replicating Bacteria
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Bacterial Infection
▪ Direct cell damage occurs when it devours the
surrounding tissue and that tissue’s nutrients.
▪ Endotoxins are lipids that are shed from the
wall of dying bacteria, stimulating fever
and inflammation.
▪ Exotoxins are live proteins released from bacteria
and are classified by the cells they target.
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Common Bacterial Infections
Table 7.1 Common Bacterial Infections
BACTERIA
INFECTION
Borrelia burgdorferi
Lyme disease: Inflammation of the connective tissues
Chlamydia trachomatis
Reproductive organs, urinary and lower gastrointestinal tracts:
Inflammation and tissue degradation
Escherichia coli - E-Coli
Gastrointestinal system: Gastritis, enteritis
Helicobacter pylori
Gastrointestinal system: Ulcers
Listeria
Inflammation in the gastrointestinal tract, often progressing to the
central nervous system, causing meningitis
Mycobacteria
Lungs: Tuberculosis
Neisseria gonorrheae
Reproductive organs
Salmonella
Gastrointestinal system: Gastritis, enteritis
(Continued)
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Common Bacterial Infections
Table 7.1 Common Bacterial Infections (cont’d)
BACTERIA
INFECTION
Staphylococcus aureus*
Skin surface: Impetigo
Subcutaneous: Cellulitis
Brain and spinal cord: Meningitis
Heart: Endocarditis
Breast: Mastitis
Lungs: Pneumonia
Streptococcus
Throat: Strep throat
Ear: Otitis media
Heart: Endocarditis
Streptococcus pneumoniae
Lungs: Pneumonia
Brain and spinal cord: Meningitis
Paranasal sinuses: Sinusitis
Heart: Endocarditis
Syphilis (Treponema pallidum)
Lesions in reproductive and gastrointestinal mucous membranes,
on the skin, progressing to the central nervous system
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Bacteria: Treatments
▪ Antibiotic medications that are designed to
attack the cell membrane or penetrate the
membrane to destroy the cell or keep bacteria
cells from multiplying
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Viruses
▪ Organisms that live off a host cell
▪ Cannot reproduce alone
▪ Depend on host cell for growth and replication
▪ Attach to and use a host cell as the resource from
which to reproduce
▪ Inject genetic material into cells
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Viral infections are grouped
into 3 categories:
• Productive viral infections are
known as persistent, actively
reproduce while infection
progresses
• Latent viral infections do not
replicate right away
• Abortive viral infections infect
the cell, do not fully replicate
Three types of viral reproduction.
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Common Viral Infections
Table 7.2 Common Viral Infections
VIRUS
TYPE
INFECTION
Adenovirus
DNA
Respiratory system: Common cold, bronchitis
Gastrointestinal system: Gastritis
Integumentary system: Conjunctivitis (eyes), rashes
Cytomegalovirus
DNA
Gastrointestinal system: Diarrhea, hepatitis, jaundice
Central nervous system: Encephalitis
Respiratory system: Pneumonia
Hepadnavirus
DNA
Gastrointestinal system: Hepatitis B
Herpesvirus
DNA
Integumentary system: Chicken pox, herpes zoster (shingles), genital
herpes
Papillomavirus
DNA
Integumentary system: Plantar warts, genital warts
Coronavirus
RNA
Respiratory system: Common cold
Hantavirus
RNA
Respiratory system: Hemorrhagic fever with renal syndrome
Morbillivirus
RNA
Respiratory system: Measles
Norovirus
RNA
Gastrointestinal tract: Diarrhea, gastroenteritis
Rhabdovirus
RNA
Central nervous system: Rabies
Rotavirus
RNA
Gastrointestinal tract: Diarrhea
Human immunodeficiency virus
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Retrovirus
Immune system: CD4+ helper T cells
Fungi
▪ Neither animal, plant, nor bacteria
▪ Spread by feeding off living organisms by
devouring decomposing material
▪ Require oxygen
▪ Thrive in warm, moist environments
▪ Usually present on the skin, particularly the webbing of the toes, soles
of the feet and other moist areas of the body
▪ Most do not cause infections in healthy people
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Common Fungal Infections
Table 7.3 Common Fungal Infections
FUNGUS
INFECTION
Candida albicans
Throat (thrush), vagina, anus/rectum,
gastrointestinal tract
Tinea
Tinea corporis (body), Tinea pedis (foot),
Tinea cruris (groin), Tinea capitis (head),
Tinea unguium (nails), Tinea manis (hands)
Various yeasts and molds
Pneumonia, chronic sinusitis
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Parasites
▪ Simplest form of animal life
▪ Organisms that live off other organisms
▪ Pathogenic protozoa and parasites can survive only in a living subject
▪ Three types:
▪ Protozoa
▪ single-celled organisms, proliferate by dividing and spreading
▪ Helminths
