S1 - Disease Ecology and Emerging Diseases

Question 1

Define ecology.

Answer 1

The study of factors influencing the abundance and distribution of organisms

Question 2

Define competition and cooperation.

Answer 2

Competition - Driving force of natural selection (Remember viruses damaging each other and competing for resources) Cooperation - Differing species working together to benefit all species involved (Remember biofilms)

Question 3

What is a biofilm?

What is quorum sensing?

Answer 3

A biofilm is a collection of bacteria cooperating and working together. Biofilms often form on hospital catheters / instruments and are responsible for many nosocomial infections

Quorum sensing is the cell-to-cell communication that regulates the density of bacteria growth so they can share resources.

Question 4

What is a habitat?

Answer 4

The physical area a species inhabits

Question 5

What is an ecological niche?

Answer 5

The habitat + behaviors of a particular species

Question 6

How many species can occupy the same ecological niche?

Answer 6

Only 1. Either one species will evolve to separate the niches, or one will out-compete the other, resulting in its extinction.

Question 7

How does climate change affect ecology (Particularly disease dynamics)?

Answer 7

1) Warming can cause a shift in timing, where epidemic peak may occur at a different time of year than it did in the past 2) Warming can cause more epidemic “cycles”, meaning that there may be two epidemic peaks in the same year 3) Warming can cause overall epidemic intensity to either increase or decrease, depending on whether the pathogen can well-tolerate the new climate.

Question 8

What is it mean for a disease to be zoonotic?

Answer 8

A zoonotic disease is a disease that has its origins in a species other than humans (This includes vector-borne diseases as well as direct zoonotic diseases)

Question 9

What does it mean for a disease to be frequency-dependent?

Answer 9

Transmission rates increase with the number of infectious people, but it doesn’t matter how geographically dense they are. (I.e. STDs and some vector-borne diseases)

Question 10

What does it mean for a disease to be density-dependent?

Answer 10

Transmission rates increase with population density of the host. (E.g. influenza)

Question 11

What is it called when an area has everything necessary for disease to spread (Pathogen, climate, resources, etc.), but humans don’t inhabit the area?

Answer 11

A silent zone

Question 12

What happens when a large population enters a silent zone?

Answer 12

There will be an epidemic

Question 13

What are the principal modes of transmission? (8) PAAWSFFF

Answer 13

Perinatal Airborne Animal bites Water-borne Sexual Fecal-oral Fomite Food-borne

Question 14

What is the name of this type of zoonotic transmission cycle?

Human –> Human –> Human

Answer 14

Direct human-to-human

(E.g. influenza)

Question 15

What is the zoonotic transmission cycle in which a disease principally found in animals is passed to a human (Who does not pass it to other humans)?

Answer 15

Direct zoonosis

(E.g. rabies)

Question 16

What is the zoonotic transmission cycle if the disease can only be passed from human to human via an insect or animal?

Answer 16

Vector-borne

(E.g. malaria)

Question 17

If a disease can only be passed to humans from animals via a vector, what is the zoonotic transmission cycle?

Answer 17

Vectored zoonosis

(E.g. encephalitis)

Question 18

(Here’s the trickiest one)

If a disease can only be passed to humans from animals via a vector, and then it is transmitted from human to human via a vector, what is the zoonotic transmission cycle?

Answer 18

Anthropo-zoonosis

(E.g. yellow fever)

Question 19

What is a reservoir?

Answer 19

A host species for a viral disease that does not usually become seriously ill from the disease

Question 20

What are some examples of common reservoirs?

Answer 20

Bats, mice, and birds

Question 21

What is the term that describes the transference of a disease from one species to another?

Answer 21

A spillover event

Question 22

How does biodiversity protect us from disease?

Answer 22

The greater the number of species in a given area, the fewer interactions humans are likely to have with a particular disease-carrying species (Remember the Lyme disease example). This is called the dilution effect.

Question 23

What is disease emergence?

Answer 23

The process by which a disease gains strength in the general population following a spillover event

Question 24

Are deer ticks born with Lyme disease?

Where do they typically get it?

Answer 24

No.

Usually, they get Lyme disease from their first blood meal (If the meal is infected, as white-footed mice often are).

Question 25

Describe the life cycle of a tick.

Answer 25

Uninfected larva hatch in late Summer –>

The feed on a (possibly) infected small animal –>

They molt and become nymphs till the end of Winter –>

In Spring/Summer/Fall they feed on vertebrates –>

Ticks that feed on deer mate and lay eggs