36 - Parasitic Infections of the GI Tract Flashcards
What are protozoa?
- A diverse group of mostly motile unicellular eukaryotic organism
There are four different classes of protozoa. What are they?
- Ameba-pseudopodia
- Flagellates-flagella
- Sporozoans-gliding
- Ciliates-cilia
Most protozoa reproduce ________ by _________
Most protozoa reproduce asexually via binary fission
Why is this asexual reproduction clinically relevant?
- This is important because if you’re infected by just one small parasite, it will replicate and make you very ill
- This allows them to have a very low infectious dose to cause disease
What type of protozoa can reproduce asexually AND sexually?
Sporozoans
What are the names of their sexual and asexual reproduction types?
Schizogony = asexual Sporogoy = sexual
What does the ability to reproduce sexually AND asexually allow for?
Allows these parasites to exist in the environment
- Dry
- Head
- GI tract pH
Very stable through all of this
How are sporozoans transmitted?
Fecal-oral route
What do many potozoans produce which protects them from the environment and aids in transmission?
Cysts
What is amebiasis-entamoeba histolytica?
- An important ameba that only causes a few thousand cases of entamoeba (disease) per year
What is an important feature of the hystolytica form?
It is the stable form
- Stable in the environment
- Protected from GI tract
- Able to do fecal-oral transmission
What is the mode of ingestion?
Ingestion of cysts via the fecal-oral route
What are the symptoms of hystolytica?
Bloody, mucous diarrhea
What intestinal disease does hystolytica cause??
- Gastrointestinal distress
What percent of symptomatic patients will present with visible or microscopic blood in their stool?
95-100%
What is a major sign of hystolytical?
BLOOD IN THE STOOL (dysentery)
What is common in bacterial dysentery that is rare in hystolytica?
Fever
So what key things do you need to remember about hystolytica?
Bloody stool with NO fever
What happens when hystolytica leads to an invasive disease?
Penetration of the intestinal wall by tophozoites
What type of lesions do histolytica form?
Flask shaped lesions
How does histolytica spread throughout the body?
Spread via the blood stream
What will a systemic infection of histolytica cause?
- Liver abscess
- Abdominal pain
- Fever
- WBC
How do you diagnose histolytica?
- Stool examination
- Antigen detection (intestinal)
What is the rapid test for histolytica?
- A dip stick test, which looks for the antigen
- This type is becoming more common
When would you use a biopsy and serology (extra-intestinal) in order to test for
If you think they have an abscess
How do you control and prevent histolytica?
- Sanitation
- Hygiene
- Proper waste water treatment
This is easy in the US… Not so easy in developing countries
What disease is caused by Giardia lamblia?
Giardiasis
How many cases do we see each year in the US?
20,000 to 30,000
There are two forms. What are they?
- Flagellated form
- Cyst form
Does the cyst form have any flagella?
No
Is giardia typically deadly?
No, usually no deaths due to giardia
Is giardia seen more commonly in males or females?
Equal
What population is giardia seen most commonly in?
Young children
Due to the fecal-oral route of transmission
What activities is giardia associated with?
Bathtub, swimming pool, lake water
Not food transmission very commonly
What time of the year does giardia peak?
Summer months - swimming
What is the pathogenesis of giardia?
Flagellated form has “plungers” that attach to the intestinal mucosa – your entire GI route can be coated with these things
Is giardia invasive?
NO
Do you see a fever with giardia?
No
What are the signature features of giardia?
- Greasy, foul-smelling stool
- Flatulence
- Abdominal discomfort
We also see outbreaks in day care centers… Why is this?
Kids, poor sanitation, care givers can contract it too
What is the difference between asymptomatic cases and symptomatic cases?
- If they are symptomatic, they are probably passing the active form
- If they are asymptomatic, they are probably passing spores
Why is giardia so infectious?
Infected individuals can shed hundreds of millions (100,000,000) of cyst per day!
Is the onset of giardia rapid or slow?
Sudden onset
How long does it last?
A few weeks
Unless it leads to chronic disease, which can last months to years
What is a major concern with chronic giardia?
Malnutrition due to malabsoption
How do you diagnose giardia?
Observing cysts in the stool or trophozoites in a diarrheal stool
You can detect antigen in the stool
How do you control giardia?
Sanitation, hygiene, water treatment, filtering water while hiking
What disease is caused by balantidium coli?
Balantidiasis
What is balantidium coli similar to?
Hystolitica
Balantidium coli is the only infection of humans that is caused by a ___________
Ciliate
What type of transmission do we commonly see?
Fecal oral transmission, frequently from pigs
Is balantidium coli invasive?
It depends… We see either trophozoites in the lumen of the gut or it can be invasive as well
What are the symptoms of acute balantidium coli?
Generally asymptomatic
What happens if an acute infection of balantidium coli becomes chronic?
You see a back and forth between diarrhea and constipation
What if the acute balantidium coli infection is invasive?
Then you will see acute disease
- Diarrhea with blood an mucous
How common is balantidium coli?
Very rare
- It’s an “odd ball”
- A couple hundred cases EVER reported
- Usually with those who ahve grown up around swine
What disease is caused by Cryptosporidium parvum?
Cryptosporidiosis
What time of the year do we typically see outbreaks?
Summer
- Kids in pool + poopy diaper
What is the life cycle of Cryptosporidium parvum like?
Very complicated
- They can have sexual and asexual reproduction within the body
Describe the general steps of the life cycle
- Ingestion of a mature oocyst with sporozoites
- Sporozoites attache to intestinal epithelium and mature
- Sexual forms of Cryptosporidium parvum develop and produce fertilized oocyts
- The infected individual will have mature oocysts in feces
How common is Cryptosporidium parvum?
