Infection Transmission and Maintenance

Transmission and Maintenance of Infection

• Horizontal Transmission - Transfer of an infectious agent from one infected individual to another
  • Types of Hosts:
    • Definitive host: The host in which the infectious agent undergoes either sexual reproduction or a critical developmental stage in its life cycle.
    • Intermediate host: A host that harbors an infectious agent for a period and makes it more readily available to a definitive host.
    • Paratenic host: A host that does not have a significant role in the infectious agent’s survival but in which the agent may be ingested, remain dormant, and be passed to another host.
  • Factors influencing the spread of infection:
    • Infectious agent: Virulence, infectivity, and survival outside the host
    • Host: Immunity, age, and susceptibility
    • Environment: Temperature, humidity, and presence of vectors
  • Routes of infection:
    • Direct contact: Skin-to-skin or mucous membrane contact
    • Indirect contact: Touching contaminated objects
    • Inhalation: Breathing in contaminated air
    • Ingestion: Consuming contaminated food or water
    • Vector-borne: Transmission through a living organism, such as mosquitos, ticks, or fleas
• Vertical Transmission: Transfer of an infectious agent from an infected parent(s) to their offspring
  • Types:
    • Transplacental: Transmission across the placenta during pregnancy
    • Transmammary: Transmission through breast milk
    • Transovarian: Transmission through the egg from parent to offspring
  • Immunological status and vertical transmission: Maternal immunity is passed to offspring during vertical transmission, offering initial protection
    • Transovarial and trans-stadial transmission in arthropods: Transmission of infectious agents through the eggs and from one developmental stage to another in arthropod vectors
• Maintenance of Infection: Survival and persistence of an infectious agent within a population
  • Hazards to infectious agents: Environmental factors, such as UV light, desiccation, and temperature fluctuations, that threaten survival
  • Maintenance strategies:
    • Reservoirs: Hosts that harbor and transmit the infectious agent without displaying clinical disease
    • Carriers: Individuals who harbor and can transmit an infectious agent but may or may not be showing clinical signs.
    • Zoonotic diseases: Diseases transmitted from animals to humans
    • Reverse zoonoses: Diseases transmitted from humans to animals

Skill-building Activities

• African swine fever:

  • Horizontal Transmission: Direct contact with infected pigs, contaminated pork products, and fomites
  • Vertical Transmission: NOT POSSIBLE

• Anthrax:

  • Horizontal Transmission: Ingestion of contaminated feed or water, inhalation of spores, direct contact with infected animals or their carcasses
  • Vertical Transmission: NOT POSSIBLE

• Aujeszky's disease:

  • Horizontal Transmission: Direct contact with infected pigs, contaminated feed or water, or respiratory secretions
  • Vertical Transmission: Transplacental and transmammary

• Bluetongue:

  • Horizontal Transmission: Vector-borne transmission (through biting insects, primarily midges of the Culicoides genus)
  • Vertical Transmission: Transplacental

• Brucellosis (Brucella abortus):

  • Horizontal Transmission: Direct contact with infected animals, inhalation of contaminated material, or consumption of contaminated milk and dairy products
  • Vertical Transmission: Transplacental and transmammary

• Classical swine fever:

  • Hospital Transmission: Direct contact with infected pigs, contaminated feed or water, or contact with infected secretions or excretions
  • Vertical Transmission: Transplacental

• Highly pathogenic avian influenza:

  • Horizontal transmission: Inhalation, direct contact, contact with contaminated feed or water
  • Vertical Transmission: NOT POSSIBLE

• Infectious bursal disease (Gumboro disease):

  • Horizontal Transmission: Contact with infected birds or their excretions, through contaminated feed, water, or equipment
  • Vertical Transmission: Transovarian

• Japanese encephalitis:

  • Horizontal Transmission: Vector-borne transmission (through the bite of infected mosquitoes)
  • Vertical Transmission: NOT POSSIBLE

• Newcastle disease:

  • Horizontal Transmission: Contact with infected birds, contaminated feed, or water, or inhalation of contaminated aerosols
  • Vertical Transmission: Transovarian

• Pullorum disease:

  • Horizontal Transmission: Contact with infected birds, contaminated feed, or water
  • Vertical Transmission: Transovarian and transmammary

• Rabies:

  • Horizontal Transmission: Bite or scratch from an infected animal, contact with saliva from an infected animal, ingestion of infected tissue
  • Vertical Transmission: Transplacental transmission is possible in some species, but rabies is not typically transmitted vertically

• Surra (Trypanosoma evansi):

  • Horizontal Transmission: Vector-borne transmission (through the bite of infected tsetse flies, horseflies, and other biting insects)
  • Vertical Transmission: Transplacental

• Transmissible gastroenteritis:

  • Horizontal Transmission: Direct contact with infected pigs, contaminated feed or water
  • Vertical Transmission: Transplacental and transmammary

• Trichinellosis:

  • Horizontal Transmission: Ingestion of undercooked or raw meat from infected animals, particularly pork, wild game, and bear
  • Vertical Transmission: NOT POSSIBLE

Explore the mechanisms of horizontal transmission of infectious agents and the roles of various host types. This quiz covers factors influencing the spread of infection, including the characteristics of infectious agents, host immunity, and environmental conditions. Challenge your understanding of infection routes and host interactions.