Lecture 4 Parasite diversity 4 Protozoa Flashcards
(32 cards)
What is a protozoan?
• animal-like eukaryote:
- no cell wall
- at least 1 motile stage in life cycle
-most ingest their food
• not a monophyletic (1 common ancestor) clade but share a basic body plan completely contained within 1 plasma membrane,
i.e. single-celled
Where do we find protozoa?
Everywhere!
• all require moisture (prone to drying out)
• many free-living but also numerous symbionts
- mutualistic, commensals, parasites
How do we classify protozoa?
• constantly under revision due to new molecular data
–>will focus on clades rather than taxonomic levels
Describe the protozoan clade Diplomonads.
no mitochondria,
-> symbionts (dependent on host)
2 nuclei, flagella
Name the Genus found in Diplomonads clade.
Giardia
Describe Genus Giardia
2 forms ( trophozoite & cyst)
• direct transmission (via
ingestion)
Describe trophozoite and cysts of Giardia
cyst-> trophozoite undergo asexual replication-> cycsts and trophozoites expelled in feces -> only cycsts can survive outside of host-> cyst can survive for weeks to months in cold water
Describe structure of Giardia found in Diplomonads?
- host cell adhesion (ventral disc)
- -> groove suction prevent being cleaved by digestion system
Describe life cycle of Giardia
Bever Fever nickname:
- wildlife imp reservoir
- > hosts for many pathogens
- direct or waterbourne
Describe characteristics of clade Alveolata in Protozoa.
- membrane-bound sacs (alveoli) under plasma membrane
- 3 phyla members:
- parasitic group Apicomplexa, cilia group Ciliophora with some parasites
Describe characteristics of Phylum Apicomplexa
found in clade Alveolata.
1 end (apical complex) contains organelles specialized for penetrating host cells & tissues • intricate life cycles (sexual & asexual stages) that often require 2 or more hosts • members: endoparasites • divided into 2 classes based on presence of conoids (found in apical complex)
What is the structure inside the apical end which release enzymes for penetrating the host?
Rhoptries
Describe Toxoplasma gondii an Apicomplexans of note.
cat parasite
- intracellular – various tissues (muscle, intestine, other)
• asexual & sexual
reproduction occur in different hosts
- sexual reproduction only in cats during intestinal phase
—->oocysts released in feces
What do 4 Toxiplasma gondii sporozites do?
they open oocyte in muscle tissue
Why is Toxoplama gondii called a cat parasite and ways of human exposure?
2 ways:
- cleaning litter box
- uncooked pork and gut
- placental infection, baby brain affected
-intermediate host can be a rat which cats eat
What happens if oocysts are eaten?
sporocysts enter host cells (extra- intestinal)
—> rapidly dividing tachyzoites accumulate in cells
• zoitcysts with bradyzoites form (baby brain)
–>persist for years
• zoitocysts big problem if in fetus
• in
~ 25% of world population • immunocompromised,
schizophrenia(?)
Links that schizophrenia can occur due to toxoplasma gondii. How?
parasite manipulate host to increase transmission b/c in brain
ex. rodents are attracted to cat, cat urine
Describe Neospora caninum in Phylum Apicomplexa.
-dogs as definitive hosts
• transplacental infection of other species
leading cause of abortion in dairy cattle
-doesn’t use humans as accidental hosts but livestock
-tachyzoites transmitted through placenta
Describe:Genus Plasmodium in Phylum Apicomplexa.
-intracellular (vertebrate blood & other tissues) • asexual & sexual reproduction occur in different hosts • cause of malaria disease known since antiquity
What 3 similarites does plasmodium have with tachyzoite of toxoplasma gondii?
apical polar ring, micronemes and rhoptries. no conoid in plasmodium
Describe history of malaria from Plasmodium
similar to yellow fever, no control if no information
-1847, notice pigment granules in blood and speen
-1891 staining techniques no
Ronald Ross:
-correctly found mosquito as vector
What is the ring stage in Plasmodium?
imp for species i.d. -some are worse than others
Adhering:
trophozoite->schizont-> merozoites->
Circulating:
merozoites-> gametocytes-> ring-> trophozoite
-merozoite penetrate RBC
So you’ve got a persistent parasite…What sort of pathology results?
continually changes _surface proteins
- –>wears out immune system
- fever & chill periodicity w/ diff types of bacteria
- cerebral malaria (RBC stick together to form clumps stuck fine capillaries, clumping in vascular region of brain
How can we control malaria?
i) control transmission via vector
• old-fashioned & new methods
–> bed nets
–>GM males break vector life cycle (sterile males)
ii) control transmission via parasites-give anti-malarial drugs
iii) control transmission via human susceptibility
