Intro to Zoonotic Disease Flashcards
What is zoonoses?
any disease or infection that is natrually transmissible from nonhuman vertebrates to humans or vice-versa
What is zooanthroponosis? Give three examples
human to animal transmission
e.g. amebiasis to dogs, TB, ascaris
What is anthrozoonosis? Give three examples
animal to human transmission
e.g. rabies, brucellosis, ascaris
What are three methods of transmision of zoonotic diseases?
- direct contact (animals-animals; animals-humans)
- environmental transmission (contaminated food and water)
- vectors
What is pathogenicity?
very binary term - ability of an organism to cause disease
What is infectivity?
The likelihood that an agent will infect a host, given that the host is exposed to the agent
What is virulence?
Degree of disesase caused - depends on host-pathogen interactions
What is an epidemic?
a widespread outbreak of an infectious disease; many poeple are infected at the same time
What are 5 features of a pandemic?
A large epidemic with:
- wide geographical extension
- significant transmission –> disease movement and extension of geographic range
- highly contagious and short incubation times –> increased attack rate and explosive spread of symptomatic disease
- minimal population immunity –> disease spread
- often severe (fatal)
Describe herd immunity
- vaccination/natural immunity of a portion of the population (or herd) provides protection to unvax/non-immune individuals
- the more immune individuals present in a population the less likely that a susceptible person will come into contact with an infected individual
What is a host?
organism that harbors a pathogen
What is a primary host?
critical to the life cycle of the pathogen
What is a dead end host?
pathogen cannot be transmitted from this host
What is a reservoir? What is the significance of reservoirs? What do reservoirs differ from?
- animals or inanimate sources harboring disease-causing organisms
- serve as potential sources of disease outbreaks
- differ from carries, amplifiers (agents of disease transmission)
What is a vector?
an orgnaisms, often an invertebrate arthropod, that transmits a pathogen from reservoir –> host
What is morbidity?
illness/clinical disease
What is mortality?
Death
What is prevelance?
total number of cases of the disease in the population at a given time
What is incidence? How do you calculate it?
a measure of the risk of developing some new condition within a specified period of time
incidence = (new cases)/(population x time-frame)
What is the species barrier effect ?
Barrier between two different species
What is a complete barrier?
no transmission
What is a partial barrier?
transmission after long period of time or transmission in the absence of disease
What is adaptation/selection?
the ability of an agent to “evolve” in a new host
What are serial passages?
pathogen modified during passage to adapt to new hosts
What are some old vs new zoontotic diseases?
old = malaria, HIV-1
new = ebola, MERS, influenza strains, zika, COVID-19
Describe the 5 different stages of zoonotic diseases and give an example for each stage
- the pathogen is present in animals, but it doesn’t infect humans under natural conditions (e.g. feline distemper)
- the pathogen can be transmitted from animals –> humans, but cannot spread human –> human (e.g. Nipha virus)
- the pathogen can be transmitted from animals –> humans and can pass between humans; however, the pathgoen is not well adapted to human and the pathogen will die out after a few cycles of transmission (e.g. ebola virus)
- the pathogen can be transmitted from animals to humans and can pass between humans; it can adapt to living in humans for long periods of time without going back to animal hosts (e.g. cholera)
- a pathogen exclusively infects humans; the pathogen may have co-evolved with humans or colonized humans recently and evolved into a specialized human pathogen (e.g. HIV)
What are three modes in which an infectious disease can be defined as “emerging”? Give an example for each mode
- a new agents appears in a new geographic area (e.g. avian influenza, HIV-1, SARS, H1N1)
- a known agent or its close relative affects a new host species (e.g. MRSA, TB, chloroquine resistant malaria, HIV-1, SARS)
- a known pathogen that increases incidence (e.g. lyme disease)
What is an endemic zoonotic? What are they often? Why do they become endemic?
- present in a population for centuries to millennia
- often neglected diseases
- occasionally occur as epidemics
- become endemic/chronic due to societal effects
Bioterrorism
Define Class A (highest risk) agents/characteristics, give examples
- can easily be disseminated or transmitted from person –> person
- result in high mortality rates and have the potential for major public health impacts
- might cause public panic and social disruption
- require special action for public health preparedness
- e.g. anthrax, botulism, plague, tularemia, ebola
Bioterrorism
Define Class B (moderate risk) agents/characteristics, give examples
- moderately easy to disseminate
- result in moderate morbidity rates and lower mortality rates
- require specific enhancements of CDC’s diagnostic capacity and enhanced disease surveillance
- e.g. salmonella, camplyobacter, pathogenic E coli, WNV, brucella, giardia
Give a few examples of infectious disease that cause chronic illness
- h pylori –> peptic ulcers and cancer
- HPV –> cervical cancer
- M. pneumoniae –> chronic asthma
What are 5 factors that affect disease transmission
- disease agent
- vertebrate hosts
- vectors
- environment
- climate change
Why are birds and bats good vertebrate hosts for diseases?
they are quite mobile, live around humans, and there are lots of species
How can serological tests help determine a diseases reservoir host?
If Abs against the agent are present, then this can implicate them as the reservoir, but could be an intermediate
What is the dilution effect?
Normal conditions: high biodiversity, fewer reservoirs in a community –> fewer infected vectors –> fewer human infections
Dilution: low biodiversity, more reservoirs in a community –> more infected vectors –> more human infections
What are three sources of human exposure to zoonotic diseases?
- movement of animals
- ecological disruption
- bioterrorism
How is animal movement a source of human exposure to zoonotic diseases?
- livestock and poultry - high quantities of meat/products move between countries
- exotic animals - pet trade, reptiles, zoo animals, wildlife
How is ecological disruption a source of human exposure to zoonotic diseases?
humans encroaching on a new habitat
Why are some disease under-diagnosed?
- pockets of infection
- shared symptoms
- diagnosis is complex or lack of inexpensive diagnostic tests
- education of pts, MDs, vets
Why are impovrished people more likely to contract a zoonotic disease?
- occupational
- food safety
What are 3 ways to surveil zoonotic diseases?
- molecular biology tools - PCR and rapid genome sequencing
- one health - doctors and vets
- international monitoring
