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INFECTIOUS DISEASE

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

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INFECTIOUS DISEASE

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  1. INFECTIOUS DISEASE Infectious Disease Process

  2. 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)

  3. 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

  4. 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

  5. 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)

  6. … • 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

  7. Malaria

  8. Giardia and Cryptosporidium

  9. Helminths Worm

  10. Prions-Creuzfeldt-Jakob disease

  11. 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

  12. 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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