Lec 1. Intro to Parasitism Flashcards
A parasite that is impacting the Canadian arctic is called _____. You can get it from eating raw meat. It’s usually not a concern because of government regulations, but it’s very prevalent in the north
trichinosis
Traditional indigenous tea from Canadian Arctic made from rhododendron leaves could combat drug-resistant _____
malaria
Parasitic relationship=
a symbiotic relationship in which one partner (parasite) has a trophic relationship with the other partner (host)
Each parasite life cycle stage typically in ___ host(s)
one host per life cycle stage
- different life stages can affect different hosts
T/F
The parasite can let its host live, but often kills it
false
parasite often harms, but rarely kills the host. The host can’t benefit them if it’s dead!
The objective of parasites is to ___
reproduce
List 4 of the main forms of parasitism
Are these categories mutually exclusive?
- Typical parasite
- Trophically transmitted parasite
- parasitic castrator
- parasitoid
Not mutually exclusive, one parasite can fall under more than one of these categories
Typical parasite=
- transmission does not require host death (may accidentally cause death)
- host can usually still reproduce
Trophically transmitted parasite=
- transmission requires host death (eg. predator-prey interaction)
- parasite rarely kills host directly
Parasitic castrator
- some typical or trophically-transmitted parasites castrate their host.
- consume so much of the host’s tissue that the host becomes infertile (some parasites use chemicals)
What might be the purpose of a parasite castrating their host?
Then the host doesn’t put energy towards reproduction, so resources are put towards body maintenance, which benefits the parasite
Parasitoid=
Transmission requires parasite to kill host directly
Describe trophically-transmitted parasites
Parasites that infect each trophic level as it passes through (eg from producer to top predator)
Often different hosts= different life stages of the parasite
Give an example of a trophically-transmitted parasite
a typical trematode
Obligate parasite=
An organism that MUST be parasitic at some point in its life
Facultative/ opportunistic parasite=
An organism that can either be parasitic or free-living
- depends on conditions (host/ enviro)
Endoparasite=
a parasite that lives inside the host
Ectoparasite=
a parasite that lives outside the host
eg. lice/ ticks
Hyperparasites
parasites of parasites
If a parasite has a direct life cycle, how many hosts does it have?
1
If a parasite has an indirect/ complex life cycle, how many hosts does it have? Describe what happens in the host(s)
Two or more hosts are required.
- 1 definitive host: this is where the parasite grows, matures, & reproduces
- 1 or more intermediate hosts: parasite might asexually reproduce here, or just grow
Definitive host=
A host required for the development of a sexually mature (adult) parasite
Sexual reproduction happens in the definitive host
Intermediate host=
A host required for a larval parasite to develop into the next stage
Vector=
blood feeding invertebrate host
eg. mosquito
Can be intermediate (usually) or definitive)
For Malaria, is the mosquito or the human the definitive host?
The mosquito! Because that’s where sexual reproduction happens
Reservoir hosts=
an animal that is infected by a parasite & serves as a source of infection for humans (zoonoses).
= host in which parasites can mature & reproduce –> helps maintain the parasite when no normal hosts are available
Paratenic hosts=
hosts in which parasite development does not occur
–> no parasite development, just a transport
- may bridge ecological/ trophic gap in parasite’s life cycle
Prevalence=
proportion of hosts examined that are infected
PrevALence= ALL cases/ population @ risk
Incidence=
Number of new occurrences of a disease in a population
iNcidence= New cases/ Pop @ risk
Intensity=
Number of parasites per infected host
= total # of parasites/ # infected hosts
Abundance=
number of parasites per host that was examined
= total # of parasites/ All hosts examined
Density=
number of parasites per unit of host tissue
eg. 20 parasites per liver tissue
eg. Parasitemia
How can we measure density when parasites are not easily counted?
Parasitemia!
% parasitemia= (parasitized RBCs/ total RBCs) x100%
Explain the difference bewteen intensity & abundance
Intensity= how bad the infection is within each host (average)
Abundance= an estimate of what’s going on in the whole population
A parasite has a mean density of 2. What does that mean?
If you get this parasite, you’ll probably get 2 of them (average)
