Disease Transmission Methods
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Questions and Answers

Which mode of disease transmission involves physical contact between individuals?

  • Airborne transmission through droplets.
  • Vector transmission via insects.
  • Direct transmission via kissing. (correct)
  • Waterborne transmission through contaminated water.

A patient contracts an illness after touching a contaminated doorknob. Which type of indirect transmission is most likely responsible?

  • Waterborne transmission
  • Vehicle transmission involving fomites (correct)
  • Airborne transmission
  • Vector transmission involving insects

Why are droplets from coughing or sneezing not considered airborne for long periods?

  • They are too large and heavy, causing them to settle quickly. (correct)
  • They are destroyed by ultraviolet radiation.
  • They quickly evaporate in the air.
  • They are too small to remain suspended in the air.

Which characteristic is essential for a microbe to be effectively transmitted through the airborne route?

<p>Resistance to drying and ability to survive outside the body. (D)</p> Signup and view all the answers

What is the primary source of contamination in waterborne disease transmission?

<p>Animal or human excreta (C)</p> Signup and view all the answers

Which of the following is the correct sequence of events in the chain of transmission?

<p>Agent → Reservoir → Exit → Mode of Transmission → Portal of Entry → Susceptible Host (D)</p> Signup and view all the answers

Which of the following diseases is primarily transmitted through insect vectors?

<p>Malaria (C)</p> Signup and view all the answers

A patient develops a skin infection after using a shared towel in a gym. This is an example of what type of transmission?

<p>Indirect horizontal transmission (D)</p> Signup and view all the answers

Insects contribute to the global burden of disease by acting as vectors. Approximately what percentage of the global disease burden is attributable to insects?

<p>4.1% (D)</p> Signup and view all the answers

Which of Koch's postulates is most difficult to fulfill when studying a disease caused by a virus that only infects humans?

<p>The cultured microorganism should cause disease when introduced into a healthy organism. (B)</p> Signup and view all the answers

How do mosquitoes transmit diseases to humans?

<p>Through saliva when withdrawing blood. (A)</p> Signup and view all the answers

A pregnant woman passes antibodies to her fetus through the placenta. This is an example of what type of immunity and transmission?

<p>Passive immunity via vertical transmission (C)</p> Signup and view all the answers

A hospital observes a spike in infections caused by antibiotic-resistant bacteria. Analyzing the 'chain of transmission,' which intervention would likely be MOST effective in breaking the chain and reducing the infection rate?

<p>Improving hand hygiene practices among healthcare workers. (B)</p> Signup and view all the answers

Contaminated soil can be a source of various infections. Which of the following diseases can be contracted through contact with soil?

<p>Tetanus (B)</p> Signup and view all the answers

Which characteristic of certain insects makes them efficient vectors of human parasites?

<p>Their filthy breeding habits and indiscriminate travel between filth and food. (B)</p> Signup and view all the answers

Considering the characteristics that enable a pathogen to persist, which factor would MOST influence a pathogen's ability to 'survive transmission in the environment'?

<p>Its resistance to desiccation and UV radiation. (D)</p> Signup and view all the answers

Besides mosquitoes, which route of transmission is commonly associated with the spread of diseases that affect the digestive system?

<p>Food and faecal-oral transmission (D)</p> Signup and view all the answers

During an outbreak of foodborne illness traced to a contaminated batch of spinach, which step in the transmission chain would be the MOST effective target for intervention to prevent further spread?

<p>Interrupting the mode of transmission. (A)</p> Signup and view all the answers

A new disease emerges with a high mortality rate. Scientists discover the pathogen can be transmitted through mosquito bites. Public health officials implement mosquito control measures. Which component of the 'chain of transmission' are these measures targeting?

<p>Mode of transmission (C)</p> Signup and view all the answers

An individual contracts salmonella after consuming contaminated food prepared by a cook who did not wash their hands properly. What type of transmission is this?

<p>Food and faecal-oral transmission (D)</p> Signup and view all the answers

An increase of which of these diseases would likely follow a period of heavy rainfall and flooding, particularly in areas with poor sanitation?

<p>Typhoid (B)</p> Signup and view all the answers

Which bodily fluid contains a balanced microflora that can act as a medium for transmission of organisms from host to host?

<p>Saliva (D)</p> Signup and view all the answers

Which of the following is the primary function of the mucociliary escalator in defending against disease?

<p>Trapping microbes in mucus and removing them from the lungs. (A)</p> Signup and view all the answers

How does gingival crevicular fluid contribute to the body's defense against infection?

<p>By acting as an antibacterial solution and containing immunological defense mechanisms. (C)</p> Signup and view all the answers

What is the main function of the blood-brain barrier?

