Intro Flashcards
What is the most dangerous animal on earth?
mosquito
What percentage of animal species are parasitic at some stage in their life?
50%
Which phylogenetic animal groups contain parasites?
All the major groups
What are some common parasites in North America?
pinworms, giardia, dog roundworms, toxoplasma, ticks
Where does the word ‘parasite’ come from?
Greek, meaning ‘one who eats at the table others’
Are parasites prokaryoyes, eukaryotes, or both?
eukaryotes. therefore not bacteria or viruses
Define protozoa
unicellular organisms
Define metazoa
multicellular organisms
Give some examples of ectoparasites
head lice, ticks, fleas
Give some examples of endoparasites
hookworm, tapeworm, tapeworm eggs, roundworm, pinworm, leishmania, plasmodium, trypanosome, giardia
Define hemiparasite
a parasitic plant that derives some or all of its sustenance from another plant
Give an example of a hemiparasite
mistletoe attaches to another plant and absorbs its nutrients. spread by birds eating the fruit and pooping the seeds out
Define host
the organism in or on which the parasite lives
Define definitive host
the organism in which the parasite reaches sexual maturity
Give an example of definitive host
the mosquito for malaria, the cat for toxoplasma
Define intermediate host
the organism in which the parasite completes part of its life cycle. parasites usually undergo a morphological or physiological change in this host
Give an example of intermediate host
humans for malaria, mice for toxoplasma
Define reservoir host
alternate animal host from which the parasite can be transmitted to humans (zoonosis) or domestic animals
Give an example of a reservoir host
the rat for toxoplasma
Define zoonosis
a parasitic disease in which an animal is normally the host, but which also infects humans
Define accidental host
one that accidentally harbors an organism that is not usually parasitic in the particular species and cannot be transmitted. parasite usually finds an immunologically privileged site (ie. brain, eyes, testes, etc)
Give an example of an accidental host
humans and the pork tapeworm Taenia solium. causes human cysticercosis
Define vector
a host that plays an active role in the transmission of the parasite. can be a definitive or an intermediate host
Give an example of a vector
female Anopheles mosquito that transmits malaria
What are some characteristics of parasites?
usually smaller and more numerous than their host, may be some degree of genetic complementation, parasite is physiologically or metabolically dependent upon its host, reproductive potential of parasites exceeds that of their host
Why are many host-parasite interactions species-specific?
because of co-evolution
What are the steps to parasite infection?
1) encounter
2) entry/attachment
3) spread within body
4) multiplication
5) damage
6) outcome- either parasite or host wins, or they coexist
What are the main modes of parasite transmission?
skin, respiratory, gastrointestinal, urogenital
vector borne, blood transfusion, organ transplant
What are the two types of vector borne transmission?
external and internal transmission
Define harborage transmission
internal vector borne transmission where the pathogen does not undergo changes within vector (mechanical vector)
Define biologic transmission
internal vector borne transmission where the pathogen undergoes changes within the vector (biological vector)
Define infectivity
ability of the organism to establish a discrete, focal point of infection
Define invasiveness
ability of organism to spread to adjacent or other tissues
Define infection
a parasite growing and multiplying within or on a host, usually accompanied by an immune response
Define pathogenicity
ability of parasite to cause disease
Define virulence
degree of pathogenicity, the ability for the organism to invade, infect, grow and cause damage despite the host’s defences. determine in part by pathogen’s ability to survive outside the host
Define symbiosis
living together
What are the four types of symbiosis?
phoresis,commensalism, mutualism, and parasitism
Define phoresis
‘to carry’. when one organism is mechanically carried on or in another species (host)
Give an example of phoresis
beetle with hitch-hiking mites, hermit crab carrying sea anemones, crab carrying a fire urchin
Define commensalism
involves one way benefit, but no harm is exerted in either direction. usually involve a feeding relationship but not metabolic independence
Give an example of commensalism
pilot fish attaches to shark and eats the debris from the shark’s prey.
egrets sit on livestock and eat insects surrounding them
sea anemone protects clown fish, which has an extra mucous layer for protection from nematocyst discharge
Define mutualism
highly inter-dependent association, often to the extent where the two cannot survive without one another
Give an example of mutualism
flagellate protozoa live in termites and digest the wood for them.
Yucca plant is only pollinated by yucca moths, and yucca moth larvae can only eat the seeds of yucca plants
Define parasitism
intimate relationship between two organisms in which one lives on, off, or at the expense of the other (host)
Give an example of parasitism
canine heartworm, malaria
