31_lecture - Chapter 31 Infection and Pathogenicity 1 host...

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Unformatted text preview: Chapter 31 Infection and Pathogenicity 1 host larger organism that supports the survival and growth of a smaller organism parasites are organisms that live on or within a host organism and are metabolically dependent on the host are any organism that cause disease 2 Host-Parasite Relationships infection a parasite growing and multiplying within or on a host may or may not result in overt infectious disease pathogen any parasitic organism that causes infectious disease primary (frank) pathogen causes disease by direct interaction with healthy host opportunistic pathogen may be part of normal flora and causes disease when it has gained access to other tissue sites or host is immunocompromised pathogenicity ability of parasite to cause disease 3 Host-Parasite Relationships latent state is the state in which no transmission of the organism occurs no symptoms are present within the host examples are herpesvirus infections, tuberculosis and leprosy 4 Host-Parasite Relationships number of organisms present the degree of virulence of pathogen virulence factors e.g., capsules, pili, toxins hosts defenses or degree of resistance 5 Factors Impacting Outcome of Host-Parasite Relationships infectious disease infection with viruses, bacteria, fungi, protozoa, and helminths signs objective changes in body that can be directly observed symptoms subjective changes experienced by patient disease syndrome set of characteristic signs and symptoms 6 The Infectious Disease Process incubation period period after pathogen entry but before signs and symptoms appear prodromal stage onset of signs and symptoms not clear enough for diagnosis period of illness disease is most severe and has characteristic signs and symptoms convalescence signs and symptoms begin to disappear 7 Course of Infectious Disease 8 Figure 31.2 source location from which pathogen is transmitted to host period of infectivity time during which source is infectious or is disseminating the organism reservoir site or natural environmental location in which pathogen is normally found sometimes functions as source of pathogen 9 The Source or Reservoir carrier infected hosts who are potential sources of infection for others types of carriers active carrier has overt clinical case of disease convalescent carrier has recovered but continues to harbor large numbers of pathogen healthy carrier harbors the pathogen but is not ill incubatory carrier is incubating the pathogen in large numbers but is not yet ill 10 The Source or Reservoir...
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31_lecture - Chapter 31 Infection and Pathogenicity 1 host...

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