<p>To filter out proteins, toxins, and most micro-organisms from entering the brain and spinal cord. (A)</p> Signup and view all the answers

Which bodily defense is MOST compromised in the alimentary and respiratory tracts and the eyes, compared to skin?

<p>The presence of a tough, keratinized outer layer. (D)</p> Signup and view all the answers

How does the immune system distinguish between the body's own tissues and foreign substances?

<p>By recognizing specific molecules on the surface of cells called antigens. (D)</p> Signup and view all the answers

What is the role of memory cells produced by B lymphocytes?

<p>To provide a faster and more effective immune response upon subsequent encounters with the same antigen. (A)</p> Signup and view all the answers

Acutely inflamed gingival tissue can lead to increased flow of what protective substance?

<p>Gingival crevicular fluid (C)</p> Signup and view all the answers

The washing/flushing action of which bodily fluid helps prevent infection?

<p>Blood (D)</p> Signup and view all the answers

What is the primary function of T lymphocytes in the immune response?

<p>Controlling immune responses and directly destroying antigens. (A)</p> Signup and view all the answers

Which type of T-lymphocyte is responsible for directly destroying virus-infected cells?

<p>Killer cells (B)</p> Signup and view all the answers

What is the primary function of helper T-cells in the immune response?

<p>Activating B-lymphocytes to produce antibodies (A)</p> Signup and view all the answers

Which of the following best describes the role of suppressor T-cells?

<p>Turning off the immune response (B)</p> Signup and view all the answers

A patient is injected with ready-made antibodies to combat hepatitis B exposure. What type of immunity is this an example of?

<p>Passive immunity (D)</p> Signup and view all the answers

Which of the following is an example of active or natural immunity?

<p>Subclinical infection (C)</p> Signup and view all the answers

Flashcards

Koch's Postulates

A set of principles establishing criteria for proving that a specific organism causes a particular disease.

Chain of Transmission

The infectious agent, reservoir, exit route, means of transmission, entry point, and a susceptible host.

Agent (in Transmission)

The specific microbe that causes an infectious disease.

Reservoir (of Infection)

The place where the infectious agent lives and multiplies.

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Horizontal Transmission

Person to person spread of disease.

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Vertical Transmission

Spread of disease from mother to child.

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Direct Transmission

A type of transmission involving immediate and direct transfer of a pathogen.

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Indirect Transmission

A type of transmission where the pathogen is transferred via an intermediate object/route.

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Fomites

Inanimate objects that can transmit disease.

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Droplet Transmission

Infectious agents spread through coughing or sneezing.

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Airborne Transmission

Infectious agents remain suspended in the air for extended times.

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Killer T-cells

Lymphocytes which cause lysis of target cells, destroying virus-infected or cancerous cells.

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Helper T-cells

Lymphocytes which activate B-lymphocytes to produce antibodies.

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Suppressor T-cells

Lymphocytes which turn off the immune response, like antibody production.

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Phagocytosis

The process where polymorphonuclear leucocytes (a type of white blood cell) engulf and digest micro-organisms to fight infection.

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Passive/Artificial Immunity

Immunity developed by receiving ready-made antibodies, providing immediate but temporary protection.

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Insect-borne infections

Infections transmitted by insects feeding, biting, or through faeces/secretions.

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Mosquito

Vector for diseases like malaria, West Nile virus, dengue fever, and yellow fever.

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Food/faecal-oral transmission

Infections transmitted via contaminated food or water, often affecting the digestive system.

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Blood/body fluid transmission

Infections spread through contact with infected blood or body fluids.

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Soil-borne infections

Infections arising from contact with contaminated soil.

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Surface transmission

Disease spread through physical contact with food surfaces, or individuals.

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Typhoid transmission

Typhoid is passed on when the insects feed or bite.

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Bloodborne Pathogen Transmission

Spread through skin breaks, like needlestick injuries. Important for DCPs.

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Sexual Transmission

Spread via genital, oral, or anal contact. Examples include chlamydia and HIV.

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Saliva Transmission

Contains bacteria, fungi, and viruses. Can transmit infections through kissing or contaminated objects.

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Disease Defense

The body's defense is categorized by preventing entry and dealing with entry.

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Mucociliary Escalator

Respiratory tract lining with mucus and cilia that traps and removes microbes.

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Skin Defense

Glands secrete fatty acids and lysozyme, substances that kill bacteria on the skin.

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Gingival Crevicular Fluid

Fluid in the gingival crevice with immunological defense mechanisms.

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Blood-Brain Barrier

Filter protecting the brain and spinal cord from toxins and most microorganisms.

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Immune System

Recognizes and destroys foreign substances (antigens).

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Lymphocytes

White blood cells that circulate in the lymphatic system; include B and T cells.

