01-02-23 - Protozoal and Helminthic Infections of the Gastrointestinal Tract Flashcards
Learning outcomes
- Recognise the various sources of protozoal and helminthic infections of the gastrointestinal tract
- Outline the clinical manifestations of infection with Cryptosporidium parvum and explain the pathogenesis of infection
- Recognise the clinical manifestations of infection associated with Entamoeba histolytica
- Explain the pathogenesis and diagnosis of Giardia lamblia infection and identify the source of infection
- Recognise the clinical manifestations of infection associated with intestinal helminth species
Giardia lamblia (G. lamblia).
How can G lamblia be transmitted?
What are the 2 stages in the life-cycle of G-lamblia?
What 2 things do we need to diagnose G lamblia?
- Giardia lamblia (G. lamblia)
- Giardia spreads easily and can spread from person to person or through contaminated water, food, surfaces, or objects.
- The most common way people get sick is by swallowing contaminated drinking water or recreational water (for example, lakes, rivers, or pools)
- 2 stages in the life-cycle of G-lamblia:
1) Trophozoite
* Flagellated and binucleated
* Adheres to brush border of upper small intestine.
2) Cyst
* Resistant wall
* Formed in large intestine
* Passes out in faeces
- 2 things we need to diagnose G lamblia:
1) 3 stool samples
2) Antigen detection assays (ELISA)
What are the 3 steps in the pathogenesis of G lamblia?
Where else can G lamblia gain access to?
- 3 steps in the pathogenesis of G lamblia:
1) Attaches to wall of upper small intestine via central ‘sucker’
2) Causes villous atrophy and therefore malabsorption
3) Cysts can remain viable in environment for 24-48 days
- G lamblia can gain access to biliary system and reside in the bile duct, which will cause a completely different syndrome
What are 3 potential clinical presentations of G lamblia?
How can it present differently in immunocompromised individuals?
- 3 potential clinical presentations of G lamblia:
1) Self-limiting diarrhoea
* In immunocompromised individuals’ chronic infection can manifest
2) If diarrhoea present - Usually foul-smelling, fatty stool
3) Can be completely asymptomatic
Cryptosporidium parvum (C. Parvum aka crypto)
What is C.parvum?
How is it transmitted?
What groups does it commonly infect?
In what climates is infected common?
What systems in the body does it infect?
Why is it difficult to sanitise water infected with C.parvum?
What is the genome of C.Parvum like?
- C.parvum is a spore-forming, single celled intracellular (coccidian) parasite
- C. Parvum can be transmitted through the faecal matter due to drinking water contaminated with faeces
- C.parvum typically infects children and immunocompromised
- Usually, infection occurs in subtropical climates
- Biliary tree/ gall bladder and respiratory tract can be affected by C. parvum
- It is difficult to sanitise water infected by C.parvum due to it being naturally resistant to chlorination and is cold resistant, so water needs to be boiled
- The genome of C.parvum is very small
What are the 4 stages in the life cycle (pathogenesis) of C. Parvum?
What is auto-infection?
- 4 stages in the life cycle (pathogenesis) pf C. Parvum:
1) Oocyst (in water)
2) Sporozoites (in intestine)
* Reproduce through asexual reproduction in order to form acute/chronic infections
3) Macro/microgamontes
* Female/male, respectively
* Can go through sexual reproduction to produce oocyst
4) Oocyst (thick/thin walled)
* Oocysts are durable
* Thick-walled cysts are stronger
* Thin-walled cysts can cause higher degree of autoinfection
* Auto-infection is the transfer of a life cycle stage of the parasite from one site to another inside the same host, usually accompanied by morphological transformation
What is the best way to prevent C. parvum infection?
When do signs and symptoms of cryptosporidium infection occur?
How long can they last for?
Can C.parvum infections be asymptomatic?
What are 8 symptoms of C.parvum infection?