▪ Multi-cellular, lay eggs inside host
▪ Ectoparasites
▪ Fleas, ticks, and lice
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Common Parasitic Infections
Table 7.4 Common Parasitic Infections
PARASITE
TYPE
Roundworm
Helminth
Gastrointestinal system: Ascariasis, trichinosis
Subcutaneous tissues and blood: Hook-worms, pinworms
Tapeworm
Helminth
Gastrointestinal system: Cestodes, cysticerosis
Flatworms
Helminth
Blood vessels and endocrine ducts: Flukes
Intestines, bladder: Schistosomiasis
Toxoplasma gondii
Protozoa
Blood, lymph tissues, central nervous system
Malaria
Protozoa
Red blood cells
Amebiasis
Protozoa
Gastrointestinal system
Giardia
Protozoa
Gastrointestinal system
Ticks
Ectoparasite
Integumentary system
Fleas
Ectoparasite
Integumentary system
Lice
Ectoparasite
Integumentary system
Bed bugs
Ectoparasite
Integumentary system
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INFECTION
Pathways of Infection Transmission
▪ Direct contact: Through touch
▪
▪
▪
▪
Hand to orifice - mouth, eye, etc
Skin to surface
Skin to skin
Open wounds
▪ Inhalation: Through the air
▪ Ingestion: Through food or water
▪ Vector: Through an insect or animal or fomite (clothes, bed)
▪ Has the ability to carry a pathogen without becoming infected.
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The Epidemiology Triangle
For an infection to occur
and allow the pathogen to
be transmitted, 3 aspects
need be present:
1. The pathogen,
2. a host and
3. an optimal environment.
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Massage and Infectious Diseases
▪ Massage is systemically
contraindicated when
infection is present.
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Structures of the Immune System
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The Immune System
▪ Structures of the immune system include
immune cells to fight infection
▪ Lymphoid tissues remove waste and neutralize
pathogens
▪ Spleen, Thymus, Tonsils, Adenoids, Lymph nodes
▪ Tolerance refers to the ability of the body to
recognize itself.
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The Immune System
▪ When a pathogen enters the body, immune cells
are stimulated to react in the immune response.
▪ If healthy, it is able to fight off common
infections.
▪ If suppressed, it takes longer to control an
infection or it is unable to fight off an infection.
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Innate Immunity
▪ First line of defense
▪ Structural
▪ Prevents pathogens from entering the body
▪ Examples: Skin, cilia, eyelashes, tears, saliva
▪ If these barriers are successful, the immune system is not
activated
▪ Chemical
▪ Inflammatory process
▪ WBC’s - White Blood Cells
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Innate immunity
▪ Leukocytes carry and secrete substances necessary to
fight infection
▪ Neutrophils, Basophils, Eosinophils
▪ Phagocytes ingest or burst pathogens
▪ Monocytes, Macrophages
▪ Lymphocytes travel via blood and attack viruses or
cancer cells
▪ Natural killer cells
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Adaptive Immunity
▪ Secondary line of defense.
▪ May take several days after exposure to the
pathogen for an antigen to develop and begin to
fight infection.
▪ Antigen is a toxin or other foreign substance that induces
an immune response in the body
▪ Antibody aka immunoglobulin is a large protein produced
mainly by plasma cells and used by the immune system to
identify and neutralize pathogens.
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Adaptive Immunity
▪ Humoral immunity - body fluids
▪ B-cells produce antibodies known as immunoglobulin
molecules in response to a specific antigen.
▪ Five categories of immunoglobulins;
▪ IgA, IgD, IgE, IgG, IgM
▪ Immunoglobulins/antibodies act as mediators to block,
neutralize, or destroy.
▪ Cell-mediated immunity
▪ T cells bind to antigens. (WBC)
▪ Stimulates natural killer cells and macrophages
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Herd Immunity
Herd immunity is a type of passive
immunity. A person has a decreased risk
of infection if one is surrounded by
healthy people who minimize the
opportunity that the person will be
exposed to an infectious agent.
Healthy people would be identified as
those who have previously had an
infection but are no longer contagious OR
those who have previously been
vaccinated against the disease.
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Massage and Immune Function
▪ There is some evidence that massage has
favorable effects on the immune system.
▪ Most research studies that have evaluated the
effects of massage on immune function have
used Swedish techniques.
▪ Research results are considered positive, but the
evidence is inconclusive.
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