Final Flashcards
What do the authors think made COVID-19 relatively unique from SARS-CoV-2?
-The ability of the virus to spread asymptomatically and presymptomatically
-(air travel) which allowed SARS-CoV-2 to have a rapid and global reach
How do you control for infected populations when you cannot tell who’s infected?
Mass testing
What is a disease? What are some possible causes of disease?
Function-impairing conditions that reduces survival or reproduction (fitness), a condition of a host– pathogens, parasites, parasitoids are possible causes of disease
What kinds of organisms and non-living things cause disease?
Bacteria, viruses, protists, fungi, prions, worms, ticks, lice, transmissible tumors
Organisms that are vertically transmitted over time from mother to child usually become what over time?
Mutualists, both organisms get mutual benefit from the relationship and host fitness is increased
Organisms that are horizontally transmitted, highly mobile with the ability to abandon the original host to jump to a new host (in and out of the body), are usually _____?
Parasitic
What are viruses made up of? What is their flow of information?
DNA → RNA → Protein
What do bacterial pathogens/parasites use to allow it to survive in the host? What do they do?
-Bacterial toxins –> secreted and damage tissues
-Antibiotics –> kills bacteria that are not the same species
What does polyphyletic mean? Why are protists polyphyletic?
-includes 2 convergent descendants but not common ancestor
-Protists are a large portion of eukaryotic diversity
-Malaria, Giardia, Amoebic dysentery (all from different ancestors but had convergent evolution)
-Almost anything can become a parasite or a pathogen if it makes sense to its ecology (costs and benefits)
-Malaria are more closely related to algae
What is a macroparasite? Can it make you sick?
-Macroparasites are organisms that have a parasitic life cycle like tapeworms, hookworms, lice, fleas, trematodes
-Macroparasites can make you sick if it overburdens you
more parasites → sick
less parasites → not really sick
What are parasitoids?
Parasitoids are macroparasites, organisms that has young that develop on or within another organism (the host), eventually killing it
How do you calculate R0 from the attack rate?
S(infinity) = e^-R0(attack rate)
-use ln to solve
What is TB caused by?
Bacterium, Mycobacterium tuberculosis
What does it mean when we say TB is in the latent phase?
Some level of TB exists in the person, but not enough to show symptoms or be infectious
How did we achieve lower TB levels in human populations?
-isolating patients
- antibiotics and vaccines
What phylum of organisms make up a large proportion of vectors?
Arthropods
Why are Aedes aegypti such efficient human vectors?
They are anthropophilic (attracted to the smell of humans), they can live in urban habitats near humans, and have high vector competence
What is the main vector that causes yellow fever and dengue to humans?
Aedes aegypti, mosquito that specializes on humans
At what stage of the life cycle does the tick become infected?
larval stage
Explain the difference between bottom-up and top-down control
Bottom-Up: lower trophic levels (eg. primary producers) control the distribution and abundance of higher trophic levels
Top-Down: higher trophic levels (eg. apex predators) control the distribution and abundance of lower trophic levels
One of the tropical neglected diseases is Dracunculiasis, caused by the guinea-worm, an endoparasite. How do we define its transmission?
Trophic Transmission: an intermediate host is consumed by a definitive host, transmitting a pathogen/parasite in the process to the new definitive host
Humans or other hosts can ingest guinea-worm by eating contaminated water or uncooked meat that have the infected copepods in/on the water/meat, these copepods have the guinea-worm inside them
What makes the river prawn different from a usual Lotka–Voltera model?
River prawns are generalist predators, meaning their abundance doesn’t rely on the snail prey abundance. If snail abundance went down, river prawns can still keep their populations at a high equilibrium since they can feed on other prey.
This means they are able to keep the snail densities at a lower equilibrium, indirectly keeping the blood flukes low as well
If prawns were specialist on snails, they might cause their own local extinction by reducing their prey population
Why do we see “damped oscillations” in the measles mathematical model (SEIR)?
Due to births– new babies are added to the population, like new susceptibles, can cause peak of infections
The models of real measles outbreaks do not match this? Why? If you were to draw the seasonality of the factor (that is variable) underneath the outbreaks what would it look like?
Transmission rate of measles is seasonal, which varies much more than birth rates
Transmission rates peak more variably
Birth rates included is also including seasonality of the disease, as birth accumulate (though the outbreak caused by a build up susceptibles causes less of a giant outbreak)
What is a common disease that has seasonality that we go through every year in California?