- The best way to prevent C. parvum infections is hygiene e.g washing hands, boiling water
- Symptoms of cryptosporidium infection occur usually a week after infection
- Symptoms can last 2 weeks to a month
- C.parvum infections can occasionally be asymptomatic
- 8 symptoms of C.parvum infection:
1) Watery diarrhoea (25-30L watery diarrhoea/day)
2) Dehydration
3) Lack of appetite
4) Weight loss
5) Stomach cramps or pain
6) Fever
7) Nausea
8) Vomiting
How are C. parvum infections treated?
What groups can they be fatal in?
What is a good selective toxicity target for C.parvum?
- C.parvum infections are typically self-limiting and is treated using dehydration treatments
- C.parvum infections can be fatal in the immunocompromised
- A good selective toxicity target for C.parvum is lipids, as it is incapable of its own lipid synthesis
C.parvum summary
Entamoeba histolytica.
What proportion of people infected with Entamoeba histolytica are asymptomatic/symptomatic?
What can increase the susceptibility of the host?
What occurs to cycsts that are ingested?
- Entamoeba histolytica
- Most infected individuals are asymptomatic
- Around 10% of infections produce symptoms
- immunocompromisation increases susceptibility of host
- Cysts ingested undergo excystation (last stage of life cycle) in terminal ileum
How does Entamoeba histolytica affect epithelial cells of the large intestine and blood vessels?
Where can Entamoeba histolytica spread in rare circumstances?
What are trophozoites?
How can Entamoeba histolytica trophozoites cause bloody diarrhoea?
What happens to resistant cysts?
- Entamoeba histolytica can adhere to epithelial cells of large intestine (lectin component)
- It can also undergo Enzymatic penetration into blood vessels
- In rare circumstances, Entamoeba histolytica can undergo haematogenous spread to distal organs e.g. liver
- Trophozoites are a growing stage in the life cycle of some sporozoan parasites, when they are absorbing nutrients from the host.
- Entamoeba histolytica trophozoites can cause bloody diarrhoea by feeding off of lysed cells in the large intestine
- Resistant cysts pass out in stool
What are 5 clinical presentations of Entamoeba histolytica infection?
How can Entamoeba histolytica infection be treated?
- 5 clinical presentations of Entamoeba histolytica infection:
1) Small superficial ulcers
2) Mild diarrhoea
3) Severe ulceration of colonic mucosa - Can lead to amoebic dysentery
4) Trophozoites may spread to liver causing abscesses
5) Overlying skin may be affected by abscesses (very rare)
- Entamoeba histolytica infection can be treated using rehydration therapy, as there is almost no fluid retention in amoebic dysentery
What is virulence of an organism?
How can disease like HIV affect the virulence of Entamoeba histolytica?
What does higher virulence of Entamoeba histolytica increase the incidence of?
- The virulence of an organism is the the severity or harmfulness of it
- Autoimmune conditions such as HIV increase the virulence of Entamoeba histolytica
- Higher virulence of Entamoeba histolytica increases the incidence of invasive Entamoeba (e.g. liver abscess)
What are the 3 types of helminths?
What are 5 different types of nematodes?
What is a type of cestode?
- 3 types of helminths:
1) Neamtodes
2) Cestodes
3) Termatodes - 5 different types of nematodes:
1) Strongyloides stercoralis
2) Trichiuris trichiura
3) Ascaris lumbricoides
4) Enterobius vermicularis
5) Ancyclostoma duodenale
- Taenia solium is a type of cestode
Which are the clinically most important helminths?
What are 3 methods of transmission of nematodes?
Which nematodes use each method?
- Clinically, the most important helminths are nematodes
- 3 methods of transmission of nematodes:
1) Through soil
2) Swallowing infective eggs
* Done by Trichiuris trichiura and Strongyloides stercoralis
3) Larval skin penetration/systemic migration through lung to intestine (autoinfection)
* Done by Ascaris lumbricoides
Strongyloides stercoralis.
