Disease Reservoir and Pathogen Transmission Flashcards
Chain of transmission
Infectious Agent Reservoir Portal of exit Mode of transmission Portal of entry Susceptible host
Chain of Infection
Reservoir Agent Mode of transmission Susceptible host (portal of entry, portal of exit) Transmission
Exposure
Introduction of a new pathogen into a susceptible population
Transmission
Adoption, establishment, and dissemination in the susceptible population. Requires a pathogen that can adapt to, and transmit between, these hosts
Reservoir
Habitat or populations in which an infectious agent normally lives, grows and multiplies
Maintain pathogens over time
Different strategies to survive in the reservoir
Animal Reservoir. Remember:
Reservoir does not mean ill
An individual can be killed by the agent but the population maintains the agent
If asymptomatic: then we consider carrier
Not all sick animals are reservoirs
Exposure and Transmission
Reservoir population Exposure Susceptible population Transmission Disease epidemic
Reservoir Examples Measles Feline Leukemia Rabies Leptosspirosis
Humans
Cats
Multiple
Rodents
Portal of exit
The method the pathogen uses to leave the body of the host
Portal of exit examples
Saliva Blood Feces Urine Vaginal secretion
Vertical Tranmission
Infection at fecundation and transplacental
Infection at fecundation
virus can attach to spermatozoa or oocyte
Transplacental
Infection in utero
Vertical transmission: transmission to eggs
Transmission of the pathogen agent during the egg development
Salmonella enterica Serovar pullorum
Mycoplasma
Vertical transmission: perinatal
At parturition (HIV) Through the colostrum/milk
Vertical Transmission: transovarial
Passage of pathogen from the adult female to eggs through the ovaries of an arthropod
Transstadial Transmission
Another transmission in arthropods is called transstadial transmission
Horizontal transmission: Direct
Directly from the reservoir to a susceptible host
limited space
Without intermediary
short time period
Horizontal transmission: Indirect
via any sort of intermediary, animate, or inanimate
Distance
intermediary
longer time period
Direct by contact
skin and mucous membrane
Direct by air
Direct projection (droplet spread): wet, large, and short range aerosoles Airborne: considered to be a form of direct transmission because disease agents do not generally survive for extended periods within aerosolized particles Waterborne (for aquatic animals only): through gills
Indirect: Vehicle
An inanimate object which serves to communicate disease
Water, food, soil
Fomite: object that can be contaminated and transmit disease on a limited scale
Indirect: vector
Arthropods who carry and transmit pathogens
Mechanical Vector
An animal that carries a pathogen from one host to another without being infected itself