Influenza “Flu Season”
Seasonality of Influenza characterized by contact rates and climate (humidity), changing R0
What does “seasonal forcing” of influenza refer to?
When the season forces an coordinated outbreak effect by increasing R0
e.g. R0 increases in winter and fall when low humidity occurs and influenza can survive outside host and spread
e.g. R0 decreases in spring and summer when high humidity occurs and influenza cannot survive outside host and cannot spread
Why is it important to use seasonal forcing functions?
There is seasonal variability due to humidity… Beta… the transmission of influenza will better at certain times of the year than others
We need a oscillating function that takes into account variation within the season to predict outbreaks, not a constant
Season and disease relationships are different elsewhere from the US, can you give examples of those?
-In the Sahel region of West Africa, short+wet season, malaria increases because mosquitoes need water to reproduce
-In Hong Kong: after rainy season, shows increase in dengue fever
-n Australia and Papua New Guinea, Ross River Virus depends on just the right amount of water in the season
What are dead end hosts? What is the R0 of a dead end host?
A host that has no subsequent secondary transmission
R0 of a dead end host is zero, 0, as they are not passing on the burden of disease to others
-Dead end hosts still get really sick / die from the disease
Why are bridge vectors important for zoonotic disease, like West Nile Virus?
-Bridge vectors are species that acquire a disease-causing agent from animals and subsequently transmits the agent to humans, they are generalists
-Bridge vectors tend to like to feed off both animal and human populations, they do not specialize on one host, hence they are able to spread the disease across multiple species, causing spillover events
What is an example of a disease that has historically emerged multiple times?
Plagues (bacterium), Bubonic plague
How old is the plague bacterium Yersinia pestis? When did it gain the ability to be transmitted by a vector?
The bacterium gained the ability to be transmitted by arthropod vector when it gained the YMT gene that allows a bacterium to exist within an arthropod body around 3000 BC
-It gained the gene via Horizontal Gene Transfer, which has 4 different possible methods: transformation, transduction, bacterial conjugation, transfection
It is hinted that YMT gene was connected to transposable genes
How can commonality be measured for pathogens’ hosts?
Phylogenetic Distance - an estimate of the evolutionary distance between each pair of organisms (the hosts) which are usually computed from DNA or amino acid sequences
Distance can be calculated via molecular clock
What characteristics of a pathogen make extinction more likely?
Generalist
has enough potential hosts in population to feed off of, will do fine whether or not a particular host population goes extinct (the one you want to conserve)
highly virulent generalist bad
What characteristics of a pathogen make extinction more likely if specialist?
Frequency Dependent Transmission
Not dependent on population size, if low pop, transmission rate will be the same, and infection will continue, extinction risk likely
What characteristics of a pathogen make extinction more likely if generalist?
Alternative reservoir species that experiences low mortality
you’ll always have reservoir species that has potential to spill over into population you wish to conserve
Batrachochytrium dendrobatidis (Bd) (a chytrid fungus) that causes chytridiomycosis severely impacted frog and toad populations, how did we discover the fungus was at fault?
Found a place in America where amphibians unaffected, then waited, and saw the fungus came in and was directly associated with mass mortality in frog populations
Is it possible to save these amphibians from the fungus disease?
Yes, people at UCSB inoculated the frogs with the disease and cured them, building their immunity and rereleasing them into the wild
How will climate change affect avian malaria?
Avian malaria will expand its range to higher elevations, hurting the native birds that use the higher elevations as refuge from the disease
What is a disease that affects bats?
White-Nose Fungus caused by Pseudogymnoascus destructans infects skin of the muzzle, ears, and wings of hibernating bats
When was the fungus first reported to be harming bats? Where did it come from?
-2009 in Upstate New York in Howes Cave started – then spread to North America
-Most likely introduced by humans from Europe or Asia – based on
Why don’t we see it in bats in Florida despite Florida being surrounded by the disease?
-Bats do not hibernate in Florida due to warm weather
Do all bats hibernate? Have those that do not hibernate (non-obligate hibernation) become infected by WNS?
No, not all bats are obligate hibernators, those are the ones that usually aren’t susceptible to WNS.
Facultative hibernators enter hibernation only when either cold-stressed, food-deprived, or both, unlike obligate hibernators, who enter hibernation based on seasonal timing cues rather than as a response to stressors from the environment.
Bats in Florida are non-obligate hibernators, facultative hibernators
For pathogens that spread asymptomatically / presymptomatically, we need a way of detecting them in individuals that don’t show obvious symptoms so that we may act, what are some ways we can do this?
-PCR
-Rapid antigens
