Protozoal Infections Flashcards
What is Entamoeba Histolytica?
A Protozoal infection which primarily affects the gut, but can cause widespread illness in the form of Amoebiasis
What is the Life Cycle of Entamoeba Histolytica?
- Cysts are ingested by host from food/water contaminated with faeces which contain cysts
- Cysts pass through the stomach and enter into the small intestine where they excyst becoming trophozoites
- Trophozoites travel to the large intestine, where they can hang out and not cause too much issue (local infiltration only)
- From the Large intestine, trophozoites can multiply through binary fission and develop into cysts, to be excreted into stools
OR trophozoites can burrow through the walls of the large intestine. If burrowing into the walls they can symptoms of dysentery. If they burrow beyond the intestinal walls into the vasculature they can spread throughout the body and cause disease anywhere
What are risk factors for getting entamoeba histolytica (i.e. how is it spread)?
Faecal-oral spread.
Infected food, water, poor sanitation, Sexual contact
What is the epidemiology of Entamoeba Histolytica
Found Globally.
Probably affects 10% of the population, but we aren’t actually very good at knowing how much there is because impossible to tell from E. Dispar
What are the clinical symptoms of Entamoeba Histolytica infection?
- Asymptomatic
- Intestinal Infection –> Dysentery, low grade fever, rectal ulceration, anal prolapse (paeds), malaise
+/- peritonitis, fulminating necrotising colitis - Extra-intestinal Amoebiasis
What are the complications of Entamoeba infection (e.g. extraintestinal complications)
Toxic Megacolon
Amoebic Granuloma
Amoebic Liver Abscess (anchovy paste pus full of trophozoites)
Post dysentery UC
Right Lung Abscess
Rarely CNS and skin involvement
How is Entamoeba Histolytica diagnosed?
(name 3 ways)
- Stool Micrscopy (>3 samples)
- Faecal ELISA
- Rapid Antigen Tests
- Serology (not useful in endemic areas)
- Endoscopt in mild/mod disease; cannot be done late because bowel too friable and could perforate
What can be seen on Stool microscopy in Entamoeba Histolytica?
TROPHOZOITE (fresh samples only): Variably sized brown stained cells, with pseudopodia which allows the trophozoites to swim around and attach onto cell walls. May have ingested RBCs
CYST: A smooth round cyst with 1-4 nuceli +/- chromatin bars
10-15um
Microscopically identical to E. Dispar
Which organism is microscopically identical to entamoeba histolytica?
Entamoeba Dispar
How is Entamoeba Histolytica managed?
Metronidazole 800mg TDS for 5/7 (Anti-trophozoite)
+
Diloxanide 500mg TDS (Anti-cystic agent) OR Paromomycin 25mg/kg/d in 3 divided doses for 7/7
(The latter especially in disseminated disease)
How can Entamoeba Histolytica spread be prevented?
- improved water sanitation practices
- extremes of temperature
- Chlorination
- iodine treatment
- sand filtration
- hand washing
What is Giardiasis?
An infection of the small bowel caused by infection through intestinal protozoal flagellate Giardia Lamblia/giardia intestinalis
What is the epidemiology of Giardiasis?
Distribution, cases and deaths
280 million cases/year
Global Distribution
10000 deaths/year
Children > Adults
What is the life cycle of Giardia Lamblia?
- Cysts are ingested by the host
- Cysts travel to the stomach. Within the stomach the low pH causes excystment
- The trophozoites enter into the small intestine and enter into the microvilli of the small intestine, destroying the brush border and disrupting digestive enzymes
- The trophozoites travel through the gut and mature.
- When the reach the colon they encyst and can be released in a bowel movement
What is the incubation of Entamoebiasis?
Unknown – can be up to 18 years, but no idea