How does Strongyloides stercoralis affect intestinal mucosa?
What is Strongyloides stercoralis one of the only geni of nematode to exhibit?
What is How does it exhibit autoinfection?
How long can this last for?
What are 4 clinical presentations of Strongyloides stercoralis?
- Strongyloides stercoralis
- Strongyloides stercoralis disrupts intestinal mucosa, leading to villous atrophy
- It is one of the only geni of nematode to exhibit autoinfection:
- Small intestine larvae will invade the intestinal mucosa of the colon or skin of perianal region, then enter circulation, then lungs, then small intestine (cycle repeats)
- This infection may persist for many years
- 4 clinical presentations of Strongyloides stercoralis:
1) Diarrhoea (may be persistent if immunocompromised)
2) Malabsorption
3) Anal pruritis (anal itching)
4) Dehydration
Trichiuris trichiura (whipworm).
How is it acquired?
What is its worldwide burden?
What are 5 ways Trichiuris trichiura (whipworm) manifests?
- Trichiuris trichiura (whipworm)
- It is acquired through ingesting eggs (classically on leafy vegetables)
- Trichiuris trichiura has a large worldwide burden of disease – up to 800 million cases
- 5 ways Trichiuris trichiura (whipworm) manifests:
1) Asymptomatic if mild infection
2) Abdominal pain
3) Nausea
4) Bloody diarrhoea
5) Rectal prolapse can occur
Ascaris lumbricoides.
What is Ascaris lumbricoides commonly known as?
How large is it?
What are some risk factors for Ascaris lumbricoides?
What are 6 clinical manifestations of Ascaris lumbricoides?
- Ascaris lumbricoides
- Ascaris lumbricoides is commonly known as ‘giant ringworm’
- Giant ringworms can typically range from 13-35cm long
- Risk factors for Ascaris lumbricoides include living in countries with poor sanitation and eating unwashed fruit and vegetables
- 6 clinical manifestations of Ascaris lumbricoides:
1) Asymptomatic (small number)
2) Allergic reactions
3) Intestinal obstruction (see opposite)
4) Malnutrition (particularly proteins) – can lead to impaired growth in children
5) Can be expelled from mouth and nose
6) Loffler’s syndrome
Enterobius vermicularis.
How large are Enterobius vermicularis?
Where do females migrate to?
How long does it take to reach the infective stage?
What are 4 symptoms of Enterobius vermicularis infection?
- Enterobius vermicularis
- Enterobius vermicularis are small nematodes (about 1cm)
- Female migrates to anus at night and lays 1000s of eggs
- Enterobius vermicularis can reach infective stage within hours
- 4 symptoms of Enterobius vermicularis infection:
1) Intense itching
2) Inflammation
3) Diarrhoea
4) Eosinophilia (high number of eosinophils)
Ancyclostoma duodenale (hookworm).
How does Ancyclostoma duodenale (hookworm) enter the gut?
What does it do when at the gut?
What condition does this cause?
How many people are affected worldwide?
- Ancyclostoma duodenale (hookworm)
- Ancyclostoma duodenale (hookworm) enters the gut through larvae penetrating the skin (most commonly through soles of feet), entering the blood stream, and migrating to gut (via lungs)
- When at the gut, it attaches to small intestine, where females lay eggs
- This causes iron deficiency anaemia, as there is blood loss of approximately 0.03ml per day per worm
- Estimated 1 billion people affected worldwide
Taenia solium (tape worm).
How is Taenia solium (tape worm) contracted?
Where can it be found?
How large can it get?
What are 4 symptoms of Taenia solium (tape worm) infection?
- Taenia solium (tape worm)
- Taenia solium (tape worm) is a cestode contracted through consuming undercooked pork and sometimes eggs
- 4 symptoms of Taenia solium (tape worm) infection:
1) Abdominal pain/cramps
2) Nausea
3) Diarrhoea
4) +/- weight loss
