Midterm 2 - Lecture 11 Flashcards
Who coined the term ‘Zoonosis’?
Rudolf Virchow
Zoonosis
- any infectious disease that may be transmitted from animals to man or man to animals
Zooanthroponosis
transmission from man to animal
Anthropozoonosis
transmission from animal to man
What animals with rabies are the most dangerous?
- cats and cows
Definition of ‘emerging infectious diseases’
Diseases of infectious origin whose incidence in humans has increased in the last two decades or threatens to increase in the near future
What are the 3 categories of emerging disease agents?
- Previously known agents in a new geographic location (bad situation)
- known agent presenting in a previously unsusceptible species (naive species)
- previously unknown agent detected for the first time… its been suggested that the agent always been present, just never identified (bad situation)
Why has no effort been made to categorize pathogens in wildlife?
- list would be enormous and lack of knowledge about existing diseases in wildlife
- however, we are getting closer with wildlife so potential for emerging diseases is increasing
What 6 factors impact emerging diseases?
- human demographics and behaviour
- technology and industry (GLOBALIZATION)
- economic land use and development
- international travel and commerce
- microbial adaptation and change
- disruption of public health measures
Disease maintenance
- each new host has to be a source infection for at least one other host to maintain disease in population
Disease propagation
- each new host has to be a source infection for more than one other host to propagate the disease in population
What does disease propagation and magnitude of disease outbreak depend on?
- spatial and temporal factors: population density, time point and duration of contact, host susceptibility, transmissibility of agent and agent virulence and host infectiousness
Spatial components that affect disease propagation and magnitude of outbreak
- distance btw infectious individuals, terrain, soils, vegetation, climate, topography
Temporal components that affect disease propagation and magnitude of outbreak
- the infected host may move across space/distance prior to contact with susceptible individual
What is the causative agent of influenza?
Orthomyxovirus
- likes to mutate = more chances the agent has at invading our immune response
What are the 3 types of influenza?
- Type A (most virulent)
- multiple species - Type B
- humans
- mild symptoms - Type C
- humans and swine
- rare
- mild symptoms
What is the most virulent strain of Influenza?
Type A
How is Influenza A classified?
- on surface antigens
- Hemagglutinin (16 types): these antigens bind the virus to the cell
- Neuraminidase (9 types): these antigens cleave neuraminic acid from mucin allowing viral release from the cell
Low vs High Pathogenic viruses of Influenza A
Low path
- very mild illness in poultry and rarely affect man
- all have the potential to convert into high path influenza viruses
High Path
- high mortality in ducks and poultry and severe to fatal diseases in man
Fowl Plague
- highly infectious
- mortality near 100%; 2-12 days after clinical signs; sudden death
- drop in egg production
- CNS signs and respiratory signs
What is the ‘problem’ with influenza?
- zoonotic-birds and pigs (pigs act as a bioreactor, a ‘vessel for mutation’)
- avian influenza binds to swine glycosides; swine generate a poor antibody response
- humans and pigs have similar internal protein genes and human influenza easily infects pigs
= swine viruses are both avian-like and human-like
What are among the most important public health risks facing humanity?
- emerging zoonotic diseases
