Factors Affecting Disease Patterns and Measures
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Questions and Answers

Which of the following is considered an intrinsic factor affecting health?

  • Animal management
  • Overcrowding
  • Climate and weather
  • State of nutrition (correct)

    • What does pathogenicity refer to in the context of disease?

  • The genetic makeup of the host
  • The physiological state of the organism
  • The quantitative ability of an organism to cause disease
  • The ability of the organism to cause disease (correct)

    • Which of the following factors contributes to the virulence of a pathogen?

  • Degree of function and fatigue in the host
  • Number of microbes required to kill 50% of the host (correct)
  • Metabolism and hormonal balance of the host
  • Age and sex of the host

    • What is the primary function of pili in certain disease-causing organisms?

    <p>To aid in adhesion to host cells</p> Signup and view all the answers

    Which type of toxin is typically released upon the disintegration of bacterial cells?

    <p>Endotoxins</p> Signup and view all the answers

    How is the virulence of an organism quantitatively expressed?

    <p>In terms of LD50</p> Signup and view all the answers

    What role does enzyme MW63 play in pathogenic bacteria?

    <p>It forms barriers to protect against phagocytosis</p> Signup and view all the answers

    Which of the following statements about extrinsic factors is true?

    <p>They consist of environmental influences on health.</p> Signup and view all the answers

    What is the formula used to determine prevalence in relation to incidence and disease duration?

    <p>P = I x D</p> Signup and view all the answers

    What factor does NOT affect the change in prevalence?

    <p>Change in disease severity</p> Signup and view all the answers

    If the incidence rate is calculated as I = P/D, what does an increase in disease duration imply for the incidence rate?

    <p>Incidence rate will decrease</p> Signup and view all the answers

    How is the Mortality Rate calculated?

    <p>No. of dead cases / total No. of animals at risk</p> Signup and view all the answers

    Which of the following best defines 'infectivity'?

    <p>Ability of disease-producing agent to establish itself in a host</p> Signup and view all the answers

    What is the case fatality rate in a population with 200 sick animals and 50 dead animals?

    <p>25%</p> Signup and view all the answers

    Which of these components are NOT included in the determination of cumulative incidence?

    <p>Total number of recoveries</p> Signup and view all the answers

    In the context of disease determinants, what does 'virulence' indicate?

    <p>Severity of disease in the host</p> Signup and view all the answers

    What characterizes an incubatory carrier?

    <p>Transmits DPA during the incubation period.</p> Signup and view all the answers

    What defines the period of communicability?

    <p>The duration the infected host can transmit the disease.</p> Signup and view all the answers

    Which of the following is an intrinsic factor contributing to disease?

    <p>Genetic disorders.</p> Signup and view all the answers

    Which statement about antigenic variation is true?

    <p>It allows DPA to evade host defenses.</p> Signup and view all the answers

    What is the primary difference between primary and secondary causes of diseases?

    <p>Secondary causes contribute but are not essential for disease occurrence.</p> Signup and view all the answers

    Which of the following is an example of a prepatent period?

    <p>Time from infection to detection of the pathogen.</p> Signup and view all the answers

    Which factor is most likely a non-living agent causing disease?

    <p>Insect bites.</p> Signup and view all the answers

    Which of the following best defines carriers in the context of DPA?

    <p>Hosts that can spread DPA without showing clinical signs.</p> Signup and view all the answers

    What does virulence refer to in the context of disease-producing agents?

    <p>The severity of a specific strain of a disease-producing agent</p> Signup and view all the answers

    What does the Secondary Attack Rate (SAR) measure?

    <p>The spread of infection within a population</p> Signup and view all the answers

    How is prevalence defined in epidemiology?

    <p>The total cases of a disease in a population at a specific time</p> Signup and view all the answers

    Which of the following is essential for calculating incidence?

    <p>The number of new cases during a specific time period</p> Signup and view all the answers

    How is cumulative incidence calculated?

    <p>Number of new cases during a period divided by the healthy individuals at the beginning of the period</p> Signup and view all the answers

    What is the primary distinction between prevalence and incidence?

    <p>Prevalence counts total cases at a specific time, while incidence looks at new cases over a period</p> Signup and view all the answers

    What does the term 'duration of infectious state' refer to?

    <p>The length of time a host can transmit the disease</p> Signup and view all the answers

    What is the primary function of fibrinolysin secreted by Strep pyogenes?

    <p>To break down fibrin barriers around infections</p> Signup and view all the answers

    Which enzyme is specifically involved in gas gangrene and contributes to tissue destruction?

    <p>Collagenase</p> Signup and view all the answers

    What type of immunity includes non-specific protective mechanisms against invading organisms?

    <p>Innate immunity</p> Signup and view all the answers

    Which component of the skin's defenses helps to remove superficial contaminants?

    <p>Desquamation of surface cells</p> Signup and view all the answers

    How does the acidity of sweat contribute to the body's defense mechanisms?

    <p>By inhibiting growth of most pathogens</p> Signup and view all the answers

    Which of the following does NOT describe a mechanical barrier in the body?

    <p>Hydrolytic enzymes in saliva</p> Signup and view all the answers

    What role do lactobacilli play in the vagina's defense mechanisms?

    <p>Maintaining an acidic pH to prevent infections</p> Signup and view all the answers

    Which of the following is a method by which the body decontaminates the skin?

