L36: Parasitic Protozoan Infections of the GI Tract

Question 1

4 classes of protozoa and their motility

Answer 1

1. Amoeba – pseudopodia
2. Flagellates – flagella
3. Sporozoan – gliding
4. Ciliates – cilia

Question 2

How to most protozoans exist in the environment and why?

Answer 2

Produce cyst forms that protect them from drying out, etc. and aid in transmission (allows them to get through the stomach)

Question 3

How to prozoa reproduce?

Answer 3

Normally by binary fission (asexual), can be with schizogony (asexual) or sporogoy (sexual)

Question 4

What organism causes amebiasis?

Answer 4

Entamoeba histolytica

Question 5

Life cycle of Entamoeba histolytica

Answer 5

Someone ingests the cyst and it breaks up so amoeboid form can come out – invades colon – can remain in lumen of colon and reproduce to cause dysentery or penetrate intestinal wall and go into circulation

Question 6

Transmission of Entamoeba histolytica

Answer 6

Fecal-oral transmission due to ingestion of cysts – trophozoites will not survive in environment or gastric acidity – asymptomatic people tend to have more cysts in their stool and pass them more often

Question 7

Intestinal disease of Entamoeba histolytica

Answer 7

Causes gastrointestinal distress, 95-100% of patients have blood in stool (dysentery) – fever is rare – gradual onset

Question 8

Invasive disease of Entamoeba histolytica

Answer 8

Penetration of intestinal wall by trophozoites, leading to flask-shaped lesion – spread via bloodstream (liver abscess – abdominal pain, fever, WBC)

Question 9

Diagnosis of Entamoeba histolytica

Answer 9

Stool examination (for eggs or cysts) or antigen detection, biopsy or serology

Question 10

Control and prevention of Entamoeba histolytica

Answer 10

Sanitation and hygiene

Question 11

How does type of stool affect presentation of Entamoeba histolytica?

Answer 11

Individuals with formed stool are more likely to have cysts

Question 12

What organism causes giardiasis?

Answer 12

Giardia lamblia

Question 13

Life cycle of Giardia lamblia

Answer 13

Exists as cysts, which enter the host and hang out on the mucosa but do not invade the cells

Question 14

Transmission of Giardia lamblia

Answer 14

Fecal-oral transmission due to ingestion of cysts from contaminated water

Question 15

Prevalence of Giardia lamblia

Answer 15

Seen often in very young children because kids are disgusting (many outbreaks occur in daycare centers), same prevalence in males and females, associated with water, occurs most often in summer

Question 16

Characteristics of Giardia lamblia

Answer 16

Exists as a cyst outside of host and trophozoite inside host – has sucking disk like a plunger

Question 17

Intestinal disease of Giardia lamblia

Answer 17

Sudden onset, causes foul-smelling, greasy, floating diarrhea; cramping, bloating, gas, NO dysentery (no blood) or fever

Question 18

How long do the specific disease last for Giardia lamblia?

Answer 18

Acute = weeks
Chronic = months to years (malnutrition due to malabsorption)

Question 19

Diagnosis of Giardia lamblia

Answer 19

Observing cysts in formed stools or trophozoites in diarrheal stools (fecal antigen detection)

Question 20

Control and prevention of Giardia lamblia

Answer 20

Sanitation and hygiene (water treatment/filtration)

Question 21

What organism causes balantidiasis?

Answer 21

Balantidium coli

Question 22

Life cycle of Balantidium coli

Answer 22

Ingested as a cyst, either stays in colon and multiples or invades wall of colon and multiplies

Question 23

Transmission of Balantidium coli

Answer 23

Only ciliated organism to affect humans; fecal-oral transmission, frequently from pigs

Question 24

Disease types of Balantidium coli

Answer 24

Chronic – diarrhea or constipation

Acute (invasion) – diarrhea with blood and mucus

Question 25

What organism causes cryptosporidiosis?

Answer 25

Cryptosporidium parvum

Question 26

Life cycle of Cryptosporidium parvum

Answer 26

Same as others but has oocysts (produced by sexual reproduction) -- attaches to intestinal epithelial cells

Question 27

Epidemiology of Cryptosporidium parvum

Answer 27

Not recognized as causing human disease until 70's, now known to be relatively common -- seen often in immunosuppressed patients

Question 28

Transmission of Cryptosporidium parvum

Answer 28

Fecal-oral -- ingestion of infectious oocysts, peaks in early summer to early fall

Question 29

Intestinal disease of Cryptosporidium parvum

Answer 29

Causes profuse watery diarrhea accompanied by cramping, fatigue, and weight loss (no blood) -- generally self-limiting but can be prolonged

Question 30

Diagnosis of Cryptosporidium parvum

Answer 30

Detection of acid-fast oocyst in stool

Question 31

Control and prevention of Cryptosporidium parvum

Answer 31

Proper sanitation and water treatment

Question 32

Isospora belli

Answer 32

Elongated oocyst, fecal-oral, usually has to do with water, diagnosed more in immunocompromised individuals -- causes fever, diarrhea, and weight loss

Question 33

Isospora belli and AIDS

Answer 33

Causes severe disease in AIDS patients -- watery diarrhea, malabsorption, weight loss, electrolyte imbalance, and potentially death

Question 34

Cyclospora

Answer 34

Comes from oocysts in feces, outbreaks associated with water and produce (raspberries!) -- disease is similar to cryptosporidiosis (watery diarrhea and cramping/fatigue/weight loss) -- more severe in AIDS patients

Question 35

Diagnosis of Cyclospora

Answer 35

Oocysts fluoresce under UV light

Question 36

Microsporidia basics

Answer 36

Obligate intracellular parasites, primitive eukaryotes, distribution is worldwide

Question 37

Infection of Microsporidia

Answer 37

Ingestion of spores

Question 38

Intestinal disease from Microsporidia

Answer 38

Chronic debilitating diarrhea, anorexia, weight loss (10-20 stools/day)

Question 39

Extraintestinal disease from Microsporidia

Answer 39

Keratoconunctivitis frequently seen, depends on organ system involved