6. Parasitic Protists Flashcards
(35 cards)
Define parasite
An organism which lives in or on another organism (its host) and benefits by deriving nutrients at the other’s expense
An example of a diplomonad
- giardia lamblia
- one agent of ‘traveller’s’ diarrhea
- one of the most common parasite infection worldwide
What are diplomonads?
The diplomonads (Greek for “two units”) are a group of flagellates, most of which are parasitic.
How is Giardia lamblia trasmitted?
- transmitted by cysts in food and water
- 14 billion cysts/day in faeces
- adheres to intestinal epithelium to absorb nutrients from the host
- not all people infected have symptoms
What is trophozoite
A growing stage in the life cycle of some sporozoan parasites, when they are absorbing nutrients from the host.
Biology of Giardia lamblia
- trophozoite has 2 nuclei and associated sets of paired flagella
- have mitochondrial remnants but no mitochondria (to make iron-sulfur proteins)
What is one of the most common parasite infections in the world?
Giardia lamblia
What are parabasalids?
Parabasalids (phylum Parabasalia) are anaerobic flagellated protists
Physiology of parabasalids
- anaerobic
- converts glucose to pyruvate by glycolysis
- convert pyruvate to acetate in an organelle known as the hydrogenosome
What is hydrogenosome
- organelle found in parabasalids
- derived from mitochondria
- independent evolution in Trichomonas and other microbes, some still with DNA
Kinetoplastids examples
•leishmania •Trypanosoma
Kinetoplastids structure and name
- name given for clump of DNA at the anterior end of the mitochondrion
- VSG coat constantly changing, avoiding immune recognition
What are kinetoplastids?
- bloodstream parasites
- group of flagellated protists belonging to the phylum Euglenozoa,
- characterised by the presence of an organelle with a large massed DNA called kinetoplast
Diseases caused by kinetoplastids
- swim in the blood stream
- chagas disease
- African sleeping sickness (spread by tsetse flies)
- leishmaniasis
What is the method of combating kinetoplastids?
- very few effective drugs and bad side effects
- however, for African SS, disease mortality rate is 100% with 5% for the drug
- no known drug effective against Chagas disease
- therefore target the insect vectors
What are ciliates?
- group of protozoans characterised by the presence of hair-like organelles called cilia
- cilia for motility and capturing food
Do ciliates cause disease?
- one species causes human disease
* balantidium coli
What disease is caused by entamoeba histolytica?
- causes the disease amebiasis
- 3rd worst parasite
- dysentery (colitis), spread in blood, and eventual liver abcess
Transmission of Entamoeba hystolytica
- transmission by faecal contamination of food or water
- cysts last several months
- cysts form trophozoites in intestine after ingestion
Phylum apicomplexa examples
All intracellular parasites
• toxoplasma gondii
• plasmodium spp. (malaria)
• cryptosporidium spp.(causes diarrhea)
What is the apical complex and where are they found?
- A group of cytoskeletal structures and associated membrane-bounded organelles
- found at the anterior end of adult obligate intracellular protozoan parasites in the phylum Apicomplexa
What is the function of the apical complex?
• used to burst out of a used host cell and to invade
Who is at risk of being affected from toxoplasma gondii?
- fatal in immunocompromised individuals
- developmental defect in infected foetus (why pregnant women shouldn’t clean kitty litter)
- otherwise, usually not severe in humans
Who is the host of toxoplasma gondii?
Definitive host is cat and common risk of exposure is in kitty litter