    <p>Mechanical removal of skin cells</p> Signup and view all the answers

    Study Notes

    Factors Affecting Disease Patterns

    • Pathogenicity: Ability of a disease-producing agent (DPA) to cause disease or morbidity.
    • Virulence: Severity of a specific DPA strain.
    • Pathogenicity and Virulence Measurement: Ratio of clinical and subclinical cases, Case mortality.
    • Duration of Infectious State (Period of Communicability): Time during which an infected host can transmit the DPA.
    • Ease of Communicability: Droplets from an infected host within a confined population can cause secondary infections, known as the Secondary Attack Rate (SAR).
    • SAR Calculation: (No. of cases in outbreak - 1ry case(s)) / (Total No. of susceptible animals - 1ry case(s)).

    Measures of Disease Occurrence

    • Prevalence "P": Amount of infected animals in a population at a specific time, regardless of when the infection occurred.
    • Prevalence Calculation: (No. of individuals infected at a particular point in time) / (No. of all individuals in the population at risk).
    • Incidence "I": Number of new cases infected in a population over a specific time period.
    • Cumulative Incidence (CI): Proportion of new cases infected during a specific period compared to the number of healthy individuals at the beginning of that period.
    • CI Calculation: (No. of individuals that become diseased during a particular period of time) / (No. of healthy individuals in that population at the beginning of that period).
    • CI Range: Values between 0 and 1.

    Relationship Between Prevalence and Incidence

    • Prevalence depends on the duration of the disease "D" and the disease incidence "I".
    • Prevalence Equation: P = I x D
    • Incidence Equation: I = P/D.

    Other Measurement Factors

    • Mortality Rate: (No. of dead cases at a given time) / (total No. of animals at risk).
    • Case Fatality Rate: (No. of dead animals at a given time) / (No. of sick animals at the same period).

    Disease Determinants (Causation)

    • Infection: Invasion of a living organism by a DPA.
    • Infectivity: Ability of a DPA to establish itself in a host, measured by ID50 (the amount required to infect 50% of susceptible hosts under experimental conditions).
    • Pathogenicity: Ability of a DPA to produce disease in a susceptible host.
    • Virulence: Severity of a disease in the host, measured by LD50 (the amount required to kill 50% of exposed hosts under experimental conditions).
    • Carrier State: Infected host that transmits a DPA without showing clinical signs.
    • Incubatory Carrier: Infected host that transmits a DPA during the incubation period.
    • Antigenic Variation: DPA can evade host defenses by changing its antigenic characteristics.
    • Incubation Period: Time between infection and the appearance of clinical signs.
    • Prepatent Period: Time between infection and the first detection of the DPA.
    • Period of Communicability: Time during which an infected host can transmit the DPA.

    Etiology of Diseases "Determinants"

    • Diseases can be caused by single or multiple factors.

    Classification of Disease Determinants

    • Primary Causes: Essential for the disease to occur.
      • Intrinsic Factors: Causal agent is part of the host.
        • Hereditary Diseases: Genetically transmitted conditions.
        • Metabolic and Hormonal Diseases: Disruptions in metabolic or hormonal processes.
        • Behavioral Disorders: Abnormal behaviors
      • Extrinsic Factors: Causal agent is not part of the host.
        • Non-living Agents: Physical or chemical agents causing harm.
        • Living Agents: Biological organisms causing disease.
    • Secondary Causes: Non-specific factors that contribute to disease occurrence.
      • Intrinsic Factors: Inherited or acquired host characteristics.
        • Age, Sex, Species, Breed, and Strain: Influence susceptibility to disease.
        • Body Confirmation, Metabolism, Hormonal Balance, State of Nutrition, Degree of Function and Fatigue, Physiological State: Can increase or decrease disease risk.
      • Extrinsic Factors (from 2ry): Environmental factors.
        • Climate and Weather, Animal Management (feeding, stable sanitation, handling, overcrowding, etc.): Impact disease development.

    Host-Parasite Relationship

    • Outcome of an invasion depends on host defenses and DPA pathogenicity/virulence.

    Microbial Factors

    • Pathogenicity: DPA's ability to cause disease.
    • Virulence: DPA's quantitative ability to cause disease, measured by LD50 (the amount required to kill 50% of animals under experimental conditions).

    Virulence Factors

    • Adherence Factors: Structures like pili help DPAs adhere to host cells, initiating infection.
    • Invasiveness: DPA's ability to invade tissues, multiply, and spread. Capsulation, which protects against phagocytosis, is an example.
    • Toxigenicity: DPAs produce toxins that harm host tissues.
      • Exotoxins: Secreted outside the cell and diffuse into the surrounding medium.
      • Endotoxins: Released when bacterial cells die.
    • Production of Certain Enzymes: Enzymes secreted by DPAs can contribute to disease progression.

    Resistance Factors

    • Host protective mechanisms, divided into two categories:

    • Non-specific Protective Mechanisms (1ry defenses) = innate immunity: Operate against most invaders.

      • Mechanical Barriers: Physical barriers preventing entry.
      • Skin: Intact skin prevents most DPAs from entering.
      • Mucous Membranes: Mucous secretions trap and remove invaders.
      • Gastrointestinal Tract (GIT): Secretions and enzymes inactivate pathogens.
      • Vagina: Acidic environment created by lactobacilli inhibits infection.

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    Factors Affecting Disease Patterns PDF

    Description

    Explore the critical factors influencing disease patterns, including pathogenicity, virulence, and the ease of communicability. This quiz also covers measures of disease occurrence such as prevalence and the calculation methods used in epidemiology. Test your understanding of these key concepts in disease dynamics.

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