Lecture 1 - Disease Ecology/Intro

What is an infectious disease?

A disease caused by a pathogen that can be transmitted between hosts.

What is the difference between infection and disease?

Infection means a pathogen is present in a host. Disease refers to the negative effects or symptoms caused by the infection.

Why is disease ecology important?

It examines how interactions among hosts, pathogens, environments, and populations determine disease transmission and impacts.

What are the three major components to consider when studying disease?

The host, the pathogen/parasite, and the environment.

What is a pathogen?

An organism or infectious agent that can cause disease in a host.

What is a parasite?

An organism that lives in or on a host and obtains resources from that host, generally harming the host.

What is a microparasite + characteristics?

A parasite that multiplies within its host, usually has a short generation time, lacks specialized infective stages, and often causes transient infections.

What is a macroparasite?

A parasite that generally does not multiply rapidly within the host and whose abundance/intensity within individual hosts is important to disease impact.

What is the major ecological difference between microparasites and macroparasites?

Microparasite impact is often related to the proportion of hosts infected, whereas macroparasite impact is often related to how many parasites individual hosts carry.

Why is prevalence especially important for microparasites?

Microparasites multiply within hosts and disease impact is often related to the proportion of the population that is infected.

Why is parasite intensity especially important for macroparasites?

Macroparasite effects often depend on the number of parasites within each host rather than simply whether a host is infected.

What is a parasitoid?

An organism whose development ultimately kills its host.

What makes viruses different from many other microparasites?

Viruses are obligate intracellular parasites that use host-cell machinery to replicate.

What are the two major components of a virus?

Genetic material and a protein capsid. Some viruses also have a membrane envelope with glycoproteins.

Why do RNA viruses often have higher mutation rates than DNA viruses?

RNA viruses generally have smaller genomes and higher mutation rates.

Why can bacteria be difficult to classify simply as parasites?

Many bacteria can be parasites under some conditions but can also be commensals, mutualists, or free-living organisms.

What is an opportunistic pathogen?

An organism that can cause disease when conditions allow it, even though it may normally live harmlessly with or outside the host.

How would you identify a microparasite from a scenario?

Look for rapid multiplication within hosts, short generation time, transient infection, and disease impact related to prevalence.

How would you identify a macroparasite from a scenario?

Look for parasites that accumulate within hosts, variable parasite burdens among hosts, and disease effects related to intensity.

If two populations have the same prevalence but one has much higher parasite intensity, which type of parasite is more likely to show different disease impacts?

A macroparasite, because the number of parasites per host can strongly affect disease impact.