BIOL 0510 - Protists & Helminths

What does the term ‘protist’ refer to?

any microbial eukaryote that isn’t an animal, plant or fungus

What does parasitology focus on?

helminths and protozoa

What are secondary endosymbioses?

multiple times, a eukaryote containing a chloroplast has been engulfed by another eukaryotic cell

What is Archaeplastida?

a plant and pigmented algae kingdom that resulted from primary endosymbiosis

What skill do Archaeplastida have?

photosynthesis

Provide an example of a member of the Archaeplastida kingdom?

Linchen Thallus

What is Lichen Thallus?

a mutualistic combination of an alga that produces and secretes carbohydrates and a fungus that provides structure

Provide an example of a member of the SAR clade

Phytophthora infestans

What is Phytophthora infestans?

a water mold that infects potato, tomato and pepper crops

What did Phytophthora infestans cause?

the potato blight that caused the Great Irish Famine

How do hyphae aid Phytophthora infestans’ mechanism of disease?

used to penetrate host cell walls

How does Phytophthora infestans absorb nutrients from the crops it infects?

using Haustoria structures that invaginate the host plasma membrane

What are zoospores?

motile spores with two different types of flagella (whiplash and tinsel)

How does Phytophthora infestans use zoospores?

to swim through films of water on leaves or in the soil to find a host

What diseases can apicomplexans cause?

malaria and toxoplasmosis

What is an apical complex?

a specialised structural organisation essential for host cell invasion

What are the names of the secretory organelles within the apical complex?

micronemes and rhoptries

What do the micronemes and rhoptries do?

secrete enzymes that facilitate host penetration

Within the apical complex, there is a polar ring. What does it do?

reorganise the host cell microtubules

What is an apicoplast?

a non-photosynthetic plastid that was derived from secondary endosymbiosis

Although it doesn’t allow for photosynthesis, why is an apicoplast essential for apicomplexans?

it has unique metabolic functions

What’s a characteristic of members of the Excavates group?

an asymmetrical appearance with a feeding groove and usually flagella

Give examples of members of the Excavates group?

Giardia, kinetoplastids and Trichonomas

What does Giardia intestinalis do?

cause giardiasis which is a common waterborne intestinal disease

What’s a key feature of Giardia intestinalis?

2 nuclei of equal size

What is Trichomoniasis?

the most common STI caused by Trichomonas vaginalis

Is trichomonas more common in women or men?

women

What are distinct features of Trichomonas?

no mitochondria but they have hydrogenosomes for anerobic metabolism

What feature do kinetoplastids share?

a mass of DNA known as a kinetoplast which is present in their single large mitochondrion

Provide examples of kinetoplastids

Leishmania and Trypanosoma cruzi and brucei

What is the cause of African Sleeping Sickness?

Trypanosoma brucei

What is the cause of Chagas disease?

Trypanosoma cruzi

What does Leishmania cause?

leishmaniasis

How does the cutaneous form of leishmaniasis appear?

as lesions that eventually ulcerate

How does the mucocutaneous form of leishmaniasis appear?

as ulcers on the nasal or oral mucosa

How does the visceral form of leishmaniasis appear?

throughout the body

What is the most severe form of leishmaniasis?

visceral

How does a person acquire leishmaniasis?

via a female sandfly which releases some of the microorganism

What happens when Leishmania enters the body?

macrophages engulf it and Leishmania replicates within them.

What makes Leishmaniasis difficult to eradicate?

it has multiple hosts and is caused by multiple different species within the Leishmania genus

What is a characteristic feature of Amobeozoa?

Terrestrial and aquatic. Use pseudopodia for movement and feeding.

