L3: Intestinal and Luminal Amoeba and Flagellates of man Flashcards
What is the phylogeny of E. Histolytica
Phylum- Sarcomastigophora Sub Phylum- Sarcodina Class- Rhizopoda Order- Amoebida Order- Schizopyrenida
What is the phylogeny of Giardia intestinalis
Phylum- Sarcomastigophora Sub-Phylum - Mastigophora Class- Zoomastigophora Order- Diplomonadida Order- Trichomonadida
Which commensal appears similar to E.histolytica
E.dispar
Which parts of the human body are infected by E. histolytica
Intestines and extraintestines
How do we identify E. histolytica
Only amoeba which feeds on red blood cells in humans
Describe the nucleus of the trophozoite of E. histolytica
Cartwheel arrangement of chromatin
What is the trophozoite phase of the entamoeba lifecycle called
A feeding animule/ feeding stage
What is the cyst phase of the entamoeba lifecycle called
The infectious stage
Describe the physical structure of an entamoeba cyst
Mature cysts have four nuclei with RNA associated to them, it is round and has a fibrous cell wall.
Immature cysts have a dark stained oval shaped structure known as a chromotoidal structure containing crystalline RNA
What is the average size of the ent cyst
10-12 um
How many fatalities are due to e hist
70k-100k
E hist is the ___ most common cause of parasitic death in the world
Third
Which groups are at risk for E. hist
- Male homosexuals
- Travelers
- Immigrants
- Institutionalized persons Eg prisoners
Where might mature cysts of E hist be found
Fecally contaminated water, vegetables, through flies
Describe the lifecycle of E hist in humans
Mature cyst ingested
Fibrous wall broken down by stomach acid causing excystation
In the large intestine the parasite forms ulcers in the small intestine wall which cause parasites to get into the blood supply. These parasites travel to the liver, brain and lungs. They do not produce cysts
Cysts are produced by commensals. When the colon absorbs water it causes trophozoites in that area to become cysts. These cysts develop to maturity and are produced in feces.
What type of parasite is E histolytica
Luminal and Intestinal
What are the three possible stages of pathogenisis
Benign- no invasive
Invasive- Ulcers
Extra Intestinal
What is the purpose of the muscularis mucosa
Provides a physical barrier for the ulcer and prevents extra intestinal spread of trophozoites
How is an ulcer formed
Proteolytic enzymes secreted by the trophozoites will erode the mucosa forming ulcers in the colon and appendix
What is an amoeboma
A pseudo tumor formed as an immune response to a tumor in the colon. It may obstruct the intestine
What is dysentery
Bloody diarrhea and soft mucusy stool, frequent visits to the bathroom and dehydration
Explain the ways in which extra intestinal infection may lead to death
Cerebral amoebiosis
Perforated colon leads to bacteria flowing into the body cavity causing a sepsis
What is the main mode of transmission of E.hist
Contact with fecal contaminated materials
Phoretic Commensalism
What test may be used to distinguish E hist from E dispar
PCR based methods
How does E hist avoid the immune system
- Secrete proteases which degrade antibodies (proteins)
They have a cytolyitc capacity which allows them to degrade host tissue thus decreasing the immune response to trophozoites
Secretions of the parasites may decrease the energy of T cells causing immunosuppresion
Which drugs treat E hist and what do they do
Iodoquinol- Asymptomatic Infections
Metronidozole- Both asymtomatic and symptomatic infections
Give an example for a freeliving ameoba which is a facultative parasite
Acanthamoeba spp - Opportunistic infection
Describe the trophozoite of Giardia Intestinalis
Pear shaped, 10-18 um in length with 4 pairs of flagella, paired nuclei and median bodies
Mitosomes not mitochondria
Describe Giardia cyst
Has a wall around it with 4 nuclei and remnants of flagella
10-12 microns
Describe the Giardia Lifecycle
Enters through mouth
Acid bath breaks down cell wall
Small intestine parasite
What are the two ways Giardia may manifest
Acute - Incubates 5-6 days - Lasts 1-3 weeks - Diahrrea, abdominal pain, bloating, vomitting -Self limiting infection Chronic -Malabsorption of fats and B12 - Recurrent symptoms - Gross discomfort - Not fatal
This amoebic infection is family associated
Giardia intestinalis
How does giardia evade the immune system
By having variation of antigens
Which drug is used to treat giardia
Metranitrozole
How is Giardia tested for
Identification of cysts or trophozoites in feces
This amoebic parasite has no cysts in its lifecycle
Trichomonas vaginalis
What is the primary mode of transmission of T.vaginalis
Sexual contact
Describe the structure of t vaginalis
4 flagella
single nucleus
two axostyles which are asymmetric
5-18 microns
What is an over the counter treatment for T vag
Vinegar douches