Very common
- Tens of thousands of cases each year in the US
- Also common in underdeveloped countries
What type of outbreak did Cryptosporidium parvum recently cause in Milwaukee, WI?
A water-borne outbreak
Who is more susceptible to Cryptosporidium parvum?
HIV/AIDS patients
How is Cryptosporidium parvum transmitted?
Via the fecal-oral route
- Ingestion of infectious oocysts
- Peaks in summer months due to community swimming pools
What intestinal disease does Cryptosporidium parvum cause?
Profuse watery diarrhea accompanied by cramping, fatigue and weight loss
Will you see blood in the stool with Cryptosporidium parvum?
NO
Not invasive = No blood
The only time you will see blood in the stool is when it is an invasive disease
How long with symptoms last
Usually self-limiting (1-2 weeks) but it can be prolonged, severe and fatal in the immunocompromised
How do you diagnose Cryptosporidium parvum?
Detection of acid-fast oocyst in stool
How do you control and prevent Cryptosporidium parvum?
Proper sanitation and water treatment
What is Isorpora belli?
Another parasite that has a very similar life cycle as Cryptosporidium parvum and results in a diarrheal illness
What is the signature shape of Isorpora belli?
The oocyst is an elongated, oval shape
What populations do we commonly see Isorpora belli in?
Immunocompromised
What are the symptoms of Isorpora belli?
- Fever
- Diarrhea
- Weight loss
What do we see in AIDS patients with Isorpora belli?
A severe disease
- Watery diarrhea
- Malabsorption
- Weight loss
- Electrolyte imbalance
- DEATH
What is Cyclospora?
Another parasite in which we find oocysts in the feces and has the ability to cause large outbreaks… There was a big outbreak in Iowa last year
When was Cyclospora first recognized as a human pathogen?
Less than 20 years ago
Where do we see Cyclospora infecting humans?
World wide
What is Cyclospora commonly associated with?
Foodborne outbreaks
What was the most recent food outbreak of Cyclospora?
Raspberries
What disease do we see with Cyclospora?
A similar disease as cryptosporidiosis
- Profuse watery diarrhea
- Cramping, fatigue, weightloss
- Prolonged duration
What happens when an AIDS patient becomes infected?
It is generally more severe and of a longer duration
How was Cyclospora first discovered?
An accidental finding - they AUTO-flouresce… They are naturally flourescent under UV light
How do we diagnose Cyclospora?
Look for flourescense under UV light
What is microsporidiosis?
A disease caused by Microsporidia
What parasites are in the Microsporidia category?
A group of hard to say/spell parasites
- Encephalitozoon
- Enterocytozoon
- Nosema
- Pleistophora
All primitive eukaryotes
Where do we see Microsporidia infections?
Worldwide
How is an infection by Microsporidia transmitted?
By the ingestion of spores
What does the infection cause?
Intestinal disease, or they may disseminate throughout the body
What population ahve we seen an increased occurance of Microsporidia in?
AIDS paitents
This is how we know most of what we know about the disease - increased occurrence in AIDS patients
What are the symptoms of an intestinal disease by Microsporidia?
- Chronic debilitating diarrhea
- Anorexia
- Weight loss
- 10-20 stools/day
What are the symptoms of an extraintestinal disease by Microsporidia?
Disseminated disease
- Keratoconjunctivitis is frequently seen as an early indicator of dissemination.
- Symptomology is dependent on organ system involved.
What is Keratoconjunctivitis?
Inflammation of the cornea and conjunctiva
A 25-year-old man living in South America became ill with intestinal cramping and watery diarrhea. Stool specimens were collected and an O & P exam was ordered by his physician. The lab performed an FEA concentration on the sample, prepared wet mounts, and examined them using UV fluorescence microscopy. Images were captured and submitted to DPDx/CDC. Figures A and B were taken at 400× magnification. What is your diagnosis? Based on what criteria?
This person is most likely infected with?
Cyclospora
Twelve 6th grade students participated in an overnight astronomy field trip to a local dairy farm. The owner of the farm provided deli sandwiches, fresh apple cider (made on the premises), and a berry fruit salad for the group’s dinner. Approximately one week after the trip, 10 of the 12 students developed moderate to severe diarrhea accompanied by intestinal cramping. Stool specimens from all the students were collected by the local health department, processed by formalin ethyl-acetate concentration (FEA), and examined. Figure A shows what was observed on a wet-mount slide of one of the concentrated specimens using UV fluorescence microscopy (500×). Figures B and C show what was observed on a modified Kinyoun’s acid-fast stained slide from the same specimen (1000×); Figure D is from a different specimen. All twelve students had the same findings in their specimens, but with different frequency of the objects. What is your diagnosis? Based on what criteria?
This person is most likely infected with?
Cyclospora or cryptosporidium
An eight-year-old boy was taken to his family physician after three days of intermittent abdominal cramping, frequent and occasionally loose, foul smelling stools, and frequent flatulence. The boy had been to a local lake one week before the symptoms first appeared. The physician requested a stool specimen be collected and an ova and parasites (O & P) exam performed. The following images were taken from a trichrome stained PVA stool smear. What is your diagnosis? Based on what criteria?
This person is most likely infected with?
?
The following images are fecal smears (trichrome stained) from a 61-year-old man with bloody and mucoid diarrhea. He frequently traveled between Texas and Mexico. What is your diagnosis? Based on what criteria?
This person is most likely infected with?
?
