lec 31: ecology of disease emergence Flashcards
what is the Epidemiogical Triad
Here to remind us how things interact
Agent (disease pathogen)
Host ( that it occupies, could be more than one type)
Environment ( that mediates the interaction)
Vector (that allows the agent to infect a host (if needed) through a third party) i.e a mosquito
Burmese python and diseases in florida
Florida has a major pet industry, (exotic pets)
these animals escape
Burmese python escaped and got in the Everglades
an area with a high diversity of mammals
the pythons have been reducing that diversity
it is a generalist predator, nothing like it in the area so no top-down control,
it kills all kinds of mammals (mammals are important here because their disease can impact us as well, since we also are mammals)
mosquitos are around and can move in between mammals they would take meals from around 70% of mammals
The hispid cotton rat!
carries dangerous virus to humans
Before: mosquitos would only take a rat meal 15%
Now: its 77% of its meal!
the host diversity has been reduced! and human health risk is now higher !
what are zoonoses (zoonotics)
diseases and infections of vertebrate animals that can be transmitted to humans
what are some ways humans can be exposed to zoonotics?
- through a disease vector like a mosquito
- close contact (ie eating)
What is zoonotic spillover, and what is the hypothesis for it in Africa (fruit bats)?
jump between non-human mammal diseases to humans
Africa hypothesis: Loss of forest cover and consumption of bushmeat drive contact between humans and wild hosts, leading to infections
Fruit bats and zoonotic spillover in Africa
fruit bats carry a bunch of diseases
they live deep in the forest
loss of forest leads them out (more contact), AND they are part of the bushmeat trade (rural Africa)
what is bushmeat ?
meat of wild animals captured in forested areas are brought to urban areas for sale
This is a major trade for rural habitants
what is a consequence of forest fragmentation?
Increases edge of contact between humans and wild reservoirs of new pathogens (example : the Nipah virus)
Nipah virus (Malaysia)
high mortality rate in pig farmers
occurred in areas converted to pig farms that were near forests
fruit orchards on the farm attracted bats
exposing the pigs to bat poop
originally mistaken as a mosquito borne disease
movement of infected pigs caused the virus to spread
What is an influenza virus
a flu virus has an outer membrane made of H and N enzymes
these help the virus attach itself to and break in and out of host cells
there are different types of H and N, particular for each virus
how does an immune response work
H and N are antigens and ttrigger and immune response (antibodies) by the host
a person’s immmunity to these antigens reduces (1) probality of infection and (2) severity of the disease
mutations in viruses can create strains that infect large numbers of people
what are the 2 ways to get new viruses?
- Antigenic drift
- Antigenic shift
what is an antigenic drift?
point mutations cause small changes in the surface antigens (H,N)
these can lead to regional epidemics in populations that have no previous exposure
what is an antigenic shift?
“genetic reassortment” the whole HN combination changes
can happen when a bunch of different viruses attack one cell
a mix-and-match
Very worrying!
produces novel flu strains and can cause pandemics!
-what does SARS stand for (coronavirus)
Severe Acute Respiratory Syndrome
