9- parasitism & disease

Flashcards reviewing parasites, pathogens, and disease models.

What is Antagonism?

An interaction where one species benefits and the other is harmed.

What is parasitism?

Relationship between two species in which one benefits (parasite) at the expense of the other species (host).

What do parasites do?

• Parasites draw resources from host

• Parasitism is usually nonfatal to host

What is a Host?

The species that is harmed in a parasitic relationship.

What are Ectoparasites?

Parasites that live outside their host.

What are Endoparasites?

Parasites that live inside their host and ectoparasites are often vectors for endoparasites

What are Hemiparasites?

Parasites that perform some photosynthesis.

What are Holoparasites?

Parasites that perform no photosynthesis.

The Ecology of Parasites Often Involves Multiple what?

Hosts and Life Stages

What is a Definitive Host?

Host in which a parasite can sexually mature and reproduce

What is an Intermediate Host?

Host in which a parasite can only reproduce asexually.

what do novel or recently introduced parasites do to their hosts?

often fatal to host species

Why are long established pathogens less likely to be fatal to host?

Evolution tends to dampen the negative consequences of parasitism

what can parasitism evolve into?

commensalism (+/0) and mutualism (+/+)

What is a Pathogen?

An organism that causes disease to its host.

What is Infectivity?

The likelihood that an agent will infect a host after exposure.

What is Pathogenicity?

The ability of an agent to cause disease, given infection.

What is Virulence?

A measure of disease severity caused by an agent.

what is the transmission vs. virulence trade off?

• More virulent you are, the less chance for transmission

• Less virulent you are, the more chance for transmission

What is a Host?

An animal or plant that acts as a biological refuge in which another (parasitic) organism may exist.

What is Susceptibility?

An individual's likelihood of becoming infected or developing a disease when exposed to a pathogen.

What are Reservoir Hosts?

Hosts that don't get sick from a parasite but can spread it to others.

What are Amplifying Hosts?

Hosts that allows parasite to replicate quickly.

What are Incidental/Dead-end Hosts?

Hosts that prevent the parasite from completing its development.

how does biodiversity play a role in transmission?

as higher biodiversity increases, then transmission decreases

how does environment play a role in transmission?

favorable conditions outside the host thatcallows the disease to be transmitted

Who are the Susceptible individuals?

Healthy individuals who can catch the disease in the SIR model.

Who are the Infectious individuals?

Sick individuals who can spread the disease to susceptibles in the SIR model.

Who are the Recovered individuals?

Individuals who have recovered and are now (possibly) immune in the SIR model.

What is the Transmission rate (𝛽)?

The likelihood that a contact between a susceptible and an infectious person results in infection.

What is the Recovery rate (𝛾)?

The speed at which infectious individuals recover.

what is dS/dt of the SIR disease model?

rate at which people are leaving the Susceptible (S) group

what is dI/dt of the SIR disease model?

rate of change of infectious individuals (I)

what is dR/dt of the SIR disease model?

rate at which infectious individuals move to the Recovered (R)

What happens when R0 > 1?

The disease will spread (each person infects more than one other person on average).

What happens when R0 < 1?

The disease will die out over time (each person infects less than one other person on average).

What happens when 𝑅0 = 1?

The disease will remain stable (no exponential growth or decline).