What are gymnamoebas?

free living amoeba that inhabit soil and aquatic environments

What are entamoebas?

parasites of vertebrates and invertebrates

When do independent unicellular amoeba form a slime mold?

when food is scarce

What is a defining feature of an environment with little nutrients?

high cAMP

What is the purpose of amoeba forming a fruiting body?

some cells sacrifice themselves to form a stiff stalk from which other cells (which become spores) can be carried away from by the wind

Provide examples of important marine and aquatic protists

water molds, red tides, sea weeds and diatoms

What are parasites?

organisms that obtain food and shelter by living on or within another organism and causes damage to that organism

In medical terms, what is a parasite?

a eukaryotic pathogenic organism that’s either a helminth or protozoa

How are parasites dependent on their host?

metabolically or physiologically

What is a host?

the organism that harbors the parasites and suffers a loss

What is a definitive host?

the organism that the parasite lives in during its adult and sexual life

What is an intermediate host?

the organism that the parasite lives in during its larval and asexual stage

What are reservoir hosts?

non-human hosts that harbor the parastite and ensure the continuity of its lifecycle but are asymptomatic

What is a paratenic host?

a host that serves as a holding place for a parasite but isn’t necessary for its lifecycle to continue

What is a vector?

an arthropod (insect) that serves as an intermediate host and is responsible for transmitting the parastic infection

Direct transmission involves…

1 host

What does indirect transmission require?

2 or more hosts

What can the duck involved in swimmer’s itch be described as?

definitve host because an adult releases its eggs within the duck

What can the snail involved in swimmer’s itch be described as?

an intermediate host because its required for larval stage

What is an obligate parasite?

a parasite that can’t survive without a host

What is a facultative parasite?

a parasite that can live in a host or in its free form

What is an endoparasite?

parasite that live inside the body

Provide an example of an endoparasite

helminth

What is an ectoparasite?

parasites that live on the host

What’s an example of an ectoparasite?

a tick

What are epiparasites?

parasite that lives in/on another parasite

What is horizontal transmission?

from infected host to neighbour

What is vertical transmission?

mother to offspring but this is rare for parasites

What is spillover?

an infectious disease moving from an animal to a human

What is spill back?

an infectious disease moving from a human to an animal

Provide examples of maternal-fetal infections?

Zika virus, chlamydia and gonorrhoea

When can maternal-fetal infections occur?

during pregnancy, during delivery or shortly after birth

What is Zika virus?

a virus spread by mosquitoes that causes pregnant women to give birth to babies with microcephaly

What causes toxoplasmosis?

Toxoplasma gondii

What are the effects of toxoplasmosis?

cyst formation in muscles and sometimes other tissues but it’s mostly asymptomatic

How does toxoplasmosis spread?

fecal oral transmission

What are some of the rare complications associated with toxoplasmosis for pregnant women?

miscarriages, fetal brain damage and still birth

What are some of the rare complications associated with toxoplasmosis for immunocompromised individuals?

Myocarditis, encephalitis and pnuemonitis

What’s a possible way for a human to contract toxoplasmosis?

through a domestic cat as approximately 1% of domestic cats in the US shed toxoplasma through their feces

What happens when humans come into contact with toxoplasma?

The oocyst of the toxoplasma organism hatches in the gut and then moves into the muscles. The immune system causes a cyst to encase the organism so it doesn’t spread elsewhere

How did mice behave when infected with toxoplasma gondii?

increased dopamine levels and affinity to cat urine

What are helminths?

macroscopic multicellular worms

What portion of the world is affected by helminths?

1/3

If a helminth has a head, it is classified as a…

cephalopod

What can be found at the anterior (head) region of a helminth?

suckers, teeth, hooks, or plates for attaching to host

What is the body of a helminth covered with?

a tough cuticle that may have ridges, spines, and tubercles

What is the significance of the tough cuticle?

protection from enzymes

How do parasites acquire nutrients?

absorption or ingestion of host body fluids

What is the result of most helminths being oviparous (egg excreting)?

in their adult form, they can’t replicate in humans

Where do helminths hide?

in immunologically protected areas

How do helminths defend themselves from the host?

large size, elaborate attachment to the host, multiple hosts, suppression of the immune system, shedding of surface antigen

What are key features of flatworms?

eye spot, ganglia, incomplete digestive system

How do flatworms move?

in an undulating motion

What are the two main groups within flatworms?

flukes (trematodes) and cestodes (tapeworms)

Provide examples of flukes

liver fluke, lung fluke and blood fluke

What’s a major disease caused by a trematode?

Schistosomiasis (snail fever)

Describe cestodes (tapeworms)

flattened ribbon shaped bodies with a scolex which has suckers or hooklets. They have no digestive system so they likely absorb nutrients

Which tapeworm are humans susceptible to?

Taenia

What are tapeworms associated with?

undercooked pork, beef and fish