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Study Notes

  • The session aims to enable students to explain Koch's postulates, detail the chain of transmission, define immunity classifications, and describe direct/indirect transmission mechanisms

Koch's Postulates

  • These postulates establish the etiologic relationship between a microorganism and a disease
  • The microorganism must be observed in every instance of the disease
  • It should be isolated and cultured in a pure form
  • When introduced into animals, the pure culture must cause the disease
  • The microorganism must then be re-isolated from the diseased animal

Transmission of Disease

  • Pathogens must be able to leave an infected host, survive transmission, enter a susceptible host, and develop/multiply in the new host to persist
  • This occurs through en mass and 1-2-1 transmission

Transmission Chain

  • The spread of infection requires an agent, a reservoir, an exit route, a mode of transmission, a portal of entry, and a susceptible host

Classifying Transmission

  • Transmission is classified as horizontal or vertical, and direct or indirect
  • Horizontal transmission is person to person
  • Vertical transmission is mother to child

Direct and Indirect Transmission

  • Direct transmission involves physical contact like kissing, touching, or sexual contact
  • Indirect transmission occurs through a vehicle (air, water, food) or a vector

Indirect Transmission Vehicles

  • Airborne transmission involves infectious agents in droplets from respiratory secretions
  • Droplets containing microbes remain suspended and can enter the respiratory tract
  • Waterborne transmission relates to water contaminated by excreta, which can cause infections during hygiene activities
  • Insects pass infections through insect feces or secretions
  • Soil can transmit infections like tetanus and intestinal worms
  • Food can transmit organisms that infect the digestive system
  • Fomites include, for example, keyboards, phones, bedding, etc

Indirect Transmission Vectors

  • Vector disease transmission occurs through mechanical or biological methods
  • For example, mosquitoes transfer disease through saliva
  • Mechanical vector disease transmission means pathogens are on the body of vectors and passed on to new hosts
  • Biological vector disease transmission means pathogens reproduce within a biological vector and infect the new host

Blood and Body Fluids

  • Some infections spread when blood/fluids from an infected person contact mucous membranes/bloodstream of someone uninfected

Saliva

  • It contains a microflora, along with fungi and viruses
  • Some infection spread by direct contact (kissing) or indirect contact (sharing toys)

Defence Against Disease

  • Defence against disease is divided into preventing ingress and dealing with ingress

Preventing Ingress

  • Ways to protect the host from the ingress of disease are tears, gingival crevicular fluid, stomach acid, blood brain barrier, saliva, mucociliary escalator, skin, blood, sweat and scabs

Mucociliary Escalator and Skin

  • The respiratory tract has mucus and cilia that trap and remove microbes
  • Skin has a keratinized outer layer whereas mucosal layers do not

Fatty Acids, Salts, Saliva, Gingival Crevicular Fluid, and Blood

  • Fats, salts, and lysozymes in sweat help destroy bacteria
  • Saliva contains antibacterial agents
  • Gingival crevicular fluid is an antibacterial solution
  • Blood entry through wounds poses a major infection risk, but blood flow and clotting can prevent it

Blood Brain Barrier

  • It is specialized filter that surrounds the brain and spinal cord
  • It prevents proteins, toxins, and microorganisms from entering, while allowing glucose through

Dealing with Ingress

  • Immune response and variable response

Immune System

  • It recognizes and destroys substances and organisms
  • It can distinguish tissues from outside elements called antigens
  • Through cells, it can destroy those enemy antigens
  • It also remembers encountered antigens for a faster response next time

Lymphocytes

  • These develop in bone marrow
  • These circulate throughout the body in the lymphatic system
  • They are divided into B and T lymphocytes
  • B lymphocytes operate through antibodies
  • B lymphocytes create humoral immune response
  • When a foreign antigen enters the blood, B-lymphocytes divide rapidly via mitosis to form a clone of plasma cells
  • B cell products include new antibodies and also "memory cells"
  • T lymphocytes control the immune response by directly destroying antigens
  • Killer cells, helper cells and suppressor cells achieve this

Phagocytosis

  • Polymorphonuclear leucocytes carry this out
  • Micro-organisms are invaded and cells phagocytose them
  • This results in a quick invasion resolution

Immunity

  • This is acquired through genetics or environmental factors to protect the host
  • Natural immunity is inherited from the parent
  • Acquired immunity is gained throughout life in response to diseases

Acquired Immunity

  • Active or Natural immunity is long lasting and developed through subclinical infections
  • Passive or Artificial develops ready made antibodies to develop immunity, that are then injected into the body

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Transmission of Disease - Biomedical & Dental Science - PDF

Description

Explore modes of disease transmission including direct contact, indirect contact, airborne, waterborne, and vector-borne routes. Learn about chain of transmission and Koch's postulates. Understand how diseases spread and methods to prevent it.

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