Intro and Immunology Flashcards
Distinguish between obligate and facultative parasitism
Obligate - must have association with host to live
Facultative - can be free living or parasitic
Over time, how may hosts/parasites evolve in relation to each other?
Obligate parasites die if their host dies, so they don’t want to be particularly virulent. It’s theorized that over time the tendency for virulence goes down.
However, it’s possible that causing damage to the host (including death) can be advantageous if the parasite is more likely to be preyed on by the definitive host (ex. infecting prey, causing it to be slow and sick, then infecting the predator).
Distinguish between permanent and temporary parasites
Permanent - Entire parasite life cycle is spent in association with host
Temporary - Have to occasionally find a host (usually ectoparasitic)
Describe a situation in which a host’s body may provide several different environments for parasites
Internal vs external environments. The environment in the small intestine of a human is different than the hair of a human. (Ex. tapeworm in gut and lice in hair)
Describe the different host types
Definitive - Host in which the parasite completes sexual reproduction
Intermediate - On the way to the definitive host, can allow changes in morphology or development
Paratenic - Allows organism to survive, but the parasite does not reproduce, develop, or change morphology
Phoretic - Temporary transfer host (ex. eggs need to be deposited on human skin but are transferred there by mosquitos)
Reservoir - Host that acts as a source of infection for another one (ex. humans are the reservoir for the influenze virus)
Alaria americana is a parasite of foxes/mink/other wild carnivores. How is it transported from the frog/tadpole hosts to something that doesn’t eat it?
Water snakes act as a paratenic host, eating infected tadpoles/frogs, and then eventually be eaten by a small carnivore
If parasite levels rapidly (exponentially) go up and then suddenly level off, what is that growth model called? What usually causes the population of parasites to level off
Asymptotic (Asymptote).
Immune system respomnse
What is it called when a parasite or virus is transmitted in high-population density environments?
Urban transmission
Why is transmission of Yellow Fever Virus unique?
It is transmitted two ways: Urban transmission and forest transmission (transmitted by other mammals in the forest)
Describe a direct/simple parasitic life cycle
Close proximity to the other host (same type of organism) gives host 2 the infection
Describe an indirect/complex parasite life cycle. Give an example.
Involves two hosts which must interact with each other. For example West Nile Virus must be transferred by mosquitos to birds
Why are humans not considered a part of the West Nile Virus cycle?
We do not act as a reservoir - we do not build up enough in our blood to pass it back to mosquitos.
What is referred to when a host cannot pass the parasite to the preferred host?
Dead end host
What is meant by the “host specificity” of a parasite?
The biochemical requirements confining a parasite to one group of organisms or even one species
Give an example of a general parasite (can survive in lots of hosts)
Trypanosoma cruzi - single celled parasite that can grow in >100 mammals species and some birds
A ______ cycle has at least one natural reservoir that is a non human animal
Zoonotic
Describe Enzootic transmission
Number of hosts infected remains relatively constant over time
Describe Epizootic transmission
Number of hosts fluctuates over time
Describe anthroponotic transmission
No non-human animals involved in the cycle (unless they are carriers - ex. malaria)
Which malaria species kills the most people worldwide?
Plasmodium falciparum
What is the difference between prevalence and incidence of an infection?
Prevalence - Percentage of hosts (carrying a single type of a parasite) in a given population at a given point in time
Incidence - number of newly infected hosts per population per unit time (ex. 25 cases/ 10 000 people/month)
Distinguish between density and intensity of an infection
Density - Average number of parasites per host (which includes non-infected hosts in a population)
Intensity - Absolute number of parasites in an INFECTED host (rules out those not infected)
How was “patient one” found during the AIDS epidemic of the 80s?
Doctors painstakingly interviewed the infected people, looking for a common sexual partner to explain how HIV became such a huge deal in New York City. Turns out many of their interviews traced back to a gay Air Canada flight attendant with frequent flights to France
What is Ecological Epidemiology?
The study of the weak points in transmission events over the life cycle of an infection, developing interventions to prevent infection (Ex. killing mosquitos to prevent spreading of malaria). Basically making the environment less receptive to transmission
How is the Dengue fever carrier “Aedes aegypti” adapted for life with humans?
Preferentially feed on humans (like our scent), can lay eggs in super small quantities of water. Generally just meant to live in human houses.
Distinguish between urban and periurban transmission
Urban - Transmission occurs in city centers with dense population
Periurban - Transmission occurs in the outskirts of cities (usually slums, poorer sanitation, more wild animals)
______ parasites live in human homes
Domestic
_______ parasites live immediately around human homes (ex. backyards)
Peridomestic
_____ infections are acquired in wild or non-populated areas
Sylvatic
What does it mean if a parasite is “infectious”?
They are not always able to infect another host in the chain of transmission, there may be a lag time
____ means one is capable of becoming infected, and the parasite can grow and develop. ____ means that the parasite may still infect someone, but not reach high enough numbers to establish itself
Susceptible, Resistant