intestinal protists Flashcards
disease causing protists are associated with
all supergroups
what is one of the leading causes of death among children under five globally
diarrhoea
-1.5 mill a year
types of diarrhoea
osmotic
inflammatory
secretory
osmotic
enterocyte malfunction, impaired absorption, enhanced secretion, excessive solutes
inflammatory
mucosal invasion and leukocytes in stool
secretory
toxin associated and excessively watery
why do low income countries have more cases of diarrhoea
vaccine preventable, furthermore the rotaviruses which cause diarrhoea leave the body in stool. if you accidentally get the stool in our mouth, you get infected
rotaviruses
e.coli, shigella, campylobacter, salmonella, vibrio cholera
three solutions for diarrhoea
- oral rehydration therapy
- vaccines
- safe drinking water
- improved hygiene
how does oral rehydration therapy work
zinc deficiency reduces the number of B and T cells through the increased risk of apoptosis and reduces their functional capacity. the element stabilises the cell membrane, and since deficiceny disrupt the intestinal mucosa, reducing burst border enzymes and increasing mucosal permeability and intestinal secretion of water.
-zinc also acts as a potassium channel blocker, inhibiting cyclic adenosine monophosphate- mediated chlorine
since deficiency reduces..
the number of B and T cells through the increased risk of apoptosis and reduces their functional capacity
intestinal protists
o Entamoeba histolytica (Amoebozoa).
o Giardia intestinalis (Excavata).
o Dientamoeba fragilis (Excavata).
o Cryptosporidium hominis, C. parvum (Chromalveolate -apicomplexan).
o Balantidium coli (Chromalveolate - ciliate).
o Blastocystis sp (Chromalveolate - stramenopile).
fecal-oral transmission
- protists ted to have similar transmission cycles
- trophozoites inhabit intestinal tract but are not infectious
- cysts are excreted and are infectious
intestinal structure
- large surface area
- 4 layers
- microvilli
- many blood and lymph vessels
parasite damage
- water absorption impaired due to epithelial damage
- crypt cells produce cells but excrete water and cl-
- water not reabsorbed with Na+
- villus blunting
gastroenteritis
gastrointestinal tract infections: nausea, vomiting, diarrhoea, abdominal distress
general disease of s.intestine indicates
excessive secretion relative to absorption
-fluid and electrolyte loss
dysentry
l. intestine
- involves blood and mucus in stool
which type of entamoeba cause disease in humans
E.Histolytica- amoebic dysentery
E.dispar vs E.histolytica
- morpholigically indistinguishable
- 10-50% of work infected by E.dispar
drug used to treat histolytica
nitroimidazole
E. histolytica
typical decal oral life cycle- infectious cysts passed through faeces. Trophozoites replicated in large intestine.
how does E.histolytica cause damage
lyses cells in a constant dependent manner. It eats its way through the epithelium and beyond.
breakdown of E.histolytica action
1) crawling and feeding
2) erosion of mucous layer for contact dependent killing
3) ECM breakdown and neutrophil killing
4) perforation of serous layers leading to peritonitis
5) access to circulatory system
Giardia
- most common parasite from human stool
- results in asymptomatic infection
- typical decal oral route
where does giardia intestinalis colonise
upper portion of s.intestine.
who first described giardia
Leeuwenhoek who found it in his own stool
guardia parasite very rarely
penetrates the cells wall unlike Amebiasis
what is used to diagnose giardia
the enterotest
common symptoms of giardia
diarrhoea, malaise, flatulence, bloating, nausea, anorexia, weight loss
pathogenesis of giardia
- attachment could cause irritation and mucosal injury
- bollus blunting and enterocyte apoptosis
- uncreased crypt cell activity: hyperplasia
- hypersecretion of cl- and water
the adhesive disk of Giardia is
important for adhesion to intestinal epithelium
- made from cytoskeleton and contractile proteins
- inhibitors of microfilament also inhibits attachment
treatment of Giardia
metronidazole cures around 85%
what is the only know human infectious ciliate
Balantidium coli
what disease does Balantidium coli cause
balantidiasis
who are most at risk of getting balantidiasis
those who work with pigs, however less than <1%
balantidiasis
fecal-oral transmission
-only known mammalian pathogen within the stramenopiles
Balatidium coli
- typical ciliate with cilia and micro and micronucleus
- nuclear dimorphism
- asymmetric division
- diarrhea or dysentery
Balatidium and diarhhea
rarely invades intestinal epithelium but then shows diarrhoea similar to Entamoeba dysentery with blood and mucus
blastocystitis is caused by
blastocysts hominis
blastocystitis
- linked to IBS
- 17 distinct subtypes- 9 found in humans, 4 are common
- controversy r.e. mode of transmission/ lifecycle
cryptosporidium
apicomplexan parasite.
causes diarrhoea and immune suppression
-often deadly diarrhoea disease of AIDS patients
apicomplexan parasite
are a large phylum of parasitic alveolates
two main cryptosporidium pathogens
C.hominis and C.parvum
Cryptosporodium and extracytoplasmic association
- sporozoites do not invade enterocyte, but attach to epithelial cells
- induce fusion of microvilli: parasite encapsulated by house membrane
why is cryptosporidium so dangerous
since the parasite is encapsulated by the host membrane- hidden from immune system
sexual reproduction and cyrptosporidium
- two rounds of asexual reproduction of zygote to generate oocysts
- thick walled ones thought to be excreted and thin walled cysts reinfect
Healthy individuals suppress merozoites release
fecal oral transmission
Cysts are resistant forms and are responsible for transmission of giardiasis. Both cysts and trophozoites can be found in the feces (diagnostic stages) (1). The cysts are hardy and can survive several months in cold water. Infection occurs by the ingestion of cysts in contaminated water, food, or by the fecal-oral route (hands or fomites) (2). In the small intestine, excystation releases trophozoites (each cyst produces two trophozoites) (3). Trophozoites multiply by longitudinal binary fission, remaining in the lumen of the proximal small bowel where they can be free or attached to the mucosa by a ventral sucking disk (4). Encystation occurs as the parasites transit toward the colon. The cyst is the stage found most commonly in nondiarrheal feces (5). Because the cysts are infectious when passed in the stool or shortly afterward, person-to-person transmission is possible. While animals are infected with Giardia, their importance as a reservoir is unclea
cysts are.. and trophozoite are…
cysts are infectious and trophozoites die outside the body so do not cause illness
cysts
resistant form and are responsible for the transmission of giardia
sporozoite
a motile spore-like stage in the life cycle of some parasitic sporozoans (e.g. the malaria organism), which is typically the infective agent introduced into a host.
3 types of protists concentrated on
Entamoeba, Cryptosporidium, Giardia
where do giardia parasites colonise
upper portions of s.intestine
adhesive disk of giardia attaches to
s.intestine- causes virus blunting and enterocyte apoptosis and hyper secretion of cl- and water
apicocomplexan
The organelle is an adaptation that the apicomplexan applies in penetration of a host cell.
