INFECTIOUS DISEASE by VlFb8K9

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									INFECTIOUS DISEASE
    Infectious Disease Process
NATURE OF INFECTIOUS DISEASES

Pathogens: microorganisms that are
 capable of causing disease
Infection: results when a pathogen invades
 and begins growing within the host
Disease: results only if and when tissue
 function is impaired (i.e. burns, skin
 lesions)
Continued…
 The body has defense mechanisms to prevent
  infection
 In order to cause disease, pathogens must be
  able to enter, adhere, invade, colonize, and inflict
  damage
 Entrance to the host: mouth, eyes, genital
  openings, wounds
 Growth of pathogens or the production of
  toxins/enzymes cause disease
 Some normal flora prevent diseases
MICROBES THAT CAUSE INFECTIOUS
DISEASES
 Bacteria: Salmonella typhi, Staphylococcus aureus
  Morphology: bacillus, coccus, spirillum
  Aerobes vs anaerobes
  Gram-negative (salmonella) vs gram-positive
   (staphylococcus)
 Viruses: apart from the host cell, have no
  metabolism and cannot reproduce
  Retroviruses: HIV and certain types of cancer
  Herpes viruses: chicken pox, cold sores, smallpox
  Rhinoviruses: common colds – mutation (rapid) leads to no
   vaccine available
  Myxoviruses & paramysoviruses: influenza, measles,
   mumps
  Rotaviruses: gastroenteritis
Continued…
Fungi: form spores
  Examples include ringworm and histoplasmosis
  Yeasts of Candida genus are opportunistic
  Antibiotics reduces normal flora, allowing yeast to
   grow
Protoza: acquired through contaminated
 food or water, or bite of an arthropod
 (mosquito)
  Diarrheal disease in the US – Giardia lamblia and
   Cryptosporidium parvum
  Malaria – Plasmodium (in tropical environment)
…
 Helminths: simple invertebrate animals, some infectious
  parasites
    Symptoms: abd. pain and diarrhea
    Swimmer’s itch in US – flatworm, Schistosoma
    Trichinella spiralis – roundworm which is ingested in
     undercooked pork from infected pigs (Cause of death =
     respiratory paralysis)
 Prions-Creuzfeldt-Jakob disease
    A rare, degenerative, invariably fatal brain disorder; believe
     caused by an unusual "slow virus" or another organism
    Typically, onset of symptoms occurs about age 60, and about
     90 percent of individuals die within 1 year.
    characterized by rapidly progressive dementia and they
     eventually lose the ability to move and speak and enter a
     coma
Malaria
Giardia   and   Cryptosporidium
Helminths Worm
Prions-Creuzfeldt-Jakob disease
OCCURANCE OF INFECTIOUS
DISEASES
 Epidemiology: study of the occurence of disease in
  populations
 Disease reservoirs: where the infectious agent survives
  (human, rodents)
    Example: yersinia pestis
 Modes of transmission
    Direct contact: occurs when a person is infected by contact with
     reservoir, inhaling infectious droplets – examples are AIDS,
     rabies, malaria, influenza, ringworm, trichninosis
    Indirect contact: the pathogen is transmitted from contaminated
     substances such as food, soil, water (Hepatitis A), clothing,
     equipment (example – tetanus)
    Horizontal vs vertical transmission
        Horizontal: transmission between individuals specifically who are
         not related as a parent is to its offspring
        Vertical: occurs from parent to offspring, e.g., in utero, during
         passage down the birth canal, or in breast milk
HOST DEFENSES AGAINST
INFECTIOUS DISEASES
 Nonspecific mechanisms are the body’s primary defense
  against disease - anatomical barriers, physiological
  deterrents and presence of normal flora (skin, low pH and
  high salinity)
    Anatomical barriers: nasal opening, skull, vertebral column, skin
    Physiological deterrents: tears, vaginal secretions, saliva, blood,
     sweat, and some tissue fluids
    Normal flora: successfully compete with pathogens
 Specific mechanisms: immunity
    Cell-mediated: uses T-cells; helper cells and killer cells; activate B
     cells
    Antibody-mediated: uses B-cells
    Both are lympatic cells
 Vaccination: produces immunity

								
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