parasitology lecture 2: intro to parasitology continued

what is an ectoparasite?

parasites that reside on the external surface of the host and cause infestations

ex) lice

what is an endoparasite?

parasites that reside inside the host's body leading to infections

examples) tapeworms

can be intracellular or extracellular (lumen of gut vs inside blood vessels)

what is an autogenic parasite?

parasites that complete their life cycle in a single ecosystem

ex) freshwater isopods that infect fish

what is an allogenic parasite?

these are parasites that complete their life cycle in more than one type of ecosystem

ex) the guinea worm

Consider autogenic and allogenic parasites. Why

might allogenic parasites tend to be more genetically

homogeneous than autogenic parasites, which might

show more genetically subdivided populations?

their ability to move between different ecosystems and transmit between diverse hosts promotes widespread gene flow and genetic mixing, preventing the formation of isolated and divergent subpopulations

Autogenic parasites may be more isolated, say to a particular waterbody, such that populations from different waterbodies cannot interact and thus become more divergent with time. In contrast, allogenic parasites may be able to move freely between such habitats via overland movements, resulting in a degree of genetic

mixing or homogenization. *from textbook

what is an obligatory parasite?

they require a suitable host to complete its life cycle. most parasites fall into this category.

what is a facultative parasite?

these parasites can adopt a parasitic existence but can also have a free-living version of itself (can survive without host)

what is an opportunistic parasite?

parasites that take advantage of certain circumstances to initiate an infection in a host they don't normally infect or in which it does not normally cause disease (think an immunocompromised person)

ex) HIV/AIDS patients with toxiplasma infection

what is a microparasite?

this is a small parasite with rapid generation time relative to their host (think bacteria, viruses, and protozoa)

what is a macroparasite?

larger parasites (even though they are still small/smaller than their hosts)

think helminths or ectoparasites like fleas or ticks

what is a hyperparasite?

these are parasites of parasites!

what are parasitoids?

organisms that spend a significant amount of their life on or within a single host. they often sterilize, kill, and/or consume the host in the process.

they straddle the boundary between predation and parasitism.

what are social parasites?

invade or lay their eggs in the nest of a hostorganism and develop on food provided in that nest

These organisms exploit other organisms; however, they donot live on or in another organism

what are kleptoparasites?

teal or scrounge food (or other resources)obtained by another organism

These organisms exploit other organisms; however, they donot live on or in another organism

what is a definitive host?

hosts in which the parasite can reach "sexual" maturity

this may mean sexual reproduction, where fertilization takes place, or some sort of other genetic recombination event

what is an intermediate host?

ones in which the parasite undergoes a needed developmental step and may even asexually reproduce but "sexual" maturation does not take place

what is an accidental host?

these hosts are accidentally infected and are not normal hosts to the parasite (think canine parasite in a human)

the parasite may or may not cause infection; unknown environment for all

what is a paratenic host?

nonessential host that increases the chance of transmission to the definitive host

- the parasites do not replicate

- does not cause disease in the paratenic host

- fills an ecological gap between the intermediate host and the definitive host

what is a resevoir host?

host that harbors the parasites and serves as an important source of infection to other susceptible hosts

- parasite can grow and multiply

- does not cause disease in resevoir host

- zoonosis: transmission of domestic and wild animal parasites to humans

what is a vector?

an organism that transmits parasites from one host to the next

many are mobile and blood-feeders

what is a biological vector?

vectors in which the parasite either develops or multiplies (or both) inside before it is successfully transmitted to a new host

example) mosquitoes transmitting plasmodium

what is a mechanical vector?

vectors that simply transfer a parasite to a host from the outside (no development or replicaton takes place)

think horseflies + trypanosoma to horses

parasitic diseases are the leading causes of death after which 3 diseases?

COVID19, tuberculosis, and HIV/AIDS

what is the lack of awareness and funding within parasitology?

many of the infections take place in tropical, less-developed countries-> out of sight out of mind attitude for people not living in these areas

illusion of non-issue for disease in more-developed countries

money for research can be scarce for these diseases (pharmaceutical companies don't want to spend money to develop drugs if people cannot pay, etc)

how does global travel and warming contribute to the crisis?

as global travel increases, more people become infected with parasites from around the world

as climate change continues and temperatures warm, vectors will keep migrating to areas they did not used to occupy

how do malnutrition and food waste contribute to the topic?

nutrient deficits can lead to conditions that weaken the immune system and increase chances of parasitic infections

caloric needs of diseased individuals may not be met or take away food sources for others (Example - A single day of a fever from acute malaria requires an intake of

~5000 